Human error identification for laparoscopic surgery: Development of a motion economy perspective

Applied Ergonomics 50 (2015) 113e125

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Human error identification for laparoscopic surgery: Development of a motion economy perspective Latif Al-Hakim a, *, Nick Sevdalis b, Tanaphon Maiping c, Damrongpan Watanachote d, Shomik Sengupta e, Charuspong Dissaranan d a

School of Information Technology and Mathematical Sciences, University of South Australia, Australia Health Service & Population Research Department, King's College, London, UK Oncology Department, Bangkok Hospital, Bangkok, Thailand d Urology Centre, Bangkok Hospital, Bangkok, Thailand e Austin Department of Surgery, University of Melbourne, Melbourne, Australia b c

a r t i c l e i n f o

a b s t r a c t

Article history: Received 24 September 2014 Accepted 4 March 2015 Available online

This study postulates that traditional human error identification techniques fail to consider motion economy principles and, accordingly, their applicability in operating theatres may be limited. This study addresses this gap in the literature with a dual aim. First, it identifies the principles of motion economy that suit the operative environment and second, it develops a new error mode taxonomy for human error identification techniques which recognises motion economy deficiencies affecting the performance of surgeons and predisposing them to errors. A total of 30 principles of motion economy were developed and categorised into five areas. A hierarchical task analysis was used to break down main tasks of a urological laparoscopic surgery (hand-assisted laparoscopic nephrectomy) to their elements and the new taxonomy was used to identify errors and their root causes resulting from violation of motion economy principles. The approach was prospectively tested in 12 observed laparoscopic surgeries performed by 5 experienced surgeons. A total of 86 errors were identified and linked to the motion economy deficiencies. Results indicate the developed methodology is promising. Our methodology allows error prevention in surgery and the developed set of motion economy principles could be useful for training surgeons on motion economy principles. © 2015 Elsevier Ltd and The Ergonomics Society. All rights reserved.

Keywords: Human error identification technique Motion economy Laparoscopic surgery

1. Introduction Extirpative and reconstructive laparoscopic techniques have become part of the standard approach in most urological surgeries (Pareek et al., 2005; Rane and Wolf, 2005). Manoeuvring laparoscopic instruments requires advanced skills (Pareek et al., 2005), increases fatigue and discomfort (Berguer, 1998) and, as a result, predisposes the surgical team to a wider range of potential errors (Etchells et al., 2003; Wiegmann et al., 2007). Literature in laparoscopy points to a variety of non-technical factors that affect the performance of and create fatigue and discomfort to surgical team during laparoscopic surgeries. These factors include, but are not limited to, posture, height of operating table, location and place of the display, level of instrument handles, level of surgical area and

* Corresponding author. Tel.: þ61 7 46311254. E-mail address: [email protected] (L. Al-Hakim). http://dx.doi.org/10.1016/j.apergo.2015.03.005 0003-6870/© 2015 Elsevier Ltd and The Ergonomics Society. All rights reserved.

design of instruments. These factors fall within the scope of a ergonomics and human factors area, traditionally known as ‘motion economy’ (Barnes, 1980). Motion economy deals with the interaction of human operators with their workplace. In this study we use the terms ‘human factors’, ‘ergonomics’ and ‘motion economy’ interchangeably. 1.1. Motion economy The literature refers to motion economy principles as ergonomics principles or guidelines (Wauben et al., 2006). Motion economy has been emphasised in the surgical literature (Philips, 2004). However, in a study conducted jointly with the European Association for Endoscopic Surgery, 89% of the 284 surgeons surveyed were unaware of ergonomics principles, though all of them stated they find ergonomics important (Wauben et al., 2006). Barnes (1980) suggested 22 principles of motion economy categorised across three areas of analysis. These are ‘use of human

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body’; ‘arrangement of workplace’; and ‘design of tools and equipment’. The first area of motion economy is related to the ‘use of human body’. This area comprises 9 principles orienting operators on efficient movement of the hands and other body parts. Examples include the preference of smooth continuous curved motions of the hand to straight-line motions involving sudden and sharp changes in direction; and having the two hands of the operator beginning and completing their motion simultaneously. The ‘arrangement of workplace’ is the second motion economy area. It includes 8 principles necessary to organise the workstation and arrange the location of tools and instruments relative to the operator's position. Examples include the requirement to have defined and fixed places for tools and materials; and the importance of arranging tools and materials in a way that permits the best sequence of an operator's hand movements. The third area of motion economy is the ‘design of tools and equipment’, which includes 5further principles that take into consideration tool and equipment handling and other design issues related to human factors. Notwithstanding its importance, this area requires extensive research and investigation and is beyond the scope of this study. Examining the traditional principles of motion economy reveals that they were designed to facilitate the performance of a single worker implementing repetitive, mechanical work with definite steps. Accordingly, not all of these principles are applicable to the surgical environment. For instance, the principle requiring gravity feed to be used to deliver material close to the point of use is not applicable to deliver sterile material and surgical instruments. Further, some motion economy principles may require adaptation to become applicable and suitable for the operative environment. For example, the principle that the motion of the arms should be symmetrical and in opposite directions requires adaptation to include diverse directions (e.g., in opposite directions for each one of the operator's hands), (see Table 1 for a list of motion economy principles and their surgical application). In addition, surgery requires team effort, specific procedures for handling sterile material and instruments, updated and accurate information and is performed on the human body as a working object. Therefore, there may be a need to add new areas to the traditional three areas of motion economy as we will discuss later. 1.2. Hierarchical task analysis and human error identification techniques Specific approaches have been designed for reducing human errors known as Human Error Identification (HEI) techniques (Stanton et al., 2009). HEI uses a predefined error mode taxonomy to detect errors and requires breaking down the humanemachine interaction into a series of actions. Hierarchical task analysis (HTA) is usually used for this purpose. Here we refer to the technique comprising both HTA and HEI as ‘HTA/HEI’. HTA describes a work system in terms of its goals. It begins with a main task defined by its intended goal and breaks down the main task into its sub-tasks. Each sub-task has a sub-goal contributing towards achievement of the main task goal (Stanton, 2006). These sub-tasks may be further analysed to their constituent tasks and so on. The level of analysis depends on complexity and required description of the tasks or their goals (Lane et al., 2006; Phipps et al., 2008). Rules guide the sequence in which sub-goals are attained to achieve the ‘higher’ goals (Phipps et al., 2008) and, accordingly, higher levels in the hierarchy influence the manner in which lower levels behave (Shepherd, 2010). Task analysis is a useful way of looking at how people interact with a system in terms of work processes, technology (machines and instruments) and

environment (Rose and Bearman, 2012). The error mode taxonomy of HEI is used to highlight potentially unforseen errors in the lowest level tasks of a HTA (Phipps et al., 2008; Shorrock and Kirwan, 2002; Stanton et al., 2009). Once the potential error or disruption is predicted, an error reduction strategy can be implemented (Shorrock and Kirwan, 2002). HTA/HEI has been used to detect potential human errors across industries (Rose and Bearman, 2012; Shorrock and Kirwan, 2002; Stanton, 2006; Stanton et al., 2009). Recently, HTA/HEI techniques have been applied to predict potential errors in healthcare services, including medication administration (Lane et al., 2006), anaesthesia (Phipps et al., 2008), endoscopic surgery (Joice et al., 1998) and patient positioning for spinal surgery (Al-Hakim et al., 2014). However, HTA/HEI techniques fail to consider explicitly the principle of motion economy and, accordingly, this may limit their applicability in operating theatres. This study aims to address this gap in the application of HTA/HEI techniques. 1.3. Why do we need to integrate principles of motion economy with HTA/HEI error taxonomy? HTA/HEI techniques are used to examine low-level sub-tasks of a task (e.g., surgery) (Stanton, 2006; Stanton et al., 2009). The HTA part is proposed as a means to describing a task (surgery) in terms of its goal and comprises a sub-goal hierarch linked by plans (Stanton, 2006). HEI includes the error taxonomy that detects errors during the execution of sub-goals or related plans. Error occurs where there is a failure to achieve the sub-goal of a planned subtask (i.e., error of execution) or the use of a wrong plan to achieve a sub-goal (i.e., error of planning) (Etchells et al., 2003; Kohn et al., 2000). In order to use an HTA/HEI technique, the analyst or observer applies HTA in order to identify what the operator should do to perform sub-tasks, and uses HEI error taxonomy to identify what could go wrong (Kirwan, 1998; Shorrock and Kirwan, 2002; Stanton, 2006). Kirwan (1998) identifies 3 interrelated components of HEI error taxonomies. These are as follows: 1. External Error mode (EEM): The EEM taxonomy forms the ‘external’ manifestation of errors as observed by the analyst (e.g., using excessive force, omitting a critical check). EEM is a reference to ‘error mode’ as stated in some HTA/HEI techniques such as SHERPA (Embrey, 1989). 2. Performance Shaping Factors (PSP): This taxonomy refers to factors shaping the ability and capacity of the operators (e.g., surgeons) to perform specific tasks (e.g., their experience or training). 3. Psychological Error Mechanism (PEM): This taxonomy represents the ‘internal’ manifestation of errors in psychologically meaningful terms (e.g., lack of confidence, memory failure). It is logical that PSP and PEM components have direct effect on the number of errors detected via the EEM component e such that one would hypothesise that errors are triggered by lack of expertise and associated lack of confidence, or erroneous omissions during a case. However, the literature reveals that errors also commonly occur in surgical procedures performed by experienced surgeons and operative teams (Al-Hakim, 2011; Joice et al., 1998; Sevdalis et al., 2008; Wiegmann et al., 2007). EEM identifies and describes errors (e.g., using wrong instrument) but does not provide the root cause or actual circumstance that drives or forces a surgeon to act erroneously. Accordingly, we argue that there are factors other than those covered in PSP and PEM that can affect the performance of experienced, highly trained surgeons and their wider teams. This study, therefore, hypotheses that motion economy contributes to the causes of senior surgical errors. However, the

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Table 1 Principles of motion economy developed and adapted for surgery. Code

Principle

Area A: use of human body A1 Hand and body motions should be confined to the lowest classification with which it is possible to perform the work satisfactorily with no shoulder movement, bended trunk or axial rotation of spine.

Type

Comments

Modified principle

Barnes (1980) specifies five classifications of hand-motions starting from finger motions up to shoulder motion. (Barnes, 1980) For laparoscopic surgery motion could include forearm motions in association with the lowest possible motions of upper arm. Shoulder motions disturb the surgeon's standing posture, create fatigue and pain and accordingly should be avoided. To achieve this, attention should be given to the following: Width and height of operating table and the level of incision area to allow surgeon to manoeuvre instruments within the grasp range, relative location of surgical team and the use of movable sterile instrument tray (mayo table) to prevent upper arm or shoulder movements in handling instruments. Tubes and tables should not prevent surgeon's hand movement. The height and the arrangement of instrument in the instrument tool (for scrub nurse). This principle is applicable to all surgical tasks, including preparing instrument table (scrub and circulator nurses), transferring and moving patient to/from operating table, adjusting patient's positioning, preparing instruments such as placing scalpel blade on knife handle. This principle is applicable to most surgical tasks. The two instruments handled by surgeon or assistant surgeons target specific, small area of organ or tissue. Surgeon moves the instrument either in opposite to each other (task such as cutting and grasping) or apart from each other's (task such as dissecting or retracting). OR nurses moves their hand spaced out when draping operating table or patients. This principle should be practiced during manoeuvering instruments. Scrub nurse should practice this principle when passing tools and instruments to surgeon. This principle may not be applicable where overhead light requires adjustment.

A2

The movement of the two hands should be balanced; hands should begin as well as complete their motions at the same time.

Original principle

A3

Motions of the arms should be made in diverse (opposite or distant out) directions and should be made simultaneously.

Modified principle

A4

Smooth continuous curved motions of the hands are preferable to straight-line motions involving sudden and sharp changes in direction. Eye fixations should be as few and as close together as possible.

Original principle

Long-period static posture should be avoided whenever possible.

New principle

A5

A6

A7a

The optimal working surface of the incision surface for open surgery should be approximately at elbow level of the surgeon. A7b The optimal working surface of the instrument handle during laparoscopic surgery should be about the elbow level of the surgeon. A7c For hand-assisted laparoscopic surgery the optimal working surface of the instrument handle should be slightly above (approximately 5 cm) the surgeon's elbow level. A8 For hand-assisted laparoscopic surgery, the dominant hand is used to manoeuvre the instruments while the non-dominant hand is placed into the operative field. Area B: arrangement of workplace B1 There should be definite and fixed places for all tools and materials. B2

B3

B4

B5a

B5b

Original principle

New principle

New principle

New principle

The work should allow surgeon to concentrate on surgical field (open surgery) or the monitor displaying the surgical field (laparoscopic surgery). The monitor and other screens should be close to each other such that the surgeon can view them without extensive eye movements. Barriers disturbing the viewing of monitors should be removed. The long-period static posture creates non-physiologic posture, musculoskeletal disorder and should be avoided whenever possible (Vereczkei et al., 2004). This can be achieved through active involvement of the surgical team. Assistant surgeon performs tasks allowing operating surgeon to change posture and exercise. For laparoscopic surgery, it is found that discomfort and difficulty rating were lowest when instrument handles were positioned at elbow level (Berguer, 1999). This means that the height of operating table should be adjusted such that the height of the instrument handles (after patient positioning and inserting the instruments) should be close to the level of surgeon's elbow. This is not the same for hand-assisted laparoscopic surgery for which the height of the instrument handle recommended to be similar to open surgery and higher from that for laparoscopic surgery (van Veelen et al., 2002). Manasnayakorn et al. (2009) investigate the optimal use of instruments for hand-assisted laparoscopic surgery and confirm the finding of van Veelen et al. (2002). Manasnayakorn et al. recommend that for hand assisted laparoscopic surgery the optimal working surface of the instrument handle should be 5 cm above elbow level.

New principle

It is important to manage the patient positioning for hand-assisted surgery with the consideration whether the surgeon is left-handed or right handed. The positioning and the location of the incision should be managed such that the non-dominant hand can be placed in the operative field and the dominant ehand is used to manoeuvre the laparoscopic instruments (Stifelman et al., 2001).

Original principle

Having definite places for instruments reduces waste for searching for them. This principle also enhances patient safety as it is prevent having instruments and material scattered randomly over the draped patient. Surgeon and anaesthetist should specify materials in material acquisition list. Store and theatre management should make the material available in the operating theatre when needed (before the start of surgery). The frequently used instruments should be located within the hand grasp on the instrument table. Instrument with more frequent use should be placed near each other (if possible) within the grasp area of the scrub nurse e sequencing instrument may be changed based on the progress of surgery. Used materials and instruments should not be mixed with unused materials to avoid contamination. Material required to be reused should be repositioned in specific location. Used materials that are no longer required should be removed from instrument table.

Tools and materials should be available when needed and should be located close to the point of use. Materials and tools should be arranged to permit the best sequence of motions.

Original principle

Used instruments and materials required to be reused should be repositioning either to their initial place, if applicable, or to specific locations. The height of the operating table and the patient positioning should be managed such that the working area (surgical or incision area) should permit good posture and easy manoeuvring of the laparoscopic instruments. For lithotomy position: The height of the operating table, the chair, the patient

Modified principle

Original principle

Modified principle

This principle applies to all type of patient positioning except lithotomy position in which surgeon may sit down.

Modified principle

See note in B5a. (continued on next page)

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Table 1 (continued ) Code

B6 B7

B8

Principle positioning and the surgery area should be managed such that the working area (incision or surgery area) should permit good posture and easy manoeuvring of the laparoscopic instruments. Provisions should be made for adequate conditions for seeing The monitor displaying the laparoscopic field should be ahead facing in the line with the surgeon's forearm to avoid axial rotation of spine and should be lower than eye level to avoid neck extraction. Sharp and delicate tools and instruments should be aligned and located to permit easy and safe handling.

Area C: work with sterile instruments and material C1 Precaution should be taken to ensure that sterile material and instruments should be handled by only surgical team members who work in the sterile area. C2 Surgeon and anaesthetist should specify the quantity and specification of the sterile materials and instruments before the start of surgery. C3 The quantity and quality of sterile material and instruments should be checked before use. C4 The hand should not hold more than one instrument or material at a time. C5 Only one sterile instrument or material should be handover at a time. C6 Small sharp tools, sponges and other usable material should be counted after use.

Type

Comments

Original principle New principle

Good illumination is the first requirement for satisfactory visual perception. This principle is applicable to surgery overhead light as well as the laparoscope. Jaschinski et al. (1998) specify two factors that create eyestrain during laparoscopic surgery; the distance of the monitor and the height of the monitor. Vereczkei et al. (2004) emphasise that the monitor should face the surgeon. Research work conducted by van Det et al. (2009) expands the study of Veresczkei et al. and concludes that the monitor should be ahead facing surgeon in the line with the forearm to avoid axial rotation of spine and should be lower than eye level to avoid neck extraction. For safety purpose the following should be followed: (1) The sharp end of instruments should be pointed in the same direction. (2) The curvature and angle of ring-handled instruments should be pointed in the same direction. (3) The ring-handles of instruments should be placed on a rolled towel or hung over the container/tray edge. (4) Blade handles should be aligned and placed over a rolled towel or special sponge.

New principle

New principle

This principle is mandatory and should be monitored during the surgery to avoid contamination and ensure patient safety.

New principle

To reduce disruption and time wasting, the surgical requirements should be specified in the material acquisition list before the day of surgery.

New principle

To reduce disruption, errors and waste in time for acquisition of tools and materials during surgery, the quantity, suitability, safety and working condition of the materials and tools should be checked and contrast with the surgery requirements before the start of surgery. The scrub nurse should not handle or handover more than one material or tool to surgeon or his assistant. This will prevent (a) handover wrong tool or material, and (b) falling a tool or material on the patient's drape or even inside the incision area.

New principle New principle New principle

Area D: work on human body (use human as a work object) New D1 Transferring a human between surfaces principle should be made safely and smoothly over horizontal surfaces.

D2

Patient's body or its parts should be moved and positioned smoothly, safely and securely.

New principle

D3

The patient positioning should be managed to achieve the surgery requirements.

New principle

D4

Surgical tasks should be performed with no harm to surgical team.

New principle

Area E: communication and team work E1 The required information for surgery should be communicated accurately and should be available whenever needed.

New principle

E2

E3

Members of the surgical team should communicate and coordinate their activities effectively and efficiently. Surgical members should synchronise their hand motion.

Sharp instruments (e.g., knifes and needles) and unconsumed material should be counted before the incision closure. This is necessary step to ensure that no sponges or small, sharp tool missing inside the patient's cavity or under the patient's drape. Following the principles for Area B will considerably facilitates the achievement of this principle. This principle deals with the transfer unconscious or anaesthetised patient between transfer trolley and operating table while the patient in supine position. This principle requires securing the level of trolley relative to the table during the transfer and careful consideration should be given to keep the patient's neck and the torso as straight as possible. The transfer should not create sudden movement of head or extremities and careful attention should be given to prevent any obstruction or dislodged of airway passage, IV infusion, catheters, or oxygen cannulas. The principle deals with the adjustment, moving and turning the patient during positioning. It deals with all aspects to ensure smooth and safety patient positioning, including having adequate number of people positioning the patient; flexing, tilting and rotating the operating table (if required), turning the patient on hard surface (no lifting); inserting bags under the patient's hip (if required), positioning hands and legs, securing patient body to operating table; preventing skin friction ee.g., legs crossed during positioning; padding the patient; preventing obstruction of airway passage, IV infusion, catheters, and oxygen cannulas. The principle requires that the positioning should expose adequately the surgical area, facilitate patient monitoring, minimise risk, achieve specific surgical requirements, allow the performance of various surgical tasks and facilitate the use of laparoscopic instruments. Some tasks during surgery may create risk to surgical team if the required protection procedure was not followed. Examples include having X-ray to patient during surgery or performing surgery on diabetic patients.

New principle

Wong et al. (2011) emphasise the criticality of information accuracy and availability during surgery as a potential contributor to the safety of patient and quality of surgery. Research works on disruption in theatres explore high correlation between the accuracy, availability of information in patient's record and surgical disruption which, in turn, predisposes surgical team to fatigue and affect their motion and movement (Al-Hakim, 2011; Al-Hakim and Gong, 2012; Etchells et al., 2003; Sevdalis et al., 2007; Wiegmann et al., 2007). This principle requires surgeons and anaesthetists to provide adequate information before surgery (e.g., required instruments, material and medical tests, sketch of the positioning). Other department should make effort to achieve the requirements and make them available when needed. Patient record should be updated accordingly. This principle ensures that surgical team perform tasks as required and eliminates error, delay and waste resulting from miscommunication.

New principle

Teamwork is critical for the success of surgery, and unlike open surgery, it is impossible for surgeon to perform laparoscopic surgery without assistants (He et al., 2013; Moorthy et al.,

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Table 1 (continued ) Code

E4

Principle

The location of the team members should be managed to facilitate the surgeon work and the performance of surgery.

Type

New principle

Comments 2005; Zheng et al., 2007). Zheng et al. (2007) classify the team activities into two categories; task-related activities (individual work) and team-related activities. The traditional principles of motion economy consider only the task-related activities. Most surgery tasks require team effort, including OR turn over, transferring patient to operating table, patient positioning, manoeuvring laparoscopic instruments. The location of the assistant surgeon and scrub nurse should be managed in a way that It helps the surgeon maneuvering instruments, facilitates passing of materials to surgeon and do not block the vision of the surgeon to the display and monitoring devices.

Code: Ai ¼ Principle ‘i’ for use of human body area; Bi ¼ Principle ‘i’ for arrangement of work place area; Ci ¼ Principle ‘i’ for work with tools and material area; Di ¼ Principle ‘i’ for work on human body area; Ei ¼ Principle ‘i’ for communication and team work area.

principles of motion economy cannot be used as such to detect error during surgery, and thus we need to use HTA/HEI taxonomy for this purpose. On the other hand, without integrating the principles of motion economy as part of our HTA/HEI taxonomies we cannot identify the root causes of errors. It is important to note that violation of motion economy principles should have more impact and create more potential errors in surgeries with long operative time or where successive surgeries performed in one session e as problems accumulate and trigger these errors. In this study, we adapted the motion economy principles presented earlier and developed additional principles to suit the operative environment. The developed principles can be used as part of error taxonomy of traditional HTA/HEI techniques, such as SHERPA (Embrey, 1989) to detect surgical errors. We use handassisted laparoscopy (HAL) for nephrectomy (HAL nephrectomy) as a case study to illustrate the importance of considering motion economy alongside HTA/HEI. HAL has been developed as an extension of conventional laparoscopic surgery and has been used to perform complex surgeries, including radical, donor and partial nephrectomy surgeries (Bishoff and Kavoussi, 2007; Stifelman et al., 2001). It provides tactile feedback allowing surgeon to use a hand to assist with performing surgical functions (Bishoff and Kavoussi, 2007; Stifelman et al., 2001), and can be used by surgeons with minimal laparoscopic training (Busby et al., 2003). The ability to use the hand also minimises the chance of injuries and permits rapid control of bleeding, if occurs (Yu and Miller, 1996). In essence, HAL combines the advantages of open and conventional laparoscopic surgeries (Stifelman et al., 2001). As an illustration of the application of motion economy principles to these procedures, manoeuvring an instrument with one hand and having the other inside the patient's cavity may cause fatigue to the surgeon as a result of asymmetrical movement of the two hands at different levels. Adjusting the operating table to achieve the optimal working level as suggested in principle A7 (Table 1) can considerably ease the work for surgeons, especially for long and complex procedures (Manasnayakorn et al., 2008). 2. Research methods Initially, an ethical approval was approved by the Research and Development Section of a large academic hospital in Bangkok to carry out the study and make observations in the hospital's operating theatres. The hospital assigned three experienced theatre nurses to facilitate the research work. The research methodology comprised three phases. In the first phase, the literature of motion economy, HTA/HEI and laparoscopic surgery was reviewed to explore the principles of motion economy, errors occurring during laparoscopic surgeries and various HTA/HEI techniques and applications. The team selected HAL nephrectomy surgery as illustrative case study. The selection was made because of the long experience of surgeons in

this type of surgery and the familiarity of the principal researcher with the lateral positioning and his previous observations of nephrectomies. In this phase, the research team explored tasks, potential errors and the role of motion economy associated with errors. Meetings were held with the theatre nurses to explore their opinions. The outcome of this phase was an initial task analysis and a draft of ergonomic requirements for the surgery and associated principles of motion economy. In the second phase of the study, the initial HTA was further analysed, and its tasks broken down into further levels of sub-tasks. The relevant principles of motion economy for each task, and the potential errors that may occur during the implementation of these tasks, were explored. In addition, the error taxonomy based on principles of motion economy was formulated. We relied on literature on human factors, patient safety, and operating theatre techniques (Barnes, 1980; Dankanich; Karwowski and Salvendy, 2010; Meyers and Stewart, 2002; Philips, 2004; Wachter, 2012) as well as on our team's ergonomics and clinical experience to select and adapt the traditional principles. In addition, we consulted related research studies on surgery (Al-Hakim, 2011; Al-Hakim and Gong, 2012; Berguer, 1999; Etchells et al., 2003; He et al., 2013; Jaschinski et al., 1998; Manasnayakorn et al., 2009; Moorthy et al., 2005; Sevdalis et al., 2007; Stifelman et al., 2001; van Det et al., 2009; van Veelen et al., 2002; Vereczkei et al., 2004; Wiegmann et al., 2007; Wong et al., 2011; Zheng et al., 2007) to develop new areas and principles for motion economy. In the third phase, an actual HAL nephrectomy was observed by the principal researcher (LH). It was conducted in a large hospital at Bangkok, Thailand by an experienced surgeon (CD) who introduced the observer and the reason for observation to the patient and to members of the surgical team. The HAL nephrectomy was carried out to remove excessive tissues (tumour) built around the patient's kidney. At this phase, the HTA for the surgery was revised based on the observed tasks and the error taxonomy was applied to explore potential errors stem from the implementation of each observed task. Observations were subsequently carried out across 12 laparoscopic surgeries to test the applicability of our methodology in capturing the latent motion economy factors that predispose surgeons to errors. 2.1. Patient positioning for HAL The patient was brought from the pre-operative area to the operating theatre using a patient trolley. The patient and procedure were identified and the patient was initially positioned supine for IV access, anaesthesia induction and intubation. The patient was then transferred in supine position to the operating table. The anaesthetised patient was positioned on the operating table. The patient position was adjusted such that the flexion of the operating table was in line with the anterior superior iliac spine. The patient was then turned on to lateral position. A bag is used to raise the

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patient's hip as required e usually an operating table with kidney rest is used but, that table was not available at the time of surgery. The lower leg was flexed to 90 at the knee to prevent the body from rolling over and the upper leg was kept straight. An armboard was used to position the patient's upper hand. The patient was padded and his position secured on the operating table using cloth tape. The operating table was rotated toward the surgeon to expose adequately the surgical field. This type of position is known as Flank position, which is a modified version of lateral position (Bishoff and Kavoussi, 2007; Stifelman et al., 2001; Yu and Miller, 1996) (Fig. 1).

3. Results In this section, we describe our revision and further development of motion economy principles applicable to surgery; the development of a suitable HEI taxonomy; and what we found via our real-time observations of the 12 laparoscopies. Among the traditional principles of motion economy stated in the literature (Barnes, 1980; Meyers and Stewart, 2002) we selected 11 principles; 5 principles from the area ‘uses of human body’ (we refer to it as Area A) and 6 principles from the area ‘arrangement of work place’ (Area B). Two principles from area A area and two principles from area B area have been modified to suit the surgical environment as shown in Table 1. We further added an extra 3 principles to Area A and another 2 new principles to area B. We also developed 3 new motion economy areas, namely ‘work with sterile instruments and material’, ‘work on human body’ and ‘communication and team work’. The new areas are identified as ‘Area C’, ‘Area D’ and ‘Area E’, respectively. Principles within the area ‘design of tools and equipment’ are beyond the scope of this paper and will not be discussed further.

3.1. New principles for traditional motion economy areas A and B We added 3 new principles to area A. The first added principle deals with long-period static posture (Verdaasdonk et al., 2008), the second is related to the optimal working surface for incision area and surgery instrument handles relative to the surgeon's elbow level (Manasnayakorn et al., 2009; van Veelen et al., 2002), and the third focuses on surgeon's hand to manoeuvre instruments for HAL (Stifelman et al., 2001). For area B, we developed 2 new principles for motion focussing on location of the monitor displaying the surgical field relative to the surgeon's eye level (Jaschinski et al., 1998; van Det et al., 2009; Vereczkei et al., 2004) and the location of the sharp and delicate instruments (Dankanich; Philips, 2004).

3.2. New principles for newly developed motion economy areas C, D and E The 6 principles for the new area ‘work with sterile instruments and material’ (area C) emphasise the following: the importance of having only sterile staff deal with sterile instruments and material, specifying the required quantity and specifications of the sterile instrument/material before surgery, checking the quality and quantity of the sterile instruments/material before use, prevent holding two instruments with one hand, handing over one tool at a time, and counting of sterile sharp instrument and sponges after use. The 4 developed principles for area D ‘Work on human body’ deal with the transferring the anaesthetised patient from transfer trolley to operating table, moving patient's parts, achieving surgery requirements and safety of the surgical team. The new motion economy area E ‘communication and team work’ comprises 4 principles dealing with the availability and quality of the required information (Al-Hakim, 2011; Al-Hakim and Gong, 2012; Etchells et al., 2003; Sevdalis et al., 2007; Wiegmann et al., 2007; Wong et al., 2011), importance of satisfying surgeon requests during surgery, synchronising and coordination of the hand motion of the surgical team (He et al., 2013; Moorthy et al., 2005; Zheng et al., 2007), and the relative position of the surgical team. In total, we have 30 motion economy principles that suit surgical performance in operating theatres. Table 1 lists the principles of motion economy for surgery with explanation, references and practical examples. The table also indicates whether the principle is original as originally developed by Barnes (1980), a modified or a new principle. 3.3. The developed HEI taxonomy The available HEI taxonomies do not include the applications of motion economy. The exact causes of errors resulting from the violation of motion economy could be inferred wrongly by the current HEI taxonomies (we elaborate this point further in the Discussion section). Violation of motion economy principles may imply high potential safety risk, for which extra resources, effort, time and/or excess precaution is required to avoid errors. Al-Hakim et al. point to other limitation of the traditional HTA/HEI. HTA/HEI approaches consider humanemachine interaction. This may not always be the case in surgical environments, where humanehuman interaction plays a major role. In addition, HTA/HEI assumes that the probability of making an error remains the same whenever the same operator performs a task. This may be not the case in a surgical environment. For instance, the probability of a surgical team making an error in moving an unconscious patient from the

Fig. 1. A sketch for Flank positioning illustrating three conditions; (a) the interior superior iliac spine should be in line with flexion of the operating table, (b) upper leg should be kept straight, and (c) the lower leg is flexed to 90 at the knee.

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trolley (patient transportation table) to the operating table is higher when the patient is obese (Philips, 2004). We thus propose that in order to use the traditional HTA/HIE techniques correctly, the HEI error taxonomy should comprise two parts; a motion economy error taxonomy (MEET) and a task error taxonomy (TET). MEET comprises principles of motion economy as stated in Table 1. TET includes the error taxonomy of the traditional HTA/HEI technique that intends to be used. In this study, SHERPA (Embrey, 1989) was used as the traditional HTA/HEI approach for predicting potential errors for TET (Table 2) and the principles of motion economy listed in Table 1 form the elements of MEET. Table 3 shows the HTA/HEI analysis of the patient positioning for HAL.

3.4. Applicability of our methodology In order to illustrate the applicability of our approach, data for 12 laparoscopic surgery were observed by the principal researcher. The observed surgeries were performed by 5 experienced surgeons who had each at least five years of experience in urological laparoscopic surgeriers. Operating time ranged from 64 min to 133 min with an average of 89 min per case. Table 4 lists the instances of observed errors captured by TET taxonomy during the operations (from initial incision to suturing the incision) and relates those errors to violation of the motion economy principles captured by the MEET taxonomy. A total of 86 errors across the 12 operations were captured by TET. The data indicate that the error rate is positively related to operative time e i.e., longer procedures were associated with higher error rate. The MEET (Table 1) shows that large number of errors captured by TET was associated with longperiod non-physiological posture resulting from one or more of the following: (a) inadequate level of instrument handles/inadequate height of operating table, (b) poor position of monitor, and (c) inadequate patient positioning e poor exposure of surgical area. long-period, non-physiological posture creates musculoskeletal disorder and stress (Vereczkei et al., 2004) that could dispose surgeons to errors (Etchells et al., 2003; Wiegmann et al., 2007). Errors and delays resulting from inadequate arrangement of instruments and lack of communication and coordination were also noticed.

Table 2 Error modes taxonomy for SHERPA (Embrey, 1989). Error type

Error code

Error mode

Action

A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 C1 C2 C3 C4 C5 C6 R1 R2 R3 I1 I2 I3 S1 S2

Action too long/short Action mistimed Action in wrong direction Action too little/too much Misaligned Right action on wrong object Wrong action on right object Action omitted Action incomplete Wrong action on wrong object Checking omitted Check incomplete Right check on wrong object Wrong check on right object Check mistimed Wrong check on wrong object Information not obtained Wrong information obtained Information retrieval incomplete Message not transmitted Wrong message transmitted Message transmitted incomplete Selection omitted Wrong selection made

Checking

Retrieval

Communication

Selection

119

Table 4 indicates that including the motion economy principles as part of the error mode taxonomy of the HTA/HEI techniques provides better understanding of the ergonomic deficiencies that dispose experienced, skilled surgeons (such as those we observed) to errors.

4. Discussion Stanton (2006) provides a comprehensive review on the development of HTA/HEI techniques and emphasises that since the first paper published in 1967 by Annett and Duncan (1967), HTA/ HEI has remained a central approach for ergonomics. HTA/HEI has been used to detect potential human errors across industries (Joice et al., 1998; Phipps et al., 2008; Rose and Bearman, 2012; Stanton et al., 2009). However, HTA/HEI faces several limitations eas follows: Practices: Al-Hakim et al. (2014) refer to the way in which an upper task is planned to achieve its goal as a ‘practice’. Different practices with different potential errors may be used to perform the same task. Al-Hakim et al. emphasise that one of the key limitations of HTA/HEI techniques is that they concentrate on examining potential errors in a predefined set of lower sub-tasks as performed, rather than examining the potential errors in the practice used to perform the upper tasks. These authors attempt to incorporate the practice adequacy as part of the error taxonomy for HTA/HEI. Communication and teamwork: Research on the integration of teamwork with HTA/HEI is limited. Annett et al. (Annett et al., 2000) and Acton and Reinach (Acton and Reinach, 2003) show the possibility of integrating teamwork and communication as part of the task plan. However, their work lacks a taxonomy for predicting potential errors arising from failure to implement adequate communication and teamwork within a work environment. Motion Economy: The traditional HTA/HEI approaches fail to take into account the principles of motion economy. Accordingly, an error resulting from such failure may be erroneously determined. The traditional principles of motion economy have been designed to suit mechanical work to be performed by single worker and, accordingly, require thorough revision and adaptation to suit the surgical environment e this is what we have attempted in this study. There has been continual development on practices used to perform laparoscopic surgeries, including HAL surgeries. The practice selection mode taxonomy of Al-Hakim et al. (2014) provides a list of practices with higher potential errors (i.e., problematic practices) which may be applied to perform tasks in an operative environment and suggests alternative practices with lower error potential. Problematic practices require more resources, time or excessive precaution to avoid errors. This work offers an opportunity to surgeons to select most appropriate practices with minimal error potential. We intend to incorporate practice selection mode with motion economy in subsequent work, aiming to provide safer practice selection to surgeons from the perspective of motion economy. The current study attempts to overcome HTA/HEI limitations through the following: a. Revising and adapting the current principles of motion economy to suit the surgical environment. b. Developing 3 new areas for motion economy principles, namely ‘work with sterile tools and material’, ‘communication and teamwork’ and ‘work on human body’. c. Benefiting from the literature on ergonomics for surgery, this research develops 17 new principles that cover wider aspects of surgical environment.

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Table 3 HTA e patient positioning for hand-assisted laparoscopic nephrectomy (urological procedure). Task A. Perform preoperative activities B. Perform anaesthesia induction C. Perform patient positioning C1. Adjust the position of the anterior superior iliac spine of the patient relative to flexion point of the operating table. C.1.1. Move and adjust the patient body as required

Plan

Do C1.1.1 and then C1.1.2, C1.1.3 simultaneously.

