Just as the airway may be intact, partially obstructed, or completely obstructed, respiratory effort may be present, obtunded, or absent. While the techniques of airway management are essentially the same whether or not there is respiratory effort, in the latter group it must be assumed that the airway is compromised and basic airway maintenance techniques must be instituted in conjunction with ventilatory support.
In addition to assessment of the airway, the presence of ventilatory effort should also be monitored. Phonation, detection of breath sounds, particularly using a stethoscope applied over the upper trachea and both lung fields, and the feel of breath on the hand are readily observable clinical signs. In the presence of spontaneous ventilatory effort an obstructed airway may present with paradoxical chest movements. As the diaphragm contracts the abdominal contents descend, causing the girth to increase, while at the same time the chest wall collapses and a tracheal tug is evident as the more mobile tissues of the neck are drawn down towards the thoracic inlet. This alternates with relaxation of the diaphragm and contraction of the abdominal muscles, reversing the abdominal and thoracic movements.
The most common form of airway compromise is snoring, which results from loss of pharyngeal tone as a consequence of a reduced level of consciousness. This is an example of inspiratory stridor, which is characteristic of supraglottic obstruction. In contrast, airway obstruction below the larynx is usually more evident during the expiratory phase (wheezing). Upper airway obstruction may also be caused, or exacerbated, by excessive salivation, gastric contents, blood, or a foreign body in the pharynx or laryngeal opening. These may obstruct the airway directly or indirectly, by stimulating laryngeal spasm, and should always be considered, as should a history of maxillofacial or neck trauma.
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