Hypercapnia in patients with acute heart failure

Non-invasive positive pressure ventilation rapidly improves the symptoms of acute heart failure (AHF). A portion of patients, however, are forced to be intubated even though intubation is associated with serious complications, and hypercapnia is often observed in AHF requiring intubation. The purpose of this study is to examine the clinical profile and management of hypercapnia in AHF patients.

We examined the arterial blood gas analysis in 193 consecutive AHF patients (73 ± 12 years, 61% men) at admission. Many patients (n = 129, 66.8%) had already been treated with oxygen by the ambulance staff. Hypercapnia (PaCO₂ at admission >45 mmHg) and hypocapnia (PaCO₂  < 35 mmHg) were observed in 33.7% and 32.6%, respectively. Whereas 16 (24.6%) hypercapnic patients were intubated, there were only one (1.5%) normocapnic and no hypocapnic patients intubated. Patients with hypercapnia are more likely to be in the New York Heart Association Class IV (96.9% vs. 78.9%, P < 0.001), to have acute onset within 6 h (50.8% vs. 25.0%, P < 0.001), and to have radiographic pulmonary oedema (84.6% vs. 57.8%, P < 0.001) than those with hypo-normocapnia. Hypercapnia was more frequent in patients with acute cardiogenic pulmonary oedema than in those with acute decompensated heart failure (51.9% vs. 23.6%, P < 0.001). At discharge, hypercapnia was observed in 17.8% of patients who were hypercapnic at admission.

Hypercapnia emerged in AHF acutely and transiently, was associated with immediate airway intervention, and was possibly involved in the pathophysiology of acute pulmonary oedema. Patients with acute onset dyspnoea should have their respiratory status carefully managed. These pathophysiological findings are expected to be utilized in treating or preventing AHF.