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Incidents, accidents and fatalities in 40 years of German helicopter emergency medical system operations

Hinkelbein, Jochen; Schwalbe, Mandy; Neuhaus, Christopher; Wetsch, Wolfgang A.; Genzwürker, Harald V.

European Journal of Anaesthesiology: November 2011 - Volume 28 - Issue 11 - p 766–773
doi: 10.1097/EJA.0b013e328348d6a8
Emergency medicine
Free
SDC

Context Currently, approximately 100 000 helicopter emergency medical service (HEMS) missions for patients are undertaken in Germany each year. Compared to the early years, risk has reduced significantly, but is still higher than commercial aviation or other airborne operations.

Objective The aim of the present study was to evaluate helicopter accidents and fatalities related to HEMS operations.

Design Retrospective study of HEMS accidents in Germany.

Setting Analysis of accidents in the published flight accident reports of the German Federal Agency for Flight Accident Investigation (40-year period from 1970 to 2009). Data were collected by telephone interview with the operators, manual search of publications and by supplemental internet information.

Main outcome measures Data were analysed per 10 000 missions. For statistical analysis, Fisher[Combining Acute Accent]s exact test was used. A P value less than 0.05 was considered significant.

Results During the period analysed, a total of 1.698 million HEMS missions (1970 vs. 2009: 61 vs. 98 471) were flown by a mean of 50 ± 27 (1 vs. 81) helicopters. To date, missions resulted in a total of 99 accidents with a mean of 2.4 ± 1.7 accidents per year (range 0–7). The accident rate was 0.57 (0–11.4) per 10 000 missions and the fatal accident rate was 0.11 (0–0.5). Some 64% of missions did not result in any injuries to occupants, whereas 19.2% were fatal. From the accidents analysed, 43.4% were due to collision with an obstacle during landing, take-off or hovering. Landing was the phase of flight most often associated with accidents (44.4%).

Conclusion The present study is the largest on HEMS accidents and the only one analysing an entire 40-year time course beginning with inception. In comparison to previous data, a significantly lower accident rate per 10 000 missions was found. Gathering data on the early years is nearly impossible, and further analysis is required to calculate the risk of fatality or identify injury patterns.

From the Department of Anaesthesiology and Intensive Care Medicine, University Hospital of Cologne, Cologne (JH, WAW), Working group ‘Emergency Medicine and Air Rescue’, German Society of Aviation and Space Medicine (DGLRM), Fürstenfeldbruck (JH, MS, CN, HVG), Medical Faculty Mannheim, Ruprecht Karls University of Heidelberg, Mannheim (JH, MS, HVG), Department for Anaesthesiology and Intensive Care Medicine, University Hospital Heidelberg, Medical Faculty Heidelberg, University of Heidelberg, Heidelberg (CN), Clinic of Anaesthesiology and Intensive Care Medicine, Neckar-Odenwald-Kliniken gGmbH, Hospitals Buchen and Mosbach, Buchen (HVG), Germany

Correspondence to Priv.-Doz. Dr. med. Jochen Hinkelbein, D.E.S.A., Department of Anaesthesiology and Intensive Care Medicine, University Hospital of Cologne, Kerpener Street 62, 50937 Cologne, Germany Tel: +49 221 478 88233; e-mail: jochen.hinkelbein@uk-koeln.de

Published online 5 October 2011

This article accompanies the following Invited Commentary:

Schoeffler P, Dualé C, Walder B. Risks of being an anaesthesiologist. Eur J Anaesthesiol 2011; 28:756–757.

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Introduction

Transportation of critically injured patients by fixed-wing airplanes1 and helicopters1,2 began as early as 1915 and 1945, respectively. In the years to follow, these war-driven experiments in the US and Germany were converted to civilian use. After preliminary test projects in the late 1960s, on 29 September 1970, the first German public rescue helicopter ‘Christoph 1’ began rescue operations at the Hospital of Munich-Harlaching. Since then, helicopter emergency medical services (HEMSs) have become increasingly important in the German emergency medical services (EMSs), and for many years now, HEMS has been fully integrated in the German EMS.3 The use of EMS helicopters for the critically ill or injured has increased significantly over the past years. Today, 81 helicopters cover the area of Germany, flying a total of approximately 100 000 combined primary and secondary missions per year.

