Prognostic Value of Oxygenated Hemoglobin Assessed during Acute Exacerbations of Chronic Pulmonary Disease

Abstract

Background: Oxygenated hemoglobin(OxyHem) is a simple-to-measure marker of oxygen content capable of predicting all-cause mortality in stable chronic obstructive pulmonary disease (COPD). Objectives: We aimed to analyze its predictive value during acute exacerbations of COPD (AECOPD). Methods: In this retrospective study, data from 227 patients discharged after severe AECOPD at RoMed Clinical Center Rosenheim, Germany, between January 2012 and March 2018, was analyzed. OxyHem (hemoglobin concentration [Hb] × fractional SpO₂, g/dL) was calculated from oxygen saturation measured by pulse oximetry and hemoglobin assessed within 24 h after admission. The follow-up (1.7 ± 1.5 years) covered all-cause mortality, including readmissions for severe AECOPD. Results: During the follow-up period, 127 patients died, 56 due to AECOPD and 71 due to other reasons. Survivors and non-survivors showed differences in age, FVC % predicted, C-reactive protein, hemoglobin, Cr, Charlson Comorbidity Index (CCI), and OxyHem (p < 0.05 each). Significant independent predictors of survival were BMI, Cr or CCI, FEV₁ % predicted or FVC % predicted, Hb, or OxyHem. The predictive value of OxyHem (p = 0.006) was superior to that of Hb or SpO₂ and independent of oxygen supply during blood gas analysis. OxyHem was also predictive when using a cutoff value of 12.1 g/dL identified via receiver operating characteristic curves in analyses including either the CCI (hazard ratio 1.85; 95% CI 1.20, 2.84; p = 0.005) or Cr (2.04; 95% CI 1.35, 3.10; p = 0.001) as covariates. Conclusion: The concentration of OxyHem provides independent, easy-to-assess information on long-term mortality risk in COPD, even if measured during acute exacerbations. It therefore seems worth to be considered for broader clinical use.