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DE GRUYTER Current Directions in Biomedical Engineering 2020;6(3): 20203156 Sergey Drobinsky*, Mark Verjans, Philipp Schleer, Benedikt Kolk, Henrike Bensiek, Klaus Radermacher, Armin Janß Workflow and Human-Centered Risk Analysis for Novel Mechatronic Rescue Aids Abstract: Paramedics face rising numbers of deployments numbers are rising . Previous studies showed that in over every year. As obstacles like stairs occur often, paramedics 60 % of all patient transports stairs and other obstacles occur, must frequently manually carry patients and are thereby which can lead to the necessity to manually carry patients, exposed to loads multitudes higher than recommended. This who cannot walk on their own . Thereby, due to the creates the need for patient transport aids (PTA), which can demographic change and the fact that over 50% of German physically support paramedics in a wide variety of transport adults are overweight, paramedics often carry loads that situations, without slowing down the transport. In this paper a significantly exceed recommended limits [3, 4]. This leads to workflow analysis for transport missions in an urban context high rates of occupational accidents and the highest rate of and basic tasks for PTAs are presented. Subsequently, the early retirements among all industries [5–7]. In future, this high-level task modelling and human-centered risk analysis problem will become worse due to increasing numbers of according to the HiFEM method are presented for the use deployments and more female paramedics, who suffer case of a patient transport over stairs with a passive PTA, like occupational injuries more often [8, 9]. a rescue chair, and an active PTA like the novel SEBARES Current patient transport aids (PTA) are differentiated in prototype. The analysis shows that conventional PTA’s have passive and active systems, depending on the level of support a simple linear use process, however, impose excessive they offer: Passive PTAs, like main stretchers, stretcher physical workloads, which cause risks like the paramedic or chairs or spine boards secure patients in a safe position, while the PTA falling down the stairs. Contrary, active PTA’s all energy for the transportation have to be provided by one reduce physical workloads, however, introduce additional or multiple paramedics themselves. Active PTAs offer concurrent steps, like identifying and correcting motorized support and can partially reduce the physical misalignments, which create further risks. In order to workload, like hydraulic stretchers during lifting or stair mitigate risks with active, stair climbing PTAs either new climbing rescue chairs during stair transports. However, kinematic designs or intelligent assistance functions, like active aids for stair transports are rarely used by emergency automatic stair detection, are necessary. medical services, as they are generally too slow or can only be used for limited use cases. Caterpillar chairs, like the Keywords: Patient Transport Aids, Human-Machine Powertraxx (Ferno, Germany), cannot be used on narrow Cooperation, Human Risk Analysis, Workflow Modelling, spiral staircases and may damage stairs as the weight is HiFEM distributed over the stair edges, while single stair climbers need to be aligned on every single stair. https://doi.org/10.1515/cdbme-2020-3156 In the scope of this work the workflow of patient transports with PTAs is analysed and basic tasks for PTAs are identified. Subsequently, a high-level task modelling and 1 Introduction risk analysis for the use case of transporting patients over stairs with a passive PTA, like the rescue chair, and an active Every year over 16 million emergency and non- PTA like the SEBARES system  is performed according emergency rescue missions are carried out in Germany and to the HiFEM method. Finally, the need for automation and human-machine cooperation in the context of patient transports is discussed. ______ *Corresponding author: Sergey Drobinsky: Chair of Medical Engineering at Helmholtz-Institute for Biomedical Engineering of the RWTH Aachen University, Pauwelsstraße 20, 52074 Aachen, 2 Materials and Methods Germany, E-mail: firstname.lastname@example.org Mark Verjans, Philipp Schleer, Benedikt Kolk, Henrike Bensiek, Klaus Radermacher, Armin Janß: Chair of First, the workflow of urban rescue missions with a PTA is Medical Engineering at Helmholtz-Institute for Biomedical analysed based on expert knowledge of a paramedic with 5 Engineering of the RWTH Aachen University, Aachen, Germany Open Access. © 2019 Sergey Drobinsky et al., published by De Gruyter. This work is licensed under the Creative Commons Attribution 4.0 License. Sergey Drobinsky et al., Workflow and Human-Centered Risk Analysis for Novel Mechatronic Rescue Aids — 2 years of experience. All steps directly related to patient transferred on the PTA. Next, the patient is first transported transport are considered without regard for concurrent on the PTA to the ambulance, then with the ambulance to the medical treatments that might be performed by paramedics. destination address and finally with the patient aid to the Subsequently, basic tasks of a PTA are identified that are destination location. During this, it may be necessary to central to the patient transport. Subsequently a high-level task transport the patient over difficult terrain (sloped, rough, soft, modelling is performed for the use case of transporting a slippery) or obstacles (curbs, stairs, doors). Additionally, it patient over stairs with passive and active PTAs and human- may become necessary to relocate the patient multiple times centered risks are identified according to the HiFEM method either due to medical reasons, like cramps, or due to transport . The use case of performing a stair transport is chosen, related reasons, like for safe transportation inside an as studies showed that it occurs frequently and causes ambulance. Therefore, it is also necessary to be able to fixate harmful postural workloads . the PTA and the patient respectively in a safe defined Passive PTAs, like the rescue chair or the main stretcher, position at any point during the entire patient transport, for provide no motorized support during patient transport, rather example during stair transport. After patient transport is all necessary transportation energy is provided by the completed, the operational state is restored for future patient paramedic. Active PTAs are defined as mechatronic rescue transports as all equipment including the rescue aid is aids that provide external energy for physical support during cleaned, examined and, if necessary, maintained. the entire or parts of the patient transport. Currently, active Based on the workflow analysis several basic tasks for PTAs can be differentiated in caterpillar systems like the EZ patient transport with a PTA are identified: maintain a Glider (Ferno, Germany) and single stair climbers like the defined safe position when unattended, move with/without Scalacombi (Alber, Germany), S-Max (AAT, Germany) or patient over different types of terrain and obstacles, facilitate the SEBARES system . Dissipative PTA’s, like braked patient relocation and enter/exit ambulance. caterpillar chairs, form a special case as they act like active PTA’s during downward transport and as passive PTA’s during upward transport. 3 Results Figure 1: Generalized workflow of a rescue mission with a PTA 3.1 Workflow Analysis Rescue missions are conducted in five stages as shown in 3.2 Human-Centered Risk Analysis figure 1: transportation request, arrival at patient site, patient transport preparation, patient transport, and restoring the During patient transport paramedics perform many operational state. concurrent tasks besides operating the rescue aid, including Incoming transportation requests can be either but not limited to communicating with patients, relatives and immediate or scheduled depending on whether an emergency colleagues and monitoring the patient state. Patient transport or non-emergency transport is required. While in emergency over stairs can be subdivided in three steps: identifying, cases transport conditions are often unknown, in scheduled planning and performing stair transport. In the following cases the use of ambulances with special equipment, e.g. for general use process is presented for performing a stair obese patients, can be planned. On arrival at the patient’s transport with passive PTAs in figure 2 and for active PTAs location at least one paramedic approaches the patient in figure 3. immediately, to provide emergency medical care if necessary For passive PTA’s the use process is linear and consists and already prepare the patient for transportation. mainly of subsequent action steps. The action steps lift Meanwhile, a second paramedic gets the appropriate rescue transport aid and carry aid over stairs impose high physical aid, which depends on various factors like patient workloads on paramedics. As some passive PTAs do not characteristics (weight, size), patient’s health state (can the need to be lifted, like the evacuation sheet (Järven patient walk/sit) and environmental factors (does an elevator Healthcare, Sweden) which is slided down the stairs, the step exist). During transport preparation, all obstacles along the is marked as optional by brackets. transport route are removed if possible and the patient is Sergey Drobinsky et al., Workflow and Human-Centered Risk Analysis for Novel Mechatronic Rescue Aids — 3 For active PTA’s the use process, compared to the high personal costs (loss in quality of life) and social costs passive case, is more convoluted, the number of tasks is (sick leaves and early retirement). Verjans et al.  show that higher, and several instances exist, where perception, unphysiological strains occur frequently with passive PTAs. cognition and action tasks are performed concurrently. Active PTAs provide external energy to reduce physical Action steps do not impose high physical workloads except loads for paramedics, however, introduce additional tasks. when transportability is not ensured and the PTA must be Thereby, main risks arise when transportability cannot be manually carried, like for example caterpillar chairs in ensured or when PTA misalignments occur. Lack of narrow curves. Single stair climbers require high precision transportability can be caused by the system specific during the step align aid before stairs, constant verification kinematic design, as is the case with caterpillar PTAs in of the current alignment while moving over stairs and, when narrow curves. In these cases, the PTA must be manually necessary, correction of misalignments. A more detailed carried with all the risks that occur with passive PTAs, high-level task model for the SEBARES system showed that however with additional risks related to the stair climbing the tasks presented in Figure 3 can be further broken down to mechanism, like higher PTA weight and larger size. PTA create a system- and user-specific task model with basic-level misalignments can occur due to problems perceiving the subtasks e.g. pressing a button or verifying the current alignment, omission of control steps or cognitive overload machine state (including perception, cognition and motoric due to distractions, e.g. during emergency situations. With actions). single stair climbers misalignments can have the severe effect During patient transport with a passive PTA excessive of the PTA falling down steps and injuring the patient and the physical workloads cause risks, which can have immediate as paramedic downstairs of the PTA. Additionally, in attempts well as long-term consequences. Failures related to short- to catch the PTA during the fall, paramedics are exposed to term physical overloads, like the paramedic stumbling or high dynamic loads which, due to the acceleration, exceed letting go of the PTA, can cause severe immediate effects the static weight force and can lead to additional injuries. like injuries to patient and paramedic. Failures related to With caterpillar PTAs misalignments can lead to the PTA suboptimal lifting technique, bad posture and repeated driving into the wall, which can create the need to manually unphysiological strains, can lead to musculoskeletal diseases lift the PTA to correct the misalignment. in the long-term. Both, short- and long-term effects, imply 4 Discussion Paramedics focus is to transport patients safely and quickly to their destination and ensure the patients well-being in the meantime. However, rising numbers of deployments and high Figure 2: High-level task model for performing a stair transport physical workloads lead to high number of occupational with a passive PTA injuries and high rates of early retirement. A study by the institute for occupational safety IFA concludes that transport aids that physically support the paramedics during patient transports, especially during stair transport, are needed . The high-level task model for stair transport with a passive PTA showed that the use process consists of few tasks, which are performed subsequently. The lack of complexity makes it easier to design safe user interaction with the system, however, risks for patient’s and paramedics safety arise due to excessive physical workloads. In order to reduce physical workloads, active PTAs provide external energy, however, also introduce additional perception, cognition and action tasks, which lead to a more convoluted use process, with many concurrent steps. Thereby, the analysis showed that two central risks for current active Figure 3: High-level task model for performing a stair transport with an active PTA PTAs arise: PTA misalignment, which can lead to the PTA falling down the stairs, and not ensured transportability, Sergey Drobinsky et al., Workflow and Human-Centered Risk Analysis for Novel Mechatronic Rescue Aids — 4 which can lead to the necessity to manually carry the PTA. new kinematic designs or intelligent assistance functions like The two current types of active PTA’s, single stair climbers obstacle recognition or automated alignment verification and caterpillar climbers, show a trade-off: Single stair need to be developed for robust and flexible stair climbing. climbers are prone to misalignments with severe effects like injuring the patient and the paramedics. Caterpillar climbers, References however, are limited in their applicability due to their long inflexible stair module, that cannot be used in narrow curves.  Schmiedel R. Leistungen des Rettungsdienstes 2016/17. Considering that, besides operating the PTA, paramedics Bremen: Fachverlag NW in der Carl Ed. Schünemann KG perform several concurrent tasks, like monitoring the  Verjans M, Schütt A, Schleer P, Struck D, Radermacher K. patient’s state or communicating with family members, high Postural workloads on paramedics during patient transport. cognitive loads during patient transport and especially in Current Directions in Biomedical Engineering 2018; 4(1): emergency situations can occur. The high number of 161–4 concurrent tasks that need to be performed to verify  Statistisches Bundesamt. Pressemitteilung Nr. 14 vom 2. April 2019 [cited 09.03.20] Available from: URL: alignment and transportability during stair transport with https://www.destatis.de/DE/Presse/Pressemitteilungen/Zahl- active PTAs can introduce additional cognitive loads and der-Woche/2019/PD19_14_p002.html. lead to cognitive overload. This in turn can lead to errors, like  Hettinger T. Gewichtsgrenzen für das höchstzulässige failing to recognize misalignments. Therefore, it is necessary Heben und Tragen von Lasten durch männliche und to limit the consequences of misalignments and their weibliche sowie jugendliche Arbeitnehmer 1981.  Maguire BJ, Hunting KL, Guidotti TL, Smith GS. occurrence as well as to help the paramedic to detect them in Occupational injuries among emergency medical services time, while maintaining transportability for all occurring personnel. Prehosp Emerg Care 2005; 9(4): 405–11 transport conditions.  Rodgers LM. A five year study comparing early retirements Solutions may either be new kinematic designs for stair on medical grounds in ambulance personnel with those in other groups of health service staff. Part II: Causes of climbers or intelligent assistance systems. The latter was retirements. Occup Med (Lond) 1998; 48(2): 119–32 shown to be a viable option to reduce mental workloads in  Pattani S, Constantinovici N, Williams S. Who retires early various domains, like assisted driving and robotic surgery from the NHS because of ill health and what does it cost? A [13, 14]. Thereby, assistance systems can be provided with national cross sectional study. BMJ 2001; 322(7280): 208–9 different levels of automation. In the analysed use case of Maguire BJ, Smith S. Injuries and fatalities among  emergency medical technicians and paramedics in the transporting a patient over stairs, assistance systems could United States. Prehosp Disaster Med 2013; 28(4): 376–82 either provide an automatic recognition and correction of  Statistisches Bundesamt. Gesundheitspersonal misalignments or only a warning and a proposal of counter (Vollzeitäquivalente vorläufig) in 1.000. [cited 09.03.20] measures. However, when designing assistance systems a Available from: URL: http://www.gbe-bund.de.  Verjans M, Phlippen L, Schleer P, Radermacher K. human- and use-centered risk analysis for the specific system SEBARES - Design and Evaluation of a Controller for a novel is essential in order to identify, which functions need to be externally guided self-balancing patient rescue aid. In: 2019 automated and to what degree, because badly designed 18th European Control Conference; 2019; 209–14. automation can lead, among others, to mode confusion or  Janß A, Lauer W, Radermacher K. Evaluation of Risk- Sensitive Systems in the OR 2009; 8(1): 257 overreliance . Therefore, further research is necessary to  Schiefer C, Hermanns I, Schuster D, Brand K, Ditchen D. either find kinematic solutions or develop assistance systems Untersuchung der physischen Belastungen von for flexible and robust stair climbing with active PTA’s. Rettungskräften beim Patiententransport in Treppenhäusern: However, when developing the latter, it may be beneficial to Institut für Arbeitsschutz; 08.2019. revaluate the relationship between paramedic and PTA from  Takada Y, Shimoyama O. Evaluation of Driving-Assistance Systems Based on Drivers' Workload. In: Evaluation of human-machine interaction to human-machine cooperation, Driving-Assistance Systems Based on Drivers' Workload; as proposed by Hoc . 2001. Iowa City, Iowa: University of Iowa; 208–13.  Schleer P, Drobinsky S, Radermacher K. Evaluation of Different Modes of Haptic Guidance for Robotic Surgery. IFAC-PapersOnLine 2019; 51(34): 97–103 5 Conclusion  O’Malley MK. Principles of human-machine interfaces and interactions 2007.  Hoc J-M. Human-Machine Cooperation. 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Current Directions in Biomedical Engineering – de Gruyter
Published: Sep 1, 2020
Keywords: Patient Transport Aids; Human-Machine Cooperation; Human Risk Analysis; Workflow Modelling; HiFEM
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