Introduction
Tragal cartilage tympanoplasty is a common surgical procedure in reconstructive otology.Reference Goodhill1 In recent years, totally endoscopic ear surgery has offered a novel perspective on otological surgery, allowing improved access and alternative minimally invasive approaches for many operations, including tympanoplasty.Reference Tarabichi2 An endoscopic approach to tympanoplasty is comparable to traditional microscopic surgery, with similar outcomes and improved recovery times.Reference Hsu, Kuo and Huang3 Totally endoscopic ear surgery is particularly suitable as a day-case procedure. Endoscopic tympanoplasty provides a unique set of challenges to otologists from a technical and human factors standpoint.Reference Keogh, Fahy, Garry, Fahy and Corbett4 The learning curve is steep for this one-handed, ‘heads-up’ technique. This is offset against superb views and the minimally invasive nature of totally endoscopic ear surgery.
Alternative approaches to the traditional ‘see one, do one, teach one’ method of surgical training, such as surgical simulators, are being increasingly utilised to improve patient safety and prevent error.Reference Kotsis and Chung5 Novel methods of ensuring trainee competency prior to performing surgery on patients have demonstrated the potential to reduce risk and mitigate error. The integration of human factors into surgical practice has shown the potential to reduce surgical error and improve patient safety.Reference Shouhed, Gewertz, Wiegmann and Catchpole6 Human factors approaches to optimising performance have been successfully adapted to medical and surgical practice, and can reduce complications associated with complex tasks.Reference O'Connor, Reddin, O'Sullivan, O'Duffy and Keogh7
First pioneered in the aviation, military and nuclear power industries, hierarchical task analysis is an approach used to deconstruct expert performance.Reference Salmon, Jenkins, Stanton and Walker8 Similar to surgery, the significant impact of errors in these high-risk professions precludes learning by trial and error.Reference Sanchez and Barach9 In addition, a detailed and comprehensive knowledge of the subtasks required to complete a procedure, and the steps required to reduce and remediate error, are of significant importance prior to undertaking a new procedure or a new technique.
Hierarchical task analysis methodology has been used in anaesthesia,Reference Phipps, Meakin, Beatty, Nsoedo and Parker10 and has shown promise as both an assessment and training tool in general surgery.Reference Sarker, Hutchinson, Chang, Vincent and Darzi11 For new surgical procedures, hierarchical task analysis can identify a correct method to deconstruct each task, improve understanding, and be used to create subtasks required to successfully complete the procedure without error. The systematic human error reduction and prediction approach (‘SHERPA’) is a human factors approach to error management; it involves error identification, followed by quantification of the frequency and severity of errors, and the subsequent identification of methods to reduce or mitigate risk at each step of a procedure.Reference Khandan, Yusefi, Sahranavard and Koohpaei12
Otolaryngology procedures have been analysed using hierarchical task analysis and the systematic human error reduction and prediction approach in the past, prior to the creation of simulation-based learning.Reference Demirel, Butler, Halic, Sankaranarayanan, Spindler and Cao13 Similar to functional endoscopic sinus surgery, totally endoscopic ear surgery involves careful preparation and management of anaesthesia, operating theatre staff, and endoscopic equipment, and both operations are suited to hierarchical task analysis and the systematic human error reduction and prediction approach.Reference Corbett, O'Connor, Byrne, Thornton and Keogh14 Functional endoscopic sinus surgery simulators have utilised task deconstruction methodology to standardise procedure and improve trainee performance.Reference Richards, Done, Barber, Jain, Son and Chang15
It is important to appreciate that no two surgeons perform the steps of any complicated surgical procedure in the same way. All surgeons, particularly otologists, have nuances and personal preferences. However, the primary steps, approach, aims and attitudes to outcomes are fundamental tenets. It is also important to recognise that many established otologists are moving towards totally endoscopic ear surgery as their primary option for otological surgery.
A hierarchical task analysis and systematic human error reduction and prediction approach for a totally endoscopic ear surgical procedure have not, to our knowledge, been described in published medical literature to date. We hope that the publication and presentation of this research will stimulate discussion and raise awareness of these approaches for the training and safe performance of totally endoscopic ear surgery.
Materials and methods
A hierarchical task analysis was created to describe the steps required to perform totally endoscopic push-through tragal cartilage tympanoplasty. A literature review of published techniques and methods was conducted, to better understand the goals of totally endoscopic ear surgery. The databases searched included Scopus, PubMed, Medline and UpToDate. Available methods of microscopicReference Cavaliere, Panetti and Lemma16 and endoscopicReference Doğan and Bayraktar17 tympanoplasty were condensed into a task and subtask listing suitable to complete a successful, error-free operation.
Push-through tragal cartilage tympanoplasty was chosen given its suitability for hierarchical task analysis, a systematic human error reduction and prediction approach, and totally endoscopic ear surgery.Reference Celik, Samim and Oztuna18 It was considered an appropriate entry-level totally endoscopic ear surgical procedure for the trainee surgeon. It allows for tragal cartilage harvesting and plenty of endoscopic manipulation, without the added difficulty of raising tympanomeatal flaps and the challenges associated with managing bleeding. Supervision is easy and operation times are short. Proficiency allows progress to more complex totally endoscopic ear surgical procedures.
All totally endoscopic ear surgical procedures were categorised according to Cohen's classification system.Reference Cohen, Basonbul, Barber, Kozin, Rivas and Lee19 All procedures included were Cohen class 3, totally endoscopic. All procedures were performed under general anaesthetic, with informed consent obtained and all risks discussed. A variety of tympanic membrane perforation sizes were treated, but they were primarily of small to medium size.
Twenty-five endoscopic tragal cartilage tympanoplasties were observed over a 12-month period in order to identify the tasks and subtasks required for the successful completion of totally endoscopic ear surgery. Expert opinion included that of three consultant otologists and one consultant anaesthetist. Structured interviews were carried out with the participants to identify a single acceptable method for each step for an otolaryngologist with no prior experience of totally endoscopic ear surgery. Semi-structured interviews with three otolaryngology resident trainees were conducted to identify areas of difficulty and concern. The consultant otologists and trainees were interviewed independently. Through the help of these participants, accurate arrangement of the subtasks required for successful, error-free totally endoscopic tragal cartilage tympanoplasty was created in the form of a hierarchical task analysis. Each step was described in chronological order, and in sufficient detail such that a trainee could follow the task list. These participants also identified areas of risk and poor patient outcomes for the systematic human error reduction and prediction approach.
The task list was refined and edited at each procedure until a single suitable method was agreed upon. The three consultant otologists were involved with refining and editing these steps by consensus. Subtask steps derived from the hierarchical task analysis were evaluated using the systematic human error reduction and prediction approach method.Reference Stanton20 This method involves the following steps: (1) describing the step according to the action required to perform the subtask; (2) classifying the tasks to identify what errors can occur; (3) considering the consequences of each error identified; (4) discovering the measures required to recover or prevent the error; (5) rating the probability and severity of each identified error; (6) identifying critical errors that would lead to a serious incident; and (7) suggesting error reduction strategies. These are the changes used to prevent the errors from occurring or to reduce the consequences of the errors.
A suitable risk matrix was adapted from the Irish Health Services Executive risk matrix in order to quantify the frequency and severity of each potential error.21 All 25 tympanoplasty procedures were carried out by a consultant otologist. The three otolaryngology resident trainees undertook independent scoring based on direct observation and experience of these procedures. The final score was reached by consensus with the trainees and consultant, and based on review of the literature where applicable. Each error was scored from 1 to 25 based on criticality and likelihood (Tables 1 and 2). Each error was analysed to determine the suitable steps required to reduce the chance or mitigate the consequence of risk.
Table 1. Error impact scoring
Table 2. Error likelihood scoring
Yrs = years
The research was carried out at the University Hospital Galway with associated personnel. The otolaryngology department of the University Hospital Galway is experienced in totally endoscopic ear surgery, and has been using the technique since 2013 for a broad range of procedures. Ethical approval was obtained from the clinical research ethical committee at the University Hospital Galway.
Results
Twenty-five endoscopic tragal cartilage tympanoplasties were observed for the purpose of the study; 14 were performed on males and 11 on females. All tympanoplasties were successful and no adverse events were identified. Patients’ ages ranged from 12 to 68 years.
A top-level task analysis was conducted, detailing eight tasks required to successfully complete the operation and ensure patient safety (Table 3). A subtask analysis of each task was produced (Table 4). Systematic human error reduction and prediction approach analysis was performed to identify errors and methods of controlling risk (Table 4). For each subtask, a measurable error was identified. Each error was scored in terms of frequency and severity according to the risk matrix. Three otolaryngology resident trainees undertook independent scoring based on direct observation and experience of these procedures. The final score was reached by consensus with trainees and consultant, and based on a review of the literature where applicable. The agreed method was deemed suitable by senior authors for familiarising any surgeon new to the procedure with each step and error. Each potential error was examined, and suitable methods of error prevention and remediation were suggested.
Table 4. Subtasks and systematic human error reduction and prediction approach
Pre-op = pre-operative; N₂O = nitrous oxide; ET = endotracheal; EAC = external auditory canal; LED = light-emitting diode; TM = tympanic membrane; BIPP = bismuth iodoform paraffin paste; post-op = post-operative
Eight principal tasks and 50 subtasks of totally endoscopic tragal cartilage tympanoplasty were identified. Error impact ranged from negligible to major. Error likelihood ranged from rare to likely. Scoring was calculated by multiplying the impact by the likelihood. Of the errors at each subtask, the highest score was eight. Seven subtasks scored eight points or higher, indicating a probability of 10 per cent with the potential for major consequences to patient safety.
Highlighting the subtask steps associated with high-risk and high frequency error was the most important part of the analysis. The subtasks with the potential for major impact included inserting and handling the endoscope, tympanic membrane manipulation, and inserting and positioning the graft. Remediation included the active management and prevention of these errors. Active management included haemostasis, irrigation and topical adrenaline application. Prevention focused on observation of the endoscope progress via the monitor.
A few of the subtask steps were associated with errors considered likely or almost certain to happen. These errors resulted in poor quality images and were deemed negligible because of the ability for swift correction; that is, endoscope cleaning and reinsertion. Some ergonomic steps were deemed likely to those unfamiliar with totally endoscopic ear surgery, such as holding the endoscope in the non-dominant hand and not resting the endoscope against the side of the external auditory meatus. These can be improved by education and practice, and remediation is uncomplicated.
Discussion
This hierarchical task analysis highlighted a number of surgical steps in totally endoscopic tragal cartilage tympanoplasty that have human factors and safety issues for the patient. These complications can involve damage to the outer ear or middle-ear structures, requiring further operative intervention. Trauma to the external auditory canal, tympanic membrane, ossicular chain, middle-ear mucosa and facial nerve are possible, and can significantly affect a patient's quality of life.Reference Carlsson, Hall, Lind and Danermark22 The hierarchical task analysis raises awareness of the surgical steps with the potential to damage these structures, allowing surgeons to focus on these areas to improve both technical and human factors based performance.
The majority of the errors are rare or unlikely to occur, and cause minor complications. Totally endoscopic ear surgery is a safe procedure when performed by an appropriately trained surgeon, and is an effective method with comparable outcomes to traditional otological surgery.Reference Berglund, Florentzson, Fransson, Hultcrantz, Eriksson and Englund23
The surgical approach is minimally invasive, performed via the external auditory canal, with a small incision on the tragus. This allows for a quicker patient recovery time and avoids a post-auricular scar.Reference Ayache, Tramier and Strunski24 High-quality images of the ear canal and middle ear allow the operation to be conducted transcanal in all but the most challenging anatomy cases, for all tympanic membrane perforation sizes.Reference Anzola and Nogueira25
The impaired depth perception during totally endoscopic ear surgery can lead to an ‘endoscopic plunge’; this can cause trauma to structures such as the external auditory canal, tympanic membrane and ossicular chain. Tympanoplasty performed with the microscope allows for both hands to be used and enables better depth perception. This reduces the risk of unintentional trauma, but at the cost of decreased visualisation when compared to the endoscope.
Other complications of totally endoscopic ear surgery include excessive heat dissipation from the endoscope itself.Reference Ozturan, Dogan, Eren and Aksoy26 Awareness of the nature of the light source and the heat produced, setting the light intensity at a minimal accepted level (e.g. less than 50 per cent), and inclusion of the complication in the surgical ‘timeout’ process can mitigate this. Anti-fog has been found to be ototoxicReference Rhee, Han, Rah, Park, Koun and Choi27 and should be wiped clean after each application.
The widespread introduction of totally endoscopic ear surgery has been questioned by some because of the technique's steep learning curveReference Kozin, Kiringoda and Lee28 and the potential for damage by untrained operators. Totally endoscopic ear surgery is a ‘heads-up’ procedure, requiring a one-handed technique. It is a heads-up procedure with improved ergonomics, thereby reducing the chronic neck and back issues frequently suffered by many otologists.Reference Ho, Hamill, Sykes and Kraft29 Ergonomics are important for successful surgery, and can be improved by familiarity with equipment and intuitive operating theatre layout. Totally endoscopic ear surgery also provides a high-definition record of pathology and surgical correction, allowing for progress to be monitored over time.
Even with its challenges, totally endoscopic ear surgery has proved useful in multiple procedures including: stapes surgery,Reference Isaacson, Hunter and Rivas30 assessment of perilymphatic fistulas,Reference Poe and Bottrill31 management of cholesteatomaReference Presutti, Gioacchini, Alicandri-Ciufelli, Villari and Marchioni32 and paediatric middle-ear surgery.Reference James33 Recently, totally endoscopic ear surgery has been used in the coronavirus disease 2019 pandemic to reduce the need for open ear surgery and the associated aerosols generated.Reference Ayache, Kutz, Isaacson, Badr-El-Dine, Nogueira and Marchioni34
The use of hierarchical task analysis in totally endoscopic ear surgery can increase an otolaryngologist's familiarity with the surgery. Hierarchical task analysis highlights areas of difficulty, which can be used to inform trainees who are inexperienced with totally endoscopic ear surgery. Increasing a trainee's familiarity with a new procedure can make the trainee more likely to safely attempt novel techniques, therefore providing more skills for the management of a wide range of pathologies. Hierarchical task analysis provides the steps required for error-free tragal cartilage tympanoplasty, allowing otolaryngologists of all levels to improve their skills.
Human factors and simulation teaching has been increasing in recent years, with mandatory training for core surgical trainees in the Royal College of Surgeons in Ireland and the UK.Reference Okhovat, Milner and Iyer35,Reference Jones, Howells, Mitchell, Burnand, Mutimer and Longman36 Learning through trial and error is no longer feasible given the potential for patient harm, and simulation teaching with manikins and task trainers is being used to bridge the gap in surgical training.Reference de Montbrun and MacRae37 Hierarchical task analysis and the systematic human error reduction and prediction approach are valuable tools for surgical training. The creation of a standardised procedure allows trainees to follow a step-by-step guide to a surgical operation, with the potential to reduce performance variation among surgeons. Human error is thought to be the cause of most adverse surgical events.Reference Suliburk, Buck, Pirko, Massarweh, Barshes and Singh38 This systematic human error reduction and prediction approach highlights areas of potential danger, and guides trainees and trainers to focus on these areas, improve surgical skills and improve patient safety.
Hierarchical task analysis can also be used for the assessment of surgical trainees, by evaluating a trainee's ability to adhere to a previously devised pathway for a surgical procedure. The trainee's performance can be compared to the agreed standard. Hierarchical task analysis and the systematic human error reduction and prediction approach are particularly useful for novel or technically challenging procedures such as totally endoscopic ear surgery. The validity of hierarchical task analysis and the systematic human error reduction and prediction approach, as applied to totally endoscopic ear surgery as a teaching tool, will need to be assessed in the future through further research.
This study had a number of limitations. Our hierarchical task analysis and systematic human error reduction and prediction approach are specific to push-through cartilage tympanoplasty, and there are multiple other methods available. Our steps would benefit users of different methods, but would not be comprehensive. Three consultant otologists were selected as experts because this is a single-institution study. These experts were selected as they are experienced in endoscopic ear surgery and are members of the institution's otolaryngology department. Another panel of experts may have assessed the important tasks and evaluated errors of this procedure differently.
• Totally endoscopic ear surgery is a novel method that can offer a unique perspective of operative and non-operative challenges
• Hierarchical task analysis is an approach used to deconstruct expert performance
• The systematic human error reduction and prediction approach involves error identification, error frequency and severity quantification, for error reduction
• These methods have not previously been described in medical literature for totally endoscopic ear surgery
• Hierarchical task analysis was used to describe the steps required for error-free totally endoscopic push-through tragal cartilage tympanoplasty
• The systematic human error reduction and prediction approach identified potential surgical errors, enabling error reduction mechanisms to mitigate these risks
It is recognised that deconstructing any surgical procedure into tasks and subtasks will result in many individual steps. This can act as a starting point to design a more efficient, trainee-focused aid, individual to each operating surgeon, which highlights key surgical steps, particularly those considered high risk. A handful of steps, such as those involving taking pictures, are not mandatory and instead reflect the preferences of this department's otologists. A tympanomeatal flap was not raised. This can be a difficult step for early-stage trainees and those migrating from microscopic techniques. Proficiency at entry-level totally endoscopic ear surgery allows smooth progression to more complex procedures. Breakdown of the steps required for raising a tympanomeatal flap would benefit trainees, but this was outside the scope of this paper. Assessment of outcomes for trainees using this hierarchical task analysis and systematic human error reduction and prediction approach has not yet been performed. We hope to undertake this research in the future.
Conclusion
The hierarchical task analysis and systematic human error reduction and prediction approach methods are valuable tools, which, through standardisation of practice, allow errors in surgery to be better recognised and more promptly addressed. Our hierarchical task analysis allows for quick reference to a correct method of endoscopic tympanoplasty and enables evaluation of a standard technique. The systematic human error reduction and prediction approach identified numerous potential errors in the completion of totally endoscopic tragal cartilage tympanoplasty; this enabled the identification of error reduction mechanisms to mitigate the risks of undergoing totally endoscopic ear surgery. We are not aware of these methods being applied to totally endoscopic ear surgery to date.
Competing interests
None declared.
