Deep inspiration avoidance and airway response to methacholine: Influence of body mass index
L Boulet | H Turcotte | G Boulet | B Simard | P Robichaud
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.