Role of hyperinflation vs. deflation on dyspnoea in severely to extremely obese subjects

To test the hypothesis that obese individuals may either hyperinflate or deflate the lung when exercising. In both cases breathlessness is an inescapable consequence. Ventilatory variables, end-expiratory lung volume and end-inspiratory lung volume, and dyspnoea score (Borg scale) were studied in 20...

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Published in:Acta Physiologica 2008-08, Vol.193 (4), p.393-402
Main Authors: Romagnoli, I, Laveneziana, P, Clini, E.M, Palange, P, Valli, G, de Blasio, F, Gigliotti, F, Scano, G
Format: Article
Language:English
Subjects:
Adult
Biological and medical sciences
Carbon Dioxide - blood
Dyspnea - etiology
Dyspnea - physiopathology
Exercise
exercise capacity
Exercise Test
expiratory flow limitation
Female
Forced Expiratory Volume
Fundamental and applied biological sciences. Psychology
Humans
hyperinflation
leg discomfort
Male
Middle Aged
Obesity - complications
Obesity - physiopathology
Obesity, Morbid - complications
Obesity, Morbid - physiopathology
operational lung volumes
Oxygen - blood
Partial Pressure
Pulmonary Ventilation
Total Lung Capacity
ventilation
Vertebrates: anatomy and physiology, studies on body, several organs or systems
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Summary:To test the hypothesis that obese individuals may either hyperinflate or deflate the lung when exercising. In both cases breathlessness is an inescapable consequence. Ventilatory variables, end-expiratory lung volume and end-inspiratory lung volume, and dyspnoea score (Borg scale) were studied in 20 class II-III obese subjects and 14 healthy controls during incremental symptom-limited cycle exercise. Ventilation increased with increasing work rate, in obese and in control subjects; most obese subjects had to increase end-expiratory lung volume to escape from flow limitation; in contrast, like controls, a few subjects deflated the lung on heavy-to-peak exercise. Dyspnoea was equal in degree at anaerobic threshold and peak exercise in obese as in control subjects, and in obese who hyperinflated as in those who deflated the lung. In particular, end-expiratory lung volume at baseline (r = -0.84, P = 0.04) was negatively correlated with changes in Borg score in obese who did not hyperinflate: the lower the former the higher the latter. On the other hand, tidal volume (r = 0.54, P = 0.045) and decrease in inspiratory reserve volume (r = 0.59, P = 0.028) were positively correlated with the Borg score in obese subjects who hyperinflated. No other independent variable correlated with the Borg score. We conclude that not all obese subjects had to increase end-expiratory lung volume on heavy-to-peak exercise. Changes in dyspnoea for unit changes in ventilation were similar in obese who did hyperinflate as well as in those who did not, suggesting that the increase in respiratory neural drive, associated with an increase in ventilation, is an important source of dyspnoea in obese as well as in control subjects.
ISSN:1748-1708
1748-1716
DOI:10.1111/j.1748-1716.2008.01852.x