Rogers G G, van der Walt W
Department of Physiology, University of the Witwatersrand Medical School, Johannesburg, South Africa.
Eur J Appl Physiol Occup Physiol. 1997;75(5):431-4. doi: 10.1007/s004210050184.
We investigated the reproducibility of the carbon dioxide (CO2) rebreathing extrapolation technique of Defares to determine the mixed venous partial pressure of CO2 (PvCO2) using a direct, rather than the commonly used indirect, extrapolation method. The PvCO2 determinations were made five times a day on four subjects who exercised for 4 h daily on a bicycle ergometer over a period of 13 days. The concentration of CO2 in the rebreathing bag was monitored continuously using a rapid-response infrared capnograph. The mean standard deviation was 1.56 mmHg (0.21 kPa) for a mean PvCO2 of 47.6 mmHg (6.3 kPa), giving a mean coefficient of variation of 3.3%. This level of reproducibility agrees favourably with the reliability of direct measurements of pulmonary arterial partial pressure of CO2. We conclude that the CO2 rebreathing extrapolation technique can give reproducible PvCO2 values when a direct method of extrapolation is used.
我们研究了Defares二氧化碳（CO₂）重复呼吸外推技术的可重复性，采用直接而非常用的间接外推法来测定混合静脉血二氧化碳分压（PvCO₂）。对4名受试者进行了为期13天的研究，他们每天在自行车测力计上锻炼4小时，每天测定5次PvCO₂。使用快速响应红外二氧化碳分析仪持续监测重复呼吸袋中的CO₂浓度。平均PvCO₂为47.6 mmHg（6.3 kPa）时，平均标准差为1.56 mmHg（0.21 kPa），平均变异系数为3.3%。这种可重复性水平与直接测量肺动脉二氧化碳分压的可靠性相当。我们得出结论，当使用直接外推法时，CO₂重复呼吸外推技术能够给出可重复的PvCO₂值。
