Conditions: Loss of the Airway
What is loss of the airway?
Loss of the airway is a potentially life-threatening situation in which an open pathway for airflow to and from the lungs is blocked. This may be temporary, but if prolonged, a lack of oxygen flow into the lungs and release of carbon dioxide from the lungs and can lead complications including brain injury.
Obstructive sleep apnea is an example of repetitive episodes of lost airway for the affected individual during sleep. “Choking” (obstruction of the upper airway by a foreign body) and laryngospasm are also examples of loss of airway.
How does loss of airway occur during or after surgery?
In a surgical context, loss of the airway is a risk when a patient is under anesthesia and cannot breathe spontaneously. Maintaining a patent and effective airway is a major component of the operating room team’s focus and loss of the airway is a rare event during or after surgery.
The mechanisms by which an airway may be lost are various, but may be categorized anatomically according to the anatomic site involving the upper airway or the lower airway lower airway.
The lower airway, consisting of the trachea, and branches from it, the bronchi and smaller bronchioles may be blocked by a foreign body, swelling, or less likely, collapse of the walls. Collapse is anatomically resisted by the stiff cartilage rings supporing the trachea, bronchi, and bronchioles. As the trachea branches to a left and a right mainstem bronchus, and each of these further divide, the airway no longer has only one pathway. This means that complete obstruction of a branch of the lower airways does not block the entire airway, providing for some oxygen delivery and carbon dioxide release.
In contrast, the upper airway is without the same rigid structure, making its collapse more favorable. The tongue is a prime candidate for occluding the upper airway, but the soft palate, sidewalls of the pharynx and the structures of the larynx, including the epiglottis and arytenoid cartilages have potential to move in such a way as to block the airway.
The larynx (voice box) is the site of natural narrowing of the airway. Swelling of the larynx poses an airway risk simply because the smaller normal airway diameter provides less leeway before development of a critical narrowing. A foreign body that may not be obstructive in the throat may become obstructive if it were to occupy the laryngeal airway. The normal movement of the vocal cords inwards is a physiologic mechanism of muscle contraction and joint movement further narrowing the airway to assist with voice production, coughing, and valsalva. Reflexive closure of the vocal cords, called laryngospasm, is an innate protective mechanism to keep the lungs from aspiration, but prolonged laryngospasm may significantly threaten the airway and oxygenation.
A tumor may also gradually narrow the airway, although in a gradual timeframe over months typically. If a tumor growth were to narrow the airway sufficiently, then smaller challenges, such as a collection of mucus or a few millimeters of swelling that would ordinarily pose no threat could become life threatening. The management of an already-narrowed airway is therefore complicated by less leeway.
Who is at risk of loss of the airway
Patient factors that increase the risk of airway loss include conditions such as decreased level of consciousness/awakeness, obesity, obstructive sleep apnea, large tongue, small mandible, decreased ability to extend the neck (including a history of spinal fusion or plating), the presence of a tumor, foreign body, or swelling of the airway. Types of procedures that increase the risk for loss of airway include major head/neck and upper airway surgery, and obstetric and cervical spine procedures.
Additionally, conditions such as lung disease and anemia (low red blood cell count) may shorten the time period during which lack of respiration can be tolerated, adding to the risk.
How is loss of the airway during or after surgerY identified?
Multiple overlapping methods of monitoring the airway are utilized in the operating room and post-anesthesia care unit (PACU). These include the following:
Continuous monitoring of the oxygen saturation with automated alarms for low readings,
Automated monitoring of carbon dioxide with each expiration, with alarms for low readings,
Observation of chest rise and fall, listening for breath sounds including with use of a stethoscope, observing coloration of the skin, verifying connections of the airway circuit tubing, seeing rhythmic expansion of the billows on the anesthesia machine, observation of condensation on the endotracheal tube or laryngeal mask airway (LMA) with exhalation, and many other assessments by providers and staff may be utilized.
In the case of surgery of the airway, the surgeon uses direct visualization as well.
How is loss of the airway treated?
Broadly speaking, identification of the cause of a lost airway determines the specific measures available for its correction. In an urgent or emergent situation, removal of an obstruction (whether by extracting a foreign body, repositioning soft tissue, as examples), placing a breathing tube (endotracheal intubation) or obtaining a surgical airway (such as tracheostomy or cricothyroidotomy) are possible means of obtaining an airway for given situations.