A SYSTEM TO SIMULATE GAS-EXCHANGE IN HUMANS TO CONTROL QUALITY OF METABOLIC MEASUREMENTS

We have developed a gas exchange simulation system (GESS) to assess th e quality control in measurements of metabolic gas exchange. The GESS simulates human breathing from rest to maximal exercise. It approximat es breath-by-breath waveforms, ventilatory output, gas concentrations, temperature and humidity during inspiration and expiration. A program mable motion control driving two syringes allows the ventilation to be set at any tidal volume (V-T) respiratory frequency (f), flow wavefor m and period of inspiration and expiration. The GESS was tested at var ious combinations of V-T (0.5-2.5 I) and f (10-60 stroke.min(-1)) and at various fractional concentrations of expired oxygen (0.1294-0.1795) ; and carbon dioxide (0.0210-0.0690) for a pre-set flow waveform and f or expired gases at the same temperature and humidity as room air. Exp ired gases were collected in a polyethylene bag for measurement of vol ume and gas concentrations. Accuracy was assessed by calculating the a bsolute and relative errors on parameter's (error = measured-predicted ). The overall error in the gas exchange values averaged less than 2% for oxygen uptake and carbon dioxide output, which is within the accur acy of the Douglas bag method.