Hypercapnic respiratory failure in COPD patients: response to therapy

The clinical course of patients with acute exacerbations of underlying COPD presenting with hypercapnic respiratory failure was reviewed.

This was a retrospective review of 138 episodes of hypercapnic respiratory failure (PaCO(2) > or = 50 mm Hg and pH < or = 7.35). Patients were admitted to the West Los Angeles VAMC Medical Intensive Care Unit between 1990 and 1994.

Of the 138 hypercapnic episodes, 74 (54%) required intubation. Comparison was made with the 64 cases in which patients responded to medical therapy. Patients requiring intubation had a greater severity of illness, with a higher APACHE II (Acute Physiology and Chronic Health Evaluation II) score (18 +/- 5 vs 16 +/- 4; p < 0.01), higher WBC, higher serum BUN, and greater acidosis (pH, 7.26 +/- 0.07 vs 7.28 +/- 0.06; p = 0.08). Those with the most severe acidosis (pH < 7.20) had the highest intubation rate (70%) and shortest time to intubation (2 +/- 2 h), and they required the longest period of time to respond to medical therapy (69 +/- 60 h). With an initial pH of < 7.25, there was a consistently higher intubation rate. Conversely, those with an initial pH of 7.31 to 7. 35 were less likely to be intubated (45%), had a longer time to intubation (13 +/- 18 h), and had a more rapid response to medical therapy (30 +/- 18 h). Of those patients requiring intubation, most (78%) were intubated within 8 h of presentation, and the vast majority (93%) by 24 h. Of those patients responding to medical therapy, half (52%) recovered within 24 h and the vast majority (92%) recovered within 72 h.

This study provides a better characterization of the response to therapy of COPD patients with hypercapnic respiratory failure. This should be useful in limiting or omitting medical therapy in high-risk patients, thereby avoiding delays in intubation as well as providing a framework for continued therapy in those more likely to improve.