Chenglong Zhu¹, Jianhua Xia², Zui Zou¹

¹School of Anesthesiology, Naval Medical University, Shanghai 200433, China.2Department of Anesthesiology, Shanