Physiologic Evaluation of Positive End Expiratory Pressure Ventilation

¹ Department of Medicine, Baylor College of Medicine and the Pulmonary Disease Section, The Methodist Hospital, Houston

The physiologic effects of positive end expiratory pressure ventilation (PEEP) were studied in 36 patients with acute respiratory failure secondary to non- obstructive lung disease. Arterial oxygen content increased in all patients while mixed venous oxygen content rose in half of them. Calculated arterial-venous oxygen content differences did not change for the group as a whole while physiologic shunt fraction decreased markedly. Very few deleterious effects of this method of ventilation were noted except for a 14 percent incidence of pneumothorax. The mean time that PEEP was required was 2.8 days and prognosis seemed to be related to the etiology of the respiratory failure. An increase in mixed venous oxygen content during PEEP seemed to impart a good prognosis and occurred more frequently among patients with respiratory failure following cardiovascular surgery; most of these patients survived their respiratory failure and over half were eventually discharged. In contrast only one of 14 patients with respiratory failure due to other causes survived after requiring the use of PEEP.