Clinical impact of episodic nocturnal hypercapnia and its treatment with noninvasive positive pressure ventilation in patients with stable advanced COPD

Abstract

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.

Figure 1

Flowchart of patient recruitment. Abbreviations: NPPV, noninvasive positive pressure ventilation; CPAP, continuous positive airway pressure; PtcCO₂, transcutaneous carbon dioxide tension; PaCO₂, arterial carbon dioxide pressure.

Figure 2

Definition of the study period. Abbreviations: eNH, episodic nocturnal hypercapnia; NPPV, noninvasive positive pressure ventilation; PtcCO₂, transcutaneous carbon dioxide tension; BNP, brain natriuretic peptide; PA, pulmonary arterial diameter; A, aortic diameter.

Figure 3

(A) SpO₂ monitoring during sleep before NPPV, (B) SpO₂ monitoring during sleep after NPPV, (C) PtcCO₂ monitoring during sleep before NPPV, (D) PtcCO₂ monitoring during sleep after NPPV. Notes: Before NPPV, nocturnal SpO₂ and PtcCO₂ monitoring showing episodic oxygen desaturations and episodic elevated PtcCO₂. After NPPV, episodic oxygen desaturations and episodic elevated PtcCO₂ were improved. Abbreviations: NPPV, noninvasive positive pressure ventilation; SpO₂, saturation of pulse oximetry; PtcCO₂, transcutaneous carbon dioxide tension.

Figure 4

Time course of serum albumin levels in patients with and without eNH. Notes: Serum albumin levels in patients with eNH showing gradual decrease in period A. Serum albumin levels in patients with eNH showing improvement in period B. Data are presented as mean ± SE. Abbreviations: eNH, episodic nocturnal hypercapnia; NPPV, noninvasive positive pressure ventilation.

Figure 5

Time course of daytime partial carbon dioxide pressure posterior to long-term noninvasive positive pressure ventilation. Data are presented as mean ± SE.

Figure 6

Comparison of the frequency of exacerbations between before and after noninvasive positive pressure ventilation. Data are presented as mean ± SE.