Predictors of nocturnal hypoxemia in stable COPD patients

Background: COPD is a heterogeneous disease with multiple variant forms. As lung function declines and the disease progresses, the risk of alveolar hypoventilation with subsequent nocturnal hypoxemia increases. It is possible that nocturnal hypoxemia with tissue hypoxia plays a key role in the evolution of comorbid extrapulmonary disease. The aim of the present study was to identify predictors of nocturnal hypoxemia in stable COPD patients.

Materials and methods: A cross-sectional observational study included 106 stable COPD patients managed at a respiratory medical center (RMC) between 2019 and 2024 who completed ambulatory computerized somnography, pulmonary function testing, questionnaire and laboratory screening. Nocturnal hypoxemia (NH) was defined according to a time to saturation under 90% (T90) index >10%. Based on the absence/presence of NH, patients were classified into groups of patients with NH (NH+) and without NH (NH-). Predictors affecting nocturnal hypoxemia were identified using multivariate analysis and logistic regression models.

Results: There was a statistically significant effect of age (OR=1.06; 95% CI: [1.02–1.12]; p=0.011), COPD Assessment Test (CAT) score (OR=1.48; 95% CI: [1.10–2.00]; p=0.009), FEV1 (% predicted) (OR=0.96; 95% CI: [0.93–0.99]; p=0.015), high-density lipoprotein (HDL-C) levels (OR=1.02; 95% CI: [1.00–1.04]; p=0.034) on nocturnal hypoxemia. Multivariate regression analysis detected a statistically significant impact on nocturnal hypoxemia of such predictors as: 1) FEV1<50% (% predicted) (OR=3.46; 95% CI: [1.15–10.46]; p=0.028), increasing the risk of NH in 3.46 times; 2) insulin resistance index (HOMA-IR) >3 (OR=3.20; 95% CI: [1.09–9.35]; p=0.034), increasing the risk of NH in 3.2 times.

Conclusions: Significant predictors of nocturnal hypoxemia in stable COPD patients may be such parameters as: decrease in FEV1<50% and change in HOMA-IR index >3, increasing the risks of nocturnal hypoxemia by 3.46 and 3.2 times, respectively. This tendency should be taken into consideration in therapy of stable COPD patients.