[Development of a new method for calibration of pneumotachograph according to flow rate--evaluation of a computer-controlled-system for assessing respiratory gas exchange using this method].

1. We evaluated the method for calibrating the pneumotachograph according to flow rate by the software on personal computer. Flow volume was detected using the approximated equation (y = 1.294x2 + 0.989x + 35.824, r = 0.976, p less than 0.01) from various mean flow rate and integration of output voltage. The error between syringe volume (21) and the estimated value on the equation was 10 +/- 8 ml (0.48 +/- 0.42%). 2) Using the method described in 1), we developed computer-controlled-system for assessing respiratory gas exchange by mixing chamber method. To evaluate the accuracy of the system as compared with the Douglas Bag method, we measured the gas parameters of the both methods for two male subjects at rest(3 and 5min) and steady state exercise (3 min., 60-240watt). The error between the both methods were within +/- 5% in ventilation(VE), mixed expired O2 (FEO2) and CO2 (FECO2) concentration, and were within +/- 8% in O2 uptake(VO2) and CO2 production (VCO2). There were high positive correlation (r greater than 0.99, p less than 0.01) between the both methods in the all parameters. These results indicate that the system in this study would be practical use, that VE can be measured in only one pneumotachograph, even if the range of flow rate was wide(e.g. from rest to heavy exercise).