Prediletto Renato, Fornai Edo, Catapano Giosuè, Carli Cristina
Institute of Clinical Physiology, National Research Council of Italy, Pisa, Italy.
BMC Pulm Med. 2007 Dec 19;7:18. doi: 10.1186/1471-2466-7-18.
Alveolar volume measured according to the American Thoracic Society-European Respiratory Society (ATS-ERS) guidelines during the single breath diffusion test can be underestimated when there is maldistribution of ventilation. Therefore, the alveolar volume calculated by taking into account the ATS-ERS guidelines was compared to the alveolar volume measured from sequentiallly collected samples of the expired volume in two groups of individuals: COPD patients and healthy individuals. The aim of this study was to investigate the effects of the maldistribution of ventilation on the real estimate of alveolar volume and to evaluate some indicators suggestive of the presence of maldistribution of ventilation.
Thirty healthy individuals and fifty patients with moderate-severe COPD were studied. The alveolar volume was measured either according to the ATS-ERS guidelines or considering the whole expired volume subdivided into five quintiles. An index reflecting the non-uniformity of the distribution of ventilation was then derived (DeltaVA/VE).
Significant differences were found when comparing the two measurements and the alveolar volume by quintiles appeared to have increased progressively towards residual volume in healthy individuals and much more in COPD patients. Therefore, DeltaVA/VE resulted in an abnormal increase in COPD.
The results of our study suggest that the alveolar volume during the single breath diffusion test should be measured through the collection of a sample of expired volume which could be more representative of the overall gas composition, especially in the presence of uneven distribution of ventilation. Further studies aimed at clarifying the final effects of this way of calculating the alveolar volume on the measure of DLCO are needed. DeltaVA/VE is an index that can help assess the severity of inhomogeneity in COPD patients.
在单次呼吸弥散试验中，根据美国胸科学会 - 欧洲呼吸学会（ATS - ERS）指南测量的肺泡容积在通气分布不均时可能被低估。因此，将两组个体（慢性阻塞性肺疾病（COPD）患者和健康个体）中按照ATS - ERS指南计算的肺泡容积与从顺序收集的呼出容积样本中测量的肺泡容积进行了比较。本研究的目的是调查通气分布不均对肺泡容积实际估计值的影响，并评估一些提示通气分布不均存在的指标。
研究了30名健康个体和50名中重度COPD患者。肺泡容积要么根据ATS - ERS指南测量，要么考虑将整个呼出容积细分为五个五分位数来测量。然后得出一个反映通气分布不均匀性的指标（DeltaVA/VE）。
比较两种测量方法时发现了显著差异，并且在健康个体中，按五分位数划分的肺泡容积似乎朝着残气量逐渐增加，在COPD患者中增加得更多。因此，DeltaVA/VE在COPD中出现异常增加。
我们的研究结果表明，在单次呼吸弥散试验期间，肺泡容积应通过收集呼出容积样本进行测量，该样本可能更能代表总体气体成分，尤其是在通气分布不均匀的情况下。需要进一步研究以阐明这种计算肺泡容积的方法对一氧化碳弥散量（DLCO）测量的最终影响。DeltaVA/VE是一个有助于评估COPD患者不均匀程度严重程度的指标。
