Category Archives: Anesthesia

To Open The Airway, Optimally Position The Head and Neck

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The most basic of airway skill is knowing how to open the airway. Sick patients may be breathing spontaneously, but be unable to maintain an open airway, leading to hypoxia. Hypoxia can easily lead to bradycardia and cardiac arrest, especially in children. Mastering basic airway management skills is essential to avoid serious complications.

Opening The Airway Technique

We’re all familiar with the 3 main ways to open the airway.

Head Tilt

Tilting the head back  tends to allow the larynx to rise away from the posterior pharyngeal structures, opening the airway.

illustration of unconscious patient receiving the chin lift maneuver

Tilting the head back, one of the easiest methods of opening an airway, often works without any additional maneuvers.

Jaw Thrust

To use the jaw thrust maneuver , grip the angles of the mandible with both hands to pull the jaw forward. This motion frequently pulls the head into extension. If you’re using cervical precautions because of potential cervical spine injury, pull upward only on the jaw, keep the head and neck stable. Pressing on the bone 1-2 cm above the angle of the jaw and below the ear is painful and may help rouse a sedated patient enough to breathe on their own.

Photo showing jaw lift in a simulated patient

Lifting the jaw by pulling it forward, even with a neutral neck position, will open the airway.

Triple Airway Maneuver

The triple airway maneuver combines the previous techniques. Tilt the head into extension and lift the angles of the jaw. Use your thumbs to pull the mouth open.

Illustration showing the triple airway maneuver

The triple airway maneuver, both tilting the head back and sliding the lower jaw forward is most effective.

While it’s easy to pull the mandible upward by placing your thumb in the patient’s mouth to grip the chin, I don’t recommend it because it’s potentially dangerous — the patient may bite you.

Why Does Tilting The Neck Open The Airway?

The larynx and surrounding structures will move when you move the head and neck and manipalute the surrounding structures. Look at the following Xrays to see why knowledge of the laryngeal anatomy makes it easier for you to open an airway.

Head and Neck Neutral

Look at the lateral Xray with the head in neutral position. The outline of the epiglottis, hyoid bone, thyroid cartilage, and cricoid cartilage are easily identified. The relationship of the larynx immediately in front of the esophagus explains why aspiration can easily occur and is always a risk

Lateral Xray of a the neutral neck showing the larynx

Xray of neck in neutral position. Note how close the trachea and esophagus are. This image shows how the epiglottis works like a trap door to open and close the larynx.

Head and Neck Fully Flexed

Now lets look at a lateral Xray of the neck flexed fully forward. When the head is flexed forward, the structures in the posterior pharynx and the tongue tend to obstruct the airway and close the larynx. You can test this by flexing your head forward as far onto your chest as you can. It becomes much harder to take a breath.

lateral Xray showing that With the head flexed fully forward onto the chest, the airway is almost fully obstructed. Visualization of the larynx wold be impossible.

With the head flexed fully forward onto the chest, the airway is almost fully obstructed. Visualization of the larynx would be impossible.

Head and Neck Fully Extended

Tilt your head back as far as you can. Your airway is now wide open. When we run up a flight of stairs and get out of breath, we tend to tilt our heads back and slightly forward to maximize airway patency and decrease airway resistence. This position is known as the sniffing position.

Now look at at the Xray to see what happens to the airway when the head is tilted backwards.

lateral Xray of the neck in full extension showing how the relationship of the larynx changes with respect to the rest of the neck structures. Extension without placing the patient in the sniffing position will hide the larynx behind the tongue, or a so-called anterior larynx.

Lateral Xray of the neck in full extension showing how the relationship of the larynx changes with respect to the rest of the neck structures.

Don’t Forget Cervical Spine Precautions

Caution: If you are using cervical spine precautions you should NOT tilt the head back. Tilting the head back with possible cervical spine injury could potentially injure the spinal cord. Maintain a neutral position in this situation and rely on jaw thrust.

It helps to know the anatomy and how your manipulations manipulate that anatomy in order to optimize your ability to manage the airway. Think of that anatomy the next time you open the airway.

For more information on opening an airway and on mask ventilation check out:

Airway Emergency: Start With The Basics of Airway Management

May The Force Be With You

Christine E. Whitten MD
author: Anyone Can Intubate: A Step by Step Guide
and
Pediatric Airway Management: A Step By Step Guide

Click on the images to preview my books at amazon.com

Button link to see inside or buy the book Anyone Can Intubate, A Step By Step Guide to Intubation and Airway Management, 5th edition on amazon  Button to see inside or buy the book Pediatric Airway Management: A Step-by-Step Guide by Christine Whitten

Preventing Airway Emergencies

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I’m in Egypt at the 35th International Conference Egyptian Anesthesia 2019. I was given the great honor of presenting my article on the 10 Rules For Approaching Difficult Intubation: Always Prepare For Failure. That article was the most read review article on the Anesthesia News site in 2018, another honor. Thank you readers. A link to that article can be found here. Please feel free to share it with your students.

I have attended many lectures at the Egyptian Conference, and the overarching emphasis on patient safety and continuously improving care is impressive.

It’s been estimated that there are at least 25 million intubations in the United States per year and 50 million worldwide. Even though the percent risk of failed airway is very small, when multiplied by large numbers of intubations the estimates of potential number of critical airway events is impressive.

During my presentation, I referred to 3 recurring themes.

  • Preparation is key
    • You can’t prevent every difficult airway situation – but you can prevent most of them
  • Your decisions, and how you make them are important
    • You can always make a bad situation worse
  • Teamwork and Communication are key
    • You cannot and should not do this alone

Let’s look at these more closely.

Preparation is Key To Avoiding Difficult Airway Situations

Patients can be difficult to intubate because of anatomy or the circumstances surrounding the intubation. For example, failed intubations are more common in emergency room settings, prehospital settings, and delivery rooms. Emergency procedures tend to have more severe outcomes than elective ones.

According to the American Society of Anesthesiologists Closed Claims review, airway complications are twice as likely to occur out of the OR. Inadequate oxygenation is 6 times as likely. This makes sense because those situations frequently are emergencies, in locations with minimal specialized airway equipment, personnel unfamiliar with your techniques, distractions, poor patient positioning, and often, poor lighting. But no matter the status of the patient and circumstances surrounding care, there are always things that can be done to optimize the situation.

Assess Your Patient

In an emergency you may not be able to perform a detailed exam, but you should perform as complete an airway exam as possible. Don’t just look at the physical characteristics without considering why those particular traits might make the intubation or the ventilation more difficult. Instead, use the criteria of why you expect difficulty to guide your planning and your actions.

Recognizing a patient with a potentially difficult airway is an opportunity that allows you to prepare ahead to have equipment, personnel, and a backup plan. It can help you decide between awake and asleep intubation, or to choose to use or not use muscle relaxants. It also can alert you to the fact that a patient may need to receive care in a different setting or with more experienced providers, if possible. It can help you prepare your team to assist you.

Take Stock of Your Resources

Intubation is a team effort. You need to have all of the right people and equipment. Sometimes that means moving a patient to a different and more optimal location, or asking for more expert help. Ask yourself the following questions:

  • What type of help do you need for this particular patient?
  • Should this patient be intubated here, or transferred to the OR or other setting?
  • Who should intubate this patient? The first attempt is often the best chance at success. For a particular patient, that may mean allowing someone with more experience to intubate.
  • What equipment do you need?
  • Do you have all the attachments?
  • Is there functioning suction?

Make sure your staff in the OR and on the ward is well trained ahead of time. If you ask for a rescue laryngeal mask airway in a can’t intubate/can’t ventilate event, you don’t want your nurse asking you what it looks like.

Use A Critical Event Check List

No one can remember everything in today’s complex medical world. Things get even worse in a crisis. It often feels as though epinephrine doubles your strength and halves your intelligence. Stress, distractions, and sometimes chaos associated with a critical event often cause highly skilled providers to forget crucial, potentially lifesaving steps and drug dosages.

Access to a critical event checklist can be lifesaving. The aviation industry has used checklists for decades. Use of such a resource in an emergency is a wise decision, not a sign of weakness.

My hospital uses the Crisis Event Checklist from Harvard, and Brigham and Woman’s Hospital.

Position Your Patient

We have all been guilt of not optimally positioning a patient for intubation only to then have difficulty visualizing the larynx. Things are worse outside of the OR where we don’t have all of the normal positioning devices.

