key: cord-0828851-9pg1yqfa
authors: Camporota, Luigi; Sanderson, Barnaby; Dixon, Alison; Vasques, Francesco; Jones, Andrew; Shankar-Hari, Manu
title: Outcomes in mechanically ventilated patients with hypoxaemic respiratory failure due to COVID-19
date: 2020-09-03
journal: Br J Anaesth
DOI: 10.1016/j.bja.2020.08.047
sha: 41cc4578fb1f4f41e06c65f052f6fea6447c58be
doc_id: 828851
cord_uid: 9pg1yqfa

nan

outcomes of a cohort of critically ill COVID-19 patients with AHRF receiving invasive mechanical ventilation with partial pressure of oxygen/inspired oxygen concentration ratio (PaO 2 /FiO 2 ratio) <300 mm Hg during their first critical care admission in a format similar to the LUNG-SAFE study 7 .

We grouped (COVID-19 vs LUNG-SAFE) patients based on the severity of oxygenation alone based on the Berlin definition of ARDS 2 . Chest radiogram characteristics were not considered in the inclusion criteria.

The study was a single-centre, retrospective, observational cohort study of adult patients admitted with confirmed COVID-19 AHRF to the Critical Care Department at Guy's and St Thomas' Hospital (GSTT) in London UK between 3 rd March and 22 nd May 2020. The study had institutional approval and with waiver of individual informed consent (reference number 10796).

Baseline patient data, clinical characteristics, lung mechanics, gas exchange and outcomes were obtained from clinical information systems (CareVue Rev.F.01, Philips, Eindhoven, The Netherlands; and other electronic patient records) using Microsoft SQL Server Management Studio v18.4 (location?). Actual or temperature corrected partial pressure of carbon dioxide (PaCO 2 ), PaO 2 and pH, were merged with contemporaneous ventilation parameters and measurements. We used the worst PaO 2 /FiO 2 ratio on critical care admission day to categorize hypoxaemia into mild (PaO 2 /FiO 2 ratio 200-300 mm Hg), moderate (PaO 2 /FiO 2 ratio 100-200 mm Hg) and severe (PaO 2 /FiO 2 ratio ≤100 mm Hg) as per the Berlin ARDS definition 2 . There were no missing data. All analyses were conducted in R version 3.6.1 (http://www.R-project.org).

Amongst the 317 critical care admissions over the study period due to COVID-19, 213 patients met our inclusion criteria of AHRF receiving invasive mandatory mechanical ventilation with PaO 2 /FiO 2 ratio <300 mm Hg, during their first critical care admission. We excluded patients receiving noninvasive respiratory support (n=48) or extracorporeal membrane oxygenation (ECMO; n=51), or readmissions (n=9). The mean (95% CI) age of the cohort was 56 (54-57) yr, 72.8% (n=155) were male, 40.4% (n=86) had hypertension and 33.8% (n=72) had diabetes mellitus as comorbidities. in the severe group, and 24% of patients in the moderate or severe AHRF groups had compliance >40 ml cm H 2 O -1 ( Figure 1B) . Overall, mean (95% CI) duration of mechanical ventilation was 15 (13.5 to 16.5) days, with longer duration of mechanical ventilation associated with more severe disease ( Figure 1C ). The critical care length of stay was longer in the moderate and severe categories compared to the mild category, but similar in the moderate and severe categories due to higher and earlier mortality in the severe category. ICU mortality was 9% in mild disease, 27.5% in moderate disease and 55.7% in severe disease, with significant differences among the three severity categories (p<0.01 log-rank), ( Figure 1D ).

Overall ICU mortality of 34.2% in our cohort was similar to the overall mortality reported in the LUNG-SAFE (35.3%) 7 cohort and in the COVID-19 cohort receiving mechanical ventilation (35%) 8 .

Similar to the LUNG-SAFE cohort and the Berlin ARDS predictive validity analyses, there was a doseresponse relationship between mortality and severity of hypoxaemia, albeit with lower mortality in the mild category.

J o u r n a l P r e -p r o o f 4 These results illustrate that although the characteristics of the COVID-19 AHRF population largely overlap with the LUNG-SAFE cohort, the COVID-19 cohort had a greater predominance of moderate (57% vs 47%) and severe (31% vs 23%) and a lower proportion of patients with mild hypoxaemia (10.8% vs 30%) compared to the LUNG-SAFE cohort 7 . Despite the greater severity of hypoxaemia compared to LUNG-SAFE, a greater proportion of patients with COVID-19 were ventilated within protective boundaries.

In conclusion, despite initial data showing high mortality in mechanically ventilated COVID-19 patients, our data show that with comparable degrees of hypoxaemia and lung mechanics to ARDS from other causes the mortality is similar to ARDS as is survival is high in mild disease. More detailed characterizations of patient phenotypes may help understand the factors associated with severity of hypoxaemia and lung parenchymal involvement.

The authors declare that they have no conflict of interests. 

Concept and design: LC, BS, MS-H Statistical analysis: BS, CaLCmporota Drafting of manuscript: LC, MS-H Acquisition, analysis and interpretation of data: All authors Critical revision of the manuscript for important intellectual content: All authors Obtained funding: LC Administrative, technical, or material support: LC, AJ Supervision: LC, MS-H Funding MS-H is supported by the National Institute for

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