The barospirator for artificial respiration designed by Thunberg1 served as a basis for the construction of the respirators now used in many hospitals for the treatment of respiratory failure in poliomyelitis. In the Thunberg barospirator the patient was entirely enclosed in an air-tight cylinder. The air pressure within this cylinder was alternately raised and lowered, resulting in an intrapulmonary exchange of air sufficient to maintain life for long periods. Thunberg aptly described the effect of the barospirator on the patient as resulting in respiration without respiratory movement. It soon became evident that this ingenious apparatus was not satisfactory for cases of prolonged respiratory failure. Drinker and Shaw2 modified the barospirator so that the patient's head would be outside the air-tight cylinder. This is the apparatus most frequently used for respiratory failure in poliomyelitis.Forty-six patients with respiratory embarrassment due to poliomyelitis were treated in the Drinker respirator at the Willard Parker Hospital in 1931. There were many others with involvement of the respiratory mechanism who survived without artificial respiration. Some patients with urgent cases were transferred to other hospitals where respirators were available, because at times all of our respirators were in use. After the first few weeks patients with bulbar lesions were not considered suitable for treatment by this method, and preference was given those with only spinal involvement.