The effect of intermittent positive pressure breathing and voluntary hyperventilation upon the distribution of ventilation and pulmonary blood flow to the lung in chronic obstructive lung disease.

Intermittent positive pressure breathing (IPPB) from an apparatus applying positive pressure to the mouth during inspiration is widely used in the treatment of obstructive lung disease. The literature has recently been well reviewed by Sheldon (1). There was early con- cern with its effects in decreasing cardiac output (2, 3), which are avoided by using equipment that gives a type III mask pressure curve and hence letting the positive pressure phase, i.e., inspira- tion, occur at a high flow rate and occupy only a small fraction of the respiratory cycle, expiration being prolonged and against zero mask pressure. This type of pressure curve is obtained with machines in current use.