Cardiac output and gas exchange during heavy exercise with a positive pressure respiratory protective apparatus.
研究了7名训练有素的消防员在150瓦和最大负荷下，使用正压呼吸防护装置时的心输出量和气体交换，发现0.4千帕的正压呼吸未损害心肺功能，反而提高了通气效率。
Cardiac output and gas exchange during heavy exercise with a positive pressure respiratory protective apparatus. Scand j work environ health 9 (1983) 471-477. Continuous positive pressure breathing effectively prevents inward leakage of noxious agents into a breathing apparatus but may interfere with venous return and cardiorespiratory performance during heavy work. Cardiac output was therefore recorded with a dye dilution method, and ventilatory variables were measured from expired air, for seven well-trained firemen at a work load of 150 W. All the variables except the invasive ones were also measured during the maximal work load that each subject could sustain for 10 min. At random the subjects worked with a mouthpiece and a face mask with and without a positive pressure of 0.4 kPa. No variable deteriorated during positive pressure breathing, although the central venous oxygen pressure increased, an occurrence indicating higher cardiac output in relation to oxygen demand. Dead space ventilation decreased, an indication of increased ventilatory efficiency. Positive pressure breathing (0.4 kPa) thus does not deteriorate cardiopulmonary function during intermediate or maximal work loads.