Take any patient with an easy airway, place him on the floor in cardiac arrest, surround him with providers whom you don’t know offering help but not knowing what you need, and that intubation will be difficult.

A more detailed discussion on positioning can be found here.

Consider Awake Intubation If You Expect Difficulty

When I was training, we didn’t have video-laryngoscopy or LMAs. Awake intubation for anticipated difficult airway was routine. If any patient looked remotely difficult we would do an awake intubation.  This made us very comfortable with the technique for emergency situations.  Blind nasal intubation and fiberoptic intubation were common procedures.

Today we don’t intubate awaken nearly as often. A main reason is that video-laryngoscopy and LMAs have revolutionized our ability to manage the majority of the challenging intubations another way. It’s fair to say that awake intubation requires more advanced skills and takes more time.

However some patients need to be intubated awake, especially if there is concern about the ability to ventilate the patient. Begin the preparation early when awake intubation is a possibility. Nasal vasoconstriction and oral drying agents take at least 20 minutes to work well. Numbing the airway must be effective. Explain to the patient what to expect and what they must do to help.

How much sedation should you give? It depends on how scary your patient is. If the first 4 steps are done well, you won’t need a lot of sedation. Use sedation cautiously. Over sedation can quickly produce apnea or make your patient uncooperative.

And remember that awake intubation doesn’t just mean fiberoptic. You can perform awake intubation with:

  • Blind nasal intubation
  • Standard laryngoscopy
  • Video-laryngoscopy
  • Via intubating or standard LMA
  • Combined techniques (e.g. Fiberoptic/LMA)

Your Decisions, And How You Make Them, Are Important

Things happen quickly during an intubation, especially in an emergency setting. It’s important to avoid unforced errors.

Call For Help Early

Oxygen desaturation once it begins will cause rapid deterioration. Don’t wait until it begins to call for help, it takes time for help to arrive and equipment to be brought.

Change Plans If Something’s Not Working.

We’re all human. Once we begin a task it is a common failing to just keep repeating the same steps over and over again, expecting that eventually it will work. This is the definition of insanity. If something doesn’t work the first time, change something.

Be Aware: Time Stands Still In A Crisis.

What seems like 1 to 2 minutes can really be 10 to 15. Force yourself to keep track of the clock. Especially pay attention to the duration of apneic periods. Lack of ventilation harms patients, not the lack of an endotracheal tube.

Know When To Stop

There are many times when we can stop and wake the patient up to do an awake intubation, or to cancel surgery and bring the patient back another day when more optimal preparations can be made — and any edema or airway trauma can have a chance to resolve.

Teamwork And Communication Are Key

You cannot and should not do this alone. I teach my students that intubation is a team effort, which means it’s a coordinated effort by a small group of people with a common goal. To succeed, everyone needs to know the problem and the plan, especially when you are expecting difficulty. If your helpers don’t know the plan, then they either could fail to do what you need them to do or could even accidentally sabotage your efforts.

Function As A Team.

Anesthesiologists really good at talking to each other and not so good at keeping the team informed. Your team can’t read your mind.

Your team also needs to be empowered to give suggestions. Everyone needs to know that if they see something, they should say something.

We need the leaders in a critical event to be open to feedback and suggestions. We need to foster a clinical environment in which all of our staff feels empowered enough to speak up when they see something.

TeamSTEPPS is an educational program whose goal is to create highly functioning crisis management teams. In TeamSTEPPS, there is something called the Two-Challenge Rule for when you feel there has been a potential breach of safety. The Two-Challenge Rule states that if your first verbal observation of a problem is not acknowledged or acted upon, then you should challenge again. If the safety issue persists, then becoming more assertive is recommended. Don’t curse, but use “CUS” words, that is:

  • I am Concerned about …
  • I am Uncomfortable because …
  • This is a Safety issue …

It’s very difficult to challenge anyone in authority. The airline industry recognized this prior to initiating industry-wide retraining in teamwork and communication. There were accident reports of airplanes crashing, flying into mountains and running out of fuel, because copilots and other flight personnel did not feel empowered to point out mistakes they had recognized. The airlines realized they had a culture that showed:

  • excessive deference to a leader;
  • hesitation of subordinates to speak up; and
  • reluctance to immediately question a clearly unusual or suspect event.

If a copilot facing personal death in an airplane crash can’t question the pilot, how easy is it for a nurse, for example, to challenge a doctor?

We Have The Power To Decrease The Incidence Of Bad Outcomes

In closed claims analyses, human error has been implicated in 80% of critical events. Human error is unavoidable and therefore we need to work hard to avoid it.

We need to carefully assess, develop a strategy for Plans A, B and C and gather our resources before we start.

We need to think carefully and reassess how our plan is going as our care proceeds. You can always make a bad situation worse.

We need to improve our skills in teamwork, leadership, and communication.

Pay attention to those three principals. If we do, then we can help make errors much less likely to occur, and much less damaging when they do.

 

May The Force Be With You

Christine Whitten MD, author

Anyone Can Intubate: A Step By Step Guide
And
Pediatric Airway Management: A Step by Step Guide

 

Click images to review my books at amazon.com

Button link to see inside or buy the book Anyone Can Intubate, A Step By Step Guide to Intubation and Airway Management, 5th edition on amazon    Button to see inside or buy the book Pediatric Airway Management: A Step-by-Step Guide by Christine Whitten

Pediatric Airway Risks: Inefficient Mechanics of Breathing

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Inefficient mechanics of breathing is one major risk factor for infants and young children because it increases work of breathing. In many ways pediatric anatomy and physiology predisposes a child to respiratory distress and respiratory failure.

(Illustrations copyright Whitten, Pediatric Airway Management: A Step By Step Guide)

Mechanics of Normal Breathing

Normal quiet breathing is effortless. The rate is neither too fast nor too slow, however, rate varies greatly depending on age and metabolic rate. The chest rises and falls easily and symmetrically. Air flows into and out of the lungs through the open airway based on changes in air pressure.

Adult Chest Cavity Anatomy Makes Breathing Efficient

Let’s start by reviewing the adult mechanics of breathing. The angulation and rigidity of the ribs during the breathing cycle maximizes efficiency in the adult. The lungs are housed in a skeletal cage formed by the ribs. In order to initiate airflow into the lungs, pressure in the lungs must drop below atmospheric pressure. The body accomplishes this by expanding the airtight chest cavity, thereby decreasing the pressure inside. Two motions are involved:

  • expansion of the rib cage by contraction of intercostal muscles
  • contraction and descent of the diaphragm

The ribs form three functional groupings. The first rib attaches rigidly to the sternum to anchor the rib cage. It hardly moves during respiration.

The 8th through 12th ribs expand mostly laterally during inhalation. This effectively increases intra-abdominal space for organs pushed downward by the diaphragm. The motion is like a bucket handle, swinging up and down toward the side away from the centerline and expanding the width of the chest cavity.

The 2nd to 7th ribs flexibly expand mostly anterior-posterior with a little lateral motion. This motion is like a pump handle — mostly up and down in the front of the chest, expanding the depth of the chest cavity.

Illustration comparing the motions of ribs 8-12 to the motion of ribs 2-7. Each set has unique movements for expanding the rib cage.

a. Ribs 8-12 expand mostly laterally, like a bucket handle. b. Ribs 2-7 expand mostly anteriorly, like a pump handle.

Diaphragmatic Contaction Is The Bellows

The diaphragms are two large dome-shaped sheets of muscle separating the thoracic cavities from the abdominal cavity. As the diaphragms contract with each inhalation, they act like a bellows. During inhalation the bellows descends and flattens, increasing intrathoracic volume and decreasing intrathoracic pressure. This pulls air into the lungs as they inflate.

During exhalation, the diaphragm and intercostals relax. As a result, the diaphragms rise and become dome shaped again, decreasing intrathoracic volume and raising intrathoracic pressure. Lungs deflate. The patient exhales. Unless there is obstruction, exhalation is passive, requiring little energy.

Full contraction of the intercostals and the diaphragm allows for much greater expansion of the chest cavity and produces a larger breath, assuming that air is free to flow into the lungs..

Illustration showing how relaxation and contraction of the diaphragm produces air flow into and out o the lungs by changing air pressure inside the thoracic cavity.

The diaphragm contracts and relaxes during breathing, expanding and contracting the volume of the thoracic cage. The associated air pressure changes inside the thoracic cavity cause the lungs to expand (a) and to deflate (b).

What Factors Affect Ease of Air Flow?

