The principal indications for mechanical ventilator are airway protection and respiratory failure. A compromised airway, or an airway at risk of compromise, may be identified by physical examination and ancillary testing.

Respiratory failure in the ED is almost always-and most appropriately-a clinical diagnosis. The decision to incubates and mechanically ventilate or to institute noninvasive ventilation support is generally made purely on clinical grounds without delay for laboratory evaluation.

 

Respiratory failure may also be easily identified with laboratory or pulmonary function data. Obtaining a PaCO2 is useful to confirm respiratory failure when a broader differential diagnosis exists-for example, obtunded patients who may be hypercarbic but might have a reversible metabolic or toxicological etiology for their conditions-but adequate stabilization and ventilation of these patients should not be delayed to wait for laboratory results.

 

Mechanical ventilator is indicated for both hypercapnic respiratory failure and hypoxemic respiratory failure. It is also indicated for treatment of certain critical conditions such as correction of life-threatening acidemia in the setting of salicylate intoxication, for intentional hyperventilation in the setting of major head injury with elevated intracranial pressure, for suspicion of clinical brain herniation from any cause, or for a patient in critical condition with cyclic antidepressant toxicity.