Simulated obesity-related changes in lung volume increases airway responsiveness in lean, nonasthmatic subjects.
OBJECTIVE
To determine if obesity-related changes in lung volume might contribute to airway reactivity, we investigated the effects of simulated mild obesity-related lung volume reductions on airway responsiveness in lean, nonasthmatic subjects.


METHODS
We simulated the lung volume reductions of class 1 obesity in eight lean, nonasthmatic subjects by externally mass loading the chest wall and abdomen, and shifting blood volume into the lung with lower limb compression (LLC). Airway responsiveness was assessed by measuring FEV(1) before and after methacholine challenge tests (1, 2.5, 5, 10, and 25 mg/mL) with the following: (1) no intervention (control); (2) external chest loading (CL); (3) LLC; and (4) CL and LLC (COMB) on separate days. Lung function was measured before and after CL, LLC, and COMB were applied.


RESULTS
The application of CL, LLC, and COMB decreased expiratory reserve volume, functional residual capacity, and total lung capacity compared with baseline. FVC and FEV(1) decreased significantly with CL and COMB, while FEV(1)/FVC did not change compared to baseline. The maximal response to the methacholine challenge increased with CL, LLC, and COMB, with a mean maximal fall of FEV(1) of 9%, 11%, and 18%, respectively, compared to a 6% fall with control.


CONCLUSIONS
We conclude that decreases in lung volume increase airway responsiveness and may account for the increased propensity for increased airway responsiveness in the obese.
Wang
Li-Ying
LY
School and Graduate Institute of Physical Therapy, College of Medicine, National Taiwan University, Taipei 100, Taiwan, ROC. liying@ntu.edu.tw
Cerny
Frank J
FJ
Kufel
Thomas J
TJ
Grant
Brydon J B
BJ
D000280:Administration, Inhalation; D000328:Adult; D001249:Asthma / Q000139:chemically induced / Q000503:physiopathology; D016535:Bronchial Hyperreactivity / Q000209:etiology / Q000503:physiopathology; D001985:Bronchial Provocation Tests / Q000379:methods; D016085:Bronchoconstrictor Agents / Q000008:administration & dosage / Q000494:pharmacology; D005105:Expiratory Reserve Volume / Q000187:drug effects / Q000502:physiology; D005541:Forced Expiratory Volume / Q000187:drug effects / Q000502:physiology; D005652:Functional Residual Capacity / Q000187:drug effects / Q000502:physiology; D006801:Humans; D008168:Lung / Q000473:pathology / Q000502:physiology* / Q000503:physiopathology*; D008176:Lung Volume Measurements; D016210:Methacholine Chloride / Q000008:administration & dosage / Q000494:pharmacology; D008954:Models, Biological; D009765:Obesity / Q000150:complications* / Q000473:pathology / Q000503:physiopathology*; D010812:Physical Stimulation / Q000379:methods; D012123:Pulmonary Ventilation / Q000187:drug effects / Q000502:physiology*; D011897:Random Allocation; D012129:Respiratory Function Tests
D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride