Yan S, Bates J H
Meakins-Christie Laboratories, Department of Biomedical Engineering, McGill University, Royal Victoria Hospital, Montreal, Quebec, Canada H2X 2P4.
J Appl Physiol (1985). 1999 Mar;86(3):874-80. doi: 10.1152/jappl.1999.86.3.874.
To investiage the effect of inspiratory threshold load (ITL) on breathing, all previous work studied loads that were much greater than would be encountered under pathophysiological conditions. We hypothesized that mild ITL from 2.5 to 20 cmH2O is sufficient to modify control and sensation of breathing. The study was performed in healthy subjects. The results demonstrated that with mild ITL 1) inspiratory difficulty sensation could be perceived at an ITL of 2.5 cmH2O; 2) tidal volume increased without change in breathing frequency, resulting in hyperpnea; and 3) although additional time was required for inspiratory pressure to attain the threshold before inspiratory flow was initiated, the total inspiratory muscle contraction time remained constant. This resulted in shortening of the available time for inspiratory flow, so that the tidal volume was maintained or increased by significant increase in mean inspiratory flow. On the basis of computer simulation, we conclude that the mild ITL is sufficient to increase breathing sensation and alter breathing control, presumably aiming at maintaining a certain level of ventilation but minimizing the energy consumption of the inspiratory muscles.
为研究吸气阈值负荷（ITL）对呼吸的影响，以往所有研究的负荷都远大于病理生理条件下可能遇到的负荷。我们假设2.5至20 cmH₂O的轻度ITL足以改变呼吸控制和感觉。该研究在健康受试者中进行。结果表明，在轻度ITL情况下：1）在ITL为2.5 cmH₂O时可感知吸气困难；2）潮气量增加而呼吸频率不变，导致通气过度；3）尽管在启动吸气气流之前吸气压力达到阈值需要额外时间，但吸气肌总收缩时间保持不变。这导致吸气气流可用时间缩短，从而通过显著增加平均吸气气流来维持或增加潮气量。基于计算机模拟，我们得出结论，轻度ITL足以增加呼吸感觉并改变呼吸控制，大概目的是维持一定水平的通气但使吸气肌能量消耗最小化。
