呼吸保護具の呼吸抵抗について : 呼吸保護具の研究 (その7)

抄録

A New device for recording air flow was described in the previos paper (J. of Science of Labour, Vol.34, No.6, 447∼452, 1558). By means of this apparatus experimental studies were carried out on the effect of an increase in the respiratory resistance of protective divices on the pattern of respiration during muscular exercise. The inspiratory resistance of the test masks used in the experiment ranged 1∼10mm H₂O and the expiratory resistance was 2.5mm H₂O at the air flow of 30l/min. Subjects were 3 healthy young men. Muscular exercise was carried out for 30 minutes on a bicycle ergometer (Fig. 1), and the work rate was regulated in the range from 2 to 7 of the relative metabolic rate. Observations were made through the whole lapse of time on the following items: pulse rate, respiration rate, inspiratory volume (l.per min.), expiratory volume (l. per min.), maximum inspiratory flow, maximum expiratory flow, maximum inspiratory and expiratory resistances. (Fig. 2) Results: 1) The inspiratory and expiratory volumes as well as the maximum air flow increased exponentially with increasing work rate. (Fig. 4, 5, 6, 8) 2) The maximum air flow on inspiration and expiration was usually twice or three times and occasionally four times as high as the average level calculated from the minute volume. (Fig. 7) 3) In the case of a mask of 10mm H₂O inspiratory and 2.5mm H₂O expiratory resistances at the air flow of 30l/min, the respiratory resistance reached occasionally 100mm H₂O on inspiration and 50mm H₂O on expiration during heavy muscular exercise. 4) The subject, wearing the test mask of 10mm H₂O inspiratory resistance at the air flow of 30 l/min, complained of difficulty of inspiration during heavy muscular exercise, and the increase in pulse rate exceeded 70-80 per min. (Fig. 13, 14) 5) The above mentioned results led the authors to the tentative conclusion that the desirable limit of the maximum inspiratory resistance at the peak air flow should be about 60mm H₂O.