An overnight increase in CO2 predicts mortality in sleep disordered breathing

Area of Science:

• Cardiology
• Pulmonology
• Sleep Medicine

Background:

• Sleep disordered breathing (SDB) is common and often overlooked.
• SDB is increasingly recognized as an independent predictor of mortality.
• The role of hypercapnia (elevated CO2) in SDB mortality is not well understood.

Purpose of the Study:

• To investigate the independent role of hypercapnia in predicting mortality among SDB patients.
• To assess mortality predictors in SDB, considering airways disease and obesity.

Main Methods:

• Retrospective analysis of 396 consecutive SDB patients.
• Cox proportional hazards regression used for univariate and multivariate analyses.
• Adjusted for confounders including age, gender, co-morbidity, and airways disease.

Main Results:

• A cohort of 322 patients (mean age 55, BMI 30.6) was followed for up to 16.7 years.
• 25% mortality observed after 10 years.
• Increased PaCO2 (ΔPaCO2 ≥ 7 mmHg) and evening hypoxemia (PaO2 < 65 mmHg) independently predicted mortality.

Conclusions:

• Overnight CO2 increase and evening hypoxemia are independent mortality predictors in SDB.
• Low minimum SpO2 can identify patients who would benefit from arterial blood gas analysis.