A variety of factors affect how easily that air flows:

  • breathing rate
    • too rapid or too slow a rate impairs air movement
  • inspired tidal volume
    • ventilating close to dead space volume causes CO2 levels to rise
  • airway resistance
    • smaller airways have higher resistance than larger airways
    • increased resistance impairs airflow
  • tissue resistance
    • increased frictional resistance of lung tissues and chest wall increases work of breathing and limits tidal volume
  • elastic recoil
    • with weaker elastic recoil, airways tend to remain partially collapsed on exhalation rather than passively reinflate to baseline
  • compliance
    • poor compliance makes it harder to distend the lungs, limiting air movement and increasing the work of breathing

Changes in any of these parameters can significantly affect adequacy of respiration and how hard it is to take a breath.

Anatomical Features That Increase Pediatric Work of Breathing

When the patient works hard to take a breath, for example against an obstruction, he generates a more negative pressure inside the chest cavity.  The intercostal muscles more fully contract. Retractions, noisy breathing, and a rocking chest wall motion are common. As respiratory failure progresses, the pattern of respiration becomes more and more inefficient and ineffective. Work of breathing increases.

In the patient exhausted to the point of respiratory collapse, or in the patient with respiratory depression due to altered mental status, there may be little effort to breathe. Hypoventilation worsens hypoxia, hypercarbia, and respiratory acidosis. Level of sedation increases, further depressing respiratory drive.

Normal infants and small children have significant anatomic predispositions to serious disruption of their mechanics of breathing if they become sick or injured.

Factors Increasing Infant Work of Breathing

The differences in the mechanics of breathing of small children compared to adults places them at much higher risk of respiratory failure.

Evaluating the degree of respiratory compromise is a judgment call. Mild or potential obstruction may have no signs or symptoms at all. In certain patients such as facial burn victims or patients having a severe allergic reaction, mild airway obstruction can convert to total obstruction quickly as edema forms. Constant reassessment is important so that you may intervene early if necessary — before the airway is lost.

The Infant’s Chest Wall Increases The Work Of Breathing

In the infant or small child, the chest wall is more box-like in shape compared to the adult’s. The ribs are more at right angles to the vertebral column and won’t be angulated like an adult until age 10 years. This makes the pediatric chest wall mechanically less efficient and limits potential lung expansion.

comparison infant vs adult rib angulation

The shape and flexibility of the infant chest, and the shape and immaturity of the diaphragmatic muscle both increase the risk of respiratory failure when the child is ill.

Babies “belly breathe”. To take a deep breath, the infant’s chest therefore expands a little and the abdomen rises a lot as the diaphragm descends, pushing abdominal contents down and out of the way.  Anything that interferes with descent of the diaphragm, such as a stomach or intestines distended with air or liquid, can seriously impair an infant’s breathing.

The infant’s chest wall is also more compliant than an adult’s, with an elastic recoil close to zero because of the lack of rib cage ossification. When the infant takes a breath against resistance, such as with airway obstruction or poor pulmonary compliance from pneumonia, the chest wall actually moves inward as the belly moves outward. The inward movement of the chest wall decreases the amount of air that enters. A rocking chest wall motion is very common in children with even partial airway obstruction.

Illustration showing the components of infant anatomy that make the mechanics of breathing inefficient, increasing risk of respiratory failure.

The inefficient mechanics of infant/toddler breathing increases the risk of respiratory failure.

Because chest wall structure and “belly breathing” limit the ability to increase tidal volume, the baby must rely on respiratory rate increases to compensate for stress. The harder a child tries to breathe, the less efficient and more labored breathing becomes.

You can see video of a toddler with croup and the signs of airway obstruction described above here.

Monitor Your Pediatric Patient Carefully

Watch for signs of airway obstruction.

chart listing the signs of airway obstruction

Infants and toddlers tire easily when they have airway or respiratory compromise. Respiratory distress can easily progress to respiratory failure. Assess your patients carefully and monitor for change. Always ask yourself: “How well is my patient breathing?” Follow the link below for discussions and video of recognizing and treating airway obstruction.

Recognizing Airway Obstruction May Save Your Patient’s Life

Click here see a video clip comparing the signs of airway obstruction in a pediatric patient with a more normal breathing pattern once the obstruction is relieved.

May The Force Be With You

Christine E Whitten MD, author:
Anyone Can Intubate: A Step By Step Guide
and
Pediatric Airway Management: A Step By Step Guide

Button to see inside or buy the book Pediatric Airway Management: A Step-by-Step Guide by Christine Whitten    Button link to see inside or buy the book Anyone Can Intubate, A Step By Step Guide to Intubation and Airway Management, 5th edition on amazon

Click on the covers to preview books at amazon.com

ETCO2: Valuable Vital Sign To Assess Perfusion

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Like pulse oximetry before it alerting us to changes in oxygenation, end-tidal CO2 monitoring, or ETCO2, is rapidly becoming an additional vital sign. We routinely use ETCO2 to provide information on ventilation. But ETCO2 can also provide valuable information on the adequacy of cardiac perfusion. It can be an essential tool in ensuring optimal, high quality chest compressions during cardiac resuscitation.

Some Physiology

Ventilation and oxygenation are different. Ventilation exchanges air between the lungs and the atmosphere so that oxygen can be absorbed and carbon dioxide can be eliminated. Oxygenation is simply the addition of oxygen to the body. Under normal circumstances, hyperventilation with room air will lower your arterial carbon dioxide content (PaCO2) significantly, but not change your oxygen levels much at all. On the other hand, if you breathe a high concentration of oxygen without changing your respiratory rate, your arterial oxygen content (PaO2) will greatly increase. However, your PaCO2 won’t change.

Oxygenation changes PaO2. Ventilation changes PaCO2.

Some History Of Old Fashioned Monitors

When I started my anesthesia training in 1980, we monitored the patient with a manual blood pressure cuff, EKG, pulse, and temperature. Pulse oximetry and capnography were not yet in clinical use. If we wanted to determine PaO2, or PaCO2, we needed to draw a blood gas. Frequent blood gas determinations, or the need to monitor continuous perfusion pressures, often necessitated placement of an arterial line.

To provide an indirect indicator of perfusion, we used a precordial stethoscope attached to an earpiece to continuously listen to heart sounds. An attentive anesthesiologist could use changes in the loudness or crispness of the heart tones to alert him or her to changes in cardiac output. As the patient got lighter or if the blood pressure rose, heart tones got louder and sharper. Low blood pressure brought muffled, faint heart tones independent of heart rate. We were essentially using our ears in place of the plethysmograph waveform that pulse oximetry would eventually provide.

Pulse Oximetry

Pulse oximetry revolutionized anesthetic safety. Pulse oximetry was a non-invasive way of measuring oxygen saturation. Oxygen saturation  is the percent of Hemoglobin (Hgb) binding sites in the blood that are carrying oxygen. Hemoglobin is a chemical molecule in the red blood cell (RBC) that carries oxygen on specific binding sites. Each Hgb molecule, if fully saturated, can bind four oxygen molecules. Depending on conditions, Hgb releases some percentage of the oxygen molecules to the tissues when the RBC passes through the capillaries.  We can measure how many of these binding sites are combined, or saturated, with oxygen. This number, given as a percentage, is called the oxygen saturation or simply O2 Sat, commonly pronounced “Oh Two SAT”. it is also referred to as SPO2. When all the Hgb binding sites are filled, Hgb is 100% saturated.

Oxygen saturation and PaO2 are NOT equivalent, and they have significant clinical differences that you can read about here.

What’s The Difference Between Oxygen Saturation And PaO2?

However, with pulse oximetry we could now measure oxygen saturation. We could immediately see in real time if our patient was hypoxemic or hypoxic and, if so, diagnose the cause and treat it before harm was done.

Watching the quality of the waveform, along with the oxygen saturation, told us valuable information about perfusion. The higher the amplitude of the wave, the stronger the pulse was. The more damped out the waveform appeared, the weaker the pulse.

With this new tool, and with the OR environment becoming increasingly noisy, use of the precordial stethoscope has largely faded away. Pulse oximetry quickly spread to ICUs, on wards, and clinics to monitor patients at risk. Pulse oximetry has become a fifth vital sign.

I believe we are seeing the same transition with end-tidal CO2 monitoring.

END TIDAL CO2 Has Many Uses

What Is ETCO2?

Capnography refers to the process of measuring the partial pressure of end-tidal CO2 in each expired breath. Providers measure the value of ETCO2 in each exhaled breath with a very thin tube inserted into the breathing circuit or the patients oxygen mask or nasal prongs.

