Design of an Endoscope Lens Shielding Device for Use in Laparoscopic Procedures

In recent years, laparoscopic surgical procedures have revolutionized many gynecological and abdominal procedures, leading to dramatic reductions in recovery time and scarring for the patient. While techniques and instruments for performing laparoscopic surgery have improved over the years, loss of vision through the endoscopic lens caused by fog, liquid, and solid debris common to laparoscopic procedures remains a significant problem. In this paper, a shielding mechanism that maintains visibility through the laparoscope by removing debris from the distal end of the lens is presented. This device provides an inexpensive and convenient alternative to the current practice of removing, cleaning, and re-inserting the laparoscope during surgical procedures. This device is shown in multiple trials to repeatably remove debris from the distal tip of the lens, thereby restoring vision for the surgeon without requiring removal or reinsertion of the endoscope. INTRODUCTION Laparoscopic surgery provides a minimally invasive alternative to often-risky open procedures. Increasingly popular in recent years, laparoscopic surgery is currently used in many medical specialties, including urology, gynecology, and gastroenterology [1, 2]. Its benefits include decreased operative trauma, decreased wound complications, shortened hospital stay, and shorter-term disability after surgery. Laparoscopic surgery is facilitated by a laparoscope, which provides a view of the anatomical structures in the abdomen and pelvis during the procedure [3]. In many laparoscopic procedures, a (5-10mm diameter) cannula sleeve is inserted into the incision to serve as an entry port for the endoscope and allow the endoscope to move with respect to the abdominal wall. A typical laparoscope consists of a lens and light source on the distal (inserted) end, an elongated lens shaft (passing through the cannula), and a camera or viewfinder on the proximal end (outside the body). One of the limitations of conventional laparoscopes is that during surgical procedures, the distal lens frequently contacts and/or is obscured by fog, blood, saline, and other particulate. This reduces or obscures the surgeon’s view of the worksite and often requires an interruption of the procedure to clear the debris. Currently, surgeons often attempt to restore vision through the endoscopic lens by wiping it on nearby organs, or removing it from the body to wipe it by hand. In a procedure where the surgeon’s vision of the working area is entirely dependent on the scope image, obfuscation of the lens can waste precious time and reduce visibility at times when it is needed most (such as those in which bleeding or other fluid loss occurs) [4]. To address the problem of lens obfuscation and its attendant procedural interruption, the current system is presented and described. This system uses a transparent film to shield the endoscopic lens from debris and thereby avoid the loss of vision common to current practice. This design consists of a single, disposable lens shielding tool that when used in conjunction with existing laparoscopes increases visibility and 1 Reprinted with permission of Sterling J. Anderson, Julia C. Zimmerman, Emily F. Houston, Kevin M. Farino, Nikolai D. Begg decrease the procedural interruptions during minimally invasive surgery. Prior Art While many solutions for cleaning the laparoscopic lens have been proposed, none has been effectively implemented nor widely adopted. Ranging from lens flushing devices to mechanical wipers to continuously-flowing air jets, these solutions seek to clean the lens once it has been fogged or soiled by debris [5,6]. Shielding, or the use of a cover over the lens to prevent the lens from actually getting dirty, provides a mechanical, repeatable solution to the problem of lens dirtying in laparoscopic surgery. U.S. Patent No. 6,193,731 discloses a method for inserting a thin sheet or film of surgical material into the abdomen via a cannula. This patent describes inserting and leaving behind this thin sheet or film of surgical material, and is thus not a lens cleaning method. The disadvantage of leaving a film behind is that it increases risk to the patient during recovery. Another use of shielding is disclosed in U.S. Patent No. 4,976,254 and No. 5,123,402 though these patents disclose a shield to prevent the surgeon or close observers from experiencing splashback of bodily fluids outside of the body. U.S. Patent No. 6,607,606 discloses a method and apparatus for shielding a lens, as in a camera, from dry particle contaminants through a rotating cleaning mechanism. The invention described in this paper serves as an add-on to current laparoscopes. It shields the lens from both solid and liquid debris and prevents contaminants from obscuring the image seen through the camera. This device is self-contained, leaving no film or residue behind in the body. DESIGN DEVELOPMENT The concept development and evaluation that lead to the selected design is presented and discussed below. Functional Requirements and Strategies In order for this device to provide a useful replacement for the current methods and devices available, it needs to meet several important criteria. Because this is a medical device, it is absolutely imperative that it pose no increased risk to the patient as a result of the device. The device must also provide adequate visibility through the scope and improve visibility in the case of partial or full lens obfuscation for at least 60 cycles per procedures. It is also absolutely necessary that the device meets FDA standards and conforms to industry standards. This requires that the device integrate with 5mm laparoscopes and 5mm cannulas as to ensure no increase in incision size. Other non-critical, though beneficial requirements include keeping device actuation time under 5 seconds and its cost under $100. An exhaustive list of all functional requirements is outlined in Table 1, in addition to metrics for evaluating the success of this device in fulfilling the functional requirements. Table 1. Functional requirements and design parameters Rank Functional Parameter Metric 1 Does not increase risk to patient Incidence of scope related complications 2 Provides adequate visibility through lens and improves visibility in the case of partial or full lens obfuscation Lens clarity 3 Meets FDA standards Obtain FDA classification and certification 4 Meets industry standards Works with 5mm trocar and does not require an incision of >10mm 5 Risk to patient in event of complications minimized 6 Procedure modification or disruption minimized Doctor training time 7 Works with existing technology Money spent by hospital to integrate the product less the cost of the product 8 Minimize time of obscured visibility Frequency of cleaning and duration of cleaning cycle 9 Minimize cost Money spent by hospital to use the product 10 Versatility of cleaning Types of obstructions the system can remove 11 Minimal interference with surgical environment Change in available workspace Strategies developed to address these requirements were assessed using the Pugh chart shown in Table 2 A product known as the EndoScrub was chosen as the control in Pugh chart evaluation. Developed by Medtronic, this device uses a combination of fluid rinse and suction to clean the lens of debris. Some of the strategies evaluated are similar to those found in prior art, such as using fluids to wash debris off the lens or using a mechanical device to wipe debris off the lens, entitled "fluid-gas" and "passive wiper" respectively in Table 2. Several novel strategies were also considered. The "sliding shield" strategy involves covering the lens with a piece of clear plastic that can be removed and replaced when dirtied by sliding the tape across the lens, similar to the paper on a doctor's examination table. Another strategy, entitled "onion," uses a stack of false lenses that are successively removed as they are dirtied. The strategy entitled "weeping lens" uses a