No later than 1 year after inception, ‘Christoph 1’ crashed during an approach to an emergency scene on 17 August 1971 and was totally destroyed. The emergency physician was fatally injured; the pilot and the paramedic were severely injured. This was the first and additionally the first fatal aviation accident related to non-military HEMS operations in Germany. Over recent years, aviation safety has been improved by regulatory measures (e.g. Joint Aviation Regulations for Flight Crew Licensing, JAR-FCL, or Joint Aviation Regulations for Flight Operations, JAR-OPS) and technological advances in aircraft design and equipment (e.g. newer helicopter types or Global Positioning System), but almost every year, several HEMS-related accidents are reported with fatal outcomes in Germany. This raises serious concerns and generates fierce disputes about the benefits for patients,4–7 its effectiveness,2,8–11 cost,2,6,8–10 and foremost, its safety in general,12–21 but also when compared to ground EMS.

Studies on HEMS accidents are rarely published. International data are available for comparison for short time spans only from three different countries.22 International studies cover a maximum of 22 years only.20,23 Nevertheless, these data are highly important in improving safety in HEMS.

The aim of this study was to analyse HEMS accidents and fatalities during the entire lifetime of the German HEMS and to compare these results with those from systems in other countries. Furthermore, the underlying factors of the accidents were analysed.

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Materials and methods

Ethical approval for this study was waived (protocol no. 2011-244N-MA from 24 March 2011) by the Medizinische Ethikkommission II, Medical Faculty Mannheim, Ruprecht Karls University Heidelberg, Germany (Chairman: Professor Dr med. J.-P. Striebel), as this study was a retrospective analysis of a publicly accessible database.

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Data acquisition

Aviation accidents related to the German HEMS from 17 August 1970 to 31 December 2009 were identified in the annually published accident reports of the Federal Agency for Flight Accident Investigation (‘Bundesstelle für Flugunfalluntersuchung’, BFU).24 In these short, publicly accessible reports, both aviation accidents and fatalities are documented. The following data were collected:

  1. Date and time of accident
  2. Location of accident
  3. Type of helicopter (manufacturer and model)
  4. Phase of flight
  5. Number of persons killed, injured or involved as well as their role in HEMS (pilot, medical crew, patient, others)
  6. Severity of the accident (accidents without injuries, accidents with minor injuries, accidents with major injuries and fatal accidents; criteria according to Table 1)24
  7. Accident characteristics (e.g. collision, engine failure, etc.)
  8. Human factors and technical problems as underlying cause
Table 1

Table 1

Missing data, as well as further information (e.g. operators,25 accident details or material damage), were retrieved by a manual internet search of available databases26{rth.info. http://http://www.rth.info [Accessed 3 December 2010]} to augment the BFU data. Additionally, all operators, at telephone interview, were asked to provide denominator data for the time span analysed. These data were supplemented by data published elsewhere.3,13,20,27–30

For the classification of injuries and the severity of the accident, standardised criteria published by the BFU were used (Table 1).

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Inclusion and exclusion criteria

Only accidents involving official German EMS helicopters within Germany and occurring within the given time span were analysed. These included primary (emergency) or secondary (interhospital) missions. Privately operated helicopters for secondary flights were excluded from the analysis because they are not clearly classified as HEMS in the databases and because of a significant lack of data.

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Data presentation

Both accident rates and fatal accident rates were calculated on the basis of helicopter number and per 10 000 missions.28 Therefore, accident rate per helicopter was calculated as accidents per year [n]/helicopters per year [n]. Accident rate per missions was calculated as accidents per year [n]/missions per year [n].