The waveform (capnogram) that you then see on the capnography monitor provides a real time recording of the patient’s respiratory rate, pattern and depth of breathing, and of course the value of CO2 exhaled. These measurements help the provider evaluate adequacy of ventilation.

The author looks at the capnography waveforms during an anesthetic to evaluate ETCO2 values and the adequacy of ventilation.

The author looks at the capnography waveforms during an anesthetic to evaluate end-tidal CO2 (ETCO2) values and the adequacy of ventilation.

ETCO2 Helps Assess Adequacy of Ventilation

We routinely measure ETCO2 for every patient in the operating room. We use it increasingly for conscious sedation provided in treatment rooms and on the wards. ETCO2 and PaCO2 are not the same value. PaCO2 is the concentration of CO2 in arterial blood. ETCO2 is the concentration of CO2 in the exhaled breath, and is close to alveolar CO2. ETCO2 is usually about 5 mmHg below PaCO2. This makes sense. If the concentration of CO2 in the alveoli were higher than in the blood stream, CO2 could not enter the lungs and would not be exhaled.

ETCO2 offers a valuable trending tool to monitor and control ventilation. It alerts us immediately if the patient hyperventilates, hypoventilates, or becomes apneic.

  • A normal trace appears as a series of rectangular waves in sequence, with a numeric reading (capnometry) that shows the value of exhaled CO2. “Normal” ETCO2 is in the range of 35 to 45 mmHg.
  • In hyperventilation, the CO2 waveform becomes smaller and more frequent, and the numeric reading falls below the normal range.
  • In hypoventilation), the waveform becomes taller and less frequent, and the numeric reading rises above the normal range.
  • Fattening of the waveform indicates an airway obstruction.
  • If the series of rectangular waves become a flat line, the patient is not breathing.

Use ETCO2 In The Perioperative Areas

I believe we should increase our use of ETCO2 in our perioperative areas and procedure rooms. Patients receiving conscious sedation on the ward or recovering from anesthesia are arguably at more risk of airway compromise than patients in the operation room. They are often under more intermittent observation. I encourage my recovery room nurses to use end-tidal CO2 monitoring when they are caring for patients at risk of hypovention or obstruction such as those:

  • exhibiting prolonged sedation,
  • with opioid induced respiratory depression,
  • history of sleep apnea,
  • any cardiovascular instability
  • any time they are worried about a particular patient.

For clinical examples of how ETCO2 can change during clinical care and how we can use ETCO2 to guide our treatment, read more here.

How Does Hypoventilation Cause Hypoxemia?

Anatomic Dead Space Affects Hypoventilation

Don’t Withhold Oxygen From That CO2 Retainer

ETCO2 Helps Verify Intubation

Esophageal intubation or accidental extubation are always risks.  Monitoring ETCO2 increases safety. The continued presence of CO2 in the exhaled breath can only mean placement of the tube in the trachea. Loss of the ETCO2 trace indicates extubation or disconnection from the circuit the ETCO2.

The shape of the capnography waveform can also indicate the severity of problems such as bronchospasm or other cause of increased resistance to breathing or exhalation.

ETCO2 Is An Early Sign Of Poor Perfusion or Cardiac Arrest

Oxygen delivery and carbon dioxide removal depend on three systems: lungs, blood and circulation. It’s important to remember that adequate oxygen absorption and delivery depends on the interaction between lung function and circulation. As soon as cardiac output starts to fall, blood perfusion through the lungs falls. CO2 now has more difficulty being carried to the lungs for exhalation. This leads to a rise in PaCO2 in the blood stream and a fall in ETCO2.

Oxygen delivery and CO2 removal from the lungs depend on lung function, blood hemoglobin concentration, and circulation. Disturbance in any of these risks respiratory distress or failure. If lung function and Hgb are stable, then changes in ETCO2 imply changes in perfusion.

Oxygen delivery and CO2 removal from the lungs depend on lung function, blood hemoglobin concentration, and circulation. Disturbance in any of these risks respiratory distress or failure. If lung function and Hgb are stable, then changes in ETCO2 imply changes in perfusion.

In the operating room, I often see a drop in ETCO2 even before blood pressure itself starts to fall. As long as there is some circulation, there will be some ETCO2 present, even if you can’t feel a weakened peripheral pulse. ETCO2 can therefore be an early warning of developing shock, or pulmonary embolus.

If ETCO2 drops to zero, then the heart has stopped. This is true even for patients who are continuing to receive manual ventilation, because although air is moving into and out of the lungs, there is no CO2 being delivered to exhale. Loss of ETCO2 can also be the first sign of cardiac arrest. A patient may still have an EKG trace in pulseless electrical activity, but not have circulation and therefore will not have a measurable ETCO2.

Here is a simplified flow chart for using ETCO2 to alert you to perfusion or ventilation problems.

ETCO2 is a valuable tool for early recognition of poor perfusion and cardiac arrest.

ETCO2 is a valuable tool for early recognition of poor perfusion and cardiac arrest.

Adequacy Of Chest Compressions

Good quality CPR depends on high quality chest compressions. When I practice with my staff during Critical Event Training, failure to perform adequate chest compressions is common, a fact that reinforces the need to routinely practice.

During one particular exercise, one diminutive RN was having trouble making her compressions meet the 2-2.5 inch depth, 100 compressions per minute on the manikin (as measured by our test device). The rest of the team encouraged her until she got it correct. The following weekend her Dad suffered a cardiac arrest in her living room. She went into action delivering chest compressions while the family dialed 911. Her father made a full recovery, and she gave credit to the training she had just received.

Good quality compressions can save lives. ETCO2 is one valuable tool we have to tell us that good quality compressions are being delivered. The higher the ETCO2 measured during compressions, the better the perfusion being supplied by CPR. The goal should be to maintain ETCO2 no lower than 10-20 mmHg. An ETCO2 below 10 mmHg is associated with poor outcome.

Good quality chest compressions will also generate a waveform on the ETCO2 capnograph that allows you to estimate the rate of compressions.

Return of Spontaneous Circulation

Return Of Spontaneous Circulation (ROSC) is accompanied by a sharp rise in ETCO2, usually within a range higher of 35-45 mmHg or higher as CO2 is now delivered to the lungs and then exhaled. This is often accompanied by a palpable pulse and a rising blood pressure.

Good news. However, the next 10 minutes are a very dangerous time for your patient. The heart is still stunned and cardiac output may still be poor. Current consensus guidelines for cardiopulmonary resuscitation (CPR) recommend that chest compressions resume immediately after defibrillation attempts and that rhythm and pulse checks be deferred until completion of 5 compression:ventilation cycles or minimally for 2min.

One study showed that perfusion remained poor for greater than 2 minutes in 25% of patients successfully defibrillated [1]. Continue to monitor that ETCO2! This is now your powerful tool to see if perfusion is adequate and being maintained. Assuming ventilation is consistent, a drop in ETCO2 during this period can indicate failing circulation. A loss in ETCO2 can mean re-arrest.

Check to make sure your endotracheal tube is still properly positioned, check a pulse, and decide your appropriate actions.

Prognosis During CPR Efforts

ETCO2 below 10 mmHg can be caused by poor compression technique.  It can also be caused by low perfusion and metabolism from prolonged shock despite good compressions — in other words the cardiac pump is damaged and failing. If high quality compressions are being delivered, and an advanced airway is in place allowing accurate ETCO2 measurements, then an ETCO2 persistently below 10mmHg after 20 minute of resuscitation is a poor prognostic sign. It can be used as an indication to consider terminating resuscitation efforts.

On the other hand if ETCO2 is above 15mmHg, or it continues to rise, that is one indication that resuscitation efforts should continue, as the brain and heart are being perfused. There are case reports of patients surviving prolonged CPR with higher ETCO2 readings.

We’ve come a long way since I had to depend on a precordial stethoscope, skin color and finger on the pulse to supplement blood pressure and EKG to assess perfusion in my patients. Capnography and pulse oximetry are powerful tools. However, don’t forget that in the absence of either, you can still look at your patient and be vigilant. Without vigilance, all the tools in the world will not protect your patient.

