Air transport by the Wellington Flight Service: a descriptive analysis of interhospital transfers over a 5-year period in the Wellington region of New Zealand

Air transport is used routinely in New Zealand for transfer of patients with serious illness or injury who require retrieval to a tertiary centre for definitive care. It is also sometimes used to return more clinically stable patients to their local hospital for ongoing care, or in rare circumstances to transport a patient back to their home for withdrawal of treatment and palliative care.1Interhospital transfer refers specifically to transports between medical facilities, as distinct from primary retrieval which denotes the transport of patients from an initial scene of accident or illness to the primary medical care facility.The Wellington Flight Service (WFS) is based in the Wellington Regional Hospital and works in conjunction with Life Flight Trust, Air Ambulance and Wellington Free Ambulance primarily to provide interhospital transport in the lower North Island and upper South Island of New Zealand. Wellington Hospital is the tertiary referral hospital for this area providing tertiary level neurosurgical, cardiothoracic, vascular, paediatric, intensive care, oncological and haematological services.Burns and plastic surgery services are provided in an adjacent smaller hospital in the Wellington region. A comprehensive database is maintained to record details of all secondary or interhospital transfers undertaken by the Wellington Flight Team.There is inherent risk associated with air transport of patients with most patients acutely ill and requiring high levels of clinical care in what is an extremely challenging environment.2-6 The recommendation is that dedicated transfer teams should be used for interhospital transport of patients,6-8 and this is the role that the WFS undertakes.To date, the workload characteristics for the WFS or other similar services around New Zealand have not been examined. Developing an understanding of current service utilisation and workload patterns would inform planning for future service and care delivery, both regional and tertiary, as well as contributing towards research evidence for Air Transport practice in New Zealand, and is an important prelude to examining patient outcomes.A 2008 report of the New Zealand Air Ambulance Reference Group highlighted both the absence of consistent and reliable data on which to base service planning long-term, and the limited New Zealand research evidence available to inform their work on clinical matters,9 suggesting a clear need for this type of work to be undertaken.This study aimed to describe and characterise the workload for the Wellington Flight Service over a 5-year period, and to identify any trends over that time.Method All missions undertaken by the WFS during the 5-year period from 1 November 2005 to 31 October 2010 were retrospectively reviewed. For each mission we extracted the time of mission, duration of mission, type of transfer, category of patient, service the patient was being transferred to/from and the medical crew in attendance. The study protocol was reviewed by the Central Regional Ethics Committee and found to conform to the New Zealand standards for observational health research. The WFS operates out of Wellington Hospital, which provides tertiary cover for public hospitals at Blenheim, Nelson, Masterton, Kenepuru, Hutt, Whanganui, New Plymouth, Hastings and Palmerston North. The current population for this region at June 2010 was 1,108,230 people.10 Transports are undertaken by fixed wing aircraft or helicopter though in some circumstances road ambulance, or very occasionally commercial flights, will be employed. At times aircraft are unavailable due to maintenance or mechanical failure, or in adverse weather conditions due to airport closure. Road transports are undertaken by the flight service over relatively short geographic distances when patients are critically ill and requiring advanced clinical care during the transfer, for example between Hutt and Wellington intensive care units (ICUs). Sometimes a transport started by air may be diverted and completed by road into Wellington. Very occasionally situations occur where tertiary care is required but emergent air retrieval is not possible, so a road retrieval with an expert tertiary team is initiated despite the associated time delays. The goal in this situation is retrieval to Wellington as soon as possible because the risk of significant morbidity or death is high if they stay where they are, meaning the relative risk of transfer is less in context. For the purposes of this review, the missions analysed in detail were those where it was the Wellington flight team who transported the patient from origin to destination, and where this was the primary purpose of their mission. A mission was designated to the 2006 review period if it occurred during 1 November 2005and 31 October 2006, or designated to the 2007 period if it occurred during 1 November 2006 and 31October 2007 and so on. Missions were defined as cretrievalsd when the patient was being transported to Wellington Hospital, or ctransfersd where they were being transported away from Wellington Hospital or between two other hospitals. Mission time was calculated from cstart missiond to cfinish missiond times as entered in the flight service database. Start mission referred to the time that the Flight Nurse began direct preparation for that specific retrieval such as phone calls co-ordinating Life Flight, ambulance, hospitals, calling in a doctor (out-of-hours), checking equipment and obtaining necessary paperwork. End mission referred to the time that the retrieval team had handed over the patient to the receiving team, completed their paperwork and equipment restocking, and were available to commence another mission. Missions excluded from the review were those for which the WFS was involved in a more logistic capacity, including missions where a non-acute patient was transported on the empty leg when an aircraft was already assigned to an acute transport (backload), the mission was referred on to another flight service (refer on), it was an elective transfer under the National Travel Assistance policy (NTA assist), assistance was provided to arrange transport (assistance), or the mission was aborted (aborted) for reasons which might include death of the patient before the transport team arrived, weather changes or irretrievable mechanical failure. Illness severity was categorised in order of severity from A to D. Category A patients were those in critical condition requiring invasive ventilation or other means of advanced life support such as pacing, vasoactive medication or an intra-aortic balloon pump: these patients required both an ICU flight nurse and a doctor with full and continuous monitoring during transfer. Category B patients had generally undergone an acute incident requiring intensive care or specialist treatment