Fig. 1

A HCO₃⁻ concentration is positively correlated with AHI (r = 0.537, P < 0.001); B HCO₃⁻ concentration is negatively correlated with LSaO₂ (r =  − 0.251, P = 0.004); C HCO₃⁻ concentration is negatively correlated with MSaO₂ (r =  − 0.394, P < 0.001)