Emergency calls are early indicators of ICU bed requirement during the COVID-19 epidemic A retrospective study in Ile-de-France region, France (preprint)

Background: The aim of our retrospective study was to evaluate the earliest COVID19-related signal to anticipate requirements of intensive care unit (ICU) beds. Although the number of ICU beds is crucial during the COVID-19 epidemic, there is no recognized early indicator to anticipate it. 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 ICU patients. Correlation curve analysis was performed to determine the best correlation coefficient, depending on the number of days the indicator has been shifted. Primary endpoint was the number of ICU patients. Results: 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. Conclusion: 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, 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.

Collective Advanced Life Support Ambulance An Innovative Transportation of Critical Care Patients by Bus in COVID-19 Pandemic Response (preprint)

Background: During the COVID-19 pandemic, as the number of available Intensive Care beds in France did not meet the needs, it appeared necessary to transfer a large number of patients from the most affected areas to the less ones. Mass transportation resources were deemed necessary. To achieve that goal, the concept of a Collective Advanced Life Support Ambulance (CALSA) was proposed in the form of a long-distance bus re-designed and equipped so as to accommodate up to six intensive care patients and allow Advanced Life Support (ALS) techniques to be performed while en route.Methods: The expected benefit of the CALSA, when compared to ALS ambulances accommodating a single patient, was to reduce the resources requirements, in particular by a lower personnel headcount for several patients being transferred to the same destination. A foreseen prospect, comparing to other collective transportation vectors such as airplanes, was the door-to-door capability, minimalizing patients’ handovers for safety concerns and time efficiency. With the project of a short-distance transfer of several Intensive Care Unit (ICU) patients together, the opportunity came to test the CALSA under real-life conditions and evaluate safely its technical feasibility and impact in time and resources saving, before it could be proposed for longer distances.Results: Four COVID-19 patients were transported over 37 km. All patients were intubated and under controlled ventilation. One of them was under Norepinephrine support. Mean loading time was 1min 39s. Transportation time was 29 min. At destination, the mean unloading time was 1min 15s. No serious adverse effect, in particular regarding hemodynamic instability or ventilation disorder, has been observed. No harmful incident, in particular no accidental extubation, has occurred.Conclusions: It was a very instructive test. Collective medical evacuation by bus for critically ill patients under controlled ventilation is suitable and easy to implement. Design, ALS equipment, power autonomy, safety and resources saving, open the way for carrying up to 6 ICU-patients over a long distance. The CALSA could bring a real added-value in an epidemic context and could also be helpful in many other events generating multiple victims such as an armed conflict, a terrorist attack or a natural disaster.

Understanding and monitoring the evolution of the Covid-19 epidemic from medical emergency calls: the example of the Paris area (preprint)

We portray the evolution of the Covid-19 epidemic during the crisis of March-April 2020 in the Paris area, by analyzing the medical emergency calls received by the EMS of the four central departments of this area (Centre 15 of SAMU 75, 92, 93 and 94). Our study reveals strong dissimilarities between these departments. We show that the logarithm of each epidemic observable can be approximated by a piecewise linear function of time. This allows us to distinguish the different phases of the epidemic, and to identify the delay between sanitary measures and their influence on the load of EMS. This also leads to an algorithm, allowing one to detect epidemic resurgences. We rely on a transport PDE epidemiological model, and we use methods from Perron-Frobenius theory and tropical geometry.