Arterial blood gas derangement and level of comorbidity are not predictors of long-term mortality of COPD patients treated with mechanical ventilation

Background and objective: Limited and inconsistent data exist on simple, readily available predictors of long-term mortality of critically ill chronic obstructive pulmonary disease patients requiring invasive mechanical ventilation. We therefore examined the influence of arterial blood gas derangement and burden of comorbidities on 90-day and 1-yr mortality of chronic obstructive pulmonary disease patients treated with invasive mechanical ventilation. Methods: We identified all chronic obstructive pulmonary disease patients (n = 230) treated with invasive mechanical ventilation between 1994 and 2004 at a Danish primary-level hospital. Data on arterial blood gas specimens and comorbidity were obtained from medical records and Hospital Discharge Registries. We used Cox's regression analysis to estimate mortality ratios according to arterial blood gas values and level of comorbidity. Results: Ninety-day and 1-yr mortality among chronic obstructive pulmonary disease patients requiring invasive mechanical ventilation was 30.8% and 40.5%, respectively. All 90-day and 1-yr mortality ratios according to arterial blood gas values were close to one and one was included in all 9596 CI. Among patients with a high level of comorbidity 90-day mortality ratio was 1.3 (95% CI: 0.6-2.7) when compared with patients without comorbidity. The corresponding 1-yr mortality ratio was 1.4 (95% CI: 0.7-2.9). Conclusion: Chronic obstructive pulmonary disease patients treated with invasive mechanical ventilation have substantial long-term mortality. Neither the levels of arterial blood gas values measured immediately before invasive mechanical ventilation was initiated nor the burden of comorbidity were strong determinants of long-term mortality among these patients.