This article discussion some of the key anatomy, physiology, and technical points to intubating an infant or small child safely. I’ve been hard at work on writing and illustrating my upcoming book on pediatric airway management so I thought I would spend some time talking about care of our littlest patients.
Providers who infrequently care for children less than two years of age are often rightfully anxious when faced with a sick child, especially if airway management is required. This is especially true if the child is less than one. Healthy respect is certainly indicated because airway complications are one of the leading causes of pediatric cardiac arrest.
Children are not small adults. From infants to toddlers to teenagers, the anatomy and physiology of the child is continuously morphing until finally reaching the adult form and function. We all know this instinctively. When we look at a child we can often tell how old he or she is simply by looking at head size, characteristics of the face, length of neck, shape of the body, and how long the arms and legs are related to the trunk. It should not be surprising that the inside of the child is changing as well.
Infants and young children are small. The head of a newborn infant can fit on the palm of my hand. The palm of a premature infant’s hand may be the same size as my thumbnail. It’s challenging to open the airway of such a small infant when adult fingers dwarf the size of the baby’s mouth and all of the instruments are smaller. And babies are fragile, with little reserve.
Like adults, children can be small or tall, lean or overweight. But unlike adults, their airway anatomy is changing shape and structural relationships as they grow. A particular 2 year old may be as tall as a particular 6 year old, or as heavy as a particular 8 year old, but all have very different airways.
Intubating an infant or small child is more of a challenge than an older child or adult both because of their anatomical differences as well as their physiologic predisposition for hypoxia. One can certainly argue that faced with elective care, that only experienced providers should manage the airways of infants and children less than two. However, medical care is not always elective.
Faced with a sick child, especially in more urgent settings, anyone who can ventilate and intubate an adult can also ventilate or intubate an infant or toddler safely —if they take the differences in anatomy and physiology into account, and are gentle and methodical in their approach. Illustrations and photos from Anyone Can Intubate: a Step by Step Guide, and Pediatric Airway Management: a Step by Step Guide.
Don’t Let Fear Stop You From Acting
It’s very common to be intimidated when treating an infant because infants are very small compared to the size of your adult hands. Premature infants are especially challenging. Infants are fragile and have little physiological reserve. However, if you prepare what you need ahead of time and use your natural anxiety to make you alert, methodical and gentle, then you will not hurt the baby.
Remember, the most important thing is oxygenation and ventilation. Even if you don’t feel you can intubate, don’t fail to open the airway or assist ventilation until someone who can arrives.
Let’s quickly review why infants and toddlers are more at risk of hypoxia.
Why Do Babies Get Hypoxic So Easily?
Infants are at much higher risk of developing hypoxia for a many reasons. Some of the major ones include:
- Metabolic Rate
- approximately double the adult metabolic rate: hypoxia develops more quickly
- Lung volumes, especially, functional residual capacity (FRC) are smaller. Smaller oxygen tank means less tolerance for apnea
- Fewer alveoli means less gas exchange surface
- Minute ventilation is dependent on more rapid rate due to limited ability to increase tidal volume
- Deadspace is higher in the infant (3 ml/kg vs adult’s 2 mg/kg)
- Chest wall/Diaphragm
- ribs more horizontal, with less ability to expand chest
- chest wall more complaint and easily collapses inward with either upper or lower airway obstruction or increased resistance to breathing
- muscles of respiration tire easily
- Nervous system
- hypoxia causes bradycardia as first response, not tachycardia
- brain is easily sedated
- Cardiac output is primarily rate dependent
- bradycardia produces hypotension and worsens hypoxia
- hypovolemia easily produces shock, decreased perfusion, and hypoxia
- Cardiac output is primarily rate dependent
It is easy to lose track of time during an intubation when the baby is apneic. Paying close attention to how well a baby is ventilated and oxygenating is imperative. Stop and ventilate if the intubation attempt is taking longer than 30 seconds to a minute. You want to stop a prolonged intubation attempt and start ventilating before the baby starts to desaturate if you can.
How Is Infant Anatomy Different?
The table and illustration summarize the major anatomical differences in the infant and toddler airway compared to the older child and adult. The younger the child, the more different the airway.
In addition, the appearance of the larynx itself is quite different. Over an above the anatomical variation, the color of the vocal cords in an infant is usually pink, rather than white, making identification more challenging.
