Effort to engage Magnification Devices in Educational Tonsillectomy-A prospective clinical trial

Tonsillectomy is still one of the most common surgical procedures in otorhinolaryngology [1]. However, over the last decades, its incidence has constantly been decreasing due to tighter indication as well as the development of alternative surgical procedures like tonsillotomy [2]. This trend mainly relies on the risks and complications which are associated with tonsillectomy: namely post-operative bleeding and pain. Primarily, non-steroidal anti-infl ammatory drugs (NSAID) like coxibes, diclofenac, ibuprofen, ketoprofen, and paracetamol, but also several opioids like codeine, tramadol, and piritramid are used in peroral or intravenous regimes [3]. Furthermore, intraoperative instillation of local anaesthetics and the surgical technique seem to reduce postoperative pain [4]. The classical “cold” dissection with ligatures or punctual bipolar coagulation has been joined in the last few years by “hot” dissecting techniques like radiofrequency, laser, diathermy, ultrasound and coblation settings. However, none of these techniques has shown any superiority to the cold steel dissection, especially when comparing the overall Abstract


Introduction
Tonsillectomy is still one of the most common surgical procedures in otorhinolaryngology [1]. However, over the last decades, its incidence has constantly been decreasing due to tighter indication as well as the development of alternative surgical procedures like tonsillotomy [2]. This trend mainly relies on the risks and complications which are associated with tonsillectomy: namely post-operative bleeding and pain. Primarily, non-steroidal anti-infl ammatory drugs (NSAID) like coxibes, diclofenac, ibuprofen, ketoprofen, and paracetamol, but also several opioids like codeine, tramadol, and piritramid are used in peroral or intravenous regimes [3].
Furthermore, intraoperative instillation of local anaesthetics and the surgical technique seem to reduce postoperative pain [4]. The classical "cold" dissection with ligatures or punctual bipolar coagulation has been joined in the last few years by "hot" dissecting techniques like radiofrequency, laser, diathermy, ultrasound and coblation settings. However, none of these techniques has shown any superiority to the cold steel dissection, especially when comparing the overall Abstract Introduction: Most educational hospitals teach the tonsil surgery just with head lights and without any magnifi cation device. This prospective clinical trial focuses on the additional workload when using a microscope or magnifying glasses for tonsillectomy.
Material and methods: four surgeons in training with no experience in tonsil surgery operated on 48 patients who underwent elective extracapsular tonsillectomy. Surgery was either performed on one patient´s side with the naked eyes plus headlamp and on the other side with magnifying glasses or a microscope. The surgeons were connected to a biofeedback device in order to monitor the breathing frequency, the heart rate variability and the masseter tone. After every operation surgeons fi lled out the NasaTLX questionnaire for evaluating the cognitive workload during surgery.
Results: There was a signifi cant difference in the questioning and the heartrate variability when using the microscope compared to the naked eyes and the magnifying glasses. However, there was no statistical difference in mean operation time for all study arms.
Conclusion: Compared to loupes the mental distress is higher when operating a microscope in the fi rst eight times. Despite the many advantages of an OR-microscope, this fact may hinder the usability of such a device in tonsillectomy. rate of postoperative haemorrhage and pain [5][6][7]. Andrea M. emphasized 1993 that the use of magnifying devices like microscopes or magnifying glasses allows precise vision and coagulation of vessels during surgery and therefore reduces postoperative bleeding [8,9]. Furthermore, precise coagulation with less collateral damage seems to reduce postoperative pain and intraoperative bleeding, too [9]. Unfortunately in our own study we found no difference in postoperative pain in 48 patients when using magnifying devices for tonsillectomy [10]. To overcome the problem of individual pain sensation, we performed tonsillectomy on one side using a microscope or magnifying glasses whereas the opposite side was operated with the naked eyes, thus following an intraindividual design. just with head lights and without any magnifi cation device. A possible reason for this could be the relatively high effort to engage any microscope in the OR and the additional workload for the trainee when dealing with another medical device. To quantify the psychological and physiological effort to engage, the ergonomics and the additional workload when using a microscope or magnifying glasses for tonsillectomy in surgical training the following clinical trial was conducted. In exhausting mental activity the heart beat becomes more regular to ensure a continuous oxygen supply of the brain.

Materials and Methods
The same procedure can be observed by physical effort. The higher the mental or physical effort of the test person, the lower is the variability of the heartbeat, which means the more regular the heart beats. Thereby, the deviations of the mean interbeat intervals get smaller. This way it can be measured how exhausting the mental workload for an organism is. All three frequencies show a suppression of the HRV by exertion and concentration [11], but the biggest difference is seen in the low frequency band, especially by the 0,1 Hz component [12,13].
The HRV was monitored during the whole operation and fi ve minutes before and afterwards continuously. This way a calibration with rest situations was given. The spectral analysis of the interbeat intervalls have been implemented with the program BIOTRACE+ (developed by MindMedia in NL). With this spectral analysis it is possible to make a differentiation of the three frequency bands listed above and to quantifi cate them. BIOTRACE uses the siscrete fourier analysis to split the time series into spectra.
As an additional indicator of physical and mental effort the masseter tonus was measured, too [14]. In situations of high tension a signifi cantly higher masseter tone is measurable through the unconscious contraction of the muscles by biting on the jaws.

Discussion
Preparation of the tonsils with a magnifying device seems very logical. The surgeon has better vision of feeding vessels, more exact preparation at the capsule and holds the perfect distance to the oral cavity [9]. Most of the experienced surgeons are using magnifying devices, i.e. loups, for almost every surgical procedure [19]. Tonsillectomy, as Class I (easiest) procedure, is one of the initial procedures in surgical training of head and neck surgery. Maybe that is why the tonsillectomy is so often done by beginners with young sharp eyes, who do not have own loupes or are not used to it. In contrast, almost every OR owns a microscope with or without spy or videooutput. For a better vision of the surgeon and for teaching purposes it makes obviously sense to use such a microscope 9 if not for the effort to engage. Two additional efforts play a role: the additional time effort of mounting the microscope (plug in, draping, plug out) and the additional mental workload when dealing with a high end medical device. The preparation of the microscope is normally done by the OR Team before or during the patient enters the OR, therefore it should not play a distinctive role in OR time management. Whereas operating a complex binocular microscope with fi xed focus and heavy lenses could be such a big mental effort for the surgeon and his supervisor, that most of the clinics worldwide do not use such a device for surgical training of tonsillectomy [20]. Handling the additional information from the microscope creates a specifi c mental workload. Dealing with this workload during tonsillectomy differs from surgeon to surgeon. Our goal was to evaluate the subjective and objective effort of magnifi cation devices in surgical beginners (no previous tonsillectomies done). Subjective data was collected by a simple questionnaire: the HFEQ-CASS. This standardized and validated questionnaire is specially designed for the workload evaluation of surgical devices [21,22]. Objective data was collected by the time measurement and the biometrical data of the surgeon.
In modern industrial engineering the ergonomics of every new assistance system (i.e. navigation systems or visualization systems) is tested many times before it comes to the market. However, only a few working groups are investigating the interaction during surgical procedures between complex automation or visualization systems and human factors [23][24][25][26][27][28][29]. This is despite the fact that surgical visualization systems and assistance systems become more prevalent and more complex. Many studies use the HRV as an indicator for mental effort but the evaluations of the results vary a lot [30,31]. There are no standard guidelines for the evaluation of the HRV. The critical point is that there are many activities which cause mental load and there is no measurement for quantifi cation [30]. The only way is to indirectly conclude the mental load from some parameters: like the HR, HRV and/or masseter tone [32,33].
The measurements of this trial show that a state of mental load dominates in surgical interventions. Preoperative the HRV is high, during the operation the HRV decreases and is suppressed. After the operation the HRV increases again. When using the microscope the HRV was signifi cantly suppressed compared to the baseline s. A similar picture can be observed with the analysis of the heart rate (HR). The HR is increased during the operation compared to the baselines. A signifi cant difference could be monitored when using the microscope compared to the baseline. Therefore, the mental load in tonsillectomy with a microscope is higher for beginners compared to the standard operation with naked eyes and a headlamp with or without magnifying glasses. Every surgeon did 8 tonsillectomies with the microscope. However, if only the last two microscope tonsillectomies would have been evaluated, there would be no statistical difference. Whether this is due to the small sample size or the learning curve remains unclear which is clearly a limitation of the study.
A similar result could be concluded from the masseter tone monitor and the respiratory frequency. But this data shows  another limitation of the study, because it is not reliable due to the fact, that breathing and the masseter tone rise just when surgeons look through a microscope and rest their eyes on the oculars. This is because of the relatively fi xed head state and the immobilization of the jaw Regarding the subjective data of the questioning, the results fi ts together: the perceived mental workload was highest when operating a microscope and only slightly higher when looking through magnifi cation glasses. Although the trainee surgeons thought that the time effort is negative when using a microscope, OR time did not reach signifi cant thresholds. The microscope procedure took a little longer in the beginning but with no signifi cance to the other study arms.
Taken together, the results of the present study suggests that the mental distress is higher when operating a microscope for tonsillectomy in the fi rst eight times. Despite the many advantages of an OR-microscope, this may hinder the usability of such devices for this procedure for beginners.