The Study of upper body angle of Fire-Fighters carrying a Patient on a Stretcher with Helmets

 

Byung-Jun Cho¹, Ga-Ram Choi², Yong-Taek Han³, Seung-Yong Kim⁴, Gyoung-Yong Kim⁵, Dong-Min Shin*⁶

¹Dept. Emergency Medical Technology, Kangwon National University, Joongang-roSamcheok-siGangwon-do,  25913,  Republic of Korea

²Republic of Korea Air Force Academy, Sangdang-gu Namil-myeon 335-1 Cheongju, Chungbuk, 28187, Republic of Korea

³Korea Fire Institute 331 Jisamro, Giheung-gu, Yongin-si, Gyeonggi-do, 17088, Republic of Korea

⁴Dept. of Management Information System, Korea National University of Transportation, 50 Daehak-ro, Chungju-si, Chungbuk,27469,Republic of Korea

⁵Yangpeong Fire Station, Kyungkang-ro 2047 Yangpeong–eupYangpeong–gun Kyungkido, 12547, Republic of Korea

⁶Dept. Emergency Medical Technology, Korea National University of Transportation, 50 Daehak-ro,

Chungju-si, Chungbuk,27469,Republic of Korea

 

ABSTRACT:

Background/Objectives: This study analyzed the upper body angle of firefighters carrying a patient on a stretcher with helmets. The purpose of the study was to reduce musculoskeletal symptoms.

Methods/Statistical analysis: Fire firefighters (N=15) with helmets performed lifting and lowering a stretcher. At this time, we compared the angles of their neck, shoulders, back, and upper body muscles. With the collected data, descriptive statistics were conducted for each part and situation.

Findings: We used an analysis method to verify the difference before and after wearing helmets. Upper body angles were calculated as follows. With a helmet, the shoulder angle at E1 while the worker was lifting down the stretcher was statistically significant (p<.05). The neck angle at E2 and E3 while the worker was lifting the stretcher was statistically significant (p<.005, p<.05). And the back angle at E2 (p<.05) and shoulder angle at E2 (p<.005) showed statistically significant values with helmet, while the worker was lifting the stretcher.

Improvements/Applications: Therefore, our results suggest that developing higher helmets will reduce the stress of neck and back and musculoskeletal fatigue.

 

 

 

1. INTRODUCTION:

According to the Ministry of Public Safety and Security, 119 ambulances were dispatched 2,535,412 times in 2015 and transferred 1,755,031 people to medical institutions. The average number of people per day was 4,808. And the average number of transferred people per each ambulance was 1,333. Compared to 2014, the number of dispatches increased by 6.1% and the number of transferred people increased by 4.6%. In recent years, the ambulance activities have been persistently increasing every year¹.

 

Firefighters in field have the duty to transfer patients who require emergency medical service due to various diseases or patients who have been injured due to unexpected accidents to hospitals. Also, firefighters have important missions of standing by for 24 hours to save the lives of people hurt by unexpected accidents. They have very difficult tasks to deal with physical and mental stresses².

 

The National Emergency Management Agency defined the stresses of firefighters as follows. A firefighter needs physical strength for his/her duty. And while s/he is reacting to dispatch and standby signals, sudden physical changes in movement are necessary. These stresses can cause various accidents and diseases for ambulance workers³. In the causes of musculoskeletal symptoms that bring pain, Kim addressed the repetitive movements using a certain body part, inappropriate posture, squatting posture, over-strength when transferring a patient using a stretcher, back twisting when moving on stairs, lack of rest, climate, and vibration. The authors also mentioned that people in the above conditions can suffer from pain in important joints, including the neck, shoulders, elbows, wrists, fingers, back, legs, etc. They stated that backaches are most common in firefighters. These include chronic backaches caused by repetitive movements, such as lifting, driving, etc. Also, acute backaches can occur in several hours or days after lifting something, slipping, or falling to the ground^4,5.

 

This indicates that firefighters are working in a very inadequate environment, as compared to people in other duties. Although ambulance workers are in a special condition that requires strong physical strength, their safety and health are at risk and they suffer from various symptoms. These factors can reduce their physical strength and have a huge negative effect on their health⁶.

 

When transferring a patient with a stretcher, firefighters must repeat sitting down and standing up within a short period of time. Since they must lay down the patient on a stretcher and lift the stretcher, a great deal of load is applied to ambulance workers. Therefore, we can estimate the occurrence of musculoskeletal injuries in reference to proper posture and lifting weight. If the emergency medical technician lifts the stretcher with an inappropriate posture, the shearing stress and compressive force can put pressure on the 4th and 5th lumbar vertebra and may cause a back problem.

Although there are many studies on musculoskeletal disease of emergency medical technicians, most of them are conducted with questionnaires. Therefore, it is difficult to investigate objective causes of the disease^7,8.

Therefore, this study seeks to investigate the difference in upper body angles and muscle activity of ambulance workers, with and without helmets, through the analysis of their upper body angle and muscle activity. We will also suggest ways to reduce their musculoskeletal symptoms.

 

2. MATERIALS AND METHODS:

2.1. Subject of study:

Fifteen participated in this study. The firefighters did not have any musculoskeletal disease, record of surgical operation, or neurological disorder. They did not have any problem with their range of motion. They implemented transfer using stretchers. Every subject fully understood the purpose and methods of this study. They participated on voluntary agreement. Physical characteristics of the participants are summarized in Table 1.

 

Table 1: Physical characteristics of the participants

 

2.2. Measuring tools and methods:

For image recording and movement analysis, we used six infrared cameras (Motion master 100, Visol, USA) to record the movements of the participants. Each high speed camera was synchronized using LAN cables. The speed of camera was set at 100 frame/s in order to get three-dimensional spatial coordinates. For that purpose, we installed a control object (width 1m, length 1m and height 2m) in which the participant could sit down and stand up. Then we activated all six cameras and recorded them for 10 seconds before removing. The total weight that the participants lifted was 64.1 kg (6.1 kg of long spinal immobilizer and a 58 kg patient). Each participant lifted 32.5 kg and the movement analysis was conducted on the participant who lifted the stretcher standing at the patient‘s legs. To find the centroid of an asymmetric object, we hung a pendulum and drew two vertical lines. Then we found the point where the two lines met. To set the reference frame in a real space, we set the direction where a participant was looking at the stretcher as ‘Y axis’. We set the vertical direction to the ground as ‘Z axis’. Then we set the cross product from Z axis to Y axis as ‘X axis’

 

 

Figure 1.Marker position

For image analysis, we attached reflective markers with 10mm size on each constituent part of the body. The locations of the markers are indicated in Figure 1. Using VISOL‘s Kwon3D XP Software Package (Ver. 4.0), we collected and processed the raw data from the attached reflective markers. As the participants repeated sitting down and standing up with a stretcher, we analyzed the angles of their neck, back, and shoulders^9,10.

 

In this study, we set three events and two phases for the experiment in order to conduct a three-dimensional image analysis of the movements that repeat sitting down and standing up with a stretcher. Event 1 is the moment when the participants are standing and are holding the stretcher. Event 2 is the moment when the participants sit down holding the stretcher and the stretcher touches the ground. Event 3 is the moment when the participants stand up with a stretcher and the stretcher is at the highest point from the ground^11,12. We regarded Events 1 and 2 as the Down Phase and Events 2 and 3 as the Up Phase. Figure 2 illustrates the distribution of events and phases.

 

To measure the muscle activity, we used Telomyo DTS (Noraxon Inc., USA) and measured electromyo graphic signal in upper body muscle. After sending the electromyo graphic analog signal to Telomyo DTS and converting it into digital signal, we conducted filtering and other signal processing using CR-XP Master program (Noraxon Inc., USA). The sampling rate of electromyographic signals was 100Hz. To remove 20-250Hz band pass filter and noise, we used a 60Hz notch filter. The collected signals went through a full wave rectification and were processed as the root mean square (RMS)^13-15. To reduce skin resistance on the parts where surface electrodes were attached, we removed hairs from the skin using a shaver and scrubbed the skin with fine sandpaper. Then we rubbed using cotton with alcohol to remove the keratin layer. The interval between two attached electrodes was 2cm. For the relevant muscles and points where the electrodes were attached. See Figure 2

 

 

Figure 2.Distribution of events and phases

 

The long spinal immobilizer (manufacturer: Ferno, USA) consists of a spinal immobilizer, head fixing string, head pad, and belt. Its weight is 6.1kg, size is 183 x 42 x 4.4cm, and maximum load is 275 kg. Its manufacturer is Ferno of USA. A rescue helmet for firefighting functions to protect the head and upper face of a firefighter from various risk factors generated at fields of fire and rescue. Its weight is 900g, the circumference is 64 cm, and color is green. It can be rapidly put on the head and its size is adjustable. The string is also adjustable in three directions, ensuring stability and perfect fixing^16,17. The manufacturer is Sancheong Co., Ltd. of Korea.

 

2.3. Data processing and analysis method:

To collect the data, 15 firefighters who participated in this study performed lifting and lowering a stretcher before and after wearing helmets. At the same time, we compared the angles of the neck, shoulders, Using SPSS ver. 21.0, we performed descriptive statistics for each situation in each part. To verify the difference before and after wearing helmets, we used a paired t-test method.

 

3. RESULTS AND DISCUSSION:

Tables 2, 3, 4 and Figure 3 indicate the upper body angle when lowering the stretcher before and after wearing helmets. In E1, the shoulder angle was 17.61±2.53° without a helmet and 21.07±4.29° with a helmet. There was a statistically significant difference between the shoulder angles (p<.05). In other events, no significant difference was observed.

 

Table 2: The angle of the neck while the worker was lifting down the stretcher with helmet (Unit : °)

 

Table 3: The angle of the waist while the worker was lifting down the stretcher with helmet (Unit : °)

 

Table 4: The angle of the shoulders while the worker was lifting down the stretcher with helmet (Unit : °)

 

 

 

 

 

Figure 3.The angle of the upper body in the lowered position of the stretcher depending on the presence or absence of the helmet.

 

Tables 5, 6, 7 and Figure 4 indicate the upper body angle when lowering the stretcher before and after wearing helmets. Regarding the neck angle in E2, it was 132.63±14.46° without a helmet and 150.13±12.17° with a helmet. The difference between these neck angles was statistically significant (p<.005). In E3, it was 173.61±3.21° without a helmet and 175.74±3.54° with a helmet (p<.05). Regarding the back angle in E2, it was 52.65±4.58° without a helmet and 58.65±5.28° with a helmet. The difference between these back angles was statistically significant (p<.05). Regarding the shoulder angle in E2, it was 40.04±1.57° without a helmet and 46.27±5.93° with a helmet. The difference between these angles was statistically significant (p<.005).

Table 5: The angle of throat while the worker was lifting the stretcher with or without helmet (Unit : °)

 

Table 6: The angle of waist while the worker was lifting the stretcher with or without helmet (Unit : °)

 

Table 7: The angle of shoulder while the worker was lifting the stretcher with or without helmet (Unit : °)

 

 

 

 

 

 

Figure 4.The angle of upper body in the stretcher position with or without a helmet

The incidence rate of musculoskeletal disease at workplace has remarkably increased. Since musculoskeletal disease occurred in all types of occupations these days, it is very important to have an appropriate posture at work to remove the risk of musculoskeletal disease. Among work-related musculoskeletal diseases, backaches are particularly frequent among nurses and ambulance workers. The symptoms are benign in the initial stage and are not regarded as serious problems. However, they get worse later, often to the degree when they considerably complicate the sufferer’s everyday life. Backaches easily recur and can become chronic. Therefore, it is crucial to have appropriate posture at work. Ambulance workers need to repeat movements with a great deal of stress. Although more and more ambulance workers suffer from musculoskeletal disease, there is a lack of scientific research on this issue and its prevention. In this study, we analyzed the upper body angle and muscle activity of 15 ambulance workers when they were carrying a patient on a stretcher with or without helmets.

 

With regard to the upper body angle when lowering a stretcher, the shoulder angle in E1 was 17.61±2.53° without a helmet and 21.07±4.29° with a helmet. The difference between these angles was statistically significant (p<.05). This movement can be defined as an angle between the trunk and the upper arm when an ambulance worker is standing up holding a stretcher. The angle was bigger when an ambulance worker was wearing a helmet. This is because the center of gravity of head leans forward due to weight of helmet. Therefore, the worker had to hold the center of gravity by making the shoulder angle bigger.

 

By looking at the upper body angle when lifting the stretcher, the neck angle in E2 was 132.63±14.46° without a helmet and 150.13±12.17° with a helmet. The difference between these angles was statistically significant (p<.005). In E3, it was 173.61±3.21° without a helmet and 175.74±3.54° with a helmet. The difference between them was statistically significant (p<.05). In E2 and E3, the neck angle was bigger with a helmet than without a helmet. This is a result of hyperextension. Barbara analyzed the state of cervical vertebra with and without a helmet. According to the results of her analysis, the cervical vertebra was hyper extended when the ambulance worker was wearing a helmet to keep the body balance¹⁷. This supports the results of our study. Moreover, Macdonald stated that turning one‘s head to one side or being off the point for more than 20 degrees can cause stress on the neck and back. In this study, the hyperextension was more serious when ambulance workers were wearing helmets, while they were off the point for more than 20 degrees^18,19. Therefore, we estimate that it can cause more load on the neck and back. Regarding the back angle in E2, it was 52.65±4.58° without a helmet and 58.65±5.28° with a helmet. The difference between these angles was statistically significant (p<.05). Regarding the shoulder angle in E2, it was 40.04±1.57° without a helmet and 46.27±5.93° with a helmet. The difference between these angles was statistically significant (p<.005). Both back angle and shoulder angle were bigger in E2 with a helmet. This is because the center of body was higher as compared to when the worker did not wear a helmet. Also, the distance between the center of the body and the stretcher was large. This is the reason why the shoulder angle was big^20-23.

 

This study has several limitations. First of all, the participants were only 15, so it is difficult to generalize the results. Second, we assumed an experimental situation instead of a real situation. Finally, in our research focus, we were limited to the upper body angle and muscle activity. Therefore, further research on the overall body targeting more ambulance workers would be needed in the future.

 

4.CONCLUSION:

In this study, we analyzed the upper body angle and muscle activity of 15 firefights when they were carrying a patient on a stretcher with or without helmets. After experimenting upper body angle and muscle activity with or without helmets, we reached the following conclusion. In our results, the difference between the shoulder angle without a helmet and  with a helmet was statistically significant. In E2 and E3, the neck angle was bigger with a helmet than without a helmet. Both back angle and shoulder angle were bigger in E2 with a helmet. This is because the center of body was higher as compared to when the worker did not wear a helmet.

 

5. ACKNOWLEDGMENT:

This study was supported by the Research Program funded by the Korea National University of Transportation in 2017. This research was supported by the Fire Fighting Safety and 119 Rescue Technology Research and Development Program funded by the Ministry of Public Safety and Security(“MPSS-fire safety-2015-83”).

 

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Received on 12.12.2017            Modified on 24.12.2017

Accepted on 20.01.2018         © RJPT All right reserved