The distribution of ventilation, diffusion, and blood flow in obese patients with normal and abnormal blood gases.

The distribution of ventilation, diffusion, and pulmonary blood flow was studied in 5 normal subjects and 10 obese patients in terms of 3 lung compartments by the method of King and Briscoe. Normal subjects and obese patients with normal arterial oxygen tension and normal or low arterial carbon dioxide tension had a relatively well ventilated and underperfused slow compartment. The ratio of alveolar ventilation to perfusion for the less well ventilated space was larger than that of the well ventilated compartment in all 5 normal subjects and in 3 of 4 obese patients with normal arterial oxygen tension. There was an uneven distribution of diffusion in relation to blood flow. The smaller flow compartment received an average of 1.5 per cent of the total diffusion. Obese patients with low arterial oxygen tension and normal carbon dioxide tension had normal alveolar ventilation, but abnormal distribution. Ventilation to the slow space was markedly decreased. The diffusion in relation to blood flow was more eve...