Submitted on December 11, 2007
Accepted on July 7, 2008
THE AIRWAY RESPONSE TO DEEP INSPIRATIONS DECREASES WITH COPD SEVERITY AND IS ASSOCIATED WITH AIRWAY DISTENSIBILITY ASSESSED BY COMPUTER TOMOGRAPHY
Nicola Scichilone1*, Alba La Sala1, Maria Bellia2, Katherine Fallano3, Alkis Togias4, Robert H Brown3, Massimo Midiri2, and Vincenzo Bellia1
1 Dipartimento di Medicina, Pneumologia, Fisiologia e Nutrizione Umana, University of Palermo, Palermo, Italy
2 Dipartimento di Biotecnologie e Medicina Legale, University of Palermo, Palermo, Italy
3 Department of Environmental Health Sciences, Johns Hopkins University, Baltimore, Maryland, United States
4 NIAD/NIH, Bethesda, Maryland, United States
* To whom correspondence should be addressed. E-mail: n.scichilone{at}libero.it.
In patients with mild COPD, the effect of deep inspirations (DI) to reverse methacholine-induced bronchoconstriction is largely attenuated. In this study, we tested the hypothesis that the effectiveness of DI is reduced with increasing disease severity and that this is associated with a reduction in the ability of DI to distend the airways. Fifteen subjects (GOLD stage I-II: 7; GOLD stage III-IV: 8) underwent methacholine bronchoprovocation in the absence of DI, followed by DI. The effectiveness of DI was assessed by their ability to improve IVC and FEV1. To evaluate airway distensibility, two sets of HRCT scans (at RV and at TLC) were obtained prior to the challenge. In addition, mean parenchymal density was calculated on the HRCTs. We found a strong correlation between the response to DI and baseline FEV1% predicted (r2=0.70, p<0.0001) or baseline FEV1/FVC (r2=0.57, p=0.001). RV% predicted and FRC% predicted correlated inversely (r2=0.33, p=0.02 and r2=0.32, p=0.03, respectively) and parenchymal density at RV correlated directly (r2=0.30, p=0.03) with the response to DI. Finally, the effect of DI correlated to the change in large airway area from RV to TLC (r2=0.44, p=0.01). We conclude that loss of the effect of DI is strongly associated with COPD severity and speculate that the reduction in the effectiveness of DI is due to the failure to expand the lungs because of the hyperinflated state and/or parenchymal damage that prevents distension of the airways with lung inflation.