Do C1.2.1 to C1.2.4 simultaneously

Comment

D3

This task facilitates the surgery and forms part of its requirement. The anterior superior iliac spine of the patient should be in line with flexion of the operating table.

A5, A8

A2, D2, E2

This task requires at least four people that they should synchronise their work. Each person should use both hands to manage the movement. The task could be misaligned or omitted.

A5

A2, D2, E2

A8 A3, A9

E2 A2, A3, D2, E2

C1, C2

D2, E2

Failure to perform this task correctly will make the work unbalanced. Potential errors: Failure to do this task correctly may: 1. Fail to achieve the surgery requirement. 2. Cause sudden head movement. 3. Cause hands or legs to slide off the operating table or cause hand to slip under the patient's body. 4. Sudden or improper movement of the torso of the patient. 5. Obstruct airway passage. Obstruct and dislodge IV infusion, catheters, or oxygen cannulas. 6. potential risk of musculoskeletal injury Good practice:  The patient should be pulled on hard horizontal surface (no lifting).  Use draw board instead of draw sheet. This task helps achieving C1.1.3 correctly. The task might be misaligned, go into wrong correct direction or performed with excessive force. Potential errors: See task C1.1.1 This check is important wherever the patient is moved. Failure to perform this task may lead to bleeding, brain damage or even death.

C1, C2

D2, E2

As above

C1, C2

D2, E2

As above

C1, C2

D2, E2

As above

C1, C2

D2, E2

As above

D3

This task is necessary to achieve the surgery requirements.

A3, A4, A5

D2, E2

C1, C2

D2, E2

The turn should be on unaffected side such that the effected side will be exposed for surgery. The width of operating table should be enough to allow the implementation of the task. This task should be managed with adequate number of people (at least four) and should be performed slowly. Good practice: The following should be considered: 1. The task should be performed on a hard horizontal surface e No pad or pillow under the patient. 2. The task does not create sudden movement of the patient's head. 3. The task does not create potential risk, damage or musculoskeletal injury. 4. The patient's legs are not crossed during positioning. 5. The patient's hands or legs are not slide off the operating table. 6. The task does not cause patient's hand to slip under the patient's body. 7. The operators should be in both side of the operating table to prevent patient turning over the operating table. See task C1.2.

C1, C2

D2, E2

See tasks C1.2.1 to C1.2.4 above.

A8

D2

For adequate support of the patient positioning.

A8

D3

If necessary and where operating rest with kidney rest is not used. This task may be needed to achieve the surgery requirements. Good practice: In some cases, the surgery requirement can be achieved by flexing the operating table with no need of raising the patient's hip. It is preferable that surgeon examines the patient physical status and decides the requirements before

Do C2.1 and C2.2 simultaneously.

C2.1. Turn the patient

C2.2.2. Check and prevent obstructions 2.2.2.1. Repeat steps C1.2.1 to C1.2.6. C3. Place long pad or pillow to support the patient's back. C4. Elevate the hip

MEET codeb

Do C1.1 and C1.2 simultaneously.

C.1.1.1. Grasp strongly the draw sheet

C.1.1.2 Count 1, 2 and 3 C.1.1.3. Move patient to correct position C.1.2. Check and prevent obstructions and/or dislodgement C.1.2.1. Check and prevent catheters from obstruction or dislodgement C.1.2.2. Check and prevent intravenous (IV) infusion tubing from obstruction or dislodgement C.1.2.3. Oxygen cannulas from obstruction or dislodgement C1.2.4. Check and prevent airways passages from obstruction. C2. Turn the patient on side 90 with the operating table

TET codea

If not (C4.1) then do C4.2

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Table 3 (continued ) Task

Plan

TET codea

MEET codeb

C4.1. Raise the patient's hip

A4

D2, D3

C4.2 Insert pillow under the hip

A4, A8

D2, D3

A2, A3, A4

B1, B2, D2, D3

C5.1.1. Fix an upper armboard to operating table

A2, A3

B1, B2, D2

C5.1.2. Rest the upper arm on the upper armboard

A2, A4

D2

C5.1.3. Secure the upper arm on the upper armboard using 3 inch tape C5.1.4. Tuck the lower arm 90 angle from elbow C5.1.5. Pad the lower arm

A2, A4

D2, D3

A2, A4

D3

A8

D2

A4, A8

D2, D3

C5.2.1. Flex the lower leg to about 90 at the knee.

A4, A8

D2, D3

C5.2.2. Flex the lower leg to about 90 at the knee C5.2.3. Keep the upper leg straight

A4, A8

D2, D3

A4, A8

D2, D3

A8

D3

C5. Position arms and legs C5.1. Position arms

C5.2. Flex legs

C5.2.4. Insert enough pillows between legs

Do C5.1; C5.2 in any order Do C5.1.1 to C5.1.5 in order.

Do C5.2.1 to C5.2.4 in order.

Comment the surgery. Good practice: The anaesthetist should monitor during this task the patient's breathing, the airway, and the IV catheters and oxygen cannulas. This task requires adequate number of operator and should be performed with care. The hip should be raised slowly and carefully (with no excessive force) to the required level. Potential error:  Create damage to the patient's skin and/or underlying tissues.  Prevent blood circulation  Expose the patient to potential injury (vena cava, vein, etc.). The above errors could occur where this task is performed: (a) without adequate number of operators, (b) using excessive force and performing it quickly, or (e) raising the patient's hip above the physical allowable limit. The type, shape and height of the pillow should be selected carefully, especially for obese patients. In some cases, eg., for slim patients, the surgery requirement can be achieved by flexing the operating table without using a bag or pillow under the hip. Potential error:  Same as for C4.1  In case of obese patient, the abdominal tissue may extend over the bag and this will increase possibility of errors [19]. The above errors could occur where this task is performed: (a) without adequate number of operators, (b) inserting the bag with excessive force, (c) using a solid inflexible bag, (d) having larger or higher bag than needed. Good practice: 1. Surgeon requires studying the physical status of the patient before the surgery and configures how to achieve surgery requirement. 2. Use operating table with kidney rest. This type of table allows surgeon to flex the table and elevate the kidney rest, if needed. To safe time, the two tasks could be performed simultaneously e requires several members of the surgical team to involve. Good practice: Fix the armboard during anaesthesia induction. Perform this task directly after turning the patient to lateral position. This task could be managed while the anaesthetist administrates the anaesthesia induction. Potential errors: 1. The armboard is not available at the time when needed. 2. The armboard does not fit to the operating table. 3. The armboard is not suitable to handle the patient's upper arm e wrong specifications. Good practice: The specification of the board should be mentioned in the surgery requirements list. Move the arm carefully and without delay. Potential errors:  Arms may cross each other causing skin friction and then damages.  Arms may slip under the patient. Potential error: Skin damage and blood blockage could occur as a result of excessive force used in securing the arm with the tape.

Potential errors: Skin damage could be caused as va result of:  Delay in performing the task.  Inadequate padding.

This task prevents the patient from rolling. Flex the leg carefully. The task requires at least two operators to prevent patient roll over and skin friction. Potential errors:  Only one operator manages the task.  Patient rolls over.  Legs cross each other.  Skin friction and damage. Potential errors: as above.

The upper leg is kept straight to maintain tension of the incision side (Yu and Miller, 1996)e Part of specific surgery requirements. Potential errors:  Neglect to perform the task.  Delay in performing the task.  Skin friction and damage.

(continued on next page)

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Table 3 (continued ) Task

Plan

TET codea

MEET codeb

Comment It is important to insert enough and suitable pillows. Potential error: Delay and excessive use of force may cause skin friction and tissue damages.

C6. Add pads or pillows wherever needed C7. Secure the patient to operating table using wide tape

A8

D3

A2, A4

D2, D3

Strap the patient's hip. Strap the legs. Strap the chest. C8. Flex the operating table

A2, A4 A2, A4 A2, A4 A4

D2, D3 D2, D3 D2, D3 D3

A4

D2, D3

Do C8.1; C8.2, C8.3 in order and repeatedly

C8.1 Flex the operating table.

Potential errors:  Skin damage and blood blockage may occur as a result of excessive force used is securing the patient's body with the tape.  Delay may disturb the patient positioning e unsecured patient's body may roll over e face down or face up- creating various damages and risks.  Securing one part and leaving another may also disturb and then unbalance the positioning. As above As above As above This task facilitates the achievement of surgery requirements. It is necessary to perform this task gradually, smoothly and carefully. The task is repeated until the surgical field exposed adequately to surgeon. Potential errors: Rapid and excessive flexion:  Create damage to the patient's skin and/or underlying tissues.  Expose the patient to potential injury (vena cava, vein, etc.).  Cause potential risk of musculoskeletal injury.  Prevent blood circulation.  May obstruct and dislodge IV infusion, catheters, or oxygen cannulas. Good practices:

A8

D3

1. It is safer to flex the tail first and if needed flex the head. 2. Flex the operating one or two steps at time smoothly and carefully e Avoid flexing the operating table fully and then reduce the flexion. 3. Check the airway, IV infusion, catheters, and oxygen cannulas after each flexion. This task is repeated until the surgery requirements are satisfied.

A4, A6, A8

D3

This task is repeated until the surgery requirements are satisfied.

A4, A8, A9

A1, A2, A4, A6, A7b, A8, D3

C9.1. Adjust the height of operating table

C1, C5

A1, A2, A4, A6, A7b, A8, D3

C9.2. Rotate the operating table toward the surgeon.

A4, A5,A6, A8

A1, A2, A4, A6, A7b, A8, D3

This task is important to ensure that the level of surgical field is confine with the motion economy requirements for hand-assisted surgery. The task could be repeated until the surgeon is satisfied. Potential errors: inadequate operating table height may force surgeon to have inadequate posture that exposes surgeon to considerable fatigue and stress. Good practice: The optimal working surface should be levelled such that the instrument handles should be slightly above elbow level. The principle facilitates the achievement of the related principles A1, A2, A4 and A6. The optimal working surface should be levelled such that the instrument handles should be slightly above elbow level. Good practice: As above. This principle facilitates the achievement of the related principles A1, A2, A4 and A6.

C8.2. Check the incision area C8.3. Adjust the flexion of operating table. C9. Adjust the operating table.

Do C9.1 then C9.2 in order then repeat in any order.

D. Drape the patient E. Prepare skin for surgery F. Start surgery a b

Codes for TET items are as used for SHERPA technique e See Table 2. The codes for MEET items are as shown in Table 1.

d. Developing error taxonomy that comprises two subtaxonomies; Motion Economy Error Taxonomy ‘MEET’, which focuses on violation of motion economy principles during surgery and Task Error Taxonomy ‘TET’, which considers the error modes of the traditional HTA/HEI approach. The failure of HTA/HEI approaches to incorporate motion economy may confuse the exact cause of errors. Errors resulting from the violation of motion economy principles could be inferred wrongly by the exciting HEI taxonomies. To illustrate this, we consider the research of Joice et al. (1998) in which the error mode taxonomy of SHERPA is modified and used to detect human errors in 20 laparoscopic gastrointestinal surgeries conducted by 8 ‘fully trained’ surgeons. Joice et al. found that the highest number of errors was the failure to hold the gallbladder. Joice et al. attribute this error to the use of inadequate force or the use of wrong

instruments (graspers, clip applicators and electrosurgical hook knives). Given the surgeons in their study were experienced and fully trained, we can conclude that there were factors other than ‘performance shaping factors’ (PSP) that led to such errors. The application of inadequate force or the selection of wrong instruments could be due to the following: 1. Psychological Error Mechanism (PEM): Lack of confidence, difficulty to concentrate due to fatigue, lack of sleep or other psychological factors. 2. Inventory management: Lack of availability of suitable instrument at the time of surgery. 3. Motion economy: The recorded errors could be due to the violation of motion economy area ‘design of tools and equipment’, which is outside the scope of the current research, or the violation of principles of other areas of motion economy as we

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Table 4 Errors captured during in vivo direct observation of 12 laparoscopic surgeries. Observed error Inability to separate tissue planes

Failure to hold tissues/organ

No.a

TET

MEET

Comments on observed violation of motion economy

2

A4

D3 þ B7

4 1

A4 A4

B7 þ A6 E4

8 2

A4 A3 þ A4

A7 þ A6 B6 þ E3 þE4

Inadequate exposure of the surgery area associated with inadequate position of the monitor. The low level of surgical area forced surgeon to use his upper arms at the time he required to turn his trunk in order to see the images in the monitor. Inadequate position of the monitor associated with long period non-physiological posture. Position of surgical team relative to surgeon. A surgeon assistant changed position and prevented surgeon to see monitor. He adjusted position based on the surgeon's request. Inadequate level of instrument handle associated with non-physiological posture. Bad illumination of the surgical field due to failure of the surgeon’ assistance to correctly orient the laparoscope.

A4

A7 þ B7 þ A6

A4 A3 þ A4

B7 B6 þ E3 þ E4

10 1 5

A4 A4

A7 þ D3 A7 þ B7 þ A6

1

A4

B6 þ E3

2

A4 þ A5

E4 þ E3

9 4

A4

B5 þ A6 þ A1

A4 þ A5 A4

E3 A6 þ B7

A4

B5 þ A6 þ A1

Inadequate level of surgical area associated with non-physiological posture forcing surgeon to use of upper arm and shoulder movement.

1 2 5 6

A4 A4 þ A5

B6 E3

Overhead lamp required orientation. Failure of assistant surgeon to synchronise hand motion

A3, A5

B5 þ A6 þ A1

2

A3, A5

B5 þ E3

2 7

A3, A5 A3, A5

E3 E4 þ E3

2 19 2 1 3 5 2

A3, A5

A6, B7

Inadequate level of instrument handle associated with non-physiological posture forcing surgeon to use of upper arm and shoulder movement. Bad illumination of the surgical field due to failure of assistant surgeon to orient correctly the laparoscope. Failure of assistant surgeon to synchronise hand motion Inadequate position of assistant surgeon associated with failure to synchronise hand motion with surgeon. Inadequate level of instrument handle associated with inadequate position of monitor.

A6, C1 A6, C1

E3 C4

Failure of scrub nurse to coordinate with surgeon's request. Scrub nurse holding two instruments in her hand and passed the incorrect one.

A1 A1

B1, B2, B3 B1, B2

I1, I3

E2

Scrub nurse searched for the required instrument/material. Searching for missing knife. Found between the patient drape. Searching for missing needle. Found inside an open envelop. Scrub nurse should open the needle envelop only when needed. Delay resulting from communication problem

C1

C3

Failure to check the quality of the instrument before the start of the surgery.

S1

C2

Failure to list all the surgery required instruments/material in the surgery requirements form before the day of surgery.

17 6 1 3

Failure to slice tissues/organ

Failure to pierce tissue/organ with suture needle.

Failure to suture skin e remove suture and repeat the task

Failure to put tissues/ organ pieces into retrieval bag eFailure to manoeuvre grasper's jaws correctly.

