This study was approved by the medical ethics committee of Arnhem-Nijmegen, The Netherlands (file 2020–6822).
Between March 24 and May 25, 2020, we collected all the data from ventilated critical care COVID-19 patients transferred by the Lifeliner 5. The data were collected from the documented flight reports in the Operational Registration and Crew Administration (ORCA) data system. Routinely monitored patient data captured by the Corpuls 3 monitor (Corpuls® Benelux, Hellevoetsluis, The Netherlands) were used to determine the exposure time to COVID-19 for each HEMS member. The exposure time to COVID-19 patients was considered to be equal to the monitor time.
The mission time comprises three time intervals (Fig. 1). It starts when landing at the referral hospital and ends when the helicopter is starting up after the patient has been delivered to the intensive care unit (ICU).
The first time interval (T1) is the time needed to collect a patient from the ICU. T1 reflects the time from the rotor-stop of the helicopter until the start up at the referral hospital. The pilot stays near the helicopter while the doctor and HCM receive an oral and written handover in the ICU. Hereafter the infective protective measures with PPE were taken, including FFP2 facemasks (3 M Aura™ 1862+), impermeable gowns (3 M™ 4565 Protective Coverall), double-disposable gloves with long sleeves and eye protection with splash guard goggles. The entire procedure was carried out with a buddy system. Once dressed up in full PPE, the COVID-19 isolation zone was entered where the actual medical patient transfer occurred. As the monitor is switched on, patient data registration (monitor time) starts.
The patient was connected to our monitor, intravenous medication syringes were switched to our syringe pumps (Braun Perfusor Space®) and finally to the respiratory tubing of our Hamilton T1 ventilator (Hamilton Medical Bonaduz, Switzerland). Compatibility of the invasive arterial blood pressure measurement system was checked and, if necessary, connected to our system (Edwards Lifesciences™, Irvine, California, U.S.A.).
Before transfer to the stretcher, all the patients were preoxygenated with 100% oxygen, sedation was deepened and neuromuscular blockade was administered if appropriate. The transport ventilator was set at the institutional settings. On inspiratory hold, the tube was clamped and the institutional ventilator was switched off fully. After reconnection to the tubing of the transport ventilator, the clamp was released from the tube and ventilation was resumed. Finally, the patient was transferred to the stretcher and wrapped in a clean bed sheet in a transport cocoon. After loading the patient into the helicopter, all equipment was checked to ensure battery charging was in progress. With the re-start of the helicopter engines, T1 ends and the second time interval (T2) starts.
T2 is the actual flight time from the referral hospital to the receiving hospital and ends with the rotor stop. During flight, the patient is monitored with the continuation of IC care by the HCM and HEMS physician. Headsets were used for communication because they are more comfortable and more compatible with PPE.
The pilot informed the receiving hospital about the exact time of arrival, so the security officer(s), fire brigade and ICU staff were present upon arrival. They wore their regular flight suit and helmet with visor down in combination with a FFP2 facemasks and medical gloves.
During the final time interval (T3), the patient was disembarked from the helicopter and brought to the receiving ICU. After the handover, the patient was connected to the institutional ventilator, syringe pumps and monitoring, the Corpuls 3 monitor was switched off, the patient data registration was stopped and the monitor time ended.
Hereafter, the HEMS-physician and HCM disinfected the stretcher and medical equipment. Before leaving the isolation zone at the ICU, PPE was removed under buddy supervision. Additionally, the HEMS pilot disinfected potentially contaminated surfaces inside the helicopter with Kohrsolin® FF dressed in full PPE [4]. T3 ended with the engine start up at the receiving hospital. This moment also ended the mission time (Fig. 1).
Pilots must meet class 1 and HCMs class 2 in accordance with the medical requirements of the European Aviation Safe Agency (EASA). All doctors were in good physical and mental condition at the time of the operation. Normally, HEMS activities of the HCM’s are combined with a position at a ground ambulance service. HEMS physicians combine their activities with clinical medicine. During this operation all crew members were solely available for critical care COVID-19 transports to avoid cross contamination. For this reason the LL5 crew was physically separated from the on-call regular HEMS team.
Before the operation started very team member was instructed how to put on and remove their PPE correctly. Initial instructions were provided by an employee of the hospital hygiene department. The training consists of two parts. During the first part an short instruction film is shown, which is used for employees of the intensive care department. During the second part of the training the procedure is performed physically. In total the training takes about 30 min. A personalized PPE package was compiled for each team member on the basis of a checklist.
At the start of the operation, each HEMS team member was questioned about COVID-19-related health complaints, as advised by the National Institute for Health and Environment (RIVM), such as flu-like symptoms, cough, shortage of breath, elevated temperature, or a fever (> 38 °C) and the sudden loss of taste and smell without nasal congestion [5]. Two weeks after ending Lifeliner 5 transport operations, the same questions were asked. One month later, every team member was requested to voluntarily donate a blood sample after written informed consent. Blood was analysed using LIAISON® SARS-CoV2 S1/S2 IgG chemiluminescence immunoassay (CLIA) technology for the quantitative determination of anti-S1/S2-specific IgG antibodies to SARS-CoV-2 in human serum or plasma samples [6].
Descriptive statistics were used to analyse the collected data from flight reports and patient monitoring (GraphPad Prism version 5.03; GraphPad software, San Diego, USA). The data were assessed for normal distribution using the D’Agostino & Pearson omnibus normality test. Non-normally distributed data were analysed using the Mann–Whitney test. A value of P < 0.05 was considered statistically significant.