Background The role of non invasive ventilation (NIV) in severe COVID-19 requiring mechanical ventilation (MV) remains a matter of debate.
Methods In this observational study of confirmed COVID-19 cases claims data of the Local Health Care Funds of MV patients were comparably analysed: spring period of 2020 (February to May) versus autumn period (October/November).
Findings In a nationwide cohort 7,490 cases were included: median age 70 (IQR 60to79) years, 66% male, hypertension 67%, diabetes 42%, cardiac arrhythmia 43%, congestive heart failure 34%, renal failure 27%. Overall, 3,851 (51%) patients primarily received invasive MV without NIV, 1,614 (22%) patients received NIV without having been escalated to intubation, and 1,247 (17%) patients had NIV failure (NIVF), defined by endotracheal intubation following NIV. Comparing cases of the first and second period, the proportion of patients who received invasive MV decreased from 74% to 39%. Accordingly, the proportion of patients with NIV without subsequent intubation increased from 10% to 28%, and those failing NIV increased from 9% to 21%. The overall median length of hospital stay decreased from 26 to 22 days, and the overall duration of MV decreased from 11.6 to 7.6 days. The NIV failure rate decreased from 49% (219/449) to 42% (927/2,185). Overall mortality remained unchanged (51% and 53% respectively). Mortality was 39% with NIV only, 52% with invasive MV and 66% with NIVF with mortality rates steadily increasing from 58% in early NIVF (day 1) to 75% in late NIV-F (>5 days).
Interpretation The utilization of NIV rapidly increased during the autumn period compared to the spring period 2020, which was associated with a reduced duration of MV and hospital stay, but not with overall mortality. NIVF rates are high and are associated with increased mortality rates, particularly in late NIVF. In contrast, NIV success is associated with the lowest mortality rates.