Emergency calls are early indicators of ICU bed requirement during the COVID-19 epidemic
Authors:   By the COVID-19 APHP-Universities-INRIA-INSERM Group, Riou Bruno 
Published: June 2020

Background

Although the number of intensive care unit (ICU) beds is crucial during the COVID-19 epidemic caring for the most critically ill infected patients, there is no recognized early indicator to anticipate ICU bed requirements.

Methods

In the Ile-de-France region, from February 20 to May 5, 2020, emergency medical service (EMS) calls and the response provided (ambulances) together the percentage of positive reverse transcriptase polymerase chain reaction (RT-PCR) tests, general practitioner (GP) and emergency department (ED) visits, and hospital admissions of COVID-19 patients were recorded daily and compared to the number of COVID-19 ICU patients. Correlation curve analysis was performed to determine the best correlation coefficient (R), depending on the number of days the indicator has been shifted. A delay ≥7 days was considered as an early alert, and a delay ≥14 days a very early alert.

Findings

EMS calls, percentage of positive RT-PCR tests, ambulances used, ED and GP visits of COVID-19 patients were strongly associated with COVID-19 ICU patients with an anticipation delay of 23, 15, 14, 13, and 12 days respectively. Hospitalization did not anticipate ICU bed requirement.

Interpretation

The daily number of COVID19-related telephone calls received by the EMS and corresponding dispatch ambulances, and the proportion of positive RT-PCR tests were the earliest indicators of the number of COVID19 patients requiring ICU care during the epidemic crisis in the Ile-de-France region, rapidly followed by ED and GP visits. This information may help health authorities to anticipate a future epidemic, including a second wave of COVID19 or decide additional social measures.

Funding

Only institutional funding was provided.

Research in context

Evidence before the study

We searched PubMed and preprint archives for articles published up to May 17, 2020, that contained information about the anticipation of intensive care unit (ICU) bed requirement during the COVID-19 outbreak using the terms “coronavirus”, “2009-nCOV”, “COVID-19”, SARS-CoV2”, “prediction” “resource” and “intensive care”. We also reviewed relevant references in retrieved articles and the publicly available publication list of the COVID-19 living systematic review.22 This list contains studies on covid-19 published on PubMed and Embase through Ovid, bioRxiv, and medRxiv, and is continuously updated. Although many studies estimated the number of patients who would have severe COVID-19 requiring ICU, very few contained assessment for early signals (from internet or social media), and we retrieved no study whose data came from suspected or infected patients.

Added values of this study

During the COVID-19 epidemic, emergency medical system (EMS) calls, percentage of positive reverse transcriptase polymerase chain reaction (RT-PCR) tests, ambulance dispatch, emergency department (ED) and general practitioner (GP) visits of COVID-19 patients were strongly associated with COVID-19 ICU patients with an anticipation delay of 23, 15, 14, 13, and 12 days respectively. Hospitalization did not anticipated COVID-19 ICU bed requirement.

Implication of all available evidence

EMS calls and ambulance dispatch, percent of positive RT-PCR, and ED and GP visits could be valuable tools as daily alert signals to set up plan to face the burden of ICU bed requirement during the initial wave of the COVID-19 epidemic, and may possibly also help anticipating a second wave. These results are important since mortality has been reported being correlated to health care resources.