Continuous positive airway pressure. The use of low levels in adult patients with artificial airways.

Twelve adult surgical patients recovering from acute respiratory failure (ARF) had a catheter inserted for measurement of pulmonary capillary wedge pressure, pulmonary artery pressure, and cardiac output; and for calculation of arterial-mixed venous oxygen content difference, physiologic shunt, and systemic and pulmonary vascular resistances. Measurements were made with 5 cm H2O continuous positive airway pressure (CPAP), during spontaneous respiration at ambient airway pressure, and then again with 5 cm H2O CPAP. During breathing without CPAP, the total physiologic shunt increased, and the PaO2/fraction of inspired oxygen concentration (FiO2) ratio decreased significantly from control values. After CPAP therapy was again introduced, the physiologic shunt decreased and the PaO2/FiO2 ratio increased significantly. This improvement in oxygenation took place without any significant change in cardiovascular status. Thus, low levels of CPAP are helpful in maintaining the pulmonary status in intubated adult patients recovering from ARF.