The U-shaped relationship between admission peripheral oxygen saturation and all-cause hospital mortality in acute exacerbation of chronic obstructive pulmonary disease: a retrospective analysis using the MIMIC III database.

Abstract

Background: Chronic obstructive pulmonary disease (COPD) and acute exacerbation of chronic obstructive pulmonary disease (AECOPD) pose global challenges, with oxygen saturation (SpO₂) levels crucial in evaluating mortality. This study explored the correlation between admission SpO₂ levels and all-cause hospital mortality in patients with AECOPD, assessing whether SpO₂ can serve as an independent risk factor for predicting in-hospital mortality in these patients.

Methods: This study involved 996 AECOPD patients sourced from the Medical Information Mart for Intensive Care (MIMIC) III database (version 1.3), with 134 fatalities. Patients were categorized into a death group (n=134) and a survival group (n=862). The average admission SpO₂ value was recorded for all 996 AECOPD patients. Subsequently, a generalized additive model (GAM) curve was employed to examine the association between admission SpO₂ levels and all-cause hospital mortality. Following this, Cox regression analysis and survival analysis were conducted to further investigate the link between admission SpO₂ and all-cause hospital mortality.

Results: The GAM curve demonstrated a non-linear, U-shaped relationship between admission SpO₂ and all-cause hospital mortality in AECOPD patients. The nadir of all-cause hospital mortality was associated with an SpO₂ of 89.5%. Notably, an SpO₂ of 89.5% served as the optimal cutoff for predicting all-cause hospital mortality. Cox regression analysis identified SpO₂ as a risk factor for all-cause hospital mortality in AECOPD patients. Patients with SpO₂ ≥89.5% exhibited independently lower death risk compared to those with SpO₂ <89.5% (hazard ratio: 0.52; 95% confidence interval: 0.37-0.74; P<0.001).

Conclusions: Admission SpO₂ level is an independent risk factor for predicting all-cause hospital mortality in AECOPD patients and can serve as a prognostic indicator. A U-shaped relationship was observed, with an admission SpO₂ level of 89.5% associated with the lowest mortality, suggesting an optimal range for improved prognosis.