We have studied the ventilating ability of various pressure breathing apparatus and the changes associated with various settings and compliances of the apparatus since 1958. The present report is concerned with the comparative study of Bird Respirator and Droger Pulmomat. The method of the investigation was follows ; The ventilator was connected to the test lung (the training thorax) and the compliance diagram was recorded by pneumotachograph. The pattern of respiration, the time ratio of in and expiration and the pressure-volume relation on each setting of the apparatus were obtained. The pressure-volume curve of the ventilator and the compliance change of the patient were studied when various artificial resistances or trachea tubes of various resistances were inserted into the respiratory circuit. Droger Pulmonat is "volume limited, pressure variable" in type, small in size and easy in setting. In comparison with the old type of Daoger Pulmonat (700 cc), the new type (1,000 cc) is markedly improved and can be safety used during anesthesia. Bird respirator has been used in Japan since 1960 and is "pressure limited, volume variable" in type. The time control and assistant respiration by a sensitivity control knob can be easily performed. The nebulizer is also attached to the apparatus. The setting of the apparatus, however, requires the skill and experiences, and errors in setting of the apparatus may result in the serious complication. Our apparatus were adjusted at Mark (4) and Mark (8), and those combined Marks give excellent control respiration during anesthesia. For the purpose of oxygen therapy and resuscitation, Mark (7) or Mark (8) sholud be used. Based upon the above investigation, we conclude that both Droger Pulmonat and Bird Respirator have excellent mechanism, and we may formulate the following requirements for the ideal respirator ; 1) The respirator should give the patient the respiration as in the physiologic status. 2) In order to manage the changes of resistance and compliance in the control respiration under anesthesia, the operator should be acquainted with the setting of the apparatus. 3) The humidity and temperature should be easily regulated, and the mixed gas of air and oxygen could be used. 4) The respiratory frequency should be adjustable independent of the ventilatory volume. 5) One should be able to read the inspiratory positive pressure and the expiratory negative pressure at any instant. 6) It should be possible to employ any room air-oxygen mixture with the device. 7) The apparatus should adapt tb any spontaneous respiratory activity which is pressent or which returns while the patient is attached to the machine.
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