The effects of PEEP on arterial oxygenation

Abstract

The effect of positive and expiratory pressure (PEEP) on arterial oxygenation depends on many factors. Two of the most important are the "quality" and the "quantity" of the physiological shunt. The "quality" depends on the mixed venous oxygen tension, and the "quantity" on the shunt fraction. Each of these factors may rise or fall with PEEP, depending on the pulmonary and circulatory state of the patient. Their ultimate balance influences the change in arterial oxygen tension.

Optimal endexpiratory airway pressure for ventilated patients

“…Acute pulmonary parenchymal failure is characterized by -a decreased functional residual capacity (FRC) [8, 14, 181, -a decrease in lung compliance [8,14,17,18], -an increased venous admixture that is mainly due to direct right-to-left shunting of blood passing nonventilated or hypoventilated alveoli [17], -an increased pulmonary vascular resistance [10].…”