Two hundred and fifteen HEMS bases from 13 European countries were invited to take part in the survey (S3). Of these, 53 HEMS bases completed the survey (25%), which were included in the analysis. Within the survey period, 171 missions were performed by the participating HEMS bases.
Characteristics of participants
Participating HEMS teams were from Germany (n=26), Denmark (n=16), United Kingdom (n=6), Luxemburg (n=2), Austria (n=2) and Switzerland (n=1). HEMS availability was quoted 51% 24-hours and 45% until sunset (4% no response). Helicopter types were quoted Airbus H135 and predecessors 55%, Airbus H145 and predecessors 26%, McDonnell Douglas (MD) 902 13%, and Agusta Westland DaVinci 2% and 4% other types. Pilot configuration was quoted 70% single pilot, 13% dual pilot, and 17% dual pilot depending on time of day. A median (range) of 4 (0-8) HEMS mission per day were performed during the study period by the participating HEMS teams.
Medical crew qualification
Medical team configuration was physician staffed in all respondents (physician/paramedic 92.5% and physician/flight nurse 7.5%). Three respondents (10%) had an additional trainee or resident physician on board. Most physicians had a median (range) experience in HEMS of 9 (0-25) years, were anesthesiologists (79%), board certified (92%), and had a special ICU training (89%).
Helicopter ventilators were able to provide only volume-controlled ventilation (VCV) in 23% of the services, whereas 77% could provide pressure control ventilation (PCV) and continuous positive airway pressure (CPAP) ventilation in addition to VCV. The most common used ventilator in the VCV only group was the Oxylog 2000 (Dräger Lübeck, Germany) and in the PCV group the Oxylog 3000 series (Dräger Lübeck, Germany). Hamilton T1 (Hamilton Medical AG, Bonaduz, Switzerland) was used in less the 10% of the participating HEMS bases. Bag/mask ventilation (BMV) was quoted as ventilator backup in all cases (55% including O2-demand option) while six respondents (11%) reported carrying an additional ventilator on board. Two teams perform blood gas analysis on board. A roll-in stretcher was available on 34% of the aircrafts.
A total of 30 ventilated patients with a median (range) age of 54 (21-100) years were transported. During the transport, the HEMS physician was accompanied in the cabin by the paramedic/flight nurse in 34% of the cases.
Sixteen patients (53%) were male. Eighty percent (n=24) of the included patients were from primary missions while six patients underwent interfacility transport (five patients from intensive care unit, ICU, and one patient from emergency department, ED). Fifteen patients (50%) suffered from trauma, seven (23%) from cardiac arrest of whom four already had a return of spontaneous circulation (ROSC) following out-of-hospital cardiopulmonary resuscitation (CPR), while one underwent helicopter transport with ongoing mechanical chest compressions using an automatic chest compression device (ACCD).
Other diagnoses of patients were neurologic/neurosurgical (n=6), acute respiratory distress syndrome (ARDS, n=2), and burns (n=1). Airway management was performed by the HEMS-team in 18 cases (60%) of which all patients underwent tracheal intubation except one patient with a supraglottic airway device (laryngeal tube). Mechanical ventilation was performed using volume-controlled ventilation in 17 (59%) and pressure-controlled ventilation in 12 (41%) patients with a median (range) tidal volume of 6 (4-7) mml/kg body weight, whereas mode of ventilation was missing in one patient. Adaptive support ventilation (ASV) or pressure support ventilation (PSV) was not used at all during transport.
Data upon vital functions and ventilator settings at first patient contact and at handover are provided in Table 1. Two patients (7%) deteriorated during flight due to underlying critical conditions as reported by the respondents. 97% of all patients had capnography monitoring (etCO2) during transport with missing information in one patient. Pulse-oximetry (SpO2) was measurable in 27 patients (90%) while in the remaining three cases, patients were in a state of circulatory shock without sufficient peripheral perfusion for SpO2 measurement. At the hospital helipad, a hospital ventilator was provided in nine cases (31%), oxygen was provided in 20 cases (69%), and a medical receiving team was provided in another 20 cases (69%). Ventilation during transfer from the helipad to the receiving department was performed using the helicopter ventilator in 25 patients (83%), using a hospital ventilator in three patients (10%) and using manual bag-ventilation in one patient (3%). During transfer to the receiving department, the HEMS team carried an emergency bag / backpack in 21 cases (72%), a BMV in 27 cases (93%) and ACCD in two cases (ACCD being active in one case, as described earlier). Handover was carried out in the ED in 19 patients (65%), in the ICU in six patients (21%) and in the percutaneous coronary intervention (PCI) suite in four patients (14%).
Patients´ devices and catheters included peripheral intravenous (IV)-lines in all but two patients (94%) whereas one had an intraosseous (IO) access and another a central venous catheter (CVC) and no peripheral IV line. Six patients had a CVC and peripheral IV-lines. A single IV-line was present in five (17%) patients, two IV-lines in 22 (73%) patients, and three IV-lines in one (3%) patient. A CVC was present in seven patients (23%) (n=2 in the internal jugular vein, n=1 in the subclavian vein, n=4 in the femoral vein). Invasive arterial blood pressure measurement was carried out in five patients (n=4 of the arterial lines were in the radial artery, n=1 in the femoral artery). A urinary catheter was present in six patients (20%). CVC, arterial lines and urinary catheters were present in patients undergoing interfacility transport.
Furthermore, an abdominal drain, bilateral chest tube and pelvic sling were present in one patient, each. Syringe pump devices for continuous drug administration were present in 14 patients (48%) of which one syringe pump was used in 10 patients, two and three syringe pumps in two patients, each, and four syringe pumps in one patient. Most frequent drug administration during flight was quoted analgesics (93%), neuromuscular blocking agents (45%), and vasopressors (43%).