The role of Continuous Positive Airway Pressure (CPAP) in Delaying or Avoiding Mechanical Ventilation in COVID-19 Respiratory Failure: A Retrospective Cohort Study

Abstract

\n Background - During the winter of 2020-2021, the second wave of the COVID19 pandemic in the United Kingdom caused increased demand for intensive care unit (ICU) beds, and in particular, for invasive mechanical ventilation (IMV). To alleviate some of this pressure, some centres offered non-invasive continuous positive airway pressure (CPAP), delivered on specialised COVID high dependency units (cHDUs). However, this practice was based largely on anecdotal reports, and it is not clear from the literature how effective CPAP is at delaying or preventing IMV. Methods - This was a retrospective observational cohort study of consecutive patients admitted to a specialised cHDU at Glasgow Royal Infirmary between November 2020 and February 2021. Each patient had a continuous record of the level of respiratory support required, and was followed up to hospital discharge or death. We examined patient outcomes according to age, sex and maximum level of respiratory support, using logistic regression and time-to-event analysis. The number of patients who could not be oxygenated by standard oxygen facemask but could be oxygenated by CPAP was counted and compared to the number of patients admitted to ICU for IMV over the same period.Results - There were 152 admissions to cHDU over the study period. Of these, 125 received CPAP treatment. Of the patients who received support in cHDU, the overall mortality rate was 37.9% (95% CI 30.3% - 46.1%)). Odds of mortality were closely correlated with increasing age and oxygen requirement. Of the 152 patients, 44 patients (28.8%, 95% CI 22.0 – 36.9%) went on to require IMV in ICU. This represents 77.2% of the 57 COVID-19 admissions to ICU during the same period. However, there were also 41 patients who received levels of respiratory support on cHDU which would normally necessitate ICU admission but who never went to ICU, potentially reducing ICU admissions by 41.8% (95% CI 32.1 – 52.2%).Conclusion - Providing respiratory support in cHDU reduced the number of potential ICU admissions by 41.8%, as well as delaying IMV for over 75% of ICU admissions. This represents a significant sparing of ICU capacity at a time when IMV beds were in high demand.