Surgeon received wrong instrument Delays in handling instruments/material to surgeon.

Surgeon receive unfit/unworkable instrument Requesting new instruments/material Total a

3 3 10 2

2 9 1

1 3

Inadequate level of instrument handle associated with inadequate position of monitor and long period non-physiological posture. Bad illumination of the surgical field due to impurities covered the laparoscope. Bad illumination of the surgical field due to failure of the surgeon’ assistance to correctly orient the laparoscope. The operating theatre has only one monitor and sometimes the assistant surgeon turned his trunk to see the images in the monitor. Such situation disabled him to orient correctly the laparoscopic. Inadequate level of instrument handle associated with poor exposure of surgery area. Inadequate level of instrument handle associated with poor position of the monitor and long period nom-physiological posture. Bad illumination of the surgical field due to failure of the surgeon’ assistance to correctly orient the laparoscope. Inadequate position of assistant surgeon associated with failure to synchronise hand motion with surgeon. This may also be due to the lack of experience. Inadequate level of surgical area associated with non-physiological posture forcing surgeon to use of upper arm and shoulder movement Failure of assistant surgeon to synchronise hand motion Long-period static and non-physiological position associated with poor position of monitor.

3 86

The number of errors represents erroneous instances captured across the 12 observed laparoscopic surgeries using TET component (SHERPA error mode taxonomy).

have defined them (Table 1). Possible contributing factors could thus be one or more of the following: (a) Height of operating table: Unsuitable height of operating table forces surgeon to have wrong posture which may create back and shoulder pain and affect the surgeon's hand and body motions (principles A1, A4, A5 and A9). As a result, surgeon's

ability to manoeuvre correctly the laparoscopic instruments (or even select the correct instruments) could be affected. (b) Location of the monitor: Inadequate location of the monitor violates the principle A7. It creates neck extraction and axial rotation of spine (van Det et al., 2009) and, as a result, may predispose surgeon to error.

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(c) Blurred vision: impurities around endoscopic camera may transmit blurred image of the surgical field and create inadequate condition for seeing (Principle B6). Violation of principle B6 may affect the surgeon's ability to manoeuvre correctly the laparoscopic instrument and hold gallbladder adequately. (d) Lack of coordination: Assistant surgeon may fail to coordinate the camera movement as required (principle D2) and affect the vision of the required surgical field. (e) Long-period static posture: The prolonged static posture during surgery (principle A6) causes leg and back pain that may affect the surgeon performance (Vereczkei et al., 2004). The above argument suggests that traditional HTA/HEI could capture various human errors during surgery but not necessarily the root causes that predispose experienced surgeons to errors. Needless to say that factors affecting the performance of experienced surgeons will also affect the performance of novice surgeons e likely even more, consistent with a significant body of evidence on surgical technical expertise. Overall, in testing our methodology in 12 laparoscopic surgeries we found it promising in capturing errors and their root causes in terms of motion economy principles. It is important to note here that in developing our methodology we have intended to complement and improve rather than replace or discard the traditional HTA/HEI techniques. The introduction of motion economy principles as part of error mode taxonomy will allow us to recognise ergonomic deficiencies that predispose surgical team to errors and plan to reduce and eliminate future errors. Though errors captured during our observation were minor disruptive events that may not give rise to postoperative complications, the accumulation of these events, however, creates stress, fatigue and musculoskeletal problems and, as a result, affects the performance of the surgical team and endangers patient safety (Etchells et al., 2003; Vereczkei et al., 2004; Wiegmann et al., 2007). It should also be noted that nontechnical errors could occur because of lack of experience and skill rather than ergonomic deficiencies. Such errors could also be captured by our methodology via TET elements. To our knowledge, this is the first attempt to use the principles of motion economy as part of HTA/HEI taxonomy. In addition to further analytical and empirical research, we believe that our developed list of principles (Table 1) can be used to educate surgeons in motion economy and other key ergonomic elements of working in the operating theatre. 5. Limitations and future research There are some limitations in this study. The first limitation is that the study did not consider an important area in motion economy, that is, the area of ‘design of tools and equipment’. It is highly possible that an error could occur because of difficulty in handling or manoeuvring an instrument as a result of its poor design. The limited number of observations is another limitation. Only 12 laparoscopic surgeries were observed. With more observations, wider range of principles may be tested and indeed further additional principles may be discovered. The third limitation of this study is that there was no observations were made to test the applicability of the selected and developed principles in traditional open surgeries. Testing the applicability of motion economy principles on open surgeries is highly needed in order to develop more generalisable principles that could be applied across numerous procedures. The fourth limitation is that our study limits its focus on motion economy. There are other areas that may contribute to surgical errors, including for instance, the location of organs or tissues under treatment, and anatomical difficulties. Psychological factors such as lack of confidence and forgetfulness may contribute

to errors and are worth of consideration. There is a possibility that some tasks are performed with practices that require excessive resources or extra precaution. Work practices are another aspect that requires further consideration (Al-Hakim et al., 2014). We are planning to consider these limitations in our future studies. We also plan to design an observational experiment to test the effect of improving motion economy according to the principles identified in this study on surgeons' performance and error reduction. 6. Conclusion This study asserts that traditional human error identification techniques fail to consider motion economy principles and, accordingly, their applicability in operating theatres may be limited. On the other hand, this study shows that traditional principles of motion economy were designed to facilitate the performance of a single worker implementing repetitive, mechanical work with definite steps. Accordingly, not all of these principles are applicable to the surgical environment and the applicable ones may require adaptation. Based on literature review and observations in theatres, this study considered two traditional areas of motion economy, i.e., ‘use of human body’ and ‘arrangement of workplace’, and created 3 new areas for motion economy, namely ‘work with sterile instruments and material’, ‘work on human body’ and ‘communication and teamwork’. A total of 30 principles of motion economy principles were identified (11 existing and 19 newly developed ones). These principles were integrated as part of an error mode taxonomy for human error identification techniques. The new error mode taxonomy comprises two parts; a motion economy error taxonomy (MEET) and a task error taxonomy (TET). A hierarchical task analysis was used to analyse the tasks of hand-assisted laparoscopic nephrectomy and the TET part of the developed taxonomy was used to identify the errors, while the MEET part was used to recognise the motion economy principles predisposing surgeons to errors. The newly developed taxonomy was prospectively tested in 12 laparoscopic surgeries performed by 5 experienced surgeons. A total of 86 errors were identified and successfully linked to motion economy deficiencies. This is a promising methodology for identifying and mitigating error-causing factors in operative environment. It is also a potentially useful way to educate surgeons about basic motion economy principles in their work. Conflict of interest Sevdalis delivers team-based safety interventions and training to hospitals internationally on a consultancy basis through London Safety and Training Solutions Ltd. Acknowledgement The project has been partially sponsored by the University of Southern Queensland and approved by the Institutional Review Board and Ethic Committee at Bangkok Medical Center (BMC), Thailand. Sevdalis is funded by the National Institute for Health Research via the ‘Collaboration for Leadership in Applied Health Research and Care South London’ at King's College Hospital NHS Foundation Trust, London, UK. The authors are grateful to the support of Dr Matinee Mapping, Assistant CEO of BMC. The authors acknowledge the thoughtful time and help of the operating room manager, Ms. Rachanee and the OR nurses Ms. Suneerat and Ms. Jantima. Special recognition is extended to the Anaesthetists and Surgeons Committee (ASC) at BMC for their support. We would like also to extend our gratitude to the anonymous reviewers for their comments and suggestions, from which our study has greatly benefited.

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