EFFECT OF CHANGE IN BODY POSITION ON LUNG VOLUMES AND INTRAPULMONARY GAS MIXING IN PATIENTS WITH OBESITY, HEART FAILURE, AND EMPHYSEMA

Abstract

The lung volume, it subdivisions, and intrapulmonary gas mixing were compared in the seated and recumbent positions in normal subjects and in groups of patients with obesity, heart failure, and pulmonary emphysema. The obese patients had significant decreases in all lung subdivisions except the residual volume. The expiratory reserve, in particular, became extremely small in the recumbent position. The slowly ventilated space in the seated position was comparable to that observed in the recumbent normal individual. Moreover, when the obese patient was recumbent, the space became even more slowly ventilated. It is suggested that ventilation-perfusion inequalities, particularly those involving slowly ventilated areas, may contribute to the arterial hypoxemia observed in some patients with obesity. By contrast, patients with congestive heart failure who also had decrease in the subdivisions of the lung except for residual volume did not demonstrate a space which was very slowly ventilated and showed no change with recumbency. Patients with pulmonary emphysema had slowly ventilated spaces which were larger than those observed in the obese patients, but they were ventilated at roughly the same rate as those of the recumbent obese patient.