Control of hypercapnia and mortality in home mechanical ventilation: the population-based DISCOVERY study.

Background: Studies on the survival of patients with home mechanical ventilation (HMV) are sparse. We aimed to analyse the impact of controlled hypercapnia on survival over 27 years among patients with HMV in Sweden.

Study design and methods: Population-based cohort study of adult patients starting HMV in the Swedish Registry for Respiratory Failure (Swedevox) during 1996-2022 cross-linked with the National Cause of Death registry. Mortality risk factors were analysed using crude and multivariable Cox regression models, including adjustments for anthropometrics, comorbidities, the underlying diagnosis causing chronic hypercapnic respiratory failure (CRF) and the control of hypercapnia (P _aCO2 ≤6.0 kPa) at follow-up.

Results: We included 10 190 patients (50.1% women, age 62.9±14.5 years). Control of hypercapnia at follow-up after 1.3±0.9 years was associated with lower mortality, hazard ratio (HR) 0.74 (95% CI 0.68-0.80) and the association was strongest in those with pulmonary disease, restrictive thoracal disease (RTD), obesity hypoventilation syndrome (OHS) and amyotrophic lateral sclerosis (ALS). Predictors for increased mortality included age, Charlson Comorbidity Index, supplemental oxygen therapy and acute start of HMV therapy. Median survival varied between 0.8 years (95% CI 0.8-0.9 (n=1401)) for ALS and 7.6 years (95% CI 6.9-8.6 (n=1061)) for neuromuscular disease. Three-year survival decreased from 76% (95% CI 71-80) between 1996 and 1998 to 52% (95% CI 50-55) between 2017 and 2019. When adjusting for underlying diagnosis and age, the association between start year and decreased survival disappeared, HR 1.00 (95% CI 0.99-1.01).

Conclusion: Controlling P _aCO2 is a key treatment goal for survival in HMV therapy. Survival differed markedly between diagnosis and age groups, and survival rates have declined as the patient group has aged.