To analyse human factors in HEMS accidents, the Human Factors Analysis and Classification System (HFACS) of Shappell31 and Wiegmann32 was used. HFACS is a general human error framework originally developed as a tool for investigating and analysing the human causes of aviation accidents.31,32 In previous investigations, the HFACS framework has been shown to be a viable tool for use within civil aviation.32,33 The underlying problems of, or factors contributing to, the accidents were classified according to the HFACS model and categorised as human factors or technical problems.31–33

When classifying the cause of aircraft accidents, defining ‘human factors’ or ‘human error’ is not straightforward. It may not simply be an error of a single individual, but rather a consequence of human interaction within a complex system, for example, omissions in maps that fail to alert crew to power lines or cables, leading to an accident. Furthermore, problems in the interaction of specific crew members [i.e. crew resource management, CRM, or crew coordination concept, CCC] are also causes of accidents.31,32

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Statistical analysis

Results are presented as mean ± standard deviation (SD). Fisher's exact test was used to analyse dichotomised variables. For the analysis, we used STATISTIKA 6.0 (StatSoft, Tulsa, USA). A P value less than 0.05 was considered statistically significant.

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Results

Helicopter accidents

During the period analysed, from 1970 to 2009, a total of 1 702 019 HEMS missions (1970 vs. 2009: 61 vs. 98 471) were carried out by a mean of 51 ± 27 (1970 vs. 2009: 1 vs. 81) helicopters. To date, these missions resulted in a total of 99 accidents with a mean of 2.5 ± 1.8 accidents per year (range 0–7). The incidence of fatal accidents was 0.5 ± 0.8 per year (range 0–3; Table 2). The Messerschmidt Bölkow Blohm BO105 type of helicopter (n = 38) was most often involved in accidents followed by Eurocopter BK117 (n = 17), Bell 206 (n = 14), Eurocopter EC135 (n = 9), Bell 222 (n = 7), Bell 412 (n = 5) and others (n = 9). Eleven of the 99 accidents occurred during night operations (11.1%).

Table 2

Table 2

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Severity of the accidents

Accidents during the specific time frame analysed were categorised according to their severity (Fig. 1). Of 99 accidents analysed, 63 were without injuries (63.6%), eight accidents were with minor injuries (8.1%), nine accidents with major injuries (9.1%) and 19 accidents were fatal (19.2%). Because for some accidents, the total number of occupants remains unknown, the total number of persons injured or killed could not be analysed. Helicopter occupants were not the only victims; one person outside the aircraft was seriously injured and two others slightly injured due to rotor downwash.

Fig. 1

Fig. 1

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Analysis of the accident rate

Both the accident rate and the fatal accident rate were calculated per helicopter and per year to facilitate comparisons with other published data (Table 3). The fatal accident rate was significantly lower than the accident rate (1 : 37.7 vs. 1 : 23.3; P < 0.05). The accident rate varied between one accident per three helicopters (1 : 3) in the year 1971 and 1 : 78 in the year 1997. The fatal accident rate varied between 1 : 3 and 1 : 81.

Table 3

Table 3

In addition to the rates per helicopter, rates on the basis of 10 000 missions were calculated. Of the helicopter accidents related to HEMS missions in Germany within the analysed time frame, an accident rate of 1.17 (range, 0.0–11.01) and a fatal accident rate of 0.47 (range, 0.0–0.11.01) were found per 10 000 missions (Table 3).

Both fatal accident rates per helicopter and fatal accident rates per 10 000 missions were significantly higher during the first 10 years of HEMS operations (1970–1979), than during the last decade (2000–2009; P < 0.05).

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Phase of flight

Landing was the phase of flight most often associated with accidents (n = 44; 44.4%) followed by en-route accidents (n = 26; 26.3%). During landing, collision with obstacles (n = 23) was the most frequent followed by ground/water collisions (n = 5; Fig. 2). For fatal accidents, obstacle collision during landing (n = 4 of 10) had also the highest incidence followed by tail rotor damage during en-route flight (n = 2 of 6).

Fig. 2

Fig. 2

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Human factors and technical problems

Human factors were the main contributors to both fatal and non-fatal helicopter accidents, including obstacle collision (n = 43; 43.3%), uncontrolled flight attitudes (n = 9; 9.9%) and ground/water collisions (n = 7; 7.7%). Technical problems overall contributed to seven (7.7%) accidents.

