Abstract:

Experiments were performed on 6 young health males during pressure breathing without trunk counter-pressure. The values of intra-pulmonary pressure used were 0, 2.0, 3.0, 3.4, 4.0, 4.4, and 5,4 kPa. The results were summarized as follows.With the increase of pressure within the lung, the compensatory function of circulatory and respiratory systems was strengthened gradully as well as the respiratory power consumption index was increased, but it was dropped as the intra-pulmonary pressure reached to 4.0 kPa. The decrease of above objective physiological indices showed that the compensatory function was weakened, which was the indication of physiological endurance limit during pressure breathing. There was a serious subjective symptom for the breathing to be continued difficulty in the experimental examples discontinued only, that may be considered as the acceptable endurance index.Th erespirafory power consumption index can ref'ecf respirodynamically physiological characteristics of subjective sensation in human during pressure breathing which may be used as a co-indicator for the evaluation of tolerance. A method of comprehensive evaluation of the tolerance of pressure breathing was presented through the experiment. The intra-pulmonary pressure of 2.0, 3.4 and 4.0-6.2 kPa was considered to be the physiological limit of safety, allowance and endurance. This study denoted marked significance for establishing physiological standard and protective measure of pressure breathing by oxygen.

Key words: pressure breathing, physiological limit, intra-pulmonary pressure