Graham Brian L, Mink Joseph T, Cotton David J
Division of Respirology, Department of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
Am J Respir Crit Care Med. 2002 Jun 1;165(11):1504-10. doi: 10.1164/rccm.2108071.
Although carboxyhemoglobin (COHb) is often increased in smokers, American Thoracic Society recommendations for adjusting the single breath carbon monoxide (CO) diffusing capacity (DL(CO)(SB)) for COHb remain optional. Using a previously described 3-equation technique, we measured DL(CO)(SB) and an index of diffusion inhomogeneity (DI) in 10 healthy, nonsmoking subjects who performed DL(CO)(SB) maneuvers both before and after increasing COHb. CO backpressure (FA(CO)) was measured from the exhaled gas of a standardized deep breath of room air that immediately preceded each DL(CO)(SB) and was validated by measurement of FA(CO) from an identical "sham" maneuver without inhaling CO. Without adjustments for FA(CO) or COHb, DL(CO)(SB) decreased with increasing COHb. This effect persisted when DL(CO)(SB) was adjusted only for FA(CO), but it was eliminated with further adjustment for the anemia effect of increasing COHb. The anemia adjustment was proportional to the fractional COHb. DI, adjusted for FA(CO), was unaffected by increasing COHb. We conclude that DL(CO)(SB) must be adjusted for both the buildup of CO backpressure and the anemia effect of increasing COHb. Adequate corrections of DL(CO)(SB) can be implemented using FA(CO) measured during a standardized deep breath immediately preceding the DL(CO)(SB) maneuver. Current American Thoracic Society recommendations for DL(CO)(SB) standardization do not adequately compensate for COHb.
尽管吸烟者的碳氧血红蛋白（COHb）通常会升高，但美国胸科学会关于根据COHb调整单次呼吸一氧化碳（CO）弥散量（DL(CO)(SB)）的建议仍为可选做法。我们采用先前描述的三方程技术，对10名健康非吸烟受试者进行了研究，在增加COHb之前和之后分别让他们进行DL(CO)(SB)操作，测量其DL(CO)(SB)和弥散不均匀指数（DI）。在每次DL(CO)(SB)操作前，从紧接着的一次标准化室内空气深呼吸的呼出气体中测量CO背压（FA(CO)），并通过在不吸入CO的相同“假”操作中测量FA(CO)进行验证。在不调整FA(CO)或COHb的情况下，DL(CO)(SB)随COHb升高而降低。仅针对FA(CO)调整DL(CO)(SB)时，这种效应仍然存在，但进一步针对COHb升高的贫血效应进行调整后，该效应消除。贫血调整与COHb分数成正比。针对FA(CO)调整后的DI不受COHb升高的影响。我们得出结论，必须针对CO背压的增加和COHb升高的贫血效应来调整DL(CO)(SB)。可以使用在DL(CO)(SB)操作前紧接着的一次标准化深呼吸期间测量的FA(CO)来对DL(CO)(SB)进行充分校正。美国胸科学会目前关于DL(CO)(SB)标准化的建议并未充分补偿COHb的影响。