Straight Blades Are Recommended
Curved blades depend on displacing the tongue and soft tissue forward to lift the epiglottis. If you can’t displace the tongue forward, you won’t be able to see the larynx.
Straight blades are very helpful in situations where there is little room to displace the tongue and attached tissues forward. Examples include:
- larynxes higher in the neck (babies are a good example)
- short chins
- short necks
- large tongues
- obesity, especially with double chins
- larynxes fixed from scar, trauma, or mass effect.
We often use straight blades in young children for multiple reasons. The pediatric larynx is located higher in the neck than an adult, and their tongues are larger relative to the size of their mouths. Babies in particular have short necks. The smaller separation between the hyoid and the thyroid cartilage also makes displacing the tongue and associated tissues forward more difficult. A straight blade lifts the epiglottis, allowing a clear view of the cords.
Choose the optimal size blade for the size the child. You can estimate size by holding the blade up against the outside of the child’s jaw and see if it is long enough to reach the larynx. As you see in the illustration, an adult blade would be way too long. However, in an emergency if you only had an adult blade, you could insert just the very tip.
In a baby or toddler, the curved MAC will often fold the child’s epiglottis down over the larynx, blocking your view of the cords.
This happens for two reasons related to the fact that the larynx is higher in the neck:
- the tissue folds in the vallecula pull the trap door of the epiglottis closed when pressed
- there is less room to displace the tongue and soft tissue under the tongue forward
If you must use a curved blade you can, if needed, use it to pick up the epiglottis.
However, to be able to see the larynx with a straight blade you have to be able to extend the head backward. If your patient can’t tilt his head back, a straight blade will be more difficult and a curved blade might be better. For a baby, this often means raising the shoulders to get the head and larynx into a good position.
Raising The Baby’s Shoulders Can Help
When positioning the head, avoid raising it too high off the intubating surface. For easier visualization, the ear canal should be roughly level with the sternal notch, regardless of age. The baby’s occiput is larger and rounder than an adult’s. Placing a small folded towel or similar thickness object under an infant’s shoulders raises the rest of the body and straightens the airway path. Toddlers have a built in sniff position due to the occiput and may not need a towel. For an older child placing the towel under the head works best.
The height of the occiput in an unconscious infant can also flex the baby’s head forward when the child lies flat in the bed. This can obstruct the airway.
The infant occiput tends to roll, making the act of balancing the baby’s head on your blade a challenge. There are several ways to deal with this tendency:
- place a rolled towel on either side of the head
- have an assistant steady the head for you
- hold the head steady with your own right hand while placing your blade. Once you see the larynx let g, lift your ETT, then intubate
- use a small, flat gel “donut” designed for this task
Don’t Block The Mouth With Your Hand
Sometimes tipping the infant’s head backwards with your right hand will allow the mouth to fall open. If it doesn’t, then open the mouth with your right index finger and thumb as far to the right side of the mouth as possible. The infant’s mouth is very small compared to the size of your hand. Failure to place your fingers far to the right can block your view and prevent insertion of the blade. .
Control Of The Tongue Is Key
Slowly lift the mandible upward as you advance the blade. Don’t pinch the lower lip between the gums/teeth and the blade as you lift. Avoid using the upper gum line or teeth as a fulcrum.
The infant tongue is much larger relative to the mouth and jaw than the adult. Failure to sweep the tongue to the left with your laryngoscope blade will leave you no room for visualization or for tube passage.
Continue to lift the jaw upward until you see the larynx.
The Larynx Looks Different In An Infant
Not only is the larynx smaller in an infant, it’s shaped differently, The epiglottis is shorter and more omega shaped. It’s softer and harder to pick up. The vocal cords tend to be pink rather than white and therefore may be harder to spot.
It’s Easy To Insert The Laryngoscope Blade Too Deep
It’s very easy to insert the blade too deeply and into the esophagus of such a tiny patient. If you can’t identify anatomy, then pull the blade back slowly while you watch. Often the larynx will drop into view.
Picking up the epiglottis with the blade tip in a child less than two years old can be hard due to its short, stiff, “U” shaped form. Meticulous placement of the tip of the blade is necessary.
The arytenoids and vocal cords in the infant and young child incline anteriorly. This slant can cause the tip of the pediatric tube to hang up on the anterior commissure during insertion. Rotating the tube to the right or left usually allows the tip to slip off the anterior commissure and pass. While there may be a blind spot at the moment of intubation, you can often see the arytenoids behind the tube. Be gentle. Pediatric airways are small, delicate and prone to edema.
