Coupled reactive flow and dissolution with changing reactive surface and porosity

Mineral dissolution flows in porous media occur in numerous industrial and natural processes. We investigate the effects of varying rock-liquid interface on mineral dissolution transport in porous media. The one-dimensional mineral-dissolution flow problem that accounts for varying reacting interface and porosity is essentially non-linear. However, a novel exact solution is derived. The exact solution reveals a four-zone structure of the flow pattern with typical mineral concentration curves in all zones. The exact solution allows for a simplified inverse solver, facilitating determination of the surface function from laboratory reactive flow tests. Accounting for surface area evolution in the governing system of equations allows for significant improvement of matching the experimental data if compared with the constant-surface model. Moreover, the comparison between the analytical model and laboratory data reveals high agreement. The values of equilibrium mineral concentration as obtained from the matching and by thermodynamic calculations exhibit close agreement.A. Altree-Williams, J. Brugger, A. Pring, P. Bedrikovetsk

Persistent air leak successfully treated with endobronchial valves and digital drainage system

A 62-year old man with severe chronic obstructive pulmonary disease developed a persistent air leak from an iatrogenic pneumothorax following Computed Tomography-guided core biopsy of a pulmonary nodule. The pneumothorax was treated with an 8.5F intercostal catheter, which was then replaced by a 28F thoracostomy tube after development of significant subcutaneous emphysema and a tension pneumothorax. The air leak showed no improvement until endobronchial valve (EBV) insertion guided by objective flow data from a digital drainage system (DDS). The air leak subsequently reduced with -20 cmH₂O suction from the DDS, and the thoracostomy tube was removed once the objective measured flow rate had sufficiently diminished. The combination of EBV insertion and suction from the DDS successfully treated the persistent air leak, with timing of thoracostomy tube removal guided by DDS flow data.Thomas James Altree, Hubertus Jersmann and Phan Nguye

Exact solution for coupled reactive flow and dissolution with porosity changes

We derive exact solution for mineral-dissolution reactive flows in porous media with porosity variations. These conditions are relevant to injection of incompatible liquids into aquifers for disposal or waste storage, rock alteration during well stimulation by acidising or invasion of corrosive, far-from-equilibrium fluids related to ore deposit formation and heap or in situ leaching in mineral processing. Despite the porosity change making the one-dimensional flow equations nonlinear, the problem allows for exact integration, and a novel analytical model is developed. It allows presenting typical curves for breakthrough concentrations and porosity evolution. The exact solution provides a tool for predictive testing of reactive models that account for porosity creation. The analytical model derived exhibits high agreement with laboratory data, which validate the model.A. Altree-Williams; J. Brugger; A. Pring; P. Bedrikovetsk

Mobile simulation unit: taking simulation to the surgical trainee

Background: Simulation-based training has become an increasingly accepted part of surgical training. However, simulators are still not widely available to surgical trainees. Some factors that hinder the widespread implementation of simulation-based training are the lack of standardized methods and equipment, costs and time constraints. We have developed a Mobile Simulation Unit (MSU) that enables trainees to access modern simulation equipment tailored to the needs of the learner at the trainee’s workplace. Methods: From July 2012 to December 2012, the MSU visited six hospitals in South Australia, four in metropolitan and two in rural areas. Resident Medical Officers, surgical trainees, Fellows and International Medical Graduates were invited to voluntarily utilize a variety of surgical simulators on offer. Participants were asked to complete a survey about the accessibility of simulation equipment at their workplace, environment of the MSU, equipment available and instruction received. Utilization data were collected. Results: The MSU was available for a total of 303 h over 52 days. Fifty-five participants were enrolled in the project and each spent on average 118 min utilizing the simulators. The utilization of the total available time was 36%. Participants reported having a poor access to simulation at their workplace and overwhelmingly gave positive feedback regarding their experience in the MSU. Conclusion: The use of the MSU to provide simulation-based education in surgery is feasible and practical. The MSU provides consistent simulation training at the surgical trainee’s workplace, regardless of geographic location, and it has the potential to increase participation in simulation programmes.Guilherme Pena, Meryl Altree, Wendy Babidge, John Field, Peter Hewett, and Guy Madder

Laparoscopic skills acquisition: a study of simulation and traditional training

Background: Training in basic laparoscopic skills can be undertaken using traditional methods, where trainees are educated by experienced surgeons through a process of graduated responsibility or by simulation-based training. This study aimed to assess whether simulation trained individuals reach the same level of proficiency in basic laparoscopic skills as traditional trained participants when assessed in a simulated environment. Methods: A prospective study was undertaken. Participants were allocated to one of two cohorts according to surgical experience. Participants from the inexperienced cohort were randomized to receive training in basic laparoscopic skills on either a box trainer or a virtual reality simulator. They were then assessed on the simulator on which they did not receive training. Participants from the experienced cohort, considered to have received traditional training in basic laparoscopic skills, did not receive simulation training and were randomized to either the box trainer or virtual reality simulator for skills assessment. The assessment scores from different cohorts on either simulator were then compared. Results: A total of 138 participants completed the assessment session, 101 in the inexperienced simulation-trained cohort and 37 on the experienced traditionally trained cohort. There was no statistically significant difference between the training outcomes of simulation and traditionally trained participants, irrespective of the simulator type used. Conclusions: The results demonstrated that participants trained on either a box trainer or virtual reality simulator achieved a level of basic laparoscopic skills assessed in a simulated environment that was not significantly different from participants who had been traditionally trained in basic laparoscopic skills.N. Marlow, M. Altree, W. Babidge, J. Field, P. Hewett and G.J. Madder

Effect of fatigue on laparoscopic skills: a comparative historical cohort study

Background: Fatigue has been shown to have a negative impact on surgical performance. However, there is a lack of research investigating its effect on laparoscopy, particularly in Australia. This study investigated whether fatigue associated with a surgeon’s usual workday led to a measurable drop off in laparoscopic surgical skills as assessed on a laparoscopic simulator. Methods: A comparative study involving two cohorts was undertaken: a study group whose data were collected prospectively was compared to a historical control group. Participants were required to reach a predetermined level of proficiency in each laparoscopic task on either a FLS or LapSim simulator. The participants in the study cohort were re-tested approximately 1 month after completing 10 h of work. The participants in the historical non-fatigued group were re-tested approximately 1 month after reaching proficiency. Comparisons between cohorts were made using a ‘decrease in score per day elapsed’ value to account for the natural attrition in skills over time and the variability in testing times within and between the two cohorts. Results: The decrease in overall score per day elapsed for fatigued participants was significantly greater than for historical non-fatigued participants, irrespective of the simulator type. Fatigue had a greater impact on certain laparoscopic skills, including peg transfer and knot tying. Participants who self-reported higher level of fatigue demonstrated significantly better skills than those who self-reported lower levels. Conclusion: Overall laparoscopic skill proficiency was reduced in the fatigued participants compared to the historical non-fatigued participants, with certain laparoscopic skills more affected than others.J. Daruwalla, N. Marlow, J. Field, M. Altree, W. Babidge, P. Hewett and G.J. Madder

Nontechnical skills training for the operating room: a prospective study using simulation and didactic workshop

Abstract not available.Guilherme Pena, Meryl Altree, John Field, David Sainsbury, Wendy Babidge, Peter Hewett, and Guy Madder

Surgeons' and trainees' perceived self-efficacy in operating theatre non-technical skills

Background: An important factor that may influence an individual’s performance is self-efficacy, a personal judgement of capability to perform a particular task successfully. This prospective study explored newly qualified surgeons’ and surgical trainees’ self-efficacy in non-technical skills compared with their non-technical skills performance in simulated scenarios. Methods: Participants undertook surgical scenarios challenging non-technical skills in two simulation sessions 6 weeks apart. Some participants attended a non-technical skills workshop between sessions. Participants completed pretraining and post-training surveys about their perceived self-efficacy in non-technical skills, which were analysed and compared with their performance in surgical scenarios in two simulation sessions. Change in performance between sessions was compared with any change in participants’ perceived self-efficacy. Results: There were 40 participants in all, 17 of whom attended the non-technical skills workshop. There was no significant difference in participants’ self-efficacy regarding non-technical skills from the pretraining to the post-training survey. However, there was a tendency for participants with the highest reported self-efficacy to adjust their score downwards after training and for participants with the lowest self-efficacy to adjust their score upwards. Although there was significant improvement in non-technical skills performance from the first to second simulation sessions, a correlation between participants’ self-efficacy and performance in scenarios in any of the comparisons was not found. Conclusion: The results suggest that new surgeons and surgical trainees have poor insight into their non-technical skills. Although it was not possible to correlate participants’ self-belief in their abilities directly with their performance in a simulation, in general they became more critical in appraisal of their abilities as a result of the intervention.G. Pena, M. Altree, J.Field, M.J.W.Thomas, P.Hewett, W. Babidge, and G. J. Madder