Bogaard J M, Overbeek S E, Verbraak A F, Vons C, Folgering H T, van der Mark T W, Roos C M, Sterk P J
Dept of Pulmonary Diseases, University Hospital Rotterdam-Dijkzigt, The Netherlands.
Eur Respir J. 1995 Sep;8(9):1525-31.
The prevalence of abnormalities in lung elasticity in patients with asthma or chronic obstructive pulmonary disease (COPD) is still unclear. This might be due to uncertainties concerning the method of analysis of quasistatic deflation lung pressure-volume curves. Pressure-volume curves were obtained in 99 patients with moderately severe asthma or COPD. These patients were a subgroup from a Dutch multicentre trial; the entire group was selected on the basis of a moderately lowered % predicted forced expiratory volume in one second (FEV1), and a provocative concentration of histamine producing a 20% decrease in FEV1 (PC20) < 8 mg.mL-1 obtained with the 2 min tidal breathing technique. The curves were fitted with an exponential (E) model and an exponential model which took the linear appearance in the mid vital capacity range into account (linear-exponential (LE)). The linear-exponential model showed a markedly better fit ability, yielding additional parameters, such as the compliance at functional residual capacity (FRC) level as slope of the linear part (b), and the volume at which the linear part changed into the exponential part of the curve (transition volume (Vtr)). Vtr (mean value Vtr/total lung capacity (TLC) = 0.79 (SD 0.07)) showed a close positive linear correlation with obstruction and hyperinflation variables, which might be due to airway closure, already starting at elevated lung volumes. The exponential shape factor K was closely correlated with b and mean values (K = 1.32 (SD 0.05) kPa-1; b = 2.96 (SD 1.16) L,kPa-1) and the relationship with age was comparable with data reported in healthy individuals. The shape factor of the linear-exponential fit showed no correlation with any elasticity related variable. Neither the elastic recoil at 90% TLC, as obtained from the linear-exponential fit, nor its relationship with age were significantly different from healthy individuals. We conclude that, for a more accurate description of the lung pressure-volume curve, a linear-exponential fit is preferable to an exponential model. However, the physiological relevance of the shape parameter (KLE) is still unclear. These results indicate that patients with moderately severe asthma or COPD had, on average, no appreciable loss of elastic lung recoil as compared with healthy individuals.
哮喘或慢性阻塞性肺疾病（COPD）患者肺弹性异常的患病率仍不明确。这可能是由于准静态放气肺压力-容积曲线分析方法存在不确定性。对99例中度重度哮喘或COPD患者进行了压力-容积曲线测定。这些患者是一项荷兰多中心试验的一个亚组；整个组是根据一秒用力呼气容积（FEV1）预测值适度降低，以及采用2分钟潮气呼吸技术获得的使FEV1降低20%的组胺激发浓度（PC20）<8mg/mL-1来选择的。这些曲线用指数（E）模型和一个考虑了肺活量中段线性形态的指数模型（线性-指数（LE））进行拟合。线性-指数模型显示出明显更好的拟合能力，产生了额外的参数，如功能残气量（FRC）水平下的顺应性作为线性部分的斜率（b），以及线性部分转变为曲线指数部分的体积（转变体积（Vtr））。Vtr（Vtr/肺总量（TLC）的平均值=0.79（标准差0.07））与阻塞和肺过度充气变量呈密切正线性相关，这可能是由于气道闭合，在肺容积升高时就已开始。指数形状因子K与b密切相关，其平均值（K = 1.32（标准差0.05）kPa-1；b = 2.96（标准差1.16）L/kPa-1），且与年龄的关系与健康个体报道的数据相当。线性-指数拟合的形状因子与任何弹性相关变量均无相关性。从线性-指数拟合获得的90%TLC时的弹性回缩及其与年龄的关系与健康个体相比均无显著差异。我们得出结论，为了更准确地描述肺压力-容积曲线，线性-指数拟合比指数模型更可取。然而，形状参数（KLE）的生理相关性仍不明确。这些结果表明，与健康个体相比，中度重度哮喘或COPD患者平均没有明显的肺弹性回缩丧失。
