Wüst Rob C I, Aliverti Andrea, Capelli Carlo, Kayser Bengt
Institute for Biomedical Research into Human Movement and Health, Manchester Metropolitan University, Manchester, UK.
Respir Physiol Neurobiol. 2008 Dec 31;164(3):291-9. doi: 10.1016/j.resp.2008.06.002. Epub 2008 Jun 8.
When measuring breath-by-breath (BbB) oxygen uptake at the mouth (V MO2 ) as the difference between the amount of inspired and expired oxygen, BbB variation in lung oxygen stores due to BbB variation in end-expiratory lung volume (VLET) introduces an error leading to a decreased signal-to-noise ratio when compared to oxygen uptake at the alveolo-capillary interface (V AO2 ). Conventional BbB measurement of oxygen uptake does not measure BbB changes in lung oxygen stores. Opto-electronic plethysmography(OEP) allows accurate monitoring of absolute lung volume changes and BbB quantification of change in pulmonary oxygen stores. To quantify BbB variation of lung oxygen stores and to assess variability in V MO2 due to BbB variation of lung oxygen stores, we measured, V MO2 and V AO2 in parallel, at rest,during transients and during steady state cycling exercise at 60, 90 and 120W in 7 healthy male subjects. Average V MO2 and V AO2 at steady state were not different (p = 0.328).Direct measurement of V AO2 reduced overall BbB variability by 24% (p < 0.0001) and variance of the difference between V MO2 and V AO2 could be explained for 55% by BbB changes in VLET and expiratory oxygen fraction. V AO2 was higher than V MO215 and 30 s after exercise onset (p < 0.01). We conclude that (1) by taking into account changes in lung oxygen stores BbB variability of oxygen uptake is reduced, (2) alveolar oxygen stores change rapidly during transients to exercise, and (3) changes in alveolar oxygen stores affect BbB oxygen uptake measured at the mouth during the cardio-dynamic phase I.
当通过测量口腔处逐次呼吸（BbB）的氧气摄取量（V MO2），即吸入氧气量与呼出氧气量之差时，由于呼气末肺容积（VLET）的BbB变化导致肺氧储备的BbB变化会引入误差，与肺泡-毛细血管界面处的氧气摄取量（V AO2）相比，会导致信噪比降低。传统的BbB氧气摄取量测量方法无法测量肺氧储备的BbB变化。光电体积描记法（OEP）能够准确监测绝对肺容积变化以及肺氧储备变化的BbB定量。为了量化肺氧储备的BbB变化，并评估由于肺氧储备的BbB变化导致的V MO2变异性，我们在7名健康男性受试者休息时、瞬态期间以及在60、90和120W的稳态骑行运动期间，并行测量了V MO2和V AO2。稳态时的平均V MO2和V AO2无差异（p = 0.328）。直接测量V AO2可使整体BbB变异性降低24%（p < 0.0001），V MO2与V AO2之差的方差中有55%可由VLET的BbB变化和呼气氧分数来解释。运动开始后15秒和30秒时，V AO2高于V MO2（p < 0.01）。我们得出结论：（1）考虑肺氧储备变化可降低氧气摄取的BbB变异性；（2）在运动瞬态期间，肺泡氧储备变化迅速；（3）肺泡氧储备变化会影响心动力第一阶段在口腔处测量的BbB氧气摄取量。
