Kendrick A H, Laszlo G
Respiratory Department, Bristol Royal Infirmary.
Thorax. 1994 Jan;49(1):82-4. doi: 10.1136/thx.49.1.82.
Carbon monoxide transfer factor (TLCO) varies inversely with the partial pressure of alveolar oxygen (PAO2). During exercise the PAO2 in the alveolar gas sample bag decreases so the TLCO increases more than would be expected from the effects of exercise alone. The effects of PAO2 on the estimation of TLCO during exercise have been investigated and studies have been performed to determine whether it is appropriate to standardise to a PAO2 of 16 kPa.
TLCO was estimated at rest and at a single level of exercise in six normal subjects using test gas mixtures of 0.3% carbon monoxide, 14% helium, and oxygen in three different percentages (17%, 21%, and 27%), remainder nitrogen. In three of the subjects an incremental exercise test with estimates of oxygen consumption (VO2) and cardiac frequency (fC) was also performed using a mixture containing 18% oxygen.
TLCO decreased as levels of inspired oxygen increased. When standardised to a PAO2 of 16 kPa TLCO became independent of the inspired oxygen concentration. The significance of the curvilinear relations of TLCO and transfer coefficient to VO2 and fC improved.
The single breath breath holding TLCO should be standardised to a PAO2 of 16 kPa when estimated during exercise.
一氧化碳转运因子（TLCO）与肺泡氧分压（PAO2）呈反比。运动期间，肺泡气样本袋中的PAO2降低，因此TLCO的增加幅度超过仅由运动影响所预期的增加幅度。已对PAO2对运动期间TLCO估计值的影响进行了研究，并开展了多项研究以确定将其标准化至16 kPa的PAO2是否合适。
在6名正常受试者静息状态及单一运动水平下，使用含0.3%一氧化碳、14%氦气以及三种不同百分比（17%、21%和27%）氧气（其余为氮气）的测试气体混合物来估计TLCO。在其中3名受试者中，还使用含18%氧气的混合物进行了递增运动试验，以估计耗氧量（VO2）和心率（fC）。
随着吸入氧气水平的升高，TLCO降低。当标准化至16 kPa的PAO2时，TLCO变得与吸入氧气浓度无关。TLCO和转运系数与VO2及fC的曲线关系的显著性得到改善。
运动期间估计单次屏气TLCO时，应将其标准化至16 kPa的PAO2。
