Ventilatory response to exercise is preserved in patients with obesity hypoventilation syndrome
Journal of Clinical Sleep Medicine, 2020
STUDY OBJECTIVES Blunted ventilatory responses to hypoxia and hypercapnia during resting conditio... more STUDY OBJECTIVES Blunted ventilatory responses to hypoxia and hypercapnia during resting conditions are common findings in patients with obesity hypoventilation syndrome (OHS). Exercise increases the work and oxygen cost of breathing and produces excessive carbon dioxide (CO₂). The aim of the present investigation was to study ventilatory responses to incremental exercise in patients with OHS. METHODS Sixty-eight obese adults with OHS (n=15), eucapnic OSA (n= 26), or simple obesity (n = 27) participated in an incremental exercise test on a cycle ergometer and an in-lab sleep study. RESULTS The peak oxygen uptake (peak VO₂) and peak pulse oxygen (peak O₂ pulse) was decreased in patients with OHS compared to patients with either OSA or simple obesity. The ventilatory response to exertional metabolic demand (nadir VE/VCO₂, ∆VE/∆VCO₂ slope and VE/VCO₂ at peak exercise) did not significantly differ among the three groups. Minute ventilation (VE), tidal volume (VT), respiratory frequency (fR), VT/fR, and inspiratory time/total time ratio (Ti/Ttot) at a given work rate were comparable among the three groups. Among the whole cohort, AHI was not independently associated with peak VO₂, and no association was found between the ∆VE/∆VCO₂ slope and resting arterial partial pressure of CO₂ (PaCO₂). CONCLUSIONS The ventilatory response to incremental exercise is preserved in patients with OHS compared to patients with OSA and simple obesity who were matched for age and body mass index (BMI). This result highlights the complexity of the respiratory control system during exercise for patients with OHS, which may be uncoupled with the ventilatory response during sleep and resting conditions.
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