机械通气限度的评估

本研究的目的是通过在最大运动量期间,用三种方法对正常者(n=13)及轻度(n=11)、中度(n=5)、重度(n=6)慢性空气流量受限者(CAL,FEV1/FVC,39%-68%)的机械通气限度进行评估。为了评估机械通气限度,将最大运动量时的通气量(VEmax)与最大的自主换气量(MVV)即计算的运动通气最大值(VEmaxcal)]进行比较。此比值与FEV1×37.5的和就是机械通气限度。所有受试者均用梯度循环测力法进行测定。肺功能和评价方法之间存在着显著的相关性(P<0.001)。当与正常受试者的肺功能相比,只有重度CAL的机械通气限度即VEmax/MVV(%)]是显著增高的(83%VS62%,P<0.05);与正常肺功能受试者相比,所有CAL受试者的VEmax/VEmaxcal(%)均有所增高,VEmax/FEV1×37.5(%)在轻重度CAL受试者中也有所增高(P<0.05)。在轻重度CAL受试者中,机械通气度VEmax/MVV(%)比VEmax/VEmaxcal(%)(P<0.05)以及VEmax/FEV1×37.5(%)(P<0.001)有所降低。这些数据表明:在评估机械通气限度时,用VEmax/VEmax和VEmax/FEV1×37.5进行计算比用VEmax/MVV计算所得值大,这种趋势在轻中度CAL受试者中更为明显。据此得出的结论是:机械通气限度的评估可以受到肺功能和VEmax变异度两方面的影响。

Estimation of Mechanical Ventilatory Limitation

The purpose of this study was to estimate mechanical ventilatory limitation during maximal exercise with the use of three methods for subjects with normal lung function (N=13) and subjects with mild (N=11),moderate (N=5), or severe (N=6) chronic airflow limitation (CAL, FEV1/FVC, 39% to 68%). To estimate mechanical ventilatory limitation, ventilation during maximal exercise (VEmax) was compared with the maximal voluntary ventilation (MVV), a calculated exercise ventilatory maximum (VEmaxCal), and the product of FEV1 times 37.5 (FEV1×37.5). All subjects performed graded cycle ergometry to volitional termination. There was a significant interaction between lung function and estimate method (P ＜ 0.001). The mechanical ventilatory limitation indicated by VEmax/MVV (%) was elevated in only the subjects with severe CAL when compared with the subjects with normal lung function (83 vs 62%, P ＜ 0.05). Vmax/VmaxCal (%) was greater in all GAL subjects and VEmax/FEV1×37.5 (%) was greater in the subjects with mild and severe CAL (P＜0.05) when compared with the subjects with normal lung function. In subjects with mild and severe CAL, the mechanical ventilatory limitation indicated by VEmax/MVV was lower than indicated by VEmax/VEmax (P ＜ 0.05) or VEmax/FEV1×37.5 (P ＜0.01). These data indicate that mechanical ventilatory limitation is greater when estimated by VEmax/VEmaxCal and VEmax/FEV1×37.5 than by the Vmax/MVV, especially for subjects with mild or moderate CAL. It is concluded that the estimation of mechanical ventilatory limitation is influenced by both the level of pulmonary function and the variable with which VEmax is compared.