Anemia and performance status as prognostic markers in acute hypercapnic respiratory failure due to chronic obstructive pulmonary disease.

Background: In patients with acute hypercapnic respiratory failure (AHRF) during exacerbations of COPD, mortality can be high despite noninvasive ventilation (NIV). For some, AHRF is terminal and NIV is inappropriate. However there is no definitive method of identifying patients who are unlikely to survive. The aim of this study was to identify factors associated with inpatient mortality from AHRF with respiratory acidosis due to COPD.

Methods: COPD patients presenting with AHRF and who were treated with NIV were studied prospectively. The forced expiratory volume in 1 second (FEV1), World Health Organization performance status (WHO-PS), clinical observations, a composite physiological score (Early Warning Score), routine hematology and biochemistry, and arterial blood gases prior to commencing NIV, were recorded.

Results: In total, 65 patients were included for study, 29 males and 36 females, with a mean age of 71 ± 10.5 years. Inpatient mortality in the group was 33.8%. Mortality at 30 days and 12 months after admission were 38.5% and 58.5%, respectively. On univariate analysis, the variables associated with inpatient death were: WHO-PS ≥ 3, long-term oxygen therapy, anemia, diastolic blood pressure < 70 mmHg, Early Warning Score ≥ 3, severe acidosis (pH < 7.20), and serum albumin < 35 g/L. On multivariate analysis, only anemia and WHO-PS ≥ 3 were significant. The presence of both predicted 68% of inpatient deaths, with a specificity of 98%.

Conclusion: WHO-PS ≥ 3 and anemia are prognostic factors in AHRF with respiratory acidosis due to COPD. A combination of the two provides a simple method of identifying patients unlikely to benefit from NIV.