A tale of two waves: a single centre retrospective cohort study assessing mortality in severe COVID-19 in first and second waves

Introduction and ObjectivesThe first and second waves of COVID-19 showed different mortality patterns in hospitalized patients (Iftimi S, et al, PLos One 2021;16(3)) but it is less clear if that holds true for severe COVID-19 patients who required respiratory support. The rationale of this study is to assess mortality difference of severe COVID-19 patients from both waves who required respiratory support.MethodsA retrospective review was conducted of all patients with severe COVID-19 requiring respiratory support including CPAP/High Flow Nasal Cannula (HFNC) admitted to a respiratory support unit at a London District Hospital in first wave (March-May 2020) and second wave (November 2020-March 2021). Mortality was assessed for CPAP/HFNC and intubation groups of each wave in accordance with age and clinical frailty score (CFS) as baseline characteristics.ResultsIn wave one, 89 patients were treated with CPAP/HFNC. 53 patients (60%) were offered CPAP/HFNC alone whilst 36 (40%) patients escalated to mechanical ventilation. In CPAP/HFNC group, 35 (66%) survived (Median age: 69, Median CFS: 2), and 18 (34%) died (Median age: 69, Median CFS: 2). In intubated group, 17 (47%) survived (Median age: 61, Median CFS: 2) and 19 (52%) died (Median age: 61, Median CFS: 2). Total 37 patients died with overall mortality 41%.In wave two, 207 patients were treated with CPAP/HFNC. Of these, 150 (73%) were offered CPAP/HFNC alone whilst 57 (27%) were escalated to mechanical ventilation. In CPAP/HFNC group, 104 (69%) survived (Median age: 66, Median CFS: 2) and 46 (31%) died (Median age: 67, Median CFS: 2). In intubated group, 33 (58%) survived (Median age 62, Median CFS: 2) and 24 (42%) died (Median age: 62, Median CFS: 2). 70 patients died in total with overall mortality 34%.ConclusionOur findings suggest overall mortality improved in second wave in severe COVID-19 patients though baseline characteristics were not significantly different. This is likely to reflect lessons relating to patient care from wave one and increasing use of steroids and IL-6 inhibitors.