Does Blacklight Illumination Improve Speed and Accuracy of Foot Pedal Activation in the Low-Light Operating Room?

Introduction

Endourologic procedures frequently require the use of equipment activated by foot pedals, including the cautery, C-arm, laser, and ultrasonic lithotripter (USL). While the use of foot pedals to activate surgical instruments offers the advantage for sterile, and hands-free operation of equipment, it also introduces the potential of inadvertent or incorrect pedal activation. This issue becomes particularly significant during endourologic procedures, which often take place in operating rooms (OR) that are dimly lit or darkened to allow surgeons to maintain visual acuity and dark adaptation while tracking the procedure on a video screen. Inadvertent or incorrect activation of fluoroscopy foot pedals may cause increased radiation exposure for the patient and staff members. ¹ Inadvertent or incorrect activation of diathermic devices or laser foot pedals can result in serious patient harm, including thermal burns, OR fires, and fatal outcomes. ^{2 –4}

Recently, the use of illuminated foot pedals was proposed as a possible method for improving the safety and efficiency of surgical foot pedal activation under low-light conditions. ⁵ However, the majority of lighting schemes for foot pedal illumination may also result in degradation of the surgeon’s visual acuity in low-light settings. To address this potential limitation, the use of “blacklight” illumination was considered as a possible method to clearly identify foot pedals, while simultaneously avoiding degradation of the surgeon’s visual acuity.

The purpose of this study was to determine the effects of blacklight illumination upon foot pedal activation, speed, and accuracy during a simulated percutaneous nephrolithotomy (PCNL), and to determine the effect of blacklight illumination upon the surgeon’s dark adaptation. In addition, this study compared blacklight illumination with several other lighting schemes, including no illumination, overhead lighting with no pedal illumination, and room lights off with glowstick pedal illumination.

Materials and Methods

Study participants

A total of 20 participants were recruited for the study, including five attending urologists, five urology residents, and ten medical students. All participants were asked to activate foot pedals under four different OR lighting conditions: 1) an OR with overhead illumination, 2) a dark OR with neither overhead nor pedal illumination, 3) a dark OR with glowstick pedal illumination, and 4) a dark OR with blacklight pedal illumination (Fig. 1). In both the glowstick and the blacklight arms, the pedals to activate the C-arm, laser, and USL were labeled magenta, green, and blue, respectively. In the glowstick arm, glowsticks were attached to the periphery of each pedal (Fig. 1) as has been previously reported by Shin et al. ⁵ In the blacklight arm, a 365 nm blacklight (Shenzhen Xin Hengstar Technology Co. Ltd., Shenzhen, China) was attached underneath the OR table and fluorescent stickers were applied to the pedals. In the blacklight group, the fluorescent stickers were designed to represent the corresponding foot pedal (i.e., universal radiation symbol for the C-arm, low- and high-power laser beam for the laser pedal and low- and high-power ultrasound wave for the corresponding ultrasound pedal (Fig. 1).

OPEN IN VIEWER

FIG. 1.

Lighting Conditions. C-arm, laser, and ultrasonic lithotripter foot pedals in (A) Bright OR with overhead lights; (B) Dark OR with no foot pedal illumination; (C) Dark OR with glowstick illumination; (D) Dark OR with blacklight illumination. OR, operating room.

For each participant, the order of lighting conditions (dark, light, glowstick, and blacklight), instrument activation sequence (C-arm, laser, and USL), and pedal orientation (left, center, and right) were randomized. Before each of the four trials, participants were familiarized with all the pedals and how to activate each device. Participants were positioned as if performing a left PCNL. At the start of each trial, subjects looked forward until instructed to activate an instrument. In each lighting setting, participants were randomized to capture an image with the C-arm six times; activate, fire, and deactivate the laser six times; and trigger the low- and high-power setting on the USL three times each (for a total of 72 activations per participant). After each pedal activation, the three pedal locations were rearranged to simulate routine pedal movement during clinical PCNL.

Results

All study assignments were successfully completed by every participant. The study included five urology attending physicians, five urology resident physicians, and ten medical students. Combined mean pedal activation times in the blacklight (5.34 seconds) and glowstick (6.77 seconds) arms were significantly faster than the no-illumination arm (8.47 seconds, p < 0.001), (Table 1). Additionally, with respect to each individual device, the mean activation time for each pedal type was significantly faster in both the blacklight and glowstick arms than in the no-illumination arm (p < 0.001 for all), (Table 2). There was no significant difference in mean activation time among attendings, residents, or students in any of the lighting conditions (p > 0.05for all), (Table 3).

Furthermore, the use of blacklight illumination resulted in a statistically significant decrease in the number of attempted (0.30 vs. 3.45, p < 0.001), incomplete (1.25 vs. 7.75, p < 0.001), and incorrect pedal presses (0.35 vs. 1.25, p = 0.035) compared with the no-illumination arm (Table 4). Similarly, glowstick illumination resulted in a decrease in the number of attempted (2.20 vs. 3.45, p > 0.05), incomplete (3.75 vs. 7.75, p < 0.05), and incorrect pedal presses (0.7 vs. 1.25, p > 0.05), although the decrease in attempted and incorrect activations did not reach statistical significance. Overall, the blacklight system resulted in the greatest objective improvement in both efficiency and accuracy. There was no significant difference in the mean number of attempted, incorrect, or incomplete pedal presses among attendings, residents, or students in any of the lighting schemes (p >0.05 for all), except that attending physicians had significantly less-attempted pedal presses in the dark than residents (p = 0.033), (Table 5).

