Material and method
This was an observational study that analysed retrospective mission data. The patient population for the rescue helicopter service at Ørland Air Base includes all of Trøndelag county and the Nord-Møre and Romsdal districts, with a total of 730 000 inhabitants over an area of approximately 56 000 km2 (6).
We compared data from the first eight months of operating the SAR Queen (14 May 2021–14 January 2022) with the equivalent eight-month operational period for the Sea King (14 May 2020–14 January 2021). All requests for emergency missions by the rescue helicopter at Ørland Air Base were included in the study. Data were retrieved from LABAS (Normann IT, Trondheim), a documentation system where the air ambulance doctor documents requests for air ambulance services from the Emergency Medical Communications Centre (EMCC) or a Joint Rescue Coordination Centre.
We registered the types of missions that the rescue helicopter undertook during the study period, divided into primary missions, search and rescue missions and secondary missions.
Primary missions are regular air ambulance missions where the patient is located outside of a hospital, while secondary missions are missions involving transfer of a patient from one hospital to another (from a lower to a higher care level). Search and rescue missions involve search for or evacuation of persons from areas that are difficult to access, for example in mountain areas or at sea.
Furthermore, we registered the number of missions that were either aborted or rejected. We were especially interested in studying whether the proportion of missions that were rejected because of adverse weather or technical problems with the aircraft had changed after the introduction of a new, modern helicopter, with facilities such as automatic de-icing of the rotor blades.
We also registered the helicopter's response time, i.e. the time from receipt of the alert until the helicopter is airborne. In addition, we registered the time from landing to departure in cases where a patient was picked up, be it from a site of injury, a hospital or an airport – here jointly referred to as on-scene time. The new helicopter type sometimes needs to land at the nearest airport instead of at the hospital. We therefore undertook an isolated investigation of any changes to the on-scene time for secondary missions, and for primary missions and search and rescue missions combined, that resulted in patient contact. The rescue helicopter also flies missions that do not end in patient contact, typically because the patient cannot be found after a search, or because the patient has been found by ground search teams.
The frequency with which a rescue paramedic or a doctor was hoisted down to undertake the mission was recorded. Hoisting is used to reach patients when landing in the vicinity is difficult. The analyses of the frequency of hoisting were undertaken only for primary missions and search and rescue missions with patient contact. Hoisting is not relevant during secondary missions transporting a patient from one hospital to another.
Finally, we registered the degree of severity of the patients' clinical condition. We used NACA scores (National Advisory Committee for Aeronautics), a well-established method for scoring the degree of severity in emergency medicine outside of hospitals (7, 8), which are registered for all air ambulance missions in Norway. We defined patients with a NACA score of 4–7 as seriously ill or injured (Table 1).
Table 1
NACA scores (National Advisory Committee For Aeronautics) for the degree of severity of disease or injury (7).
| NACA score | Definition | Examples |
|---|
| 0 | No injury or disease | |
| 1 | Slight injuries/diseases without any need for acute medical care | Transient hypotension, abrasions |
| 2 | Injuries/diseases requiring medical treatment, but hospital admission not indicated | Moderate soft-tissue injury; normal birth; discharged patient transferred to another hospital for care |
| 3 | Injuries/diseases that are not life-threatening but requiring hospital admission | Mild concussion; fractures; large wounds; mild asthma, non-specific chest pain; cancer without organ failure |
| 4 | Injuries/diseases that are potentially life-threatening | Acute coronary syndrome; fracture of large tubular bones; burns 20–30 % |
| 5 | Life-threatening injuries/diseases requiring immediate treatment | Suspected internal cranial pressure; large, complicated fractures; suspected rupture of the viscera with circulatory effects |
| 6 | Injuries/diseases transported after successful resuscitation of vital signs | Injury to the central nervous system with disturbed respiration or circulation; thoracic injury; respiratory or circulatory arrest |
| 7 | Dead on site or within the period that the service is responsible for treatment, after resuscitation attempts. | |
The study was submitted to the Central Norway Regional Committee for Medical and Health Research Ethics (REK Midt), which considered it as quality assurance and hence not subject to approval. Approval by the data protection officer at St. Olavs Hospital was also obtained prior to implementation of the study.
Descriptive statistics were produced using IBM SPSS Statistics 27 (IBM Corporation, Armonk, NY, USA).