May The Force BeWith You

Christine E Whitten MD, author
Anyone Can Intubate: A Step By Step Guide
and
Pediatric Intubation: A Step By Step Guide

Button link to see inside or buy the book Anyone Can Intubate, A Step By Step Guide to Intubation and Airway Management, 5th edition on amazon      Button to see inside or buy the book Pediatric Airway Management: A Step-by-Step Guide by Christine Whitten

References

1. Pierce AE, Roppolo LP, Owens PC, Pepe PE, Idris AH. The need to resume chest compressions immediately after defibrillation attempts: an analysis of post-shock rhythms and duration of pulselessness following out-of-hospital cardiac arrest. Resuscitation. 2015 Apr;89:162-8. doi: 10.1016/j.resuscitation.2014.12.023. Epub 2015 Jan 15.

# 1 Review Article for Anesthesiology News 2018: 10 Rules for Approaching Difficult Intubation by Christine Whitten

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And the numbers are in, my review article for Anesthesiology News was actually THE MOST viewed article on the site for the whole year!

I’m afraid working overtime over the holidays and family trips have gotten in the way of posting this December but I’m already hard at work for 2019, including a new article for Anesthesiology News.

In the meantime please enjoy this review on the “10 Rules for Approaching Difficult Intubation: Always Prepare for Failure.”

 

I have included the longer formal link below in case the short link above fails to connect.

<http://email.robly.com/mpss/c/_AA/0aMdAA/t.2nw/xS2STNZ0SF23cnKkPrcuPA/h12/yaw471FzMiRzPvmq3J-2B95tGwWZ-2Bry3oaHm6R8jrhYQAorOJynxVBXZoVufu9oObYy5vTHg0MZa0zdQgMBlp281H0uKpuMK-2FuThcIxXMjfOFp76d-2BA9L-2B3BUALaB8i8T-2B2D3iTZ1v2ZGUSc9J-2B1fCHgmhvc50I51wIPPwgiy1zsVWTpQmHC3Hp8hAvZ-2BcZliG0CNe-2Brc77KYOZxVnL6-2Btff5EMscZznppuc8SJG-2By1r8zCD9TBKbOAeTjYbaRjwEf>

 

May The Force Be With You!

Christine E. Whitten MD
author
Anyone Can Intubate: A Step By Step Guide, 5th Edition
and
Pediatric Airway Management: A Step Be Step Guide

Button link to see inside or buy the book Anyone Can Intubate, A Step By Step Guide to Intubation and Airway Management, 5th edition on amazon  Button to see inside or buy the book Pediatric Airway Management: A Step-by-Step Guide by Christine Whitten

Please click on the covers to preview at amazon.com

Conscious Sedation: Is Your Patient Breathing?

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Change in mental status can occur from conscious sedation or opioid administration, hypotension, sepsis, head trauma, acid-base imbalance, alcohol, drugs, or toxins. Change in level of consciousness often affects breathing, sometimes to the point of causing severe hypoxia, arrythmias and cardiac arrest. Let me repeat that. Anything that alters consciousness can alter respiration, which can lead to the vicious cycle of hypoventilation, hypercarbia, and hypoxia. If you don’t recognize inadequate respiration —and treat it— the patient can suffer injury or die. Let’s look at a common clinical example of altered consciousness — conscious sedation.

Everyday, in all of our practices, we purposefully try to alter our patient’s level of consciousness in order to tolerate a procedure. We often take the safety of procedural conscious sedation for granted. After all, we’re only giving a little sedation to make the patient relaxed, calm and more comfortable. Although problems are rare, patients can become hypoxic, hypercarbic, and apneic with conscious sedation, and some have died. The deaths of the celebrities Michael Jackson in 2009, and Joan Rivers in 2014 were related to hypoxia from loss of the airway under deep sedation. Respiratory depression represents the principal potential risk introduced with conscious sedation. If left unrecognized and untreated, it can be the cause of serious complications.

Sleep and Sedation Affect Respiration

To understand why mental status change increases respiratory risk, let’s start with the respiratory effects of sleep.

Janet Smith is a 44 year-old healthy patient who is scheduled for correction of a trigger finger with ambulatory surgery under conscious sedation tomorrow at the surgicenter. She’s worried, so it takes her a long while to fall asleep. When she finally does sleep, her respiratory drive begins to change.

Does oxygen saturation change with normal sleep? For healthy young people between 19-25 years of age, there appears to be no change in oxygen saturation with sleep (1). Other studies looking at a more varied population up to age 64 did find up to an 11% drop in oxygen saturation(2,3,4). Adding a comorbidity such as chronic bronchitis is also associated with saturation drops of about 10%. So the answer seems to depend on age, presence of comorbidities and how ventilation changes with sleep for that particular person due to such things as snoring.

With normal non-REM sleep, PaCO2 rises about 3-7 mmHg as the body’s response to increased CO2, or hypercarbia, is blunted. Tidal volume and respiratory rate decrease. Pharyngeal muscles as well as muscles of the tracheobronchial tree relax, increasing airway resistance and predisposing to potential obstruction, such as snoring.

Although some of us sleep more deeply than others, we usually awaken easily if someone talks to us, or the alarm goes off. If we obstruct our airway and begin to snore, we typically rouse ourselves enough to take a deep breath and turn over. When we don’t easily rouse from sleep induced airway obstruction then we may have sleep apnea. Now, let’s look at how giving sedation to a patient like Janet Smith interferes with her ability to rouse.

Conscious Sedation

When Janet gets to the preop area, she’s nervous and tells her nurse that she didn’t sleep much the night before. Her anesthesia provider gives her 1 mg of midazolam IV to relax her. Her care team then takes her to the OR.

With light conscious sedation she will continue to respond to verbal commands. Cognitive function and coordination may be impaired. She can still carry on a conversation, although she may not remember details of it.  Cardiac and ventilatory function are usually not altered a lot. Like natural sleep, it’s common for the patient’s respiratory rate and tidal volume to decrease slightly. She’ll lie comfortably on the OR bed while we’re attaching her monitors and going through the final safety checks.

Moderate Sedation

Of course, many patients like to nap during their surgical procedure and in this case the anesthesiologist starts a background infusion of propofol at a low rate of 25 mcg/kg/hr to induce a moderate level of conscious sedation while things are being set up. Using this technique, the level of propofol in Janet’s bloodstream builds slowly and she will get progressively sleepier until she’s moderately sedated.

With moderate sedation, a patient still responds to commands, but she might require a tap on the shoulder to rouse and answer a question. She still shouldn’t require any help holding her airway open, but there may be more of a tendency to snore, especially if the patient has a history of snoring. Snoring is a sign of airway obstruction and is a warning sign that the patient needs to be monitored more closely.

Injecting local anesthetic can be a bit painful. As the surgeon gets ready to inject the local anesthetic the anesthesiologist will often give just a little more sedation so that the patient does not remember the injection. This could be more midazolam, or a short acting opioid like fentanyl. However, in this case Janet is given a small bolus of 50 mg of propofol IV. The strategy behind this technique is to temporarily induce a deeper level of sedation during the local anesthetic injection itself. Sedation from a Propofol bolus wears off in a few minutes, allowing Janet’s level of consciousness to return back to the prior moderate level of sedation for the rest of the procedure.

Deep Sedation

With deep sedation the patient is not easily arousable, but will still respond with repeated or painful stimulation. The deeply sedated patient might occasionally require help holding her airway open and spontaneous ventilation might become inadequate. Cardiovascular stability is usually maintained.

Janet tolerates the injection well and appears to be sleeping. However, after the injection is finished, the anesthesiologist notices that Janet is no longer breathing well. Her airway is obstructed. He tips her chin back and lifts her jaw to open her airway and she takes a deep breath. He has to periodically shake her shoulder for the next few minutes to remind her to take deep breaths. After about 2 minutes she starts breathing well again on her own.

Unconsciousness: General Anesthesia

What just happened? It can be easy to take a patient from deep sedation to general anesthesia. With general anesthesia the patient is completely unresponsive and airway support of some type is often required, even when the patient is breathing spontaneously. Cardiovascular changes are common. After the extra Propofol bolus was given, Janet continued to breathe well — as long as she was being stimulated by the pain of the injection. After that stimulus stopped, she slipped into an even deeper plane of sedation. The same scenario can happen postoperatively upon arrival in the recovery room when stimulation ceases (see prior discussion).

Perhaps Janet was just more sensitive to sedatives than some patients. Perhaps it was because she was sleep deprived from her insomnia the night before. Maybe it was the speed with which she got repeated doses of medications in such a short time that added up to too much sedation.

