IMPAIRMENT of respiration presents a serious therapeutic problem in poliomyelitis. Single or multiple involvement of the components of the respiratory mechanism frequently decreases the patient's arterial oxygen saturation in cases of the spinal and bulbar types during the acute and convalescent stages of the disease. Accurate diagnosis of the nature of the respiratory defect is an essential step in the treatment of the patient. From a physiologic viewpoint, the various disturbances in pulmonary function in poliomyelitis may be resolved into two general types, ventilatory deficiency and alveolar deficiency. Defective ventilation may occur with paralysis of the diaphragm or of the intercostal muscles or with depression of the respiratory center. Alveolar deficiency, or inadequate gas transfer between the pulmonary alveoli and the blood, may result from parenchymal lesions in the lungs, e.g., pulmonary edema, atelectasis, focal hemorrhage and pneumonia. A similar classification was suggested in 1941 by Cournand and Richards1