A Concentric Tube Robot System for Rigid Bronchoscopy: A Feasibility Study on Central Airway Obstruction Removal

Abstract

New robotic systems have recently emerged to assist with peripheral lung access, but a robotic system for rigid bronchoscopy has yet to be developed. We describe a new robotic system that can deliver thin robotic manipulators through the ports of standard rigid bronchoscopes. The manipulators bend and elongate to provide maneuverability of surgical tools at the endoscope tip, without endoscope motion. We describe an initial feasibility study on the use of this system to bronchoscopically treat a central airway obstruction (CAO). CAO is prevalent and can be life-threatening in patients with large tumors, and conventional rigid bronchoscopic treatments place patients at risk of complications including broken teeth, neck trauma and damage to oropharyngeal structures due to significant forces induced by bronchoscope tilting and manipulation. In this study, we used an ex vivo ovine airway model to demonstrate the ability of a physician using the robotic system to efficiently remove tissue and restore the airway. Pre- and post-operative CT scans showed that the robot was able to reduce the degree of airway obstruction stenosis from 75 to 14% on average for five CAO resections performed in an ex vivo animal model. Using cadaver experiments, we demonstrated the potential of the robotic system to substantially reduce the intraoperative forces applied to the patient's head and neck (from 80.6 to 4.1 N). These preliminary results illustrate that CAO removal is feasible with our new rigid bronchoscopy robot system, and that this approach has the potential to reduce forces applied to the patient due to bronchoscope angulation, and thereby reduce the risk of complications encountered during CAO surgery.

Keywords: Bronchoscopy; Central Airway Obstruction; Robotics.

Figure 1:

Needle-sized robotic manipulators enabled by pre-curved, concentric tubes: (a) functional principle, showing the degrees-of-freedom offered by each tube, (b) concentric tube manipulator shown next to daVinci ProGrasp™ laparoscopic forceps for scale.

Figure 2:

Robotic system for CAO resection: (a) an image of the robot, where the inset shows the needle-sized, robotically-controlled tool manipulators extending out from the bronchoscope, (b) conceptual rendering of the operating room for robot-assisted bronchoscopy (top), and a conceptual rendering of a robotic CAO removal (bottom).

Figure 3:

Force-sensing overtube developed for intraoperative loading experiments: (a) exploded rendering of the overtube, where insets show an image of the fabricated device (top left) and sensor signal conditioning (bottom right), (b) example loading data showing multi-component force sensing with high signal-to-noise and negligible cross-talk.

Figure 4:

Robotic CAO resection: (a) robotic system deployed into an ovine ‘pluck’ model, (b) endoscopic view during the surgery, (c) axial and sagittal CT scan of the obstruction before surgery (where cyan indicates the obstructed airway, A_obstructed), (d) endoscopic view post-surgery, (e) axial and sagittal CT scan post-surgery, showing full restoration of the airway. Please refer to the accompanying video.

Figure 5:

Reconstructed CT volume renderings of the central airway obstructions for all specimens, both pre- and post-surgery, where the degree of airway restoration is apparent in the bottom row.

Figure 6:

Intraoperative loading experiments: (a) image of the experimental setup for conventional bronchoscopy, (b) exemplary force measurements during one conventional ridge tracing experiment, where numbered insets show the endoscopic view that corresponds with the numbered force landmarks in the graph, (c) image of the experimental setup for robotic bronchoscopy, (d) exemplary force measurements during one robotic ridge tracing experiment, and (e) average maximum forces generated during each experiment showing a substantial reduction in the applied force. Please refer to the accompanying video.

Figure 7:

Neck hyperextension during conventional bronchoscopy, where inset cartoon shows neck/scope angulation and red arrows illustrate loading: (a) anterior access, (b) posterior access.