Principles of Critical Care > Part IV. Pulmonary Disorders > Chapter 44. Liberation from Mechanical Ventilation Constantine A. Manthous, Gregory A. Schmidt, Jesse B. Hall

Key Points

"Respiratory failure occurs when the lungs and respiratory pump fail to exchange oxygen and carbon dioxide adequately (see Chap. 31). Hypoxemic (type 1) respiratory failure usually results from flooding or collapse of the distal airspaces leading to intrapulmonary shunt and inadequate arterial oxygenation despite generous concentrations of inspired oxygen (see Chap. 38). Hypercapnic (type 2) respiratory failure results from inability to sustain sufficient alveolar ventilation to eliminate the CO₂ produced from aerobic metabolism. Perioperative respiratory failure, a special case of types 1 and 2, results when postoperative pain and recumbency result in atelectasis and hypoxemia or when medications to alleviate pain reduce respiratory drive, leading to hypercapnia. Shock-related respiratory failure is another special case in which the underperfused respiratory muscles are unable to compensate for the acidosis resulting from inadequate global tissue perfusion. Mechanical ventilation substitutes for the respiratory pump until these disturbances have been reversed adequately to allow resumption of spontaneous breathing and gas exchange...."