Remember, the cricoid ring is smaller than the opening between the vocal cords. You can sometimes insert an ETT through the cords but not beyond the cricoid. Forcing a tube can cause traumatic swelling. If the tube won’t pass, use a smaller one.
Do Ask For Cricoid Pressure If You Can’t See Larynx
Head position and movement of surrounding tissues shifts cartilages and may affect your ability to see the vocal cords. Sometimes the larynx lies anterior to your field of view during laryngoscopy. This view is often described as an “anterior larynx” and it commonly occurs with poor head positioning, as well as in patients with obesity, larynxes located higher in the neck than average, and in patients with poorly developed mandibles or weak chins. Ask your assistant to provide cricoid pressure when you can’t see the larynx during intubation.
Providing cricoid in an infant or young child may mean using just one finger to press on the larynx rather than two. Use light pressure as the soft cartilage is easily distorted and the larynx compressed. Heavy cricoid pressure in an infant can distort the airway and make intubation more difficult.
Stop And Ventilate If You Have Problems
Infants and young children can’t hold their breaths as long as an adult before the onset of hypoxia. If you have trouble intubating, stop and ventilate before trying again. During awake intubations let the patient rest and breathe oxygen. Lack of ventilation hurts patients, not the lack of an endotracheal tube. The baby will get hypoxic quickly when apneic.
Remember, if mask ventilation is difficult that you can always place an LMA or other subpraglottic device to allow easier ventilation while you get extra help, prepare for a different approach, or if the intubation is elective even wake the patient up.
Minimal swelling can cause tracheal obstruction because the larynx and trachea are so small. One mm circumferential swelling in an adult with a 10 mm trachea causes only a 44% decrease in cross-sectional area. If an infant with a 4 mm trachea develops 1 mm circumferential edema from coup, or any other cause, there is a 75% decrease in area. Thus swelling from infections or trauma can have a much more devastating effect.
In addition, a little change in airway width causes a big change in resistance to breathing. A normal infant’s 4 mm diameter larynx has 16 X the resistance to flow of a normal adult larynx of 8 mm. The infant has less ability to compensate for increased resistance to airflow. So infections like croup and epiglottitis, or an asthma attack narrowing terminal bronchi, or an aspirated peanut stuck in the esophagus but compressing the soft trachea can all place serious limits on the infant or toddler’s ability to breathe.
Verify tracheal placement
Always verify ETT placement carefully. Sound over an infant’s chest and abdomen transmit easily and esophageal intubation can be missed if you are not cautious.
If you fail to recognize esophageal intubation, your first sign may be hypoxia, bradycardia and potentially cardiac arrest.
Secure The ETT At The Correct Depth
The tip of the tube should be midway between the larynx and the carina. Securing the tube at the correct depth in an infant is especially critical. Too deep and it will easily block a mainstem bronchus. Too shallow and extubation is likely when the baby moves. In addition, when using a cuffed tube, the cuff must be below the cords and below the cricoid cartilage. since the infant trachea is so short, margin for error is also limited.
Endotracheal tubes have depth markings in centimeters. You should insert an uncuffed tube until the lowest most prominent mark is level with the vocal cords. Insert cuffed tubes until the cuff just passes through the cords, and is below the cricoid ring.
The depth of insertion can be estimated as:
(age in years divided by 2) plus 12
The most familiar formula for calculating endotracheal tube depth applies to children greater than 2 years of age. Note: Depth ATL (at the lip) calculations are in centimeters.
Depth ATL (at the lip) = (age in years/2) + 12
For infants and children younger than 2 years of age, calculate endotracheal tube depth by using the formula: [Hazinski, M.F., (Ed.) (2002) Textbook of Advanced Pediatric Life Support. American Heart Association.]:
Depth ATL (at the lip) = Calculated uncuffed ETT ID x 3
Endotracheal tube depth of insertion formulas have been clinically validated for the neonatal patient population, for patients weighing more than 750 grams up to 4 kilograms [Peterson, J., et al. (2006) Accuracy of the 7-8-9 Rule for Endotracheal Tube placement in the neonate. Journal of Perinatology 26; 333-336].
Depth ATL (at the lip) = weight (Kg) + 6
The chart in Figure 7-1 has suggested sizes. Although these formulas are reasonably accurate, you still must verify bilateral breath sounds as individual variability in height, and therefore pulmonary anatomy, is common in children of the same age.
