Variable-Stiffness Nasotracheal Intubation Robot with Passive Buffering: A Modular Platform in Mannequin Studies

Intubation is a critical medical procedure for securing airway patency in patients, but the inconsistent skill levels among medical practitioners necessitate the advancement of better robotic solutions. While orotracheal intubation robots have been widely developed, nasotracheal intubation remains essential in specific clinical scenarios. However, nasotracheal intubation robots are still underdeveloped and lack buffer protection mechanisms to ensure safety. This study presents a novel variable-stiffness nasotracheal intubation robot (NIR) with passive buffering. The proposed NIR is a modular platform capable of performing the main steps of nasotracheal intubation, validated through mannequin studies via teleoperation. We proposed a variable-stiffness fiberoptic bronchoscope (FOB) control module for the FOB distal end control, and validated its dual functionality in experiments: low-stiffness mode provides passive buffering during nasal cavity navigation, with a frontal peak force of 2.8 N and a lateral peak force of 0.12 N; high-stiffness mode enhances load-bearing capacity for near-glottis navigation, with a frontal bearing force of 4.9 N and a lateral bearing force of 0.42 N. Additionally, a compact ($\mathbf{74} \times \mathbf{64}\times \mathbf{53}$ mm, 150 g) FOB feeding module with passive failure protection was designed to limit the max frontal impact force to 2.3 N.