U29 - Advancing Airway Management: Proof-of-Concept Fabrication of a Pneumatically-Steerable Endotracheal Tube

Introduction: : Endotracheal (ET) intubation is a procedure for establishing oxygenation, ventilation, and preventing aspiration in patients requiring airway management. In the U.S. alone, more than 215,000 ET intubations are performed annually in prehospital settings. Despite advancements in training and equipment, prehospital and clinical providers continue to face challenges during intubation—particularly in patients with complex airway anatomy. Failed first-pass intubation increases the risk of complications by 33%; examples include hypoxia, aspiration, hypotension, soft-tissue trauma, and cardiac arrest.
Conventional ET tubes were designed over 125 years ago and cannot easily navigate the anatomical curvature of the airway. The human airway includes two major bends—the oropharyngeal and laryngeal curves—that form s-curved paths leading to the trachea. These curves can obstruct a clinician’s line of sight and create resistance as the tube advances—particularly in patients with unique anatomic features or traumatic injuries. A standard ET tube consists of a polyvinyl chloride (PVC) shaft and an inflatable distal cuff that forms a circumferential seal against the tracheal wall; this relatively rigid linear design limits its ability to conform to the aforementioned anatomical curvatures during insertion.
To address this challenge, we introduce the Soft Robotic Novel Endotracheal Tube System (SR-NETS), a proof-of-concept device that leverages compliant materials and pneumatic actuation to enable steerability at the distal end. By integrating independently controlled pneumatic channels onto a tube body, the SR-NETS aims to improve maneuverability and alignment with the tracheal axis during insertion. The objective of this work was to describe the development, fabrication, and preliminary characterization of SR-NETS.

Materials and

Methods: : The SR-NETS prototype was fabricated by integrating three pneumatic channels onto silicone tubing with an 8 mm inner diameter and 10 mm outer diameter. Each channel was cast using a two-part Ecoflex (Smooth-On, LLC) silicone—either 00-20 or 00-30—into negative molds and cured for four hours. After curing, channels were adhered to the tubing using Sil-Poxy (Smooth-On, LLC) adhesive. A 1.47 mm inner-diameter pilot line was inserted into each channel before sealing. A jig was used to align components, center the tubing, and maintain geometry during curing to reduce misalignment and leakage.
Each pneumatic channel was fabricated to dimensions approximately 40 mm in length, 6 mm in width, and 1.1 mm in total thickness, with the pneumatic membrane region measuring approximately 0.65 mm thick. Channels also featured an extruded tip region designed to promote targeted deformation during actuation. For quality control, each adhered channel was pressure tested individually to confirm sealing and inflation.
A benchtop testing platform was developed to assess angular actuation of the distal tube. The setup included a lab stand for vertical alignment, a shortened stylet inserted into the tube for support, and a large protractor mounted behind the tube to track angular motion. Each pilot line was connected to a syringe and an inline pressure gauge to allow manual pressurization of individual channels. This setup allowed for visual and quantitative assessment of angular displacement during pressurization.
In summary, the described experimental platform provided the foundation for characterizing actuation behavior and performance of different silicone materials.

Results, Conclusions, and Discussions:: The SR-NETS prototype exhibited a larger profile and distinct cuff design compared to conventional ET tubes. Standard size 8mm I.D. ET tubes feature a outer diameter of approximately 11.2 mm and inflate to around 32.3 mm at 25 cmH₂O. In contrast, the SR-NETS prototype exhibited a slightly larger deflated diameter of 15.5 mm. When pressurized, tubes fabricated with Ecoflex 00-20 reached an average outer diameter of 50 mm at 103.8 mmHg (141.1 cmH₂O), while those made with Ecoflex 00-30 reached 48 mm at an average pressure of 278.4 mmHg (378.5 cmH₂O). This increase in cuff pressure is expected due primarily to the lower compliance of silicone compared to PVC, combined with the SR-NETS design that integrates tube actuation with cuff expansion.
To evaluate device steerability, angular displacement of the distal tube was measured during single-channel pressurization. Devices made with Ecoflex 00-20 demonstrated an average deflection of 8°, while those made with Ecoflex 00-30 reached an average of 22°. These results reveal a trade-off between cuff expansion and actuation strength. Ecoflex 00-20 provided greater expansion with less pressure but resulted in smaller angular displacement. Ecoflex 00-30 produced more localized deformation and greater deflection—indicating potential viability for navigating airway curvature.
Limitations in the current prototype stem primarily from fabrication challenges related to Sil-Poxy adhesive use. Despite improvements from the fabrication jig, inconsistency in sealing, occasional leaks, and partial blockage of pneumatic channels remain common. To overcome these limitations, a multistep mold process is under development to embed the pneumatic channels directly into the wall of a unified silicone tube. This refined design aims to reduce the device profile to 11 mm outer diameter while preserving steerability and structure.
Future work will characterize SR-NETS fabricated with four Ecoflex formulations (00-20, 00-30, 00-35 Fast, and 00-45) by comparing maximum pressure to failure, pressure versus angle of actuation, and volume versus angle of actuation. These experiments will guide material selection and refine actuation performance for clinical application.
Overall, this work represents an important first step toward developing a steerable, soft-robotics-enabled ET tube capable of improving intubation and first-pass success rates during airway management.

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