Jansons H, Fokkens J K, van der Tweel I, Kreukniet J
Lung Function Department, University Hospital, Utrecht, The Netherlands.
Respir Med. 1998 Jan;92(1):18-24. doi: 10.1016/s0954-6111(98)90026-9.
The single-breath (SB) method for determining the transfer factor for carbon monoxide (TLCO) is of limited value for the detection of diffusion disorders on the alveolar level, because the results are influenced by unequal distribution of ventilation and diffusion. The rebreathing method (RB) is thought not to be influenced by these inequalities. To the authors' knowledge, no study has measured both TLCORB and TLCOSB systematically and compared them with regard to the influence of unequal ventilation and diffusion. Therefore, the present study measured total lung capacity (TLC) as well as TLCO, both with the RB vital capacity method and the SB method, using the same apparatus in 10 healthy subjects and in 35 patients with chronic obstructive pulmonary disease (COPD). These patients are known to have increased unequal ventilation and diffusion in comparison with healthy subjects. In the healthy subjects, a small difference was found between TLC measured with the RB method (TLCRB) divided by the predicted value (TLCRB/pred) and TLCSB/pred (mean difference 0.07; SE = 0.02); no significant difference was found between TLCORB divided by the predicted value of TLCOSB (TLCORB/pred) and TLCOSB/pred. In the COPD patients, however, TLCRB/pred was larger than TLCSB/pred (mean difference 0.17; SE = 0.02) and TLCORB/pred was larger than TLCOSB/pred (mean difference 0.23; SE = 0.05). Multiple regression analysis revealed that in the COPD patients, 54% of the variance of the difference between TLCRB/pred and TLCSB/pred, and 76% of the variance of the difference between TLCORB/pred and TLCOSB/pred, were explained by parameters related to unequal ventilation and diffusion. In 25 of the 35 COPD patients, TLCOSB/pred was less than 0.8, whereas in 11 of these 25 patients, TLCORB/pred was more than 0.8. This difference was significant (P = 0.0005). In these 11 patients, the SB measurement resulted in the incorrect diagnosis of a diffusion disorder on the alveolar level. The RB method, however, never resulted in the diagnosis of a diffusion disorder when TLCOSB/pred was larger than 0.8. It is concluded that in a significant number of COPD patients, TLCOSB is below the normal range, whereas TLCORB is not below the normal range. This difference between TLCORB and TLCOSB is related to the combined effect of unequal ventilation and diffusion, and is of clinical importance for the detection of a diffusion disorder on the alveolar level.
单呼吸（SB）法测定一氧化碳转运因子（TLCO）在检测肺泡水平的弥散障碍方面价值有限，因为结果会受到通气和弥散分布不均的影响。重复呼吸法（RB）被认为不受这些不均一性的影响。据作者所知，尚无研究系统测量TLCORB和TLCOSB并比较它们在通气和弥散不均一性影响方面的差异。因此，本研究使用同一设备，采用RB肺活量法和SB法，对10名健康受试者和35例慢性阻塞性肺疾病（COPD）患者测量了肺总量（TLC）以及TLCO。已知这些患者与健康受试者相比，通气和弥散不均一性增加。在健康受试者中，RB法测量的TLC（TLCRB）除以预测值（TLCRB/pred）与TLCSB/pred之间发现有微小差异（平均差异0.07；标准误=0.02）；TLCORB除以TLCOSB的预测值（TLCORB/pred）与TLCOSB/pred之间未发现显著差异。然而，在COPD患者中，TLCRB/pred大于TLCSB/pred（平均差异0.17；标准误=0.02），且TLCORB/pred大于TLCOSB/pred（平均差异0.23；标准误=0.05）。多元回归分析显示，在COPD患者中，TLCRB/pred与TLCSB/pred之间差异的54%的方差，以及TLCORB/pred与TLCOSB/pred之间差异的76%的方差，可由与通气和弥散不均一性相关的参数解释。在35例COPD患者中的25例中，TLCOSB/pred小于0.8，而在这25例患者中的11例中，TLCORB/pred大于0.8。这种差异具有显著性（P = 0.0005）。在这11例患者中，SB测量导致了肺泡水平弥散障碍的错误诊断。然而，当TLCOSB/pred大于0.8时，RB法从未导致弥散障碍的诊断。结论是，在相当数量的COPD患者中，TLCOSB低于正常范围，而TLCORB不低于正常范围。TLCORB与TLCOSB之间的这种差异与通气和弥散不均一性的综合作用有关，对于检测肺泡水平的弥散障碍具有临床重要性。
