Pascoe Christopher D, Donovan Graham M, Bossé Ynuk, Seow Chun Y, Paré Peter D
Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada; Center for Heart Lung Innovation, St. Paul's Hospital, Vancouver, British Columbia, Canada
Department of Mathematics, University of Auckland, Auckland, New Zealand;
J Appl Physiol (1985). 2014 Dec 15;117(12):1502-13. doi: 10.1152/japplphysiol.00713.2014. Epub 2014 Oct 16.
Deep inspirations (DIs) taken before an inhaled challenge with a spasmogen limit airway responsiveness in nonasthmatic subjects. This phenomenon is called bronchoprotection and is severely impaired in asthmatic subjects. The ability of DIs to prevent a decrease in forced expiratory volume in 1 s (FEV1) was initially attributed to inhibition of airway narrowing. However, DIs taken before methacholine challenge limit airway responsiveness only when a test of lung function requiring a DI is used (FEV1). Therefore, it has been suggested that prior DIs enhance the compliance of the airways or airway smooth muscle (ASM). This would increase the strain the airway wall undergoes during the subsequent DI, which is part of the FEV1 maneuver. To investigate this phenomenon, we used ovine tracheal smooth muscle strips that were subjected to shortening elicited by acetylcholine with or without prior strain mimicking two DIs. The compliance of the shortened strip was then measured in response to a stress mimicking one DI. Our results show that the presence of "DIs" before acetylcholine-induced shortening resulted in 11% greater relengthening in response to the third DI, compared with the prior DIs. This effect, although small, is shown to be potentially important for the reopening of closed airways. The effect of prior DIs was abolished by the adaptation of ASM to either shorter or longer lengths or to a low baseline tone. These results suggest that DIs confer bronchoprotection because they increase the compliance of ASM, which, consequently, promotes greater strain from subsequent DI and fosters the reopening of closed airways.
在使用致痉剂进行吸入激发试验之前进行的深呼吸（DIs）可限制非哮喘受试者的气道反应性。这种现象被称为支气管保护作用，而在哮喘受试者中这种作用严重受损。深呼吸预防1秒用力呼气量（FEV1）下降的能力最初被归因于对气道狭窄的抑制。然而，只有在使用需要深呼吸的肺功能测试（FEV1）时，在乙酰甲胆碱激发试验之前进行的深呼吸才会限制气道反应性。因此，有人提出，预先进行的深呼吸可增强气道或气道平滑肌（ASM）的顺应性。这将增加随后深呼吸过程中气道壁所承受的应变，而这是FEV1操作的一部分。为了研究这一现象，我们使用了羊的气管平滑肌条，使其在有或没有模拟两次深呼吸的预先应变的情况下受到乙酰胆碱引起的缩短。然后测量缩短后的条带对模拟一次深呼吸的应力的顺应性。我们的结果表明，与预先进行的深呼吸相比，在乙酰胆碱诱导缩短之前存在“深呼吸”会导致对第三次深呼吸的反应中再伸长增加11%。这种效应虽然很小，但已被证明对关闭气道的重新开放可能很重要。预先进行的深呼吸的效果会因气道平滑肌适应较短或较长长度或较低的基线张力而消除。这些结果表明，深呼吸具有支气管保护作用，因为它们增加了气道平滑肌的顺应性，从而促进了随后深呼吸产生的更大应变，并促进了关闭气道的重新开放。
