EFFECTS OF INTERMITTENT POSITIVE PRESSURE BREATHING IN SIMULATED PULMONARY OBSTRUCTION

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Abstract
Clinical experience suggests that mechanical assistance with intermittent positive pressure breathing (IPPB) fails to improve alveolar ventilation in about one-half of all patients with severest emphysema in acute respiratory failure. The inability of the writers to study all parameters of ventilation and gas exchange before and during IPPB in these very ill patients suggested the design of a variable resistance valve which would simulate their type of expiratory obstruction. Five normal subjects were studied repeatedly with and without obstruction and with and without IPPB assistance. The data suggest design of a patient-cycled respirator capable of delivering very high flow rate at pressures which are decreasing rather than increasing during the inspiratory cycle and which is sensitive enough for free choice of respiratory rate. A negative expiratory phase would increase the transpulmonary pressure drop and thus aggravate airway closure.