Distinctive features and long-term survival of reversible and chronic hypercapnic patients with COPD

Hypercapnic respiratory failure due to chronic obstructive pulmonary disease (COPD) is an indicator of poor prognosis compared to that for normocapnic patients. On the other hand, there exist particular patients who are hypercapnic during an acute exacerbation of COPD but revert to normocapnia after adequate therapy. The aims of this study were: 1) to document the admission characteristics of such patients in terms of clinical and laboratory findings; and 2) to analyse the long-term course and survival of chronic and reversible hypercapnic and normocapnic patients. Fifty-six consecutive patients, admitted with an acute exacerbation of COPD, were enrolled and divided into three groups according to arterial carbon dioxide tension (Pa,CO2) at first admission: 22 chronic hypercapnic (group 1), 15 reversible hypercapnic (group 2) and 19 normocapnic (group 3) patients. Age, sex, smoking history, white blood cell count, serum sodium, potassium, urea and albumin levels and pulmonary function tests at first admission were similar in the three groups. The haematocrit level was significantly higher in group 1 compared with the other groups. Groups 1 and 2 had lower pH, arterial oxygen tension (Pa,O2) and arterial oxygen saturation (Sa,O2) and a higher Pa,CO2 than group 3. The Pa,CO2 was also higher in group 1 than in group 2. The presence of cor pulmonale was significantly higher in group 1 compared with groups 2 and 3 (81.8 versus 60 and 10.5%, respectively). During the follow-up period, a significant increase was observed in airway obstruction associated with progressive hypercapnia and hypoxaemia in chronic hypercapnic patients, and 12 of 15 (80%) reversible hypercapnic patients progressed to a chronic hypercapnic status. The survival analyses after 10 yrs of follow-up revealed comparable survival durations in chronic and reversible hypercapnic patients (median of 8.86 versus 9.52 yrs, p > 0.05). In conclusion, despite careful monitoring of particular characteristics in chronic and reversible hypercapnic patients at the time of admission, no long-term predictivity of these features for either the course of the disease or survival could be found.