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Effects of chest wall strapping on mechanical response to methacholine in humans

2006; American Physiological Society; Volume: 101; Issue: 2 Linguagem: Inglês

10.1152/japplphysiol.00379.2005

8750-7587

Roberto Torchio, Carlo Gulotta, Claudio Ciacco, Alberto Perboni, Marco Guglielmo, Flavio Crosa, Mario Zerbini, Vito Brusasco, Robert E. Hyatt, Riccardo Pellegrino,

Respiratory Support and Mechanisms

We examined the effects of chest wall strapping (CWS) on the response to inhaled methacholine (MCh) and the effects of deep inspiration (DI). Eight subjects were studied on 1 day with MCh inhaled without CWS (CTRL), 1 day with MCh inhaled during CWS (CWS on/on ), and 1 day with MCh inhaled during temporary removal of CWS (CWS off/on ). On the CWS on/on day, MCh caused greater increases in pulmonary resistance, upstream resistance, dynamic elastance, residual volume, and greater decreases in maximal expiratory flow than on the CTRL day. On the CWS off/on day, the changes in these parameters with MCh were not different from the CTRL day. Six of the subjects were again studied using the same protocol on CTRL and CWS on/on days, except that, on a third day, MCh was given after applying the CWS, but the measurements before and after the inhalation were made without CWS (CWS on/off ). The latter sequence was associated with more severe airflow obstruction than during CTRL, but less than with CWS on/on . The bronchodilator effects of a DI were blunted when CWS was applied during measurements (CWS on/on and CWS off/on ) but not after it was removed (CWS on/off ). We conclude that CWS is capable of increasing airway responsiveness only when it is applied during the inhalation of the constrictor agent. We speculate that breathing at low lung volumes induced by CWS enhances airway narrowing because the airway smooth muscle is adapted at a length at which the contractile apparatus is able to generate a force greater than normal.