Deep inspiration avoidance and airway response to methacholine: Influence of body mass index.
OBJECTIVE
To evaluate the effects of deep inspiration avoidance response to methacholine inhalation in 23 nonobese (body mass index between 18 kg/m2 and 30 kg/m2) and 27 obese (body mass index 30 kg/m2 or greater), nonatopic, nonasthmatic normal subjects.


METHODS
Each subject had four methacholine challenges. In tests A and B, the first postmethacholine forced expiratory volume in 1 s (FEV1) was measured at 30 s and 3 min postinhalation, respectively; tests C and D were single-dose tests (using the final dose of test B), with the first postmethacholine FEV1 being obtained at 3 min, without (test C) or with (test D) 20 min of deep inspiration avoidance before inhalation.


RESULTS
The mean provocative concentrations inducing a 20% fall in FEV1 on tests A and B were 80.6 mg/mL and 28.5 mg/mL (P<0.0001) in nonobese subjects, respectively, and 56.3 mg/mL and 21.5 mg/mL (P<0.0001) in obese subjects, respectively. No significant differences were observed in test A or B between control and obese subjects. Mean falls in FEV1 for tests C and D were 20.3% and 40.0% (P=0.0003) in nonobese subjects, respectively, and 18.5% and 23.6% (P>0.05) in obese subjects, respectively.


CONCLUSIONS
As previously observed in patients with asthma, the present study found that nonasthmatic obese subjects had no increase in the fall in FEV1 after deep inspiration avoidance before methacholine, whereas nonobese subjects did, suggesting that obesity alters airway function. No significant changes were found between groups for symptom perception.
Boulet
Louis-Philippe
LP
Unité de recherche en pneumologie, Institut de cardiologie et de pneumologie de l'Université Laval, Hôpital Laval, Québec City. lpboulet@med.ulaval.ca
Turcotte
Hélène
H
Boulet
Geneviève
G
Simard
Barbara
B
Robichaud
Patricia
P
D000328:Adult; D015992:Body Mass Index; D001985:Bronchial Provocation Tests; D016085:Bronchoconstrictor Agents / Q000008:administration & dosage*; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D001239:Inhalation; D008297:Male; D016210:Methacholine Chloride / Q000008:administration & dosage*; D008875:Middle Aged; D009765:Obesity / Q000503:physiopathology*
D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride