Abstract
Objectives
The objective of this study was to determine if a flexible robotic system caused increased tissue reaction when accessing the oropharynx and hypopharynx compared to intubation controls in only 2 scenarios: high speed tissue impact and multiple unit insertions and retractions. The data obtained were submitted as part of the entirety of information submitted for FDA approval.
Methods
This study consisted of 5 groups of Yorkshire pigs (2 animals per group). On Day 0, all animals were intubated. For group 1 (control), a second endotracheal tube was advanced to just above the vocal cords. In abrasion groups 2 and 3, the flexible robotic system was advanced against the oropharyngeal and hypopharyngeal tissues, respectively. In blunt trauma groups 4 and 5, the flexible robotic system was advanced at maximum speed (22 mm/s) to collide with oropharyngeal and hypopharyngeal tissues, respectively. Pre- and post-procedure endoscopic assessments of tissue reaction were performed daily for 4 days. An independent reviewer graded tissue reaction using a 0–3 point scale.
Results
Tissue reaction scores at each observation time point for all test groups were less than or equal to control scores except for one instance of moderate scoring (2 out of 3) on Day 2 for an animal in the blunt trauma group where reaction was likely intubation-related rather than device impact related. Otherwise, all flexible robotic system-treated animal scores were less than 1 by Day 4.
Conclusions
In this limited study, the flexrobotic system afforded surgical access to the oropharynx and hypopharynx without an increased level of abrasion or tissue trauma when compared to intubation alone.
1
Introduction
Historically, there has been significant morbidity associated with surgical management of neoplasms of the oropharynx, hypopharynx and larynx. Prior to the widespread acceptance of minimally invasive transoral surgery techniques described by Vaughan in 1978 and advanced by several others , traditional surgical approaches to these anatomically “hard-to-reach” subsites often required mandibulotomy, tracheostomy, along with other transcervical approaches. The more traditional and “invasive approaches”, while still necessary in cases of advanced disease, have a greater potential for disfigurement of what some may argue is the most humanizing and visible part of their bodies, i.e., the face and neck, and a more detrimental effect on post-operative swallowing function .
With recent advances in robotic technologies, especially at the beginning of 21st century, transoral robotic surgery (TORS) has built upon existing transoral surgery techniques and has gained momentum as a valuable modality for reducing morbidity while optimizing oncologic management in select cases . In 2003, Haus et al. first evaluated the potential for robotic endoscopic surgery using a porcine model and in 2005, McLeod and Melder introduced the da Vinci robot (Intuitive Surgical Inc., Sunnyvale, CA) for TORS in an initial report resecting a vallecular cyst. While TORS has continued to gain widespread acceptance over the past decade, certain limitations and shortcomings have been noted. Some of these limitations are specific to the configuration of the da Vinci surgical systems, for example, multiple arms and camera must negotiate the narrow conduit of the oral cavity toward the surgical site, the surgeon must sit in a console away from the patient, prolonged setup time, need for extensive operating room staff training and limited access to certain hard-to-reach subsites of the laryngopharynx , at least in part, due to the lack of a flexible camera.
The Flex® Robotic System is a robot-assisted platform based on a flexible and steerable scope technology that surgeons can use to navigate toward the surgical site using an integrated high-definition endoscopic system. Once positioned, the scope can become rigid to provide a stable platform through which flexible instruments can be deployed .
While the Flex® Robotic System design appears advantageous for TORS of the oropharynx and laryngopharynx, it was necessary to further characterize its safety for routine use as part of the FDA approval process. This study was designed to determine if the Flex® Robotic System caused increased tissue reaction when accessing the oropharynx and hypopharynx compared to intubation controls using a porcine model for only 2 specific surgical parameters.
2
Materials and methods
An innovative animal model was designed to compare the local tissue reaction caused by advancing the Flex® Robotic System through the upper aerodigestive tract to a standard technique, namely, intubation, which has known incidences of mucosal injury and is advanced in a fashion technically similar to that of the Flex® Robotic System. A large porcine model was chosen specifically, given the similarity in anatomic dimensions of the pig and human oropharynges. There also is precedent for using the porcine model for the study of transoral robotic surgical systems . This study was performed as part of the submission process for FDA approval.
