The copyright holder for this preprint is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. It is made available under a CC-BY 4.0 International license. Objectives: To determine if there is an association between survival rates in intensive care units (ICU) and occupancy of the unit on the day of admission. Design: National retrospective observational cohort study during the COVID-19 pandemic. Setting: 90 English hospital trusts (i.e. groups of hospitals functioning as single operational units). Participants: 6,686 adults admitted to an ICU in England between 2nd April and 1st December, 2020 (inclusive), with presumed or confirmed COVID-19, for whom data was submitted to the national surveillance programme and met study inclusion criteria. Interventions: N/A Main Outcomes and Measures: A Bayesian hierarchical approach was used to model the association between hospital trust level (mechanical ventilation compatible) bed occupancy, and in-hospital all-cause mortality. Results were adjusted for unit characteristics (pre-pandemic size), individual patient-level demographic characteristics (age, sex, ethnicity, time-to-ICU admission), and recorded chronic comorbidities (obesity, diabetes, respiratory disease, liver disease, heart disease, hypertension, immunosuppression, neurological disease, renal disease). Results: 121,151 patient-days were observed, with a mortality rate of 20.8 per 1,000 patient days. Adjusting for patient-level factors, mortality was higher for admissions during periods of high occupancy (>85% occupancy versus the baseline of 45 to 85%) [OR 1.18 (95% posterior credible interval (PCI): 1.00 to 1.38)]. In contrast, mortality was decreased for admissions during periods of low occupancy (<45% relative to the baseline) [OR 0.79 (95% PCI: 0.69 to 0.90)]. Conclusion and Relevance: Increasing occupancy of beds compatible with mechanical ventilation, a proxy for operational strain, is associated with a higher mortality risk for individuals admitted to ICU. Public health interventions (such as expeditious vaccination programmes and non-pharmaceutical interventions) to control both incidence and prevalence of COVID-19, and therefore keep ICU occupancy low in the context of the pandemic, are necessary to mitigate the impact of this type of resource saturation. Trial Registration: N/A.
Wilde, H., Mellan, T., Hawryluk, I., Dennis, J. M., Denaxas, S., Pagel, C., … Vollmer, S. J. (2021). The association between mechanical ventilator availability and mortality risk in intensive care patients with COVID-19: A national retrospective cohort study. MedRxiv. https://doi.org/10.1101/2021.01.11.21249461