Purpose: Episodic nocturnal hypercapnia (eNH) caused by rapid eye movement (REM) sleep-related hypoventilation is often noted in patients with advanced COPD. The purpose of this study was to clarify the clinical significance of eNH and the effectiveness of eNH-targeted noninvasive positive pressure ventilation (NPPV).
Patients and methods: We enrolled patients with stable, severe, or very severe COPD with daytime arterial partial oxygen pressure PaO2 ≥55 mmHg and daytime arterial partial carbon dioxide pressure PaCO2 <55 mmHg, who underwent overnight transcutaneous carbon dioxide pressure (PtcCO2) monitoring from April 2013 to April 2016. We retrospectively compared clinical characteristics, daytime blood gas analysis, frequency of exacerbation, serum albumin levels, and ratio of pulmonary artery to aorta diameter (PA:A ratio), between patients with COPD with and without eNH. For those with eNH, we applied NPPV and compared these clinical characteristics before and after NPPV.
Results: Twenty-one patients were finally included in this study. Ten patients (47.6%) were evaluated to have eNH. These patients had lower albumin levels (p=0.027), larger PA:A ratio (p=0.019), and higher frequency of exacerbations during the last year (p=0.036). NPPV for the patients with eNH improved daytime PaCO2 compared with that 12 months after NPPV (p=0.011). The frequency of exacerbations 1 year before NPPV decreased 1 year after NPPV (p=0.030). Serum albumin levels improved 1 year after NPPV (p=0.001).
Conclusion: In patients with stable severe or very severe COPD, eNH may be a risk factor of exacerbations, hypoalbuminemia, and pulmonary hypertension. NPPV may be effective against hypoalbuminemia and acute exacerbations. However, further study is necessary to validate these findings.
Keywords: COPD; intelligent volume-assured pressure support; nocturnal hypoventilation; noninvasive positive pressure ventilation; pulmonary hypertension; sleep disorders.