Characteristics of trauma patients treated by Helicopter Emergency Medical Service and transported to the hospital by helicopter or ambulance

Abstract

Introduction

Trauma patients treated by the Helicopter Emergency Medical Services (HEMS) can be transported to the hospital either by helicopter or by ambulance, in both cases accompanied by the HEMS physician. The objectives of this study are first to compile an overview of patients treated and transported by the HEMS team with either the helicopter (patients transported by helicopter, PTH) or with the ambulance (patients transported by ambulance, PTA). In addition, to evaluate whether the existing information systems obtain relevant data for researching the decision-making process. The second objective is to identify potentially influencing factors that could be significant for further research.

Methods

All patients in the period from 1 January 2011 until 31 December 2020, treated by HEMS and subsequently transported to hospitals were included in the study. To avoid overrepresentation of the PTA group, a random sample was taken, creating two groups in a 1:2 ratio (PTH n = 724, PTA n = 1448). Differences in patient and treatment characteristics between PTH and PTA were compared using t-tests, Mann-Whitney U tests, and chi-square tests.

Results

PTH accounted for 12.2% of all transports. Approximately two-third of the patients were male and the mean age was around 40 years. PTH had lower iEMV (initial Eye opening, best Motor response, best Verbal response) and iRTS (initial Revised Trauma Score) scores, were more frequently transported to a level 1 trauma centre, underwent more prehospital treatments and were roughly twice as far from their hospital of arrival compared to PTA.

Conclusion

The current dataset is, after some modifications, suitable to provide a comprehensive overview of patients treated by HEMS in the Netherlands. A predictive model could be developed using this dataset, which should include factors such as the patient’s location, age, distance to the hospital, physician on duty, mechanism of injury and overall injury severity.

Introduction

In 1995, the first Helicopter Emergency Medical Service (HEMS) was introduced to prehospital care in the Netherlands. HEMS has been introduced as an enhancement to regular ambulance emergency service. A helicopter as transport modality was chosen to quickly deliver specialized medical care to emergency services on the trauma site.

Although distances are relatively short compared to other countries, ground transport to a level 1 trauma centre can still be as long as 40 to 60 min [1]. At this moment around 65% of the Dutch population has access to this specialized medical care within 20 min [2]. The addition of HEMS has been shown to have beneficial effects on survival in several countries [3,4,5,6]. However, studies are difficult to compare because the primary purpose of using HEMS differs worldwide [5,6,7,8]. In several countries, HEMS is used mainly as transport modality for the patient, whereas the ultimate goal of HEMS in the Netherlands is to bring additional specialized medical care to the scene of the critically ill or injured patient [2, 4, 9,10,11]. The team consists of a physician (anaesthesiologist or trauma surgeon), a specialized flight nurse and a pilot [9]. The HEMS team provides prehospital additional therapy, such as the induction of general anaesthesia, inserting of a chest tube, resuscitative thoracotomy or amputation of an entrapped limb [4]. The HEMS team makes the decision to transport the patient to the hospital either by ambulance or by helicopter. Most patients are transferred to the hospital using an ambulance, accompanied by the HEMS physician. The factors influencing this decision are yet unknown, as a comprehensive overview of the patients transported by HEMS in the Netherlands is currently lacking, and there are no established guidelines or decision trees. Although factors such as time to the nearest appropriate hospital and the need for lifesaving interventions during transport are suggested to influence the choice between helicopter and ambulance transport [2], their actual impact remains unclear. Examining the patient population treated by the HEMS team could reveal differences in characteristics between patients transported by helicopter (PTH) and patients transported by ambulance (PTA). This could serve as a preliminary basis for further research using regression models to identify the most significant factors in the decision-making process. Findings from this research could then be used to optimize the allocation of HEMS resources, enhance patient outcomes, and refine transport protocols, ultimately improving the effectiveness and efficiency of HEMS operations in the Netherlands.

The first objective of this study is to compile an overview of patients treated and transported by the HEMS team of Lifeliner 3, operated by Radboudumc in Nijmegen, the Netherlands, and to evaluate whether the existing information systems provide relevant data for researching the decision-making process. The second objective is to conduct a univariate comparison of patients transported by helicopter versus those transported by ambulance, to identify potential influencing factors that could be significant for further investigation. Comparison is based on patient characteristics, mechanism of injury, injury severity, prehospital treatments and the location of departure.

Methods

Inclusion

All patients treated by HEMS and subsequently transported to hospitals in the period from 1 January 2011 until 31 December 2020 were included in the study. Patients who passed away during transport were excluded. Data was extracted from the existing database of the Lifeliner 3, managed by the physicians on duty.

Variables

Collected data included: date of event, age, sex, type of incident, location of the scene, location of the hospital of destination, transport modality to the hospital, prehospital diagnosis, physiological parameters (heart rate, saturation, blood pressure), initial Glasgow Coma Scale (iGCS), initial Revised Trauma Score (iRTS), prehospital treatments.

Type of incident

Was divided into ten groups: cardiopulmonary resuscitation, fall from height, burning injury, drowning/suffocation, traffic accident, equestrian sports, intoxication, entrapment, stabbing/shooting and other.

Injury severity

Was based on three variables: the initial Glasgow Coma Scale (iGCS) [12] when arriving at the scene of event (initial Eye opening, best Motor response, best Verbal response (iEMV)), the Revised Trauma Score (RTS) [13] when arriving at the scene (iRTS), performed prehospital treatments and transport to a level 1 trauma centre. Both iEMV and iRTS scores were also divided in groups. For EMV, a common classification is: low EMV score (3–8), moderate EMV score (9–12), and high EMV score (13–15) [12, 14]. For RTS the groups were: severe RTS score (0–5), moderate RTS score (6–11), and mild RTS score (12) [15].

Prehospital treatments

Included: airway manoeuvres, cardiopulmonary resuscitation, mechanical ventilation, thoracentesis, thoracostomy, sealing a chest wound, bone needle, pericardiocentesis, applying a tourniquet, placing a femoral nerve block, staunching a bleeding, splinting a fracture, repositioning a fracture, perform amputation, splinting with sager for femoral fractures, resuscitative thoracotomy.

Location

The incident location data was checked, evaluated and supplemented to ensure accuracy and minimize bias. In cases where data was missing or incomplete, information was retrieved from the pilot’s database free text box or dispatch address. Ambiguous addresses were converted to coordinates. Distances between the incident location and the hospital were calculated based on three metrics: air distance (straight-line distance in kilometers), driving distance (in kilometers by road), and driving time (in minutes using a standard car under normal traffic conditions) using the website https://nl.distance.to/. Flying time was calculated with a formula from Zwakhals et al. [16], specially developed for the Dutch HEMS. Data was edited and calculated in Microsoft Excel 2013 and IBM SPSS statistics 25.

To adjust for the differences in driving time between normal cars and ambulances driving under emergency conditions, a multiplying factor was derived from a sample of 100 ambulance rides recorded in the database of Ambulance Zorg Limburg-Noord. The factor was obtained by dividing the actual driving time by the estimated time, calculated by https://nl.distance.to/ for the same route.

Statistical analyses

88% of all patients were transported by ambulance. To avoid overrepresentation of this group, a random sample was generated using Microsoft Excel 2013, creating two groups in a 1:2 ratio (PTH n = 724:PTA n = 1448). This ratio was chosen to provide a representative sample and enable a statistically balanced comparison between the two groups. These groups were compared, based on the variables mentioned above. Continuous data were presented as means with standard deviation (SD). Due to the large sample size, continuous variables such as age, distance, and time adhered to the central limit theorem, allowing differences between the PTH and PTA groups to be analyzed using independent t-tests. Categorical data were presented as medians with interquartile ranges (IQRs) or percentages and were analyzed using Mann-Whitney U tests or Chi-squared tests, as appropriate.

Results

Between 1 January 2011 and 31 December 2020, a total of 5964 patients were transported to a hospital by the HEMS team. Of these, 2172 patients were included in the study, with 726 patients transported by helicopter (12.2%) and 1448 by ambulance (24.3%). The characteristics of the included patients are presented in Table 1. Two patients died during helicopter transport, resulting in a total of 724 PTH. Approximately two-thirds of the patients in both groups included males. The mean age in the PTH group was 36.4 ± 25.5 years, compared to 41.5 ± 24.7 years in the PTA group (p < 0.001). Despite the difference in mean age, both groups showed similar age distributions (Fig. 1). For example, young children were transported most frequently in both groups. Specifically, patients aged 0–3 years accounted for 11% of all transports.

