Cala S J, Wilcox P, Edyvean J, Rynn M, Engel L A
Thoracic Medicine Unit, Westmead Hospital, Sydney, New South Wales, Australia.
J Appl Physiol (1985). 1991 May;70(5):1983-90. doi: 10.1152/jappl.1991.70.5.1983.
We measured the O2 cost of breathing (VO2resp) against external inspiratory elastic (E) and resistive loads (R) when end-expiratory lung volume, tidal volume, breathing frequency, work rate, and pressure-time product were matched in each of six pairs of runs in six subjects. During E, peak inspiratory mouth pressure was 65.7 +/- 1.8% (SD) of the maximum at functional residual capacity. However, during resistive runs, peak inspiratory mouth pressure was 41.1 +/- 2.8% of the maximum at functional residual capacity. In 36 paired runs, where both work rate and pressure-time product were within 10%, VO2resp for E was less than for R (81 and 96 ml/min, respectively; P less than 0.01). During loaded and unloaded breathing with the same tidal volume, we measured the changes in anteroposterior diameter of the lower rib cage in five subjects. In four subjects we also recorded the electromyograms of several fixator and stabilizing muscles. During E and R, the change in anteroposterior diameter of the lower rib cage was -116 +/- 5 and -45 +/- 4% (SE), respectively, of the unloaded value (P less than 0.01), indicating greater deformation during E. Although the peak electromyographic activity was 72 +/- 16% greater during E (P less than 0.01), there was no difference between the loads for area under the electromyogram time curve (P greater than 0.05). However, the time to 50% peak activity was less during R (P less than 0.02). We conclude that, even when work rate and pressure-time product are matched, VO2resp during R is greater than that during E. This difference may be due to preferential recruitment of faster and less efficient muscle fibers.
在六名受试者的六组配对实验中，当呼气末肺容积、潮气量、呼吸频率、工作负荷以及压力-时间乘积相匹配时，我们测量了呼吸的氧气消耗（VO2resp）与外部吸气弹性负荷（E）和阻力负荷（R）之间的关系。在弹性负荷实验中，吸气末口腔峰值压力为功能残气量时最大值的65.7±1.8%（标准差）。然而，在阻力负荷实验中，吸气末口腔峰值压力为功能残气量时最大值的41.1±2.8%。在36组配对实验中，当工作负荷和压力-时间乘积均在10%以内时，弹性负荷实验中的VO2resp低于阻力负荷实验中的VO2resp（分别为81和96毫升/分钟；P<0.01）。在潮气量相同的有负荷和无负荷呼吸过程中，我们测量了五名受试者下胸廓前后径的变化。在四名受试者中，我们还记录了几块固定肌和稳定肌的肌电图。在弹性负荷和阻力负荷实验中，下胸廓前后径的变化分别为无负荷值的-116±5%和-45±4%（标准误）（P<0.01），表明弹性负荷实验中的变形更大。尽管弹性负荷实验中的肌电图峰值活动比阻力负荷实验中的高72±16%（P<0.01），但肌电图时间曲线下面积在两种负荷之间没有差异（P>0.05）。然而，阻力负荷实验中达到峰值活动50%的时间更短（P<0.02）。我们得出结论，即使工作负荷和压力-时间乘积相匹配，阻力负荷实验中的VO2resp也大于弹性负荷实验中的VO2resp。这种差异可能是由于优先募集了速度更快但效率更低的肌纤维。
