Exaggerated respiratory chemosensitivity and association with SaO2 level at 3568Â m in obesity

To investigate whether obesity is associated with alterations in respiratory chemosensitivity, we compared the ventilatory response to hypoxia (HVR) and hypercapnia (HCVR) in 9 obese men (BMI: 37.0 ± 4.3 kg m−2) and 10 lean men (BMI: 25.8 ± 4.8 kg m−2). HVR (ΔV˙E, L min−1 per ΔSaO2, %) was measured by a progressive isocapnic hypoxia technique, and HCVR (ΔV˙E/ΔPETCO2, L min−1 Torr−1) was measured by a progressive hypercapnic method. HCVR, was greater (p < 0.001) in the obese men (2.68 ± 0.78) than in the lean men (1.4 ± 0.45) as was HVR (p < 0.05) (1.26 ± 0.65 versus 0.71 ± 0.43, respectively). The difference (ΔSaO2%, 4.30 ± 3.69 and 10.54 ± 3.45 in the lean and obese men, respectively, p < 0.01) between daytime (86 ± 1 and 86 ± 1%) and nighttime SaO2 (81 ± 3 and 76 ± 4%) at a simulated altitude of 3658 m was significantly (p < 0.05) correlated with both HVR (r = 0.51) and HCVR (r = 0.48). These results suggest that chemosensitivity in mildly obese men is increased, not blunted. Furthermore, otherwise healthy, obese individuals have the potential for significant desaturation during sleep at high altitude possibly due to exaggerated sleep-disordered breathing.