Effect of intermittent positive pressure breathing on the cardiac output of patients with chronic pulmonary disease.

The effect of various intermittent positive pressure breathing devices on cardiac output has been studied by Motley’ in a group of normal patients. He found that decreases in cardiac output were directly related to the height of the mean mask pressure. It was part of his conclusion that intermittent positive pressure breathing could be used without decreasing cardiac output when the pressures were properly regulated. Maloney,”3 however, has pointed out the possible harmful effects of intermittent positive pressure type respirators. He has indicated that in patients with respiratory and/or circulatory failure these effects might be life threatening. At present the effects of IPPB on the large group of patients who are neither normal nor have circulatory insufficiency have not been fully delineated and are subject to controversy. In recent years IPPB has become a more frequently employed and generally accepted form of therapy in the treatment of severe pulmonary emphysema. Because of this it appeared to us almost imperative that an appreciation of the effects of IPPB on this group of patients should be available. It would seem that in order to relate changes in cardiac output to the therapeutic situation more than a quantitative estimation of drop in cardiac output was necessary. Specifically it was hoped to make serial determinations of cardiac output. In this way the duration of therapy could be evaluated and in addition, the recovery phase following cessation of treatment could be explored. The dye dilution technique with its present modification offered an excellent method of making such repeated measurements.4-7