but would not be ventilated or on advanced life support, but at risk of deterioration to the level where these may be required. Examples include patients with acute myocardial infarction, subarachnoid haemorrhage, spinal injury or multi-trauma. This group of patients required an ICU or specialist flight nurse although use of a doctor was viewed as discretionary. Category C patients were usually post-treatment or investigation and not requiring intensive clinical care during flight. This patient group were usually accompanied by a Transit Care flight nurse. Category D would essentially be repatriation patients, accompanied by a flight nurse but only because they were with another patient. Results Over the 5-year period reviewed the WFS completed 4046 transport missions, although they were contacted regarding a total of 7635 missions, averaging 1527 per year (Figure 1). On average 2.2 missions a day were completed, with the proportion of missions for which the flight service were contacted but not primarily involved in transport increasing from 40% in the 2006 review period to 51% in the 2010 period. The proportion of retrievals to transfers was equal overall, with the trend for lower rates of retrievals from 2006 to 2009 reversing in 2010 when 58% of transports were retrievals to Wellington Hospital. Fixed wing aircraft were used to transport 70% of all patients, helicopters 18% and road ambulances for 11% of all completed transports. Commercial flights were used less than 1% of the time. Over the 5-year period reviewed, helicopter transports steadily decreased from a high of 23% of all transports undertaken for the 2006 period down to 13% for 2010 (Figure 2). Figure 1 Figure 2 *In the 2006 period commercial transports accounted for 1% of overall transports. For logged missions where it was not a WFS primary transport the numbers were fairly consistent, except for missions carried out as a backload, with 5% of missions aborted, 17% elective transfers carried out by someone else under a national travel assistance policy and 5% referred on to another service. Missions that were designated as backloads increased steadily going from 9% in the 2006 period up to 25% for 2010. The characteristics of the transported patients are outlined in table 1. Most patients were 25 years or older (81% in total). They were residents of the greater Wellington area and adjacent regions (96% in total) with the single largest transported group being those usually domiciled in the Nelson/Marlborough region (44%). Cardiology services requested 16% and cardiothoracic 9% of transports, with transfers and retrievals in fairly even proportions. Other services had high proportions of retrievals including ICU which accounted for 9% of transported patients overall (71% were retrievals), neurosurgery at 14% of transports (64% were retrievals); and obstetrics with 7% of transports (65% were retrievals). Table 1. Age range DHB domicile Service/DRG (transfers and retrievals) % of overall transports % for the service which were retrievals < 12 months 3% Taranaki 5% Cardiology 16% 53% 1 - 4 years 3% Hawke's Bay 2% Cardiothoracic 9% 50% 5 - 17 years 5% Whanganui 4% Gen Medicine 7% 28% 18 - 24 years 7% Mid Central 7% Gen Surgery 6% 48% 25 - 49 years 23% Capital Coast 13% Intensive Care 9% 71% 50 - 74 years 42% Hutt Valley 9% Obstetrics 7% 65% 75 years plus 16% Wairarapa 11% Neurosurgery 14% 64% Nelson-Marlborough 45% Orthopaedics 6% 31% Canterbury 1% Paediatrics 6% 50% South Canterbury 1% Other 19% 37% Twenty-one percent of transported patients overall were in critical condition (category A), 17% requiring invasive ventilation, and 51% not classified as critical but nonetheless requiring intensive clinical care (category B). The trend for category A critical transports and ventilated patients gradually increased over the 5 years reviewed from 16% up to 26% and 13% up to 21% respectively, while proportionately it was the category C non intensive clinical care transports decreasing from 34% down to 19% over the 5-year period Category A: Most Category A transports were retrievals (81%) under the care of intensive care (33%) or neurosurgery (26%), with other services represented including cardiology (5%), cardiothoracic (7%), general medicine (6%) and general surgery (6%). Compared to the figures for all transports, a higher proportion of critically ill patients were transported by helicopter (28% versus 18% overall) and road (29% versus 11% overall), and only 43% by fixed wing aircraft (versus 70% overall). Category B: The highest proportions of Category B patients (59% retrievals) were under the care of cardiology (24%), obstetrics (12%), neurosurgery (10%), cardiothoracic (8%) and paediatrics (8%). The mode of transport was similar to the proportions for overall transports at 71% fixed wing, 20% helicopter and 9% road. The median mission time for all transports was four hours and 30 minutes (IQR 3h29m to 6h). A higher proportion of transports occurred on weekdays (between 14 and 17%) than weekends (10 and 11%) and this trend remained constant over the 5 years reviewed. A high proportion of missions (69%) started between the hours of 7am and 4pm, but 26% started between 4pm and midnight, and 6% between midnight and 7am. Of those starting after midnight a high proportion (71%) were retrievals to Wellington Hospital, and most (90%) were critically ill or requiring intensive care (category A or B patients). Overall 9% of missions took 8 hours or longer from the logged start time to logged final completion. 11% of the missions undertaken by fixed wing aircraft lasted 8 hours or more compared to only 3% of road transports and 1% of helicopter transport missions. Proportionately, 75% of these long missions were category A or B patients, and 55% of the patients were under 50 years of age. In terms of clinical services 16% were under the care of paediatrics and 9% under the care of orthopaedics although these services accounted for only 6 % of overall transports each. Conversely 12% were under the care of cardiology, 10 % under neurosurgery, and 4% under cardiothoracic specialities but respectively these services accounted for 16 %, 14%, and 9% of overall transports. When the services are considered individually 22% of all paediatric 14% of all orthopaedic and 11% of general medicine transfers took 8 hours or more. A doctor accompanied the patient in 34% of overall transports, the trend showing a steady increase from 28% in the 2006 period up to 43% of transports in the 2010 period. Over the period of review a total of 18 Category A patients were transferred without a doctor present, and 13 of these patients were ventilated during this transport. In 8 cases the patient was being transferred back to a secondary hospital for withdrawal of treatment and palliative care. A doctor was involved in the transfer of 14% of category B cases during the study period, and less than 1% of Category C cases. A midwife was present for 4% of overall transports.