Predictors of survival in patients with chronic obstructive pulmonary disease receiving long-term oxygen therapy

Chronic obstructive pulmonary disease (COPD) affects 2-4% of the UK's population and has significant mortality, however prognostication is difficult. Long-term oxygen therapy (LTOT) has been identified by the Gold Standards Framework as a clinical indicator of advancing disease. We hypothesised the ADO index (for 'Age, Dyspnoea and airflow Obstruction'), which predicts mortality, could be applied to our LTOT population to help identify patients with poor prognosis. We aimed to compare this to the Medical Research Council dyspnoea scale, body mass index, forced expiratory volume in 1 s and gas transfer.

This was a retrospective study on 136 patients with COPD started on LTOT, June 2003 to August 2010. Data were collected from LTOT databases and medical records. Patients' length of survival was calculated from initiation of LTOT. Patients were grouped by individual parameters. Survival rates at 6 months, 1 year and 4 years were calculated. GraphPad Prism V.5.0 software was used to construct Kaplan-Meier curves and perform log-rank tests.

The ADO index discriminated survival at 6 months, 1 year and 4 years, p=0.0027. Low body mass index (<20) was associated with poor prognosis after 1 and 4 years, p=0.0015. Medical Research Council grade predicted survival at 4 years. Diffusion capacity of the lung for carbon monoxide (DLCO)% predicted and forced expiratory volume in 1 s (FEV₁)% predicted did not predict survival.

This study showed wide variation in survival in a patient population on LTOT. The ADO score could be used as an early trigger for referral to palliative services, thus enhancing end-of-life care, which improves quality of life in COPD. A prospective study of this application would be required to prove this hypothesis.