2.1
Animal welfare
This study was sponsored by Medrobotics Corporation and was performed at an independent test facility (CBSET, Inc.) in compliance with the Food and Drug Administration Good Laboratory Practice Regulations. The experiment was approved by the CBSET, Inc. Institutional Animal Care and Use Committee (IACUC) complying with all applicable regulations governing the care and use of laboratory animals. All procedures and conditions of testing were in compliance with the USDA, AWA /AWR and the National Research Council guidelines .
2.2
Anesthesia and perioperative procedures
Animals were pretreated with buprenorphine (0.01 mg/kg, IM) followed by inhalant isoflurane delivered via nosecone. Once sufficiently anesthetized, each animal underwent a pre-treatment assessment of the oral cavity, oropharynx and hypopharynx, which was video recorded by endoscopy. Next, animals were endotracheally intubated and maintained with isoflurane inhalant anesthetic. For the duration of the procedure and while under general anesthetic, animals were maintained in the dorsal recumbent position while monitoring body temperature, ECG and pulse-oximetry.
2.3
Study design, test device and procedure
The Flex® Robotic System is depicted in Figs. 1 and 2 . Standard endotracheal tubes were used for intubation control animals. Mouth gags, which are used as standard practice in porcine transoral surgery, were only used in animals undergoing Flex® Robotic System access in the non-control groups. The senior author served as the operating physician and a blinded 3rd party physician with no company affiliation was tasked with grading tissue trauma based on captured images. All animals underwent a procedure on Day 0 under anesthesia, a pre-test assessment of the intended test areas was performed and then intubation with a standard endotracheal tube was performed. The number of flex insertion and removals were chosen to represent 2 theoretical surgical circumstances. Two passes would represent the average number of insertions for a routine procedure. Six passes would represent the conceptualized maximum number of passes in a most unusual clinical circumstance. A high speed impact injury would clearly be accidental, yet knowledge of what damage could occur was felt to be essential.
This study consisted of 5 groups of 10 male Yorkshire pigs (2 animals per group) as outlined below.
2.3.1
Group 1 – Endotracheal intubation only, control
A second # 6 endotracheal tube was inserted past the oropharyngeal and hyopharyngeal tissues as far as, but not contacting the vocal cords. The endotracheal tube was then removed and this process was repeated either twice (2 ×) or 6six times (6 ×).
2.3.2
Group 2 – Abrasion testing, shallow access
The Flex Scope was advanced against the oropharyngeal tissues 2 × or 6 × followed by a single manual release . Manual release of the Flex Scope involves opening a safety latch and then removing the flex unit.
2.3.3
Group 3 – Abrasion testing, deep access
The Flex Scope was advanced against hypopharyngeal tissues 2 × or 6 × followed by a single manual release.
2.3.4
Group 4 – Maximum speed blunt trauma test, shallow access
The Flex Scope was advanced at maximum speed (22 mm/s) to collide with the oropharyngeal tissues 2 × or 6 × followed by a single manual release .
2.3.5
Group 5 – Maximum speed blunt trauma test, deep access
The Flex Scope was advanced at maximum speed (22 mm/s) to collide with the hypopharyngeal tissues 2 × or 6 × followed by a single manual release .
2.4
Assessment procedure
The test areas (oropharynx and hypopharynx) for each animal were video-recorded using an Olympus GIF-2TH180 gastroscope (Tokyo, Japan) on Day 0 before testing, immediately after the completion of testing and on Day 1 (24 ± 2 h after the completion of Day 0 testing), Day 2, Day 3, and Day 4.
For assessments after Day 0, Telazol (2 mg/kg, IM) and isoflurane inhalant were administered and video recordings from the assessment time points were captured and stored for review. These video-recordings were later provided unidentified and randomly assigned to a blinded 3rd party physician for grading of mucosal tissue trauma. Assessments were performed by scoring each of the test areas in quadrants for both shallow and deep access. The recordings were assessed for each animal using the grading scale in Table 1 . Examples of grading using this scale for Animal 6 are depicted on pretest assessment in Fig. 3 (Grade 0) and post-procedure day 0 in Fig. 4 (Grade 1).
| Grade | Characteristic |
|---|---|
| 0 | No response/No edema/No swelling |
| 1 | Mild tissue reaction: Edema, Ecchymosis, submucosal hematoma ≤ 2 cm |
| 2 | Moderate tissue reaction: Edema, Ecchymosis, submucosal hematoma ~ 3-4 cm |
| 3 | Severe tissue reaction: Edema, Ecchymosis, submucosal hematoma > 4 cm |
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