Fig. 1

Age distribution between patients transported by helicopter (PTH) and those transported by ambulance (PTA) (p < 0.001)

Table 1 Summary of patients characteristics and on-scene location information

The median EMV score was 7 (IQR 3–11) in the PTH group and 8 (IQR 3–14) in the PTA (p < 0.001). The median RTS score was 10 (IQR 8–11) in the PTH group and 10 (IQR 8–12) in the PTA group (p < 0.001). The PTH group included more patients with severe EMV scores and fewer with mild EMV scores, compared to the PTA group. For RTS, the PTH group had more patients with severe RTS scores, whereas the PTA group included more patients with high RTS scores. Distribution is presented in Fig. 2.

Fig. 2

Distribution injury severity estimation scores: initial Eye opening, best Motor response, best Verbal response (iEMV) & initial Revised Trauma Score (iRTS)

Mechanism of injury and prehospital treatments

Mechanisms of injury differed significantly between PTH and PTA groups for five different mechanisms, as indicated in Table 2. In both the PTH and PTA groups, most common incidents were traffic accidents (42% of total, however significantly different between both groups), followed by “other” incidents (20% of total) and falls from height (17% of total). The “other” category comprises of “feeling unwell” (65%), unknown/other (26%), maritime accident (1%), train accident (7%), aviation accident (1%). The PTH group included more “traffic accidents” and “equestrian sports”, while PTA group had more “cardiopulmonary resuscitation”, “intoxication” and “stabbing/shooting”.

Seven out of 17 prehospital treatments were significantly more performed in PTH compared to PTA and none of the prehospital treatments were more performed in the PTA compared to PTH (Table 3). This includes procedures such as (mechanical) ventilation, gastric tube insertion, airway securing and fracture splinting. Additionally, when considering the total number of prehospital treatments, the PTH group received overall more treatments compared to the PTA group. Only 4.7% (n = 34) of the patients in the PTH group received no prehospital treatments, compared to 34.2% (n = 495) in the PTA group. In the PTH group, most of the patients received three prehospital treatments (n = 217), whereas in the PTA group most patients received no prehospital treatments (34.2%, n = 495), followed by two treatments (21.1%, n = 305).

Table 2 Mechanisms of injury

Table 3 Prehospital treatments

Location

PTH were located further away from their hospital of arrival than PTA, on average roughly twice as far, as shown in Table 1. (airline distance PTH = 48.0 km; PTA = 24.4 km (p < 0.001) driving distance PTH = 62.4 km; PTA = 32.4 km (p < 0.001)). In the PTH, 703 patients (97%) were transported to a level 1 trauma centre, which is significantly more compared to the 1280 patients (88%) from the PTA group.

Calculated from real life ambulance driving times, the ambulance was 1.6 times faster than the calculated driving time for normal cars. Considering the correction factor (ambulances are allowed to drive faster than regular cars), PTH were still transported significantly faster, with an average speed improvement of 54% (p < 0.001).

Discussion

This study aimed to improve the current lack of a comprehensive overview of patients transported by HEMS in the Netherlands by describing and analyzing all patients transported by the Lifeliner 3, from 2011 to 2020. The study evaluated the existing database to identify gaps and facilitate the incorporation of new relevant variables for future research. Additionally, it aimed to identify potential factors influencing the decision-making process regarding the mode of transport, which are relevant for further investigation.

The current dataset provides a solid basis for understanding the profile of patients treated by HEMS. With some modifications, the dataset includes enough potential variables to develop a predictive model. First, consistent with other database studies [17, 18], approximately two-thirds of the patients were male. Although age was statistically significantly lower in the PTH group, as also found in the study by Andruszkow et al. [18], the age distribution was comparable between both groups, suggesting that this difference may not be clinically relevant. Notably, in both groups, the largest number of transported patients were between the ages of 0 and 3 years, which is in contrast to findings from other studies. In the study by Andruszkow et al. [18], patients aged 16–54 years were transported 16 times more often than those aged 1–15 years. Studies by Haut et al. and Abe et al. only included patients aged 15 and older [19, 20]. Our results suggest that transport by helicopter is utilized more frequently for children in the Netherlands compared to other countries. This might be explained by the limited number of hospitals in our region with pediatric intensive care facilities. When transport times are expected to be minimized by air transport, the HEMS team opts for the air route for children.