There was no significant difference in dark adaptation between no illumination (134.8 cd/m²) and either the blacklight (134.5 cd/m², p > 0.05) or glowstick arms (135.8 cd/m², p > 0.05), but all three were significantly different from the overhead illumination arm (140.5 cd/m², p < 0.001), (Table 6).

In response to the questionnaire, all participants (100%) recommended the use of illuminated pedals for endourologic procedures, with 90% preferring the blacklight illumination system while 10% preferred glowsticks. All participants (100%) subjectively felt that pedal illumination decreased mistakes, provided a sense of security, and made pedals easier to use. 95% felt that pedal lighting improved overall efficiency. All participants (100%) felt that the blacklight was beneficial, vs 75% of participants reporting glowsticks were beneficial. Around 10% of participants reported that the glowsticks were disruptive to their vision, while no participants reported that blacklight was disruptive to vision. The questionnaire responses are shown in Table 7.

Discussion

Inadvertent or incorrect activation of surgical foot pedals is a common problem, which is well characterized in the literature. In a survey of 241 urologists, 43.6% of respondents expressed dissatisfaction with conventional foot pedals. The reasons behind their discontent included losing contact with the foot pedal, having to look down at pedals before activation, and unintentionally activating the wrong pedal, resulting in harm to the patient. ⁷ Similarly, a study involving 45 laparoscopic surgeons revealed that 42% of the subjects were dissatisfied with current diathermic foot pedals. ⁸ This study also demonstrated that 91% of subjects occasionally experienced slipping off surgical foot pedals, and that in over 70% of these instances, they restored correct foot position by looking down and making visual contact with pedals.

The inability to visually identify a foot pedal or the inadvertent activation of the wrong pedal can lead to various adverse outcomes posing risks to both patient and staff safety. These potential hazards include thermal burns, fires, radiation exposure, and surgical errors. An analysis of injuries and deaths related to diathermic devices, as documented by the FDA’s Manufacturer and User Facility Device Experience database, found that between 1994 and 2013, inadvertent activation of diathermic devices was responsible for causing 182 thermal burn injuries and 3 fatalities. ³ The activation of surgical energy devices in the presence of oxygen is by far the most common cause of OR fires, while the second most common cause is laser emissions. ⁴ Additionally, it has been observed that confusion of foot pedals can result in inadvertent activation of fluoroscopy, resulting in inappropriate radiation exposures for both staff and patients. ¹ Given that the current C-arm pedal technology lacks an automatic timeout, avoiding unintentional radiation exposure is particularly challenging. In settings requiring low light, such as endourologic procedures, the implementation of blacklight foot pedal illumination could minimize or eliminate these perilous errors.

While previous efforts to optimize surgical foot pedals have predominantly focused on improving the ergonomics of surgical pedals, with proposals ranging from specialized techniques, including complex ergonomic guidelines to complete pedal redesigns, these proposals have encountered significant challenges in terms of cost, usability, and standardization. ^{7,9 –11} Another possible solution focuses on the development of a permissive diathermy switch in which a trainee’s activation of foot pedals would be controlled by a second switch operated by a senior surgeon. ¹² In contrast, a notable example of illuminated technology, the LightMat ultrathin light strip (Lumitex Inc., Strongsville, OH) used to illuminate surgical retractors, has demonstrated remarkable improvement in surgical outcomes and is steadily gaining popularity in various surgical specialties. For instance, its application on scalp retractors in minimally invasive cochlear implantation was found to reduce tissue trauma, length of hospital stay, and size of surgical scars. ¹³ Additionally, light strips were successfully used by craniofacial surgeons to complete cleft palate surgeries without relying on bulky, unwieldy headlamps. ¹⁴ The use of illuminated retractors has also proven beneficial in procedures to repair pediatric genitourinary trauma and to correct anomalies of the reproductive system. ^15,16 These widespread adoptions of illuminated devices across surgical disciplines underscore the potential advantages that could also be implemented in the field of Urology.

