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Biomedical subjects

G B Hanna

Publications and source records attributed to G B Hanna.

At least 19 recordsLinked to original sources
PubMed2006

Mechanical properties of the human abdominal wall measured in vivo during insufflation for laparoscopic surgery.

BACKGROUND: Carbon dioxide insufflation of the peritoneal cavity for laparoscopic surgery offers a unique opportunity to measure some mechanical properties of the human abdominal wall that hitherto have been difficult to obtain. METHODS: The movement and change of the abdominal wall during insufflation to a pressure of 12 mmHg was studied in 18 patients undergoing laparoscopic surgery using a remote motion analysis system that does not compromise the sterility of the operative filed. These data together with the known abdominal wall thickness of each patient (measured by preoperative ultrasound scanning) enabled estimates of mechanical stiffness. RESULTS: The findings showed that the abdominal wall changes from a cylinder to a dome during inflation, and that its area is increased by 15%. A volume, averaging 1.27 x 10(-3)m(3), results from expansion, reshaping of the abdominal wall, and displacement of the diaphragm. The abdominal wall is stiffer in the transverse plane than in the sagittal plane (Young's modulus, 42.5 +/- 9.0 kPa vs 22.5 +/- 2.6 kPa; p = 0.03; paired t-test). CONCLUSIONS: Measurements of mechanical properties of the abdominal wall in patients undergoing laparoscopic surgery were obtained using a remote motion analysis system.

Abdominal Wall↗
PubMed2006

Competence assessment of laparoscopic operative and cognitive skills: Objective Structured Clinical Examination (OSCE) or Observational Clinical Human Reliability Assessment (OCHRA).

BACKGROUND: There is no agreed system that is acknowledged as the ideal assessment of laparoscopic operative and cognitive skills. A new approach that combines Objective Structured Clinical Examination (OSCE) and Observational Clinical Human Reliability Assessment (OCHRA) was developed and used to assess trainees' operative and cognitive skills during laparoscopic training courses. METHODS: Performance of 60 trainees participating in 3-day essential laparoscopic skills training (cognitive and psychomotor) courses were assessed and scored using both OSCE and OCHRA. RESULTS: The study showed significant inverse correlations between the number of technical errors identified by OCHRA and the scores obtained by OSCE for individual tasks performed either by electro-surgical hook or laparoscopic scissors (r = -0.864 and r = -0.808, respectively). Significant differences between trainees were observed in relation to both overall OSCE scores and OCHRA parameters: execution time, total errors, and consequential errors (P < 0.001). CONCLUSIONS: OCHRA provides a discriminative feedback assessment of laparoscopic operative skills. OCHRA and OSCE are best regarded as complementary assessment tools for operative and cognitive skills. The present study has documented significant variance between surgical trainees in the acquisition of both cognitive and operative skills.

Cholecystectomy, Laparoscopic↗
PubMed2005

Consensus guidelines for validation of virtual reality surgical simulators.

The Work Group for Evaluation and Implementation of Simulators and Skills Training Programmes is a newly formed sub-group of the European Association of Endoscopic Surgeons (EAES). This work group undertook a review of validation evidence for surgical simulators and the resulting consensus is presented in this article. Using clinical guidelines criteria, the evidence for validation for six different simulators was rated and subsequently translated to a level of recommendation for each system. The simulators could be divided into two basic types; systems for laparoscopic general surgery and flexible gastrointestinal endoscopy. Selection of simulators for inclusion in this consensus was based on their availability and relatively widespread usage as of July 2004. Whilst level 2 recommendations were achieved for a few systems, it was clear that there was an overall lack of published validation studies with rigorous experimental methodology. Since the consensus meeting, there have been a number of new articles, system upgrades and new devices available. The work group intends to update these consensus guidelines on a regular basis, with the resulting article available on the EAES website (http://www.eaes-eur.org ).

Computer Simulation↗
PubMed2005

Analysis of errors enacted by surgical trainees during skills training courses.