In our case, the anesthesiologist was watching carefully and noticed immediately that he needed to assist Janet’s breathing. Janet’s level of sedation could have eventually become light enough, or her CO2 levels high enough, to allow her to start breathing again on her own. The question is whether she would start breathing again quickly enough — before she became hypoxic or extremely hypercarbic. Prolonged hypoxia and hypercarbia can cause complications, including potential cardiac arrest. And hypoxia and hypercarbia both depress mental status, which, if severe enough can further depress respiration, making complications more likely.

Sedation Is A Continuum

All four stages of sedation are a continuum. At any point with just a little more sedation or a little less stimulation, your patient can stop breathing well. In my job as an anesthesiologist, I see on a daily basis how easy it is to overshoot and cause a patient to become apneic using moderate to deep sedation. And if the patient is frail or sick, or extremely old or young, sometimes even a small dose of sedative or opioid, — one that would normally induce just light sedation — can cause apnea and hypoxia. Sedation, and its effect on respiration, are not just dose related, they depend on the status of the patient receiving that dose and what else is happening to that patient at that time. Be vigilant.

Related Articles

May The Force Be With You

Christine Whitten MD, author

Anyone Can Intubate: A Step By Step Guide
and
Pediatric Airway Management: A Step By Step Guide

Button to see inside or buy the book Pediatric Airway Management: A Step-by-Step Guide by Christine WhittenButton link to see inside or buy the book Anyone Can Intubate, A Step By Step Guide to Intubation and Airway Management, 5th edition on amazon

Click the cover to preview or purchase book at Amazon.com

References

  1. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC459897/pdf/thorax00225-0033.pdf
  2. Gimeno F, Peset R. Changes in oxygen saturation and heart frequency during sleep in young normal subjects. Thorax 1984;39(9):673-675.
  3. Block AJ, Boysen PG, Wynne JW, Hunt LA. Sleep apnea, hypopnea and oxygen desaturation in normal subjects. A strong male predominance. N Engl J Med. 1979 Mar 8;300(10):513–517. [PubMed]
  4. Douglas NJ, Calverley PM, Leggett RJ, Brash HM, Flenley DC, Brezinova V. Transient hypoxaemia during sleep in chronic bronchitis and emphysema. Lancet. 1979 Jan 6;1(8106):1–4. [PubMed]

The MAC Blade, The Vallecula, and the Hyoepiglottic Ligament

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Correct placement of the tip of the MacIntosh , or MAC, blade is critical to successful intubation. When learning to intubate, novice intubators often prefer the MAC blade because:

  • curved shape makes it easier to insert under the upper teeth,
  • wide area makes it easier to balance the head on the blade during the lift,
  • easier to control the tongue with the side flange.

However, if you don’t have the tip of the blade positioned properly in the vallecula, you wil not lift the epiglottis and you will have a poorly view of the larynx. Why is this?

How The MacIntosh (MAC) Blade Works

A quick review of the anatomy is warranted. The vallecula is the mucosa covered dip between the back of the tongue and the epiglottis. The hyoepiglottic ligament runs under the vallecular mucosa and connects the hyoid bone to the back of the epiglottis.

Illustration showing the hyoepiglottic ligament running in the vallecula to connect the hyoid bone with the epiglottis

The hyoepiglttic ligament connects the hyoid bone to the back of the epiglottis

Lateral Xray clearly showing the hyoid bone, the epiglottis and the vallecula connecting them

Lateral Xray clearly showing the hyoid bone, the epiglottis and the vallecula connecting them

The curved MAC blade is designed to match the curve of the tongue and to put point pressure on the hyoepiglottic ligament. With pressure in the vallecula on this ligament, the epiglottis is pulled upward. The curved blade can then pull the tongue and soft tissue under the tongue forward, bringing the glottis into view.

The tip of the curved blade presses on the vallecula, allowing you to lift the epiglottis by pulling on the folds at its base. The glottis is revealed with the epiglottis hanging above it.

The tip of the curved blade presses on the vallecula, allowing you to lift the epiglottis by pulling on the folds at its base. The glottis is revealed with the epiglottis hanging above it.

In this video, posted on YouTube by AIMEairway.ca, you can see that if you lift too early, when the blade is not placed far enough into the vallecula to engage the ligament, then pressure from the blade tip does not lift the epiglottis. Advancing a little farther, placing the tip in the vallecula does lift the epiglottis.

If you advance the blade tip too far into the vallecula, it will press on the base of the vallecula and force the epiglottis down, obscuring your view of the glottis. The difference between lifting too early or too late (by placing the blade tip too shallow and too deep respectively) can be just a mm or two.

Size of the MAC Blade matters

MAC blades come in different sizes to match your patient. However, you must choose the correct size to apply th­­­e correct point pressure on the hyoepiglottic ligament. The correct size blade must be long enough to reach into the vallecula. You can estimate the correct size by holding the blade adjacent to the patient’s lower jaw and measuring it against the projected location of the vallecula.

Illustration showing how to estimate the size of a laryngoscope blade for intubating an infant or young child

Laryngoscope blades come in different sizes and you should choose the optimal size if you can.

Blade Too Short

If the blade is so short that it doesn’t reach the vallecula, then lifting the blade will not lift the epiglottis (see video above). Indeed may fold it downward over the glottis.

Blade Too Long

On the other hand, you can use a longer MAC blade. The key to success with a longer blade is to avoid inserting the blade too deep, and covering the larynx. You must restrain yourself and insert only to a depth sufficient to place the blade tip in the vallecula. You will know if you have placed the blade too deep because the larynx will be hidden under the blade.

Photo of view during laryngoscopy, on the left the esophagus is seen "tented" to appear like the larynx, on the right the larynx.

If you insert your blade too deep you will hide the larynx underneath, as on the left. This action also tents the esophagus and can made it mimic the glottic opening if you are not careful.

When using a longer blade in a small patient, you will find that you will have a fair amount of blade outside the mouth. In this case you must be especially careful to avoid lips and teeth.

Altering the Angle Of The MAC Blade To Optimize View

As you can imagine from the above anatomical relationships, a very small change in angle at the handle will markedly alter the angle, location and point pressure of the tip. Any angulation of the blade must be done carefully to avoid damaging the teeth.

Insertion: Always Protect Those Lips and Teeth

Insertion of the blade should always be delicate and deliberate With the mouth open as wide as you can, insert the blade slightly to the right of the tongue. Don’t hit the teeth as you insert. If necessary, you can tilt the top of the handle slightly to insert the blade into the mouth, then rotate the blade back, scooping it around the right side of the tongue as you do so.

Avoid catching the lips between the blade and the teeth. I use my right index finger to sweep the lips out of the way of the blade as I insert it. You may need to angle a curved blade slightly to pass the teeth and then return the blade to a more neutral position once it has entered the mouth.

How To Know You’re In The Vallecula

With experience, you will develop good instincts on how deep to insert the blade. Always look for the tip of the epiglottis as you insert the blade. Once you see it, continue to advance the blade — usually close to its maximum depth if it’s the correct size. Simultaneously sweep the tongue to the left as you advance. Once you see the full epiglottis you can now start to transfer the weight of the patient’s head onto the blade as you lift. Again, watch for the lips. Leave your blade toward the left side of the mouth with the tongue pushed out of the way. Continue to advance until

As you lift, the pressure from the tip should lift the epiglottis. If it doesn’t, carefully slide the tip a little deeper into the vallecula to engage the ligament and try again.

The list of posts below leads to other articles on intubation technique.

May The Force Be With You

Christine E Whitten MD

Author of Anyone Can Intubate— a Step By Step Guide
and
Pediatric Airway Management— a Step By Step Guide

LINKS TO PRIOR DISCUSSIONS WITH MORE DETAILS OF HOW TO INTUBATE:

 

Button link to see inside or buy the book Anyone Can Intubate, A Step By Step Guide to Intubation and Airway Management, 5th edition on amazon Button to see inside or buy the book Pediatric Airway Management: A Step-by-Step Guide by Christine Whitten

Please click my book covers to preview on amazon.com

Learning Intubation: Head Position Effects Laryngeal View

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When first learning intubation,  a beginner often concentrates on memorizing the key laryngeal anatomy. This is important of course. If you can’t recognize the vocal cords, you will not be able to successfully intubate. However, even more important to learning intubation is understanding how the larynx relates to the other structures in the head and neck. In order to intubate you must manipulate those other structures to bring the larynx into view.

A prior post, When Learning Intubation Is Hard, described in detail some of the most common barriers to learning to intubate. Here I will concentrate on helping you see how head position effects your ability to see the larynx.