Blacklight is a form of UV-A light, which radiates just along the low-wavelength boundary of visible light in the range of 350–400 nm, but when used in combination with fluorescent stickers, may intensely illuminate objects. ¹⁷ Although blacklight does produce very low-level radiation, the World Health Organization’s International Commission on Non-Ionizing Radiation Protection found that blacklight applications of UV-A operate below exposure limits, and do not require radiation safety precautions. ¹⁸

Amid the challenges posed by conventional foot pedals, it becomes evident that achieving precision and safety in surgical procedures involves more than just pedal design. The human visual system plays a crucial role in this delicate dance within the operating room. ¹⁹ It is not just about the surgeon’s skill, but also their ability to perceive and respond swiftly to the evolving surgical environment. This brings us to the concept of dark light adaptation, a facet of visual acuity that holds immense relevance in the realm of surgery. The capacity to discern subtle nuances in the surgical field, distinguish vital structures, and execute precise movements under low-light conditions can be the difference between success and unforeseen complications. This is where the potential advantages of blacklight illumination come into play, offering not only enhanced visibility but also the preservation of dark adaptation during critical phases of surgery. One potential advantage proposed by this study regarding blacklight illumination pertains to its capacity for preserving dark adaptation, contrasting with other light sources. Within the retina, cones predominate in well-lit conditions, while rods predominate in dark conditions. ²⁰ This concept aligns with the “duplicity theory” of vision, which underscores the transition between these two photoreceptor systems. Notably, when the rod system is fully adapted to darkness, it can operate with several hundred times more sensitivity than the cone system. ²¹ Consequently, during endourologic procedures, the practice of turning off operating room lights is a common strategy to facilitate enhanced visualization of subtle differences among arteries, veins, stones, and surrounding anatomical structures. However, it is essential to recognize that achieving full dark adaptation can be a time-intensive process, spanning up to 40 minutes. ¹⁹ Additionally, it can be rapidly compromised by exposure to substantial amounts of light. Hence, the preservation of dark adaptation holds paramount importance in maintaining a surgeon’s visual acuity during these procedures.

The level of dark adaptation can be measured using a chart with increasingly darker boxes visible at progressively lower luminance levels and asking subjects to identify the darkest box they can see. The higher the luminance in cd/m², the darker adaptation the subject has attained. ¹⁹ In our study, we found that blacklight illumination preserved subjects’ dark adaptation compared with overhead illumination, but there was no statistically significant difference when compared with glowstick illumination. However, there are significant differences between the amount of light produced by short wavelength blacklight and the visible light produced by glowsticks. Initially, this may appear to be a discrepancy. However, according to the duplicity theory of vision, the transition between rods in dark conditions and cones in light conditions is largely binary. This binary transition may account for the similar preservation of dark adaptation between the two systems, despite significant differences in the amount of light produced.

While objective measurements did not reveal a statistically significant difference in levels of dark adaptation between the glowsticks system and the blacklight system, it is important to recognize that blacklight is superior to glowsticks in various other aspects. Most importantly, while glowsticks are a temporary light source created by a short-term chemical reaction between two substances, blacklight illumination is produced by electrically powered fluorescent lamps, lasers, and light-emitting diodes, which can be powered by AC electricity or batteries. ^22,23 Additionally, subjective evaluations pertaining to individual surgeon preferences markedly favored blacklight illumination over glowstick illumination. One plausible rationale for this preference is that the blacklights system incorporates fluorescent stickers that enable swift visualization and identification of each individual pedal. In contrast, while glowstick illumination facilitates the identification of each set of pedals, distinguishing individual pedals can remain challenging (I.e., high vs low power on ultrasonic lithotripter and laser), (Fig. 1).

While foot pedals have historically been employed in dimly lit ORs without illumination for many years, it is imperative not to use this precedent as a rationale for perpetuating the use of nonilluminated pedals. The introduction of blacklight-illuminated pedals has demonstrated substantial advantages, including enhanced activation speed and a reduction in attempted, incomplete, and erroneous pedal presses. Importantly, these improvements were evident across users of varying skill levels. The potential implications of these enhancements for staff and patient safety are significant, suggesting the likelihood of substantial safety improvements in the clinical setting.

Our study is subject to several limitations. First, it is important to acknowledge the limitations inherent to the bench-top model employed in our study. A PCNL procedure performed on a human patient inherently introduces a multitude of variables that extend beyond the scope of measurements conducted in this study. However, it is worth noting that due to the substantial interpatient variability, the bench-top model allowed for a greater degree of result standardization. Additionally, our study is constrained by its focus on simulating a single procedure at a single institution. To generalize the findings and broaden the scope of applicability, it is imperative that future investigations explore the impact of blacklight illumination on surgical foot pedal activation in diverse specialties and various surgical settings. Finally, this study did not specifically investigate cost effectiveness, but following study completion, we created a reusable, portable prototype for a nominal fee. The battery-powered prototype was attached to the foot pedal using double-sided adhesive tape, covered with a waterproof bag, and turned on using an activation switch. The combination of battery power and a waterproof bag could minimize concerns for electrical shock. We believe that the ease of set up, low cost, and improved speed and safety of pedal activation could allow for widespread adoption of this technology.

Conclusion

Blacklight illumination of fluorescently labeled foot pedals significantly improved the speed, accuracy, and efficiency of instrument activation during a simulated PCNL. Compared with three other lighting conditions, blacklight illumination of surgical pedals was optimal for maximizing speed, minimizing errors, maintaining dark adaptation and improving surgeon satisfaction.

Author Disclosure Statements

The following authors have nothing to disclose: G.E.M., H.Y., J.M., A.K., A.S.A., D.P., D.B., C.R., and Z.O. D.D.B. has a patent covering lighted foot pedals.