Sturdy Gavin A, Hillman David R, Green Daniel J, Jenkins Sue C, Cecins Nola M, Eastwood Peter R
Department of Pulmonary Physiology, Sir Charles Gairdner Hospital, Nedlands, WA 6009, Australia.
Respir Med. 2004 Jan;98(1):1-8. doi: 10.1016/j.rmed.2003.07.005.
Progressive threshold loading (PTL) is a common test of respiratory muscle endurance. Healthy naive subjects improve endurance with successive exposures to PTL by altering their breathing responses, thus necessitating a familiarization period before reproducible measures can be obtained. This study sought to determine whether a similar "learning effect" is evident in patients with COPD, and what the mechanism of any such effect may be.
Ten subjects with COPD (FEV1 34+/-13% predicted) underwent PTL on four occasions (>24 h apart). During PTL measurements were obtained of breathing pattern and maximum threshold pressure (Pthmax) achieved. Maximum inspiratory pressure (PImax) was measured on each occasion.
Over the four tests PImax improved by 21+/-16% (SD) (P<0.05) and Pthmax by 32+/-21% (P<0.05) with a plateau in these measures achieved by test three. Pthmax/PImax was unchanged, being 61+/-11% at test one and 67+/-12% at test four. In contrast to healthy subjects, PTL was not associated with increased expiratory time or decreased end-expiratory lung volume.
In contrast to PImax and Pthmax, which changed with successive tests, a single measure of the ratio Pthmax/PImax may present a useful guide to the endurance capacity of the respiratory muscles in patients with COPD.
渐进性阈值负荷（PTL）是呼吸肌耐力的常见测试。健康的未接触过该测试的受试者通过改变呼吸反应，在连续接触PTL时可提高耐力，因此在获得可重复测量结果之前需要一个熟悉期。本研究旨在确定慢性阻塞性肺疾病（COPD）患者中是否存在类似的“学习效应”，以及任何此类效应的机制可能是什么。
10名COPD患者（预测FEV1为34±13%）分四次进行PTL测试（每次间隔>24小时）。在PTL测试期间，获取呼吸模式和达到的最大阈值压力（Pthmax）的测量值。每次测试均测量最大吸气压力（PImax）。
在四次测试中，PImax提高了21±16%（标准差）（P<0.05），Pthmax提高了32±21%（P<0.05），在第三次测试时这些测量值达到平台期。Pthmax/PImax未改变，第一次测试时为61±11%，第四次测试时为67±12%。与健康受试者不同，PTL与呼气时间增加或呼气末肺容积减少无关。
与连续测试中发生变化的PImax和Pthmax不同，单次测量Pthmax/PImax比值可能为COPD患者呼吸肌的耐力能力提供有用的指导。