Larynx Location In The Neck

To feel your own larynx, place your hand on the front of your neck, with thumb and forefinger on either side of the firm, roughly cylindrical shape in the midline.

Illustration showing Relationships thyroid and cricoid cartilage to cricothyroid membrane

Relationships thyroid and cricoid cartilage to cricothyroid membrane

The adult larynx lies opposite the 5th, 6th cervical vertebrae, as opposed to the infant larynx that lies opposite the 2nd, 3rd and 4th. The fact that the infant larynx is higher in the neck leads to greater risk of airway obstruction and a need to slightly alter technique during pediatric intubation. A link to how to intubate the pediatric patient is located at the end of this article. Here we will concentrate on the adult.

The larynx is located in front of the esophagus in the neck. The opening to the larynx, called the glottis, and the opening to the esophagus are immediately adjacent to each other. Misidentification of the esophagus as the glottic can lead to esophageal intubation.

Illustration showing how easy it is to insert a laryngoscope blade too deeply and hide the larynx during intubation of an infant or small child

It’s very easy  to insert the laryngoscope blade too deep, as in the right picture. If too deep you will not see recognizable anatomy because you are looking down the esophagus and hiding the larynx.

 

Photo of view during laryngoscopy, on the left the esophagus is seen "tented" to appear like the larynx, on the right the larynx.

If you insert your blade too deep you will hide the larynx underneath. This action also tents the esophagus and can made it mimic the glottic opening if you are not careful.

How The Larynx Relates To Other Structures

Look at this lateral Xray  of a head in neutral position. The outline of the epiglottis, the hyoid bone, the thyroid cartilage and the cricoid cartilage are easily identified. Notice the relationship of the larynx to the esophagus. The larynx lies in front of the esophagus but the opening to the larynx (the glottis) and the esophagus are right next to each other. Accidental esophageal intubation is a risk with every intubation.

Lateral view Xray showing the distinct outlines of the parts of the larynx and their relationship to the jaw, tongue and cervical spine.

Lateral view Xray showing the distinct outlines of the parts of the larynx and their relationship to the jaw, tongue and cervical spine.

Now imagine yourself intubating this patient. what would you have to do to bring the larynx into view? How deep would you have to insert a Macintosh blade to  place the tip in the vallecula? How deep would you need to insert a Miller blade to lift the epiglottis?

Here is a CT scan of another adult patient. Notice that in this second patient the larynx is located higher in the neck.

Normal CT side view showing relationship of laryngeal structures to external anatomy

Normal CT side view showing relationship of laryngeal structures to external anatomy

Whereas the epiglottis in the first patient is low behind the tongue, this patient’s epiglottis is higher. The depth of insertion and the strategy to lift the epiglottis will change from patient to patient. Straight blades often work better in patients with a larynx higher in he neck and this may be one of those patients.

How Does Neck Position Affect The Larynx During Intubation

Let’s look at a lateral Xray of our first patient, but now with his head tilted all the way back in full extension. Patients with respiratory distress, will often tilt their heads back. You can see that this position more fully opens the airway and decreases resistance to breathing.

lateral Xray of the neck in full extension showing how the relationship of the larynx changes with respect to the rest of the neck structures. Extension without placing the patient in the sniffing position will hide the larynx behind the tongue, or a so-called anterior larynx.

Lateral Xray of the neck in full extension showing how the relationship of the larynx changes with respect to the rest of the neck structures. Extension without placing the patient in the sniffing position will hide the larynx behind the tongue, or a so-called anterior larynx.

During intubation, we need to tilt the head back to bring the axis of the oral and pharyngeal axes into alignment. But if the patient is not in a good sniffing position,  with the head moved slightly forward  in addition to being tilted, the larynx may remain hidden behind the tongue during laryngoscopy.

Let me rotate this image to show you what I mean.

Lateral neck Xray showing how extreme head extension, without the sniffing position, can make visualization of the larynx difficult.

Lateral neck Xray showing how extreme head extension, without the sniffing position, can make visualization of the larynx difficult.

You can now see how anterior that larynx would look during laryngoscopy. Pushing down on the cricoid cartilage might help rescue a difficult intubation in a situation like this, but optimal head and neck positioning from the beginning would work better.

When getting ready to intubate, always glance at the side of your patient and assess whether the head and neck are in an optimal position before you start. If it’s not optimal, try to fix it. That several seconds can save you, and your patient, potential trauma.

Head Position Also Affects Laryngeal Opening

As long as we are looking at X-rays, let’s look at our first patient with his head flexed fully forward. When the head is flexed forward, the structures in the posterior pharynx and the tongue tend to obstruct the airway. You can test this by flexing your head forward as far onto your chest as you can. It becomes much harder to take a breath.

lateral Xray showing that With the head flexed fully forward onto the chest, the airway is almost fully obstructed. Visualization of the larynx wold be impossible.

With the head flexed fully forward onto the chest, the airway is almost fully obstructed. Visualization of the larynx would be impossible.

While no one would position a patient’s head this way for intubation, it’s common for novices to place too many pillows under the head trying to obtain a good sniffing position. If the head is too high, the patient, and the intubator, will not be able to tilt the head back.  In other words, our novice intubator, trying to maximize sniffing position, sabotages himself. Again, prior to intubation take a look to the side of your patient. Try to tilt the head back (or have the patient tilt their head back).

When learning to intubate, learn the anatomical relationships, not just laryngeal anatomy.  A good intubator understands that knowledge of how those structures move in relationship to each other gives you the power to manipulate that anatomy to give you the best possible view during intubation.

Please share with your fellow students. I’ve included a list with links below to previous posts on learning intubation to help you perfect your skills. Feel free to ask questions. Let me know if there are any topics that you would find helpful.

May The Force Be with You

Christine Whitten MD, author
Anyone Can Intubate, A Step By Step Guide
and
Pediatric Airway Management, A Step By Step guide

LINKS TO PRIOR DISCUSSIONS WITH MORE DETAILS OF HOW TO INTUBATE:

 

Button to see inside or buy the book Pediatric Airway Management: A Step-by-Step Guide by Christine Whitten  Button link to see inside or buy the book Anyone Can Intubate, A Step By Step Guide to Intubation and Airway Management, 5th edition on amazon

Please click on the covers to preview my books at amazon.com

Announcing My Latest Article Has Been Published: “10 Rules for Approaching Difficult Intubation”

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I’m excited. My latest article, titled, “10 Rules for Approaching Difficult Intubation,
Always Prepare for Failure” has just been released in the journal supplement Airway Management, published by Anesthesiology News.

Managing the difficult airway is one of the most challenging, risk ridden, and downright scary clinical problems in anesthesia. The article makes the point that although we all know that a “can’t intubate, can’t ventilate” scenario can happen to anyone at anytime, many of us practice as though it will never happen to us. We must always prepare for failure. In the article, I’ve provided practical information from my 38 years of experience on how to recognize, manage, and protect our patients with challenging airways.

While there is a lot of information for the novice, there are also clinical pearls for the experienced intubator. I’m hoping you will find this information helpful to you, and to your trainees.

You can find the article on-line here, where you can also download a pdf version to share:

https://www.anesthesiologynews.com/Review-Articles/Article/08-18/10-Rules-for-Approaching-Difficult-Intubation/52456

In addition to my article, please read the others as well. This issue is full of helpful, well written submissions. I have always found Anesthesiology News to provide interesting and timely updates and well written reviews, and this issue is no exception.

May The Force Be With You

Christine E. Whitten MD. author
Anyone Can Intubate, A Step By Step Guide
and
Pediatric Airway Management, A Step By Step guide

Button to see inside or buy the book Pediatric Airway Management: A Step-by-Step Guide by Christine Whitten     Button link to see inside or buy the book Anyone Can Intubate, A Step By Step Guide to Intubation and Airway Management, 5th edition on amazon

Please preview my books at amazon.com by clicking on the covers.

 

Bilateral Tension Pneumothorax: Harder To Diagnose

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Tension pneumothorax is a life-threatening emergency. We all know the signs of tension pneumothorax:

  • unilateral breath sounds (breath sounds absent on affected side),
  • thorax may be hyperresonant,
  • jugular venous distention,
  • tracheal deviation to the opposite side,
  • maximum heart sounds shifted to the opposite side, and often
  • tachycardia
  • hypotension

However diagnosis is more difficult if the patient is suffering from bilateral tension pneumothoraces. We think about bilateral tension pneumothorax occurring with trauma cases. Yet the three cases I’ve seen in my career were complications of intubation and emergency airway management. Continue reading →

PostObstructive Pulmonary Edema

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Patients with postobstructive pulmonary edema (or P.O.P.E.) develop sudden, unexpected and potentially life-threatening pulmonary edema after relief of airway obstruction.  It can be mild or severe. My first experience with it was in 1983.