Extension of the neck causes the endotracheal tube to rise within the trachea. Inadvertent extubation can occur of the tube is too high. Flexion of the head causes it to descend, possibly causing mainstem intubation (Fig. 7-58 a,b,c). “The hose follows the nose” is a useful memory aide. This means that you must be constantly alert to potential misplacement of an endotracheal tube.
Check For A Leak
Since airway tissue is friable and edema so devastating in such a small airway, it’s important to check for a leak after intubation to make sure you have not inserted too large a tube. The chart above has some suggested sizes for age but all children are different.
Listen at the child’s mouth for a leak when using an uncuffed tube. You want to hear an air leak around the tube at about 15-20 cm of water pressure after the child’s lungs are fairly well inflated. A leak at this pressure allows adequate lung inflation but avoids excessive pressure on the tracheal wall.
The absence of such a leak means that the tube may be pressing excessively on the inside the cricoid ring, which can damage the mucosa. Excessive pressure can also potentially injure the recurrent laryngeal nerves, causing transient or permanent vocal cord paralysis.
A leak is too large if it prevents effective inflation of the lungs. Upsize the uncuffed endotracheal tube one half size if the leak occurs at less than 10 cm H2O.
Downsize by one half size if there is no leak at 20 cm H2O or if there is resistance to passing the ETT into the trachea.
Remember that because the cricoid is more elliptical than round in the small child, you may still have a small leak despite the fact that the tube may be causing mucosal pressure. If the tube was somewhat tight going in and the leak is small, consider whether changing it to a smaller size is prudent.
A problem with uncuffed tubes is that if too small a tube is inserted, then you may not be able to provide adequate tidal volumes because of too large an air leak around the tube. Too large a leak forces the need to repeat the laryngoscopy and replace the tube, actions that increase the risk of trauma and edema.
Use of cuffed tubes avoid this problem. We talked about cuffed tubes in pediatric patients earlier. When using a cuffed tube, you can seal the leak with the cuff, avoiding repeat laryngoscopies and tube changes. When sealing the leak, always inflate the cuff until the leak just stops. (follow this link)
However, occasionally you will insert a cuffed tube and then find that there isn’t a leak — even though the cuff is still deflated.
In this case you should not automatically inflate the cuff, since this might result in overinflation, which can also damage mucosa and potentially injure the recurrent laryngeal nerve as it travels through the cricoid ring.
On the other hand, when the cuff remains deflated, the folds from the deflated cuff can potentially cause mucosal injury because pressure against the mucosa is now uneven.
In this situation you should consider downsizing a cuffed ETT that does not have a leak with the cuff still deflated, to a smaller one that requires some inflation. This is especially true if the tube will be in place for a longer period of time. To make the decision to change the tube you must balance:
- the risk of edema and trauma from the repeat laryngosopy and tube exchange
- the length of time the tube will be in place (a 30 minute OR case offers a different risk profile than days in the ICU)
- how difficult it was to place the tube
Ask for Help
When intubating, don’t hesitate to ask for help. Also, if you are experienced in infant airway management, unless time is critical, you should have a more experienced provider with you before you start in case of problems. Once hypoxia develops in an infant or small child during an airway emergency, the time before cardiovascular collapse is short.
Let’s Look At Some Key Steps for Intubating An Infant
Successful Intubation Does Not Mean The Infant or Child Is Completely Safe
Complications from intubation can occur in any patient at any time but infants and small children are at higher risk because their airways are smaller, they lack cardiorespiratory reserve, and in many ways they are predisposed to respiratory distress and failure.
Potential complications that can more easily happen in an infant are:
- Mainstem intubation and accidental extubation
- trachea is short and movement of head can shift ETT up or down 1-2 cm, which can be enough to malposition the tube, especially in premature infants
- kinking of the endotracheal tube: because it’s tiny, thin and very flexible
- because too large a tidal volume or too high inflation pressure can cause barotrauma easily. A tidal volume of 7 ml/kg in a 3 kg baby is 21 ml, less than two tablespoons.
Monitor your intubated child carefully and be prepared for emergencies.
May The Force Be With You
Christine Whitten MD,
author Anyone Can Intubate: A Step By Step Guide, 5th Edition &
Pediatric Airway Management: A Step-by-Step Guide
Illustrations copyright C. Whitten MD 2016
Please click on the covers to see inside my books at amazon.com