Higher body mass index (bmi) is associated with Improved continuous positive airway pressure (cpap) outcomes in patients with hypoxic Respiratory failure secondary to covid-19

ABSTRACT

Background During the COVID-19 pandemic, the use of continuous positive airway pressure (CPAP) for type 1 respiratory failure (T1RF) has been shown to possibly delay or avoid the need for intubation.1 However, no study has identified patient characteristics that may be associated with more favourable outcomes. We hypothesised that patients with a higher body mass index (BMI) would have better outcomes with CPAP as they are more likely to have undiagnosed obstructive sleep apnoea (OSA) and upper airway resistance. Methods We retrospectively reviewed use of CPAP in a ward setting for T1RF secondary to COVID-19 between 20.3.20 and 20.4.20. In addition to patient demographic data and co-morbidities, we assessed Oxygen requirements pre-CPAP, mean CPAP pressures and survival with CPAP alone (CPAP success). Results 41 ward patients received CPAP. Patients' baseline characteristics are shown in table 1. All were deemed suitable for intubation and ventilation (I&V) prior to commencing CPAP. Nine out of 41 (22%) did not require I&V and survived to discharge with CPAP alone. CPAP failed in 32 patients (78%);30 required I&V (ITU survival 67%) and two patients were palliated. Patients with CPAP success all had BMI >25 kg/m2 (median BMI 30.0 (28.1-37.0) kg/m2). This was significantly higher than in those where CPAP failed (47% had BMI >25 kg/m2;median 24.9 kg/m2 (22.9-28.1), p=0.005). 37.5% (n=12) of patients where CPAP failed had a smoking history, (of which only 1 (8.3%) had a diagnosis of COPD), compared to 0% of CPAP success patients (p=0.023). Conclusion In our small cohort, CPAP alone was successful in 22%. This was lower than another recent study (1), however, our patient cohort had more co-morbidities. Patients with a higher BMI had significantly greater CPAP success. This may be due to an increased number of undiagnosed OSA in this cohort and merits further investigation. While smokers had an increased risk of CPAP failure, none of the patients were current smokers and there was limited data on pack-year history. Further studies are necessary to identify factors that may point to greater CPAP success during COVID-19.