Submitted on January 28, 2009
Revised on June 16, 2009
Accepted on June 16, 2009
MECHANICAL EFFECTS OF OBESITY ON AIRWAY RESPONSIVENESS IN OTHERWISE HEALTHY HUMANS
Roberto Torchio1, Alessandro Gobbi, Carlo Gulotta, Raffaele L. Dellaca2*, Marco Tinivella, Robert E Hyatt, Vito Brusasco3, and Riccardo Giovanni Pellegrino4
1 CARDIOPULMONARY FUNCTION TESTING LAB.
2 Politecnico di Milano University
3 University of Genoa
4 Centro di Fisiopatologia Respiratoria e dello Studio della Dispnea
* To whom correspondence should be addressed. E-mail: raffaele.dellaca{at}polimi.it.
We investigated whether obesity is associated with airway hyperresponsiveness in otherwise healthy humans and, if so, whether this correlates with a restrictive lung function pattern or a decreased number of sighs at rest and/or during walking. Lung function was studied before and after inhaling methacholine in 41 healthy subjects with body mass index ranging from 20 to 56 . Breathing pattern was assessed during a 60-min rest period and a 30-min walk. The dose of methacholine that produced a 50% decrease in the maximum expiratory flow measured in a body plethysmograph (PD50MCh) was inversely correlated with body mass index (r2=0.32, p<0.001) and waist circumference (r2=0.25, p<0.001). Significant correlations with body mass index were also found with the maximum changes in respiratory resistance (r2=0.19, p<0.001) and reactance (r2=0.40, p<0.001) measured at 5 Hz. PD50MCh was also positively correlated with functional residual capacity (r2=0.56, p<0.001) and total lung capacity (r2=0.59, p<0.001) in men, but not in women. Neither PD50MCh nor body mass index correlated with number of sighs, average tidal volume, ventilation, or breathing frequency. In this study airway hyperresponsiveness was significantly associated with obesity in otherwise healthy subjects. In obese men, but not in women, airway hyperresponsiveness was associated with the decreases in lung volumes.
