Airway obstruction, one of the most serious and potentially life-threatening problems a patient can have, can occur in any patient given the right combination of mental and physical conditions. Respiratory insufficiency and failure from both upper or lower airway obstruction share many of the same symptoms and signs. Being able to recognize the signs of airway obstruction may save your patient’s life.
Facing Increased Oxygen Demand
Normal quiet breathing is effortless. The rate is neither too fast nor too slow, although it varies greatly depending on age and metabolic rate. The chest rises and falls easily and symmetrically. With increased physical activity, a person’s metabolic rate increases. He or she meets this need for more oxygen by increasing tidal volume, respiratory rate and cardiac output.
The ability to breathe effectively depends on muscle coordination. The opening between the vocal cords, called the glottis, widens when we inhale due to dynamic contraction of the muscles — reducing resistance to breathing. These muscles can contract more forcefully if needed. The harder you try to breathe, the wider the larynx opens, up to a limit. The result is both faster inflow and outflow of air as effort demands. During exhalation, the glottis naturally narrows as the muscles relax.
When oxygen demand increases, intercostal muscles and diaphragm contract more fully. If the airway is open, this produces greater chest cavity expansion and a more negative intrathoracic pressure that more fully fills the lungs. Respiratory rate rises. Heart rate and cardiac contractility increase, delivering more oxygen carrying blood cells.
Signs of Airway Obstruction
As obstruction develops, the patient must work harder and harder to exchange air. Dyspnea, exercise intolerance, and noisy respiration develop. However, the patient with mental status compromise cannot always tell you that they are dyspneic or having difficulty breathing, making it vital that you recognize the clinical signs of developing obstruction.
Think about the type of airway obstruction most of us see often: snoring. First, the accessory muscles of respiration — the sternocleidomastoid and scalene neck muscles — become tense and rope-like as they lift the clavicles, allowing fuller expansion of the chest and drawing in more air.
The diaphragm descends maximally, pushing the abdominal contents downward and outward, further decreasing intrathoracic pressure. The harder the patient tries to breathe against airway obstruction (either upper or lower) the more negative pressure is generated inside the chest. Think of what happens when you cover the end of a vacuum cleaner hose with your hand. You can feel the skin being sucked inward because airflow is blocked. This pressure differential sucks the soft tissue between ribs and at the sternal notch inward. These are respectively called rib retractions and a tracheal tug.
As respiratory failure progresses, the pattern of respiration becomes more inefficient and ineffective. With mild to moderate obstruction you will see these common patterns of retractions:
- abdomen below the breast bone (substernal)
- abdomen below the rib cage (subcostal)
- soft tissue between ribs (intercostal muscles or rib retractions)
With severe obstruction you will see all of the above plus retractions of the:
- neck soft tissue above the collar bone (supraclavicular)
- soft tissue at the sternal notch (tracheal tug)
- sternum toward the spinal column (sternal)
Obstruction can produce a rocking chest motion, called paradoxical breathing. With inhalation, the diaphragm descends maximally, pushing the abdominal contents down and out and generating increased negative pressure. This negative pressure pulls the chest wall inward, resulting in the abdomen rising and the chest falling during inhalation — the opposite of normal breathing. During exhalation the chest rises and the abdomen falls. The more compliant or flexible the chest wall, as in young children, the easier this is to see.
With continued obstruction the jaw and tongue are pulled backward. The head starts to bob and the nostrils flare. The lower jaw is pulled backwards with each breath as the tongue is pulled down over the airway. The head may bob. Breathing often becomes noisy. There may be stridor, snoring or grunting. However, be forewarned: with complete obstruction noisy breathing stops. Silent breathing in the presence of significant airway obstruction is not necessarily a good thing.
Assessing Your Patient
Whenever you assess your patients you should always look carefully for signs of obstruction or respiratory compromise.
- Is the respiratory rate normal, increased, or decreased?
- Does tidal volume seem adequate? Chest wall motion can be subtle, especially under clothing. You may need to expose the chest to assess movement.
- How much air is moving in and out of the mouth? When in doubt, place your hand over the nose or mouth. If you don’t feel air movement then tidal volume is inadequate. When wearing gloves, use the back of your hand or wrist to improve your ability to feel airflow.
- If the patient is wearing an oxygen mask, watch for condensation inside the mask.
- Listen to the chest. Are breath sounds faint or absent breath?
- Is there stridor, snoring, grunting, wheezing?
- Look for other signs of airway obstruction showing respiratory dysfunction such as use of accessory muscles, tracheal tug, rib retraction, rocking chest motion, nasal flaring, and head bobbing
- What is the patient’s mental status? Remember that confusion and agitation can be early signs of hypoxia and hypercarbia. Don’t be fooled into sedating an hypoxic patient.
- Skin color? Cyanosis is not always blue. Look for pale or dusky skin. Cyanosis is often a late sign and may not be visible in severe anemia.
- Pulse and blood pressure?
- Oxygen saturation?
I listed oxygen saturation last because as invaluable as it is, your ability to observe and assess the patient is even more important. Almost all of us can sense when a patient is not doing well. If you wait until your oxygen saturation monitor alarms, you have missed an opportunity to intervene before your patient gets into trouble. Trust your instincts and look more closely when that suspicion is triggered. And keep checking —a patient about to deteriorate can change quickly.
Severe respiratory compromise, such as pneumonia or pulmonary edema, often shares many of the same signs as airway obstruction. This is because the patient automatically seeks to improve oxygenation by using the same mechanical improvements to airflow.
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 — all of which increase sedation and further depress respiratory drive. Allowed to progress to the extreme end point, the patient with respiratory depression can become apneic with little warning.
When hypoxia first develops, adult patient’s frequently get hypertensive and tachycardic. As severe hypoxia progresses, you’ll often see slowed respirations. Beware the patient in severe respiratory distress and tachypnea who suddenly converts to quiet, slow, breathing without improvement in overall condition. Hypotension, cyanosis, and impaired consciousness frequently follow. Bradycardia can develop. These signs often indicate that cardiac arrest is imminent. You must act immediately.
Evaluating the degree of airway obstruction or respiratory compromise is a judgment call and requires constant vigilance. Remember, 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.
By identifying problems early you may be able to keep your patients respiratory status from deteriorating before airway intervention is needed. Constant reassessment is important so that you may intervene early if necessary — before the airway is lost.
May the force be with you