INCREASED AIRWAY CLOSURE IS A DETERMINANT OF AIRWAY HYPERRESPONSIVENESS

¹ Woolcock Institute of Medical Research, Camperdown, NSW, Australia; Cooperative Research Centre for Asthma, Camperdown, NSW, Australia; and University of Sydney, Sydney, Australia
² Woolcock Institute of Medical Research, Camperdown, NSW, Australia; Cooperative Research Centre for Asthma, Camperdown, NSW, Australia; University of Sydney, Sydney, Australia; and Dept Respiratory Medicine, Royal North Shore Hospital, St Leonards, NSW, Australia

^* To whom correspondence should be addressed. E-mail: dcha7069{at}woolcock.org.au.

	Abstract

To investigate whether increased airway closure is a component of airway hyperresponsiveness (AHR), airway closure was compared during induced bronchoconstriction in 62 asthmatic, 41 non-asthmatic non-obese (control) and 20 non-asthmatic obese (obese) subjects.

Airway closure and airway narrowing were measured by spirometry as the %FVC and (FEV₁/FVC), or forced expiratory ratio (FER). Multiple regression analyses were used to assess the determinants of AHR, assessed by the dose response slope (DRS).

DRS was increased in asthmatics compared to controls (P<0.001), but did not differ between obese and controls. The spirometric predictors of logDRS were baseline FER, FER, BMI and %FVC (R²_adj=0.36, p<0.0001). There was a negative relationship between BMI and logDRS in the regression, suggesting a protective effect.

These findings suggest that the extent of airway closure during induced bronchoconstriction is a determinant of AHR, independent of the level of airway narrowing. However, after adjusting for airway closure, obesity appears to protect against AHR.

This article has been cited by other articles:

				D. G. Chapman, N. Berend, G. G. King, B. E. McParland, and C. M. Salome Deep inspirations protect against airway closure in nonasthmatic subjects J Appl Physiol, August 1, 2009; 107(2): 564 - 569. [Abstract] [Full Text] [PDF]

				M. Baroffio, G. Barisione, E. Crimi, and V. Brusasco Noninflammatory mechanisms of airway hyper-responsiveness in bronchial asthma: an overview Therapeutic Advances in Respiratory Disease, August 1, 2009; 3(4): 163 - 174. [Abstract] [PDF]