BACKGROUND: Despite the emphasis on medical error as a major cause of hospital morbidity and mortality, there has been little published work on errors committed by trainees. This issue is particularly relevant to the training of surgeons and was addressed by our study. METHODS: Sixty simulated laparoscopic cholecystectomies performed on restructured pig tissue models by 60 surgical trainees provided the study material. The unedited videotapes were analyzed by observational HRA of the component steps of the procedures. Ten generic forms of observable error types were used to categorize patterns of failure. Error probabilities with specific instruments were also calculated. RESULTS: A total of 1067 errors were identified by observational HRA: 331 consequential and 736 without consequence (ie, total error rate of 18 [SD +/- 10]) per procedure. The study documented a wide variation in the number of errors between the 60 trainee surgeons. The important underlying factors for the trainee errors were (1) omission of important steps, (2) execution of steps in the wrong sequence, and (3) use of excessive force. These 3 errors accounted for 92% of consequential errors. CONCLUSIONS: This study has shown that trainees vary considerably in their propensity to commit errors. This variability indicates that the surgical training in component skills for laparoscopic surgery should be flexible and individualized. Three mechanisms account for the majority of errors and indicate that skills training in surgery has to be structured, menu driven, and tailored to individual needs.

Animals↗
PubMed2004

Effect of fixation of shoulder and elbow joint movement on the precision of laparoscopic instrument manipulations.

BACKGROUND: Motion analysis of the upper limb and the surgical instruments is used for objective assessment of endoscopic manipulations. The aim of this study was to investigate the effect of fixation of shoulder and elbow joint movement on the precision of laparoscopic instrument manipulations. METHODS: Two experiments were conducted to correlate hand movement with instrument tip during free and restricted movement of the shoulder and elbow joints. A three-dimensional infrared optical tracking system has been used. Five subjects participated in the study, and each completed the range of movements twice. End points were velocity (m/s), angular velocity (r/s) and acceleration (m/s2). RESULTS: There was a weak correlation for all end points between the instrument tip and individual joint movement during free upper limb movement (r < 0.4). With restricted movement of the shoulder and elbow joints, the correlation between hand movement and instrument tip was found to be good for the velocity (r = 0.66 for flexion; r = 0.72 for abduction; r = 0.56 for supination) and angular velocity (r = -0.83 for flexion; r = -0.48 for abduction; r = -0.70 for supination), but weak for the acceleration (r < 0.4). CONCLUSIONS: The characteristics of hand movements do not correlate with movement of the laparoscopic instrument tip when the upper limb is unsupported. The precision of laparoscopic surgical manipulations is increased if both joints (shoulder and elbow) are supported.

Elbow Joint↗
PubMed2004

Analysis of technical surgical errors during initial experience of laparoscopic pyloromyotomy by a group of Dutch pediatric surgeons.

BACKGROUND: The adoption of laparoscopic pyloromyotomy (LPM) by pediatric surgeons has been limited due to concerns about long execution times and higher-than-expected morbidity. The aim of the present study was to examine the performance of LPM by pediatric surgeons during the initial stages of their experience. METHODS: Complete videotapes of 50 early LPM performed in one hospital were subjected to Observational Clinical Human Reliability Analysis (OCHRA) by an independent team. RESULTS: This series had a total morbidity of 6% (one intraoperative bleed, one gastric perforation, one incomplete pyloromyotomy). Using OCHRA, we identified 77 consequential and 233 inconsequential errors (mean of 6 +/- 5.4 per operation, 16.7% total error probability) during an average operative time of 29.8 min. Eighty percent of the errors were of the execution type. A high probability of error was observed with the use of the following key instruments: holding graspers (68%), retractable blade (79%), and splitting forceps (77%). The OCHRA system confirmed that task III was the hazard zone for LPM. Excessive force (task III) resulted in gastric perforation and bleeding from the pyloric mass. Movement in the wrong direction and misorientation in tissue planes were the external error modes underlying misaligned cuts of the pyloric mass and poor tissue splitting (task zones II and III). CONCLUSIONS: This early series of LPM was associated with an appreciable execution error rate, largely due to the poor functionality of the specific instruments used for the procedure. Human factors identified by the external error modes played a subsidiary but important role, underscoring the importance of skills training and experience (proficiency-gain curve).