The Case

In 1983, we didn’t have pulse oximetry, end-tidal carbon dioxide monitoring or even automated blood pressure cuffs. The patient was a healthy 6’3” tall and 250 lbs , 20 year old man. All muscle and clearly in great shape. He had just had knee surgery under general anesthesia and was on the verge of waking up.

He was coughing vigorously on the endotracheal tube. Four people held him down. My resident, fearful he night hurt himself or the team, extubated him while he was still coughing and before he was following commands. Unfortunately the patient was still in stage 2, when the airway reflexes are hyperdynamic.

Within seconds the patient went into laryngospasm, intense spasmodic closure of the vocal cords and other laryngeal muscles. There followed several minutes of struggling to re-establish an open airway. Finally the spasm broke with the use of positive pressure and the patient awoke.

However the mood in the room quickly turned from relief to concern. Our patient started to panic, claiming that he couldn’t breathe. His color was poor. He was wheezing badly, with pink frothy sputum bubbling out of his mouth. He was awake enough to communicate with us but so panicked that he started to fight the team of caregivers. Continue reading →

Anatomic Dead Space Affects Hypoventilation

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Understanding anatomic dead space is important to recognizing subtle hypoventilation. Hypoventilation from sedation, pain medications, anesthesia in the immediate postoperative period is common. The most obvious sign is slowing of the rate of breathing. A more subtle sign is that tidal volume becomes shallower. Having a tidal volume close to, or smaller than the patient’s dead space can lead to significant hypercarbia, hypoxia, and respiratory failure. This article discusses the concept of dead space and it’s clinical use in recognizing hypoventilation and preventing hypoxia and hypercarbia. Continue reading →

GlideScope Technique For Intubation In Small Mouths

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The GlideScope Video Laryngoscope (GVL) is an extremely useful tool for managing challenging intubations, but it can be more difficult to use if your patient has a small mouth and a high arched, narrow palate. The problem: once the GlideScope is in place in a small mouth, maneuvering the endotracheal tube around it and into the posterior pharynx can be challenging. If you can pass the endotracheal tube (ETT) at all, the cuff tends to scrape against the teeth, risking rupture. However, there is a modified GlideScope technique you can use in those situations. Continue reading →

Difficult Intubation In A Newborn

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Difficult neonatal intubation can occur unexpectedly. We’re ready to perform neonatal resuscitation in the delivery room. We may be less ready to have to deal with a difficult neonatal airway at the same time. Recently I, and my colleagues, had to manage an unanticipated difficult neonatal intubation in labor and delivery.

The Case

The baby was born extremely edematous, and in respiratory distress. Although it was easy to ventilate the baby using the NeoPuff, airway swelling prevented the neonatologist  from identifying the epiglottis and vocal cords. The anatomy was too distorted. Following protocol when faced with a difficult intubation, the neonatologist called a “Code White”, an overhead page that in my hospital summons help from anesthesia, nursing, respiratory care and pharmacy to assist with either a emergency pediatric cardiac arrest or emergency intubation.

As a responding anesthesiologist, I too was unable to see landmarks during laryngoscopy. Continue reading →

NITROUS OXIDE: SHOULD WE USE IT?

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When I was training, we used nitrous oxide on just about every anesthetic. It was easy to use. It was inexpensive. It didn’t tend to effect hemodynamics so it was useful in less stable patients when combined with an opioid. It helped speed induction through the second gas effect. It was not metabolized so renal and liver insufficiency were of less concern.

However, with all of the more recent investigation into reasons for cognitive dysfunction or decline in infants and the elderly following anesthesia, a lot more is now known about the pharmacologic disadvantages of nitrous oxide (1, 2, 3). Continue reading →

Intubation During Cardiac Resuscitation

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Intubation during cardiac resuscitation is often challenging because of the circumstances surrounding the intubation. Excitement and apprehension accompany this life saving effort. If you don’t intubate often, you’re likely to be nervous. Even experienced intubators get excited in emergency situations, but we control our excitement and let the adrenaline work for us, rather than against us.

Step one, therefore, is to remain in control of your own sense of alarm. The leaders, which includes the person in control of the airway, must stay calm. If you appear panicked, the rest of your team will follow your lead.

Step two is to quickly assess the situation. Is the patient being ventilated? Ventilation takes priority over intubation. Is there suction available? Without suction you many not be able to see the glottis, and you won’t be able to manage emesis. What help do you have? The intubator almost always needs some assistance in having someone hand equipment, or assist with cricoid pressure, among other tasks. As I tell my students, intubation is a team sport.

Finally you need to assess what position the patient is in, and how can you optimize that position. The patient is often in a less than optimal position while chest compressions are in progress. You usually find the patient in one of two awkward positions: on the ground or in a bed. This article discusses techniques to better manage intubation during cardiac resuscitation, especially with the patient in an awkward position. Illustrations are copyright from Anyone Can Intubate, 5th Edition.  Continue reading →

When Learning Intubation Is Hard

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Learning to intubate is easier for some people than for others. Sometimes, no matter how knowledgeable you are about the theory of the intubation technique, the novice can still struggle to bring it all together to pass the endotracheal tube. The anatomy can be confusing. Understanding how to place the laryngoscope blade and manipulate that anatomy can be challenging. And all the while you must be ever vigilant to protect those precious front teeth, avoid hypertension and tachycardia, and breathe for the patient at regular intervals.

I believe there are 4 chief barriers that inhibit learning how to intubate:

  1. Failure to visualize how the outside anatomy links with the inside anatomy makes it hard to predict how deeply to insert the blade.
  2. A mistaken belief that placing the laryngoscope blade itself is all that is needed to align the axes of the airway and reveal the larynx.
  3. Failure to grasp the dynamic nature of the larynx, and the need to actively manipulate it during intubation.
  4. A lack of understanding that intubation is not a sequence of isolated steps, but is instead a complex dance of interacting steps, each setting the stage for the next.

This discussion is going to assume some knowledge of the basic intubation technique. If you’d like to review those basics you can find links for multiple prior in depth discussions at the end of this article. (Illustrations and animation from Anyone Can Intubate, 5th edition, C Whitten MD.) Continue reading →

Communication In A Crisis: A Case of Respiratory Depression In A Child:

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When I’m teaching communication in a crisis to my Perioperative/OR nurses, I often recount the story of what happened during one particular child’s recovery years ago. This case, involving a 2 year old child who developed respiratory depression in the recovery room, demonstrates how good communication in a crisis, including the ability to challenge an authority figure, can improve patient safety and allow collaborative teamwork in a crisis management situation. Continue reading →

Airway Emergency: Start With The Basics of Airway Management

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We have just finished another round of Critical Event Training for my hospital’s Anesthesia and OR staff. One of the scenarios we ran was how to manage a failed airway emergency: the dreaded “can’t intubate-can’t ventilate” airway emergency scenario.

As an instructor, it’s important for me to set the stage realistically. The more real the scenario, the more the providers will learn and be able to apply the information should they ever find themselves in a comparable situation. I must observe as the trainees respond to the emergency, and then help the trainees self-analyze what went well — or not so well — during the scenario. Of course, discussion of how things went during a training scenario always leads to sharing of examples from past real life scenarios. And after 37 years of practice I’ve had a lot of sharable experiences.

One past case we discussed is particularly appropriate for those students around the country who are just beginning to learn airway management because the solution rested in basic airway management techniques. This case, involving an intubation in an ICU patient that turned into a “can’t intubate/can’t ventilate” emergency demonstrates how returning to the basics of airway management can sometimes be the way to save your patient from harm. All illustrations from Anyone Can Intubate 5th Edition. Continue reading →

Close Call In Honduras With A Nosebleed

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I recently visited Honduras with a Head and Neck surgical team where we had a close call with a potential airway obstruction due to a blood clot. The case illustrates how a provider should never make assumptions, because if those assumptions are wrong, you can endanger your patient.

After a long day in the OR, while we were packing up to leave, a nurse from the ward ran in and said that one of the patient’s who had had a septoplasty that day for chronic sinusitis was bleeding. I immediately started setting up the OR again while our surgeon went over to the ward. Continue reading →