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Discussion

The present study is the largest study of HEMS accidents and the only one analysing the complete lifetime of HEMS activities within a single country. Since aviation safety, especially in HEMS systems, has received increasing attention during recent years, studies analysing accidents and accident rates have become more and more important.20 Although regulations and aircraft technology have been enhanced in the last years, the number of accidents has increased.12,14,16,20 This raises serious concerns and generates fierce disputes about the benefits for patients,2,4–7,34 the effectiveness of the system,8–11 the resulting costs2,6,8–10 and system safety of HEMS missions.12,14–21 Multiple studies have addressed this question, but their results have been controversial.3,5,8,11,17 Whereas some studies found genuine patient benefit for rescue or related services,4,34–36 others found a significantly higher risk, longer transport times or no clear impact on survival rates.37–39

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Severity of the accidents

In the present study, most accidents analysed (63.6%) were without injuries of the occupants. This ratio agrees with data presented by Thies et al.20 (62.5%) who also analysed the German HEMS system, but used another database and a different time frame. In contrast to the present study, in the United States, Bledsoe40 found that 30% of accidents did not result in injuries. Whereas nearly one fifth of all our accidents were fatal accidents (19. 2%), the percentage of accidents with minor or major injuries was comparable (8.1 vs. 9.1%, total 17.2%). In their study, Thies et al.20 also analysed the German HEMS systems according to accidents and fatalities, and found only 6.25% fatal accidents but 31.25% accidents with injuries. Nevertheless, the fatal accident rate of the present study is clearly lower than the rate reported by Baker et al.12 for the United States, and this has support from Bledsoe40 who found that 32% of all accidents resulted in fatalities. In comparison to the percentage of accidents in other general or commercial airline operations,41 the fatal accident rate in HEMS operations was found to be significantly higher.

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Analysis of accident rates

For HEMS missions in Germany, an accident ratio of total vs. fatal, 1.17 to 0.47 (Table 3) was found per 10 000 missions. Without any specific analysis, these accident rates seem quite high. However, for sufficient data interpretation, the time course must be taken into account and interpreted appropriately. Whereas the rates were quite high at the beginning of HEMS operations in the 1970s (>11 in 1971), they fell significantly during the following years (<0.5 after 2006). Therefore, the mean rates must be interpreted carefully.

Our data differ only slightly from a recently published study by Thies et al.20 analysing HEMS accidents between 1980 and 2001. Compared to another report from Germany by Lippay28 analysing HEMS between 1973 and 1994, there was a significant decrease in the accident rate (0.91 vs. 0.54, P < 0.05), although data for fatal accidents were not presented. When looking at international data, this clear trend is not reported for all countries – some even observed an increase in the number of HEMS accidents.40,42

Holland and Cooksley17 analysed a 10-year period with 51 164 missions for HEMS in Australia. They report similar accident rates per 10 000 missions for their specific time frame. Although both systems and regional structures are very different (short-distance rural vs. long-distance desert area), accident rate and fatal accident rate are comparable (not significant).

It is noteworthy that the accident rate per EMS helicopter in Germany seems to be quite high. In an international systematic review,22 data for accident rates on the basis of 10 000 missions were comparable with Australia17 and Germany.3,20,28 In contrast, the data for the USA19 had a five-fold higher rate, due to the reasons given above. For fatal accident rate per 10 000 missions, the same similarities for Australia and Germany, and differences for the USA, were found. Although the reasons for the discrepancies in international data were not analysed in the present study, we can speculate that many factors in a HEMS system such as operating hours, type of flights, or regulations, as well as the impact of the aeromedical system including the number and types of helicopter, indication or distances of HEMS missions, could all be relevant influencing factors.

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Phase of flight

HEMS accidents related to landing were the most often reported in the present study (44.4%). This is in agreement with other published data20,43 and other aviation areas.33 In these cases, collision with an obstacle was the dominating cause.

