Peslin R, Jardin P, Bohadana A B
J Appl Physiol Respir Environ Exerc Physiol. 1983 May;54(5):1202-8. doi: 10.1152/jappl.1983.54.5.1202.
We examined the possibility that cyclic gas exchange between alveolar space and the surrounding tissue, induced by alveolar pressure variations, could interfere with plethysmographic measurements of thoracic gas volume (TGV). A model study suggested that TGV could be overestimated by up to 100 ml and that the phenomenon could account for some of its previously reported negative frequency dependence (J. Appl. Physiol.: Respirat. Environ. Exercise Physiol. 52: 739-747, 1982). As the error would be mainly due to CO2 exchange and be proportional to its partial pressure (PCO2), we studied in nine normal subjects the influence of increasing alveolar PCO2 from 30 to 50 Torr on TGV measurements at panting frequencies (f) of 0.5 and 2-2.5 Hz. Contrary to model predictions, CO2 tended to decrease TGV estimates at low frequency and to increase them at high frequency. As a consequence, frequency dependence of TGV (delta TGV/delta f) was less at high than at low PCO2 (-39 +/- 32 vs. -84 +/- 49 ml x Hz-1, P less than 0.001). The data are not satisfactorily explained but suggest that gas exchange is not an important factor in TGV measurements.
我们研究了肺泡压力变化引起的肺泡腔与周围组织之间的周期性气体交换可能干扰胸内气体容积（TGV）体积描记测量的可能性。一项模型研究表明，TGV可能被高估多达100毫升，并且该现象可以解释其先前报道的一些负频率依赖性（《应用生理学杂志：呼吸、环境与运动生理学》52: 739 - 747, 1982）。由于误差主要归因于二氧化碳交换且与其分压（PCO2）成正比，我们在9名正常受试者中研究了将肺泡PCO2从30 Torr增加到50 Torr对0.5 Hz以及2 - 2.5 Hz的呼吸频率（f）下TGV测量值的影响。与模型预测相反，二氧化碳在低频时倾向于降低TGV估计值，而在高频时倾向于增加TGV估计值。因此，TGV的频率依赖性（δTGV/δf）在高PCO2时低于低PCO2时（-39 ± 32与-84 ± 49毫升×赫兹-1，P < 0.001）。这些数据虽未得到令人满意的解释，但表明气体交换在TGV测量中并非重要因素。
