In the autumn of 2019, DRF Luftrettung investigated the topics of infectious droplets and pathogens when transporting patients with diseases, and started the first scientifically-accompanied field test in cooperation with BZH, the German consulting centre for hospital epidemiology and infection control in Freiburg. The recently published findings from this study will enable initial conclusions about transmission pathways to be drawn, which the hygiene management team at DRF Luftrettung can use to build upon.

Within the scope of the project, 16 test runs were performed on board DRF's H145 and EC135 helicopters, 11 of which were on the ground and five in the air. Two scenarios were depicted and diversified within the course of the study. One of these was a worst case scenario, simulating a major pathogen release, and the other depicted an alternating, less extreme pathogen release. An oxygen nebuliser level with the patient's head was used to recreate the droplets being released. The test simulated a droplet release similar to that which would occur if the spontaneously breathing patient or person coughed or sneezed in the cabin, as well as on the basis of the intentional or accidental disconnection of a breathing tube. Air flows were detected by means of fluorescence, and thus also the movements of the droplets. Their spread was made visible with UV light. The tests were carried out both with and without a curtain dividing cabin and cockpit in order to be able to draw conclusions about if and to what extent pathogens spread into the cockpit from the cabin.

Results indicated that with a spontaneously breathing patient there is a risk of pathogens not only spreading in the cabin, but also in the cockpit. The probability of infection depends on various factors like the type of pathogen, the transmission pathway and the exposure time. In the worst case scenario, such as a massive emission of droplets, there was a high probability of the pathogens not just settling on the surfaces in the entire cabin, but also spreading to the cockpit if there is no dividing curtain. In the presence of a curtain, the particles landed on it. During the second test, with a short droplet emission equivalent to a cough or brief separation from a breathing tube in real life, there were deposits around the patient but not in the cockpit. This implies that the duration of droplet release determines the range and the degree of contamination. Variables such as ventilation settings for heating or air conditioning, flight direction or flight manoeuvres were also taken into consideration.

These findings enable measures to be taken regarding patient and occupational protection. It is crucial to clean all surfaces in the cabin after transporting a highly infectious patient, because the restricted space obviously increases the risk of contamination in comparison to a normal hospital room. Separating the cockpit and the cabin can generally also provide additional protection. Medical crews absolutely must wear personal protective equipment.

“The hygiene management team at DRF Luftrettung has set itself the goal of optimising the already high hygiene standards in emergency medicine above and beyond the legal guidelines,” reports Raimund Kosa, coordinator of hygiene management. “This was also where the idea for the scientifically-accompanied field test came from. At the start of the study, we could not have predicted that the topic would be quite so explosive in the wake of the coronavirus pandemic, but it makes the importance of our work even clearer.”

In the course of the coronavirus pandemic, DRF Luftrettung has implemented extensive measures to protect its staff and patients. These include the mandatory use of PPE and strict hygiene measures at its HEMS bases, as well as increasing training courses on hygiene for crew members. In addition, 11 EpiShuttles have been procured. These segregated stretchers provide optimal protection for patients and crew. The stations that have this equipment will also be ready for action more quickly after each operation, as the time-consuming disinfection of helicopters after missions with highly infectious patients will no longer be necessary.

The operator concludes that aside from cockpit separation, another aspect worthy of study is alternative disinfecting technologies because, until now, there has not been any procedure that is approved by aircraft manufacturers on account of avionics and the diversification of technical components.