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Human factors and technical problems

Human factors were the commonest cause of fatal and non-fatal helicopter accidents (Fig. 2). Surprisingly, these ranged from a simple obstacle strike (e.g. with the rotor) to intentionally performed inappropriate flight manoeuvres. Colett44 also found that obstacle strikes were a common cause of HEMS accidents. Throughout the world, human error causes or contributes to approximately 75–80% of all aircraft accidents.33,45,46

Technical defects and external causes play only a minor role in accident mechanisms and were rarely reported. Usually, they caused only slight damage to the helicopters or slight injuries to individuals. The incidences of technical defects and external impacts were identical in a recent study on HEMS accidents.3

These results are confirmed by many other authors, who also found similar figures for other countries as well as for other aviation fields.20,33,40 Nevertheless, compared to the latter, the risk profile for HEMS is clearly higher, due perhaps to adverse conditions, unknown landing sites and stress,19,29,47 and perhaps this is the explanation.28,47

It is important not to overlook the risk–benefit aspects when evaluating effects and problems of HEMS systems. Although accident risk in HEMS operations may be higher compared to ground-based EMS in Germany,13 several studies reported an improvement in outcome when transporting major trauma patients by HEMS,48 including a significant reduction in mortality in this specific group.5 As it was not the intention of the present study to perform a risk–benefit analysis in HEMS, this interesting and important question cannot be answered with the present data. A recently published systematic review identified 15 studies on this topic.2 Here, the cost and effectiveness of HEMS varied considerably between all studies analysed. Despite generally being more expensive than ground-based EMS, a number of studies found HEMS to be cost-effective.

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Limitations

Data retrieval for the present study was complicated due to a lack of data in more than one database, especially for the early accidents. In recent years, accident analysis and prevention have become more and more important. Whereas in the 1970s, such approaches were uncommon, Safety Management Systems (SMSs) are nowadays standard in companies for internal and external quality assessment. Therefore, data from the early years may be incomplete as incidents were not reported to the aviation authority.

One of the major difficulties encountered in this study was that Germany does not have a centralised compulsory reporting system for HEMS flight hours and the number of missions performed. This problem is not new and has been reported both for other aviation areas23 and in other countries.17 Without valid denominator data, sufficient interpretation of the results is difficult. Moreover, comparing data from different studies compounds the difficulty as some studies rely on 10 000 missions and others on 100 000 flying hours.22 In the present study, for the analysed time frame, data based on 100 000 flying hours were not available for Germany, preventing comparison with several other studies.

The reports published by the BFU are very short and contain direct accident-related details (e.g. date, time, helicopter model, injuries, etc.) only. For sufficient data analysis and data interpretation in the context of aviation crashes, knowledge of contributing factors is important, but these could not be analysed in the present study. Although 11 of 99 accidents occurred during the night, and approximately 10 of 81 helicopters do night operations in Germany, calculation of specific day or night-accident rates was not possible. Whereas the total number of missions per year could be retrieved, assigning them to day or night-operations was impossible.

Privately operated helicopters for secondary flights were excluded from the analysis, as they are not clearly classified as HEMS in the databases and due to a significant lack of data. The same applies to a small number of military helicopters mostly used for off-shore search and rescue missions.

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Conclusion

The present study analyses a 40-year period of HEMS operations and is to date the largest available report for Germany. HEMS missions are more risky than other aviation operations, but risk resembles that of ground EMS missions in Germany.13 During the time frame analysed, 99 accidents of varying severity were reported. HEMS-related accidents and fatal accidents occurred with an incidence of 80.8% (n = 80 of 99) and 19.2% (n = 19 of 99), respectively. Both the accident rate and the fatal accident rate per 10 000 missions in German HEMS operations fell significantly in recent years.

The majority of accidents occurred during landing. Although gathering data on the early years is nearly impossible, further analysis is required to calculate fatality risk, injury patterns and accident causes in a more detailed approach.

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Acknowledgements

All authors made substantial contribution to this study. No other person made substantial contributions. The authors have no conflicts of interest to declare.

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Keywords:

accident; air-rescue; aviation; crash; helicopter emergency medical service; rescue helicopter

© 2011 European Society of Anaesthesiology