Long-term mortality in patients with chronic obstructive pulmonary disease requiring acute non-invasive ventilation with and without obstructive sleep apnoea

Abstract

Introduction: Chronic obstructive pulmonary disease (COPD)/obstructive sleep apnoea (OSA) overlap syndrome (OVS) is associated with higher mortality compared with COPD alone in stable outpatients. However, the prognosis of patients hospitalised with acute hypercapnic respiratory failure (ARF) is unclear.

Methods: In this retrospective cohort study, 124 patients with COPD and 44 patients with OVS were treated with positive airway pressure (PAP) for ARF and followed up for a median of 20.6 months (IQR 3.80-53.4). Patients treated in the emergency or intensive care units and did not continue PAP on the wards were excluded. We compared patient characteristics and overall survival.

Results: Mean (SD) age of participants was 71 (9.7) years and 51% were males. Patients with OVS had a higher prevalence of hypertension (75% vs 50.0%, p=0.004) and type 2 diabetes mellitus (45.5% vs 19.4%, p<0.001). There was no difference in arterial pH or carbon dioxide levels at presentation. On univariate analysis, mortality was lower in OVS compared with patients with COPD alone (HR 0.57, 95% CI 0.37 to 0.87). Median survival was 51.0 (95% CI 38.1 to 93.7) months in OVS and 27.7 (95% CI 16.9 to 35.1) months in COPD alone. Median survival in OVS prescribed home PAP therapy was significantly higher (59.0 months) compared with OVS not discharged on therapy (36.1 months), and to patients with COPD, irrespective of home therapy prescription (p=0.022). After adjusting for multiple known confounders, patients with OVS still appeared to have lower mortality; however, this was no longer statistically significant (HR 0.75, 95% CI 0.45 to 1.24).

Discussion: We found that patients with COPD and ARF requiring non-invasive ventilation may have higher mortality rates compared with patients with OVS. Patients with OVS treated with home PAP had lower mortality compared with patients not prescribed PAP on discharge. These findings suggest that patients with COPD who present with ARF may benefit from early diagnosis of OSA and initiation of long-term PAP therapy.

Keywords: COPD Exacerbations; Non invasive ventilation; Sleep apnoea.

Figure 1. Study flow chart demonstrating cohort selection. ABG, arterial blood gas analysis; AHI, apnoea-hypopnoea index; COPD, chronic obstructive pulmonary disease; FEV₁/FVC, forced expiratory volume in 1 s to forced vital capacity ratio; NIV, non-invasive ventilation; OVS, overlap syndrome; PaCO₂, partial pressure of carbon dioxide. *Patients excluded for diagnoses other than COPD included in online supplemental eTable 1.

Figure 2. Kaplan-Meier curves demonstrating survival time from hospital discharge with index admission with acute hypercapnic respiratory failure until death between patients with OVS (dashed red) and patients with COPD alone (solid blue). Patients with OVS have lower mortality compared with patients with COPD alone; however, this was no longer statistically significant when analysed using multivariate Cox proportional hazards model. COPD, chronic obstructive pulmonary disease; OVS, overlap syndrome.

Figure 3. Kaplan-Meier curves demonstrating survival time from hospital discharge with index admission with acute hypercapnic respiratory failure until death between patients with COPD not treated with PAP therapy (solid dark blue), patients with COPD treated with PAP therapy (dashed red), patients with OVS not treated with PAP therapy (dashed green) and patients with OVS treated with PAP therapy (solid light blue). COPD, chronic obstructive pulmonary disease; OVS, overlap syndrome; PAP, positive airway pressure.