Beyond mean and maximum CO₂: introducing hypercapnic burden as a marker of sleep-related hypoventilation
Authors' conclusion
This underscores the heterogeneity of nocturnal hypoventilation in OHS and the potential value of more nuanced markers in individual patients, as daytime hypercapnia might not be present yet, and maxCO2 and meanCO2 do not account for low or intermittent but cumulative CO2 elevations. Identifying such outliers is clinically important, as these patients may be at heightened risk of progression or may respond differently to interventions such as non-invasive ventilation.
Study context
- Population
- Patients meeting obesity hypoventilation syndrome (OHS) criteria who underwent polysomnography with transcutaneous capnography
- Participants
- 31 patients
- Outcome
- Correlation of hypercapnic burden (area above transcutaneous CO₂ thresholds of 45 mmHg [thresh45] and 50 mmHg [thresh50]) with classic nocturnal hypercapnia metrics
Methodological detailssingle-center, retrospective
- Single-center
- Retrospective
Main finding
As reported in the abstract
maxCO₂ vs thresh45, Spearman's rho
0.906
p < 0.000001
maxCO₂ vs thresh50, Spearman's rho
0.953
p < 0.000001
meanCO₂ vs thresh45, Spearman's rho
0.918
p < 0.000001
meanCO₂ vs thresh50, Spearman's rho
0.937
p < 0.000001
Observational data: associations, not effects.
Further findings
Correlation of these metrics with % predicted forced vital capacity (FVC%)
- Significant negative correlations with FVC% (respectively, as printed), Spearman's rho
- −0.49, p = 0.01 and −0.45, p = 0.02
- Did not outperform classic metrics; several outliers showed better alignment of FVC% with threshold-based indices than with meanCO₂
Original publication
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