Overall, the distribution of the mechanism of injury between the PTH and PTA groups was similar, although there were some statistically significant differences. In both groups, traffic accidents were the most common cause of injuries treated. While this finding is consistent with other studies [11, 17, 18], patients involved in traffic accidents were significantly more likely to be transported by helicopter. In contrast, the ambulance was chosen twice as often for patients requiring cardiopulmonary resuscitation or for those with gunshot or stab wounds. According to Spoelder et al. [2], it is crucial to assess the need for life-saving interventions during transport, as performing medical procedures in the confined space of a helicopter can be challenging. Therefore, it is important to estimate the likelihood of a patient’s condition deteriorating during transport. Patients who have undergone cardiopulmonary resuscitation or have gunshot or stab wounds can deteriorate quickly and unexpectedly, which may explain why ambulance transport is more frequently chosen for these cases.

Overall, the data suggest that PTH were more severely injured. This is indicated by the higher frequency of lower iEMV scores and lower iRTS scores, the need for more prehospital treatments, and a higher percentage of patients being transported to a level 1 trauma center. These findings are consistent with other database studies [17, 18], although those studies used the Injury Severity Score (ISS) [21] to assess injury severity rather than combining these different variables. The comparison between GCS, RTS and ISS scores is not straightforward. Galvagno et al. [22] only found a correlation between the RTS and the ISS. Toschlog et al. [23] only found a weak correlation between GCS and ISS. Despite these weak correlations, all these studies using different injury scores suggest that PTH were more severely injured compared to PTA. Another indicator of injury severity was the number of prehospital treatments administered to each patient. On average, PTH received more prehospital treatments than PTA. Notably, only 4.7% of PTH received no prehospital treatments, which is seven times lower than the corresponding percentage of 34.2% in the PTA group. Therefore, it may be important to consider not only which prehospital treatments are administered, but also the quantity of treatments given.

Another distinctive difference between PTH and PTA was the distance to the arriving hospital. Saving up time could save lives, and the location of PTH were roughly twice as far away from the hospital of arrival compared to PTA. Although a helicopter can fly in a straight line with higher and constant speed, loading and unloading of the patient can take up to 15 min. If the distance to the destination is less than a 20-minute drive, ambulance transport could be a faster modality, particularly in the Netherlands, which has a well-developed infrastructure in a small geographic area. Our results suggest that HEMS teams take this into account, as only 38 out of 724 transports (5%) were performed by helicopter within a 20-minute driving distance. In more than half of these cases, helicopter transport was chosen due to the patient’s location, where ambulance access was challenging or impossible, such as on beaches or in sandy natural areas. These findings suggest that the decision to utilize helicopter transport might be significantly influenced by the distance to the receiving hospital, and highlights the importance of considering the characteristics of the patient’s location.

Strengths and limitations

One of the key strengths of this study is the homogeneity of the data, as all data were collected from the same helicopter service, geographical area, and team members. This consistency enhances interrater reliability compared to other database studies, where differences in medical teams and country-specific circumstances can introduce variability. As a result, our study provides a more controlled environment to identify potential factors that could influence the choice of transport mode for further investigation and possible regression analysis. Another strength also presents a limitation: the large sample size. While the large sample size strengthens the findings statistically, it is essential to consider the clinical implications and relevance of the results. Therefore, when interpreting the data, it is important to view the large sample size as a strength but also to exercise caution in drawing clinical conclusions.

Future research

Although there are statistically significant differences between the two populations, it is not possible to determine whether these factors actually played significant roles in the decision-making process between PTH and PTA. To address this in future research, improvements should be made to the existing database. Preliminary estimates suggest that transporting patients by helicopter results in a time savings of 54% compared to ambulance transport. However, this estimate is an approximation due to the lack of precise real-time data.

Additionally, data should be collected on the time required to load a patient into the helicopter, as well as whether secondary transport to the helicopter is necessary and the reasons for these choices. Furthermore, secondary outcome measures such as morbidity and mortality should be included in the database to better evaluate the benefits of utilizing the helicopter as a transport modality. Finally, information about the physician involved in each case should be recorded, as this may be a crucial factor in decision-making. This would also allow for the assessment of whether physicians’ decisions are consistent with each other and provide a basis for evaluating those decisions based on patient outcomes and cost-effectiveness.

In conclusion, this study is the first to provide a comprehensive overview of patients treated by HEMS in the Netherlands. After some modifications, the current dataset will be suitable for capturing this patient population and facilitating further research. A predictive model could be developed using this dataset, which should include factors such as the patient’s location, age, distance to the hospital, physician on duty, mechanism of injury, and overall injury severity.