Child↗
PubMed2004

Time-motion analysis of operation theater time use during laparoscopic cholecystectomy by surgical specialist residents.

BACKGROUND: Data on man-machine interfaces in the operation theater are essential to the improvement of surgical efficiency. This study analyzed the activity of the operating team during laparoscopic cholecystectomy by surgical trainees. METHODS: The endoscopic image and overview of the operating room were recorded during 20 laparoscopic cholecystectomies performed by specialist residents. Time-motion analysis of the recorded tapes was performed. RESULTS: The median (interquartile range [IQR]) for theater time was 134 +/- min (IQR, 52 min). The components of operative time for the surgeon were 26% for insertion of access ports and wound closure, 57% for intracorporeal endoscopic work, and 17% for instrument change. Only 52% of the scrub nurse time was related to the operation. Machine and video setup, adjustment of ancillary equipment together, and delivery of instruments and items requested by the surgeon and scrub nurse accounted for 13% of the circulating nurse time. CONCLUSIONS: With the current nonergonomic theater design and structure, a significant proportion of theater time during routine uncomplicated laparoscopic surgery is used for nonoperative functions. The study highlights the need for improved ergonomic design, integrated bus operating systems under the control of the surgeon, and multifunctional laparoscopic instruments.

Cholecystectomy, Laparoscopic↗
PubMed2004

Characterizing the "gold standard" image for laparoscopic surgery.

BACKGROUND: The term "gold standard" is often used to describe preferred display devices, frequently without substantiating evidence. A meaningful and objective measure of display quality for endoscopic surgery is required. METHODS: Typical colors from five tissue types were arranged in a striped pattern and displayed on four devices: a medical-grade cathode ray tube monitor, a liquid crystal display, a digital light projection display, and an obsolete cathode ray tube (CRT) monitor. The breadth and color contrast of the stripes were adjusted until the patterns became indiscernible to 12 subjects. The data provide a discernibility threshold. RESULTS: The liquid crystal display (LCD) monitor provided the best image. The medical grade and obsolete CRTs were second and third, respectively, and the projection display provided the most inferior image. CONCLUSIONS: A meaningful and relevant measurement of image display quality for laparoscopic surgery based on the discernibility threshold is provided. Of the devices tested, the LCD is the best in terms of image, although the CRT may be preferred at off-axis viewing angles. The projection system, however, offers compensatory ergonomic advantages.

Benchmarking↗
PubMed2004

Cardiovascular autonomic function in patients with hemodynamic instability at induction of capnoperitoneum: a case-control study.

BACKGROUND: This study hypothesized that patients in whom bradycardia and hypotension develop with induction of positive-pressure capnoperitoneum have an underlying autonomic cardiovascular dysfunction. METHODS: A case-control study was conducted to examine the baseline autonomic function of patients in whom bradycardia and hypotension develop with induction of positive-pressure capnoperitoneum. The control group consisted of patients who maintained normal cardiac rhythm and blood pressure during the same procedure. Two groups of tests were performed: bedside stress tests of cardiovascular autonomic function (response graded 1 (normal) to 4 (severely abnormal) and heart rate variability analysis (spectral and time domain components). RESULTS: The study evaluated 6 patients in the bradycardia group and 10 in the control group. The group in whom bradycardia had developed scored significantly worse on the bedside stress tests than the control group (for grades I to IV: chi2 = 6.5, p = 0.022; for trend: chi2 = 5.6, p = 0.018). In contrast, both groups had similar baseline autonomic tone, as measured by heart rate variability. CONCLUSIONS: Patients in whom bradycardia and hypotension develop with induction of positive-pressure capnoperitoneum have cardiovascular autonomic dysfunction, which is identifiable by bedside stress tests of autonomic function.

Autonomic Nervous System↗
PubMed2004

Identification and categorization of technical errors by Observational Clinical Human Reliability Assessment (OCHRA) during laparoscopic cholecystectomy.

HYPOTHESIS: Surgical operative performance benefits from analysis of the mechanisms underlying technical errors committed during surgery. DESIGN: Prospective study using the Observational Clinical Human Reliability Assessment (OCHRA) system and complete unedited videotapes of the operations. SETTING: Three National Health Service hospitals within the United Kingdom. PATIENTS: Two hundred consecutive patients with symptomatic gallstone disease. INTERVENTIONS: Elective laparoscopic cholecystectomy for symptomatic gallstone disease by surgeons, who were blind to the nature and objectives of the study, using their usual operative technique. MAIN OUTCOME MEASURES: Surgical consequential and inconsequential operative errors. RESULTS: The analysis of 38 062 steps of the 200 laparoscopic cholecystectomies performed by 26 surgeons identified 2242 errors. The mean +/- SD total, inconsequential, and consequential errors per surgical procedure were 11.0 +/- 8.0, 8.0 +/- 6.0, and 4.0 +/- 3.0, respectively. Dissection of the Calot triangle (second task zone of the operation) incurred more total errors (6.5 +/- 5.4) compared with the first (2.9 +/- 2.8, P<.001) and third (5.1 +/- 3.9, P<.05) task zones. This translated to a higher error probability (6.9% vs 3.5% for the first and 5.5% for third task zones). The combined sharp and blunt dissection method had fewer errors than the blunt/teasing dissection technique (9.45 +/- 7.6 vs 13.9 +/- 7.3, P<.001) although different surgeons were involved. The most serious consequences were encountered during dissection with the electrosurgical hook knife. CONCLUSION: This study has confirmed that the Observational Clinical Human Reliability Assessment system provides a comprehensive objective assessment of the quality of surgical operative performance by documenting the errors, the stage of the operation in which errors are enacted most frequently, and where these errors have serious consequences (hazard zones).

Cholecystectomy, Laparoscopic↗
PubMed2003

Effect of the angle between the optical axis of the endoscope and the instruments' plane on monitor image and surgical performance.

BACKGROUND: The aim of the study was to examine the effect of the angle between optical axis of the endoscope and the instruments' plane (OAIP) on the monitor display angle (approach angle between the two instruments on a two-dimensional monitor) and endoscopic task performance. METHODS: Two experiments were carried out in the Advanced Dundee Endoscopic Psychomotor Tester (ADEPT) using a standard two-dimensional video endoscopic system. In the first experiment, the monitor display angle was measured during use, with OAIP angles ranging between 0 and 80 degrees (at 10 degrees increments) and manipulation angles varying between 45 and 120 degrees (at 15 degrees increments). In the second experiment, 10 surgeons tied 500 intracorporeal knots with OAIP angles of 0 degrees (optical axis in the same plane as the instruments), +15 degrees and +30 degrees (viewing above the instruments' plane), and -15 and -30 degrees (optical axis looking from below instruments' plane). The end points were the execution time and knot quality score (KQS). RESULTS: In the first experiment, instruments entered the visual field from lateral sides of the monitor with an apparent 180 degrees monitor display angle with a 0 degrees OAIP angle, whereas the monitor display angle approached the actual manipulation angle between the two needle drivers when an 80 degrees OAIP angle was used. In the second experiment, the instruments appeared to enter the image field from the side of the surgeon when the endoscope viewed the instruments from above, whereas instruments entered the field from the opposite side to the surgeon when the endoscope viewed instruments' plane from below. As a result, use of 0 and +15 degrees OATP angles yielded significantly shorter execution times: 70 s compared to 83, 93, and 77 s for +30, -30, and -15 degrees OAIP angles ( p < 0.001), with KQS of 39 degrees and 40 vs 38, 36, and 34%, respectively ( p = 0.257). CONCLUSIONS: The angle between the optical axis of the endoscope and instruments' plane determines how the instruments appear to enter the operative field. The monitor display angle between the instruments is different from the real manipulation angle unless the OAIP angle is near 80 degrees. The apparent entry of instruments into the operative field becomes intuitive for the surgeon only if the endoscope is viewing from above or in the same plane as the instruments. Hence, the best performance for endoscopic knot tying is obtained with this configuration, and execution time increases significantly with viewing from below the instruments' plane.

Endoscopes↗
PubMed2001

Influence of handle design on the surgeon's upper limb movements, muscle recruitment, and fatigue during endoscopic suturing.

BACKGROUND: Thus far, little has been done to investigate the kinematics (motion analysis) and kinetics (muscle work, muscle fatigue, comfort) of surgeons during laparoscopic surgery. Therefore, we set out to study these ergonomic aspects of task performance in the dominant upper limb of surgeons during endoscopic suturing. METHODS: Three different handles - conventional finger loop, rocker, and ball handle prototype - were compared in a study involving 10 surgeons suturing porcine enterotomies with each of the three instruments. The endpoints were performance parameters, motion analysis and muscle work, and fatigue of the surgeon's dominant upper limb; subjective scores for comfort level and maneuverability were also elicited from the subjects. RESULTS: Task quality and efficiency during endoscopic suturing, were significantly better with the ball and rocker handle needle drivers than with the finger loop instrument, with lower angular velocity at the elbow and shoulder joints, more pronation, and less supination. The integrated muscle work was much lower for both the rocker and the ball handles. Significant muscle fatigue, especially of the arm flexors and deltoid, was observed only with finger loop instruments. Comfort and maneuverability rating scores were higher with both handles than with the conventional finger loop. The ball handle was easier to maneuver, but it was somewhat less comfortable than the rocker system. CONCLUSION: A different pattern of joint movements, a reduction in muscle power exerted during endoscopic suturing, and hence an absence of muscle fatigue were documented with ergonomic needle drivers (rocker and ball) when compared to the conventional finger loop instruments. These differences translate to better and more efficient task performance with enhanced comfort.

Animals↗
PubMed2001

Reliability of the Dundee Endoscopic Psychomotor Tester (DEPT) for dominant hand performance.

BACKGROUND: The Dundee Endoscopic Psychomotor Tester (DEPT) was developed as a means of obtaining an objective assessment of endoscopic performance using a single hand. This paper evaluates the reliability of the system. METHODS: Twenty medical students were tested on the DEPT for four runs using the dominant hand. Test-retest reproducibility and coefficient alpha to measure the internal consistency were used as indexes of the reliability of the DEPT system. RESULTS: A positive correlation was found between different runs in all outcome measures of the DEPT. Coefficient a was > 0.7 for all parameters. CONCLUSION: DEPT provides a reliable method for the objective assessment of single-handed endoscopic performance in terms of aiming and force exerted on the target plate.

Clinical Competence↗
PubMed2001

Reliability of the Advanced Dundee Endoscopic Psychomotor Tester for bimanual tasks.

OBJECTIVE: To evaluate the reliability of the Advanced Dundee Endoscopic Psychomotor Tester (ADEPT). DESIGN: The Advanced Dundee Endoscopic Psychomotor Tester was developed for objective evaluation of bimanual endoscopic tasks. The system is in several aspects relevant to an actual endoscopic environment, and initial studies showed a strong correlation with clinical competence. Twenty medical students were tested on ADEPT (10 runs in 2 sessions). Their performances for 2 sessions were analyzed by the Spearman rho correlation to examine test-retest reliability. Coefficient alpha was used to indicate the internal consistency of the system. RESULTS: There was no significant improvement in task performance during the 10 runs. A positive correlation on ADEPT performance was found between the 2 test sessions. A coefficient alpha of.98 was observed between the different tasks of ADEPT. CONCLUSION: These findings confirm that ADEPT is a reliable system for assessment of bimanual endoscopic task performance.

Clinical Competence↗
PubMed2001

The performance of master surgeons on standard aptitude testing.

BACKGROUND: Identification of the desired psychomotor abilities of optimal surgical performance, if possible, would be useful in the selection of surgical trainees. The aim of this study was to determine the level of these abilities among endoscopic consultant surgeons held in high regard by their peers. METHODS: Twenty endoscopic consultant "master" surgeons were tested on three aptitude tests: the Gibson Spiral Maze Test (error score measures eye-hand coordination), the Crawford Small Parts Dexterity Test (execution time indicates manual dexterity), and the Space Relations Test (correct scores reflect visuo-spatial ability). Their performance was compared with that of 20 medical students and the reference norm as provided by the tests' manuals. RESULTS: The median scores of master surgeons fell in the 20th, 24th, and 30th percentiles, whereas the scores of medical students fell in the 50th, 20th, and 65th percentile of norm reference for the Gibson Spiral Maze, Crawford Small Parts Dexterity, and Space Relations tests, respectively. The master surgeons enacted significantly fewer errors (Gibson Spiral Maze), had similar execution times (Crawford Small Parts Dexterity), and lower visuo-spatial scores (Space Relations) than medical students. CONCLUSION: The level of eye-hand coordination and manual dexterity of master surgeons was found to be higher than that of the average norm including medical students, while their visuo-spatial ability was lower.

Aptitude Tests↗
PubMed2001

What do master surgeons think of surgical competence and revalidation?

BACKGROUND: There has been on-going debate and public interest in surgical competence in recent years. METHODS: A Delphi reiterative opinion survey was conducted among master surgeons on selection of surgical trainees, methods of assessment of progress of surgical trainees, and revalidation of established consultant surgeons. RESULTS: Selection-the current methods of trainee selection were considered inadequate and in need of revision. The important attributes recognized by group are cognitive factors, innate dexterity, and personality. Important aspects of personality include decision-making ability, insight, team spirit, and emotional stability. Assessment during training-the majority view was that this should be based on clinical judgement/skills, operative skills, and cognitive ability. Assessment of technical ability should be based on standardized checklists. Research within training programs was encouraged but academic achievement does not reflect surgical competence. There was a majority verdict for an exit clinical examination. Revalidation-the group agreed on the need for competence checks during the professional career of surgeons. These should cover knowledge, clinical, operative, and humanistic skills; but expressed concern on the feasibility of a revalidation system that can reliably assess the range of skills needed for surgical competence. There was a majority vote against an internal appraisal system. External assessment by nationally appointed 'assessors' was considered preferable. CONCLUSIONS: Both selection and assessment of surgical trainees require changes and standardization. Although revalidation is necessary, concern was expressed on the reliability and validity of existing and proposed systems.

Clinical Competence↗
PubMed2001

Ergonomics of hand-assisted laparoscopic surgery.

Hand-assisted laparoscopic surgery (HALS) facilitates complex or advanced laparoscopic operations without appreciable loss of the advantages of the total laparoscopic approach. The internal hand enables atraumatic exposure and stretching of tissue planes, finger dissection, restores palpation of internal organs and structures, and provides a rapid and effective means of hemostasis. Particularly during complex surgery performed on the liver and pancreas, this ability to control bleeding by placing pressure between the index finger and thumb reduces the stress on the surgeon. HALS does, however, carry a number of ergonomic problems that are consequent on the encroachment of the hand and device on the workspace. It also imposes an awkward lordotic stance, hence back and shoulder strain on the surgeon. These problems can be resolved by further development of the hand-access devices and also with modifications of existing laparoscopic instruments, or the design and development of HALS-dedicated specific instrumentation. Further progress and increased scope of HALS will only be achieved with designs based on ergonomic research.

Equipment Design↗