Figure 2.

(A) Absolute change of muscle sympathetic nerve activity (MSNA) and (B) oxygen saturation (O₂ saturation) during isocapnic hypoxia and (C) absolute change of MSNA and (D) carbon dioxide exhaled (End-tidal CO₂) during hyperoxic hypercapnia in patients with metabolic syndrome plus obstructive sleep apnea (MetS + OSA), patients with metabolic syndrome without obstructive sleep apnea (MetS – OSA) and normal control subjects. Note that, either during isocapnic hypoxia or during hyperoxic hypercapnia, MetS + OSA group had higher MSNA responses than control subjects. In addition, during isocapnic hypoxia MetS + OSA patients have higher MSNA responses compared with MetS – OSA patients. *P < 0.05 versus control; ^†P < 0.05 versus MetS – OSA.