Complete airway obstruction leads to asphyxia (hypoxia plus hypercarbia) and cardiac arrest within five to ten minutes. Partial airway obstruction (increased airway resistance) may result in increased fluctuations of intrathoracic pressure, increased work of breathing, decreased respiratory response to carbon dioxide, hypoventilation with hypoxia and hypercarbia, cerebral congestion and edema, pulmonary edema, cardiovascular disturbances, exhaustion, and secondary apnea with cardiac arrest. A patent airway thus is the key to resuscitation and life-support.
In the unconscious patient, hypopharyngeal obstruction by the base of the relaxed tongue occurs always when the neck is flexed and almost always when the head is in the mid-position. This is dependent upon head-jaw position and occurs regardless of whether the patient is prone or supine. While gravity may aid in drainage of liquid foreign matter, it does not counteract hypopharyngeal softtissue obstruction.
Complete airway obstruction is recognized by inability to hear or feel air flow