Arterial blood gas analysis as a predictor of sleep apnea severity in obese patients - preliminary findings from a cross-sectional study

Background: Obesity is the most important risk factor for the development of sleep-related breathing disorders (SRBD). While polysomnography (PSG) calculates the apnea–hypopnea index (AHI) which defines disease severity, arterial blood gas (ABG) analysis may provide simple physiological markers reflecting ventilatory impairment and risk of hypercapnic respiratory failure. Aim: To investigate associations between ABG parameters and AHI in obese patients with suspected SRBD. Methods: PSG and ABG analysis was done in 62 obese adults. Correlations between AHI and ABG parameters (pH, PaCO₂, PaO₂, cHCO₃⁻ and SBE) were assessed. Results: The cohort included 62 patients (48 men, 14 women), mean age 48.8±8.2 years, body mass index (BMI) 36.5±6.3 kg/m². AHI correlated positively with PaCO₂ (r = 0.339, p = 0.007) and cHCO₃⁻ (r = 0.258, p = 0.043), and was inversely associated with PaO₂ (r = –0.321, p = 0.011). SBE and pH showed no significant correlation. When controlling for BMI and sex, these associations attenuated and were no longer statistically significant, while BMI and male sex remained independently associated with higher AHI. Conclusion: In this obese cohort, ABG markers of hypercapnia (PaCO₂) and metabolic compensation (cHCO₃⁻) correlate with higher AHI, while PaO₂ correlates inversely. However, when controlling for sex and BMI in these patients, significance was weaker, with obesity and male sex being independent predictors of apnea severity. Even though these associations weakened after adjustment, ABG remains clinically useful for recognizing obese patients at risk of hypercapnic respiratory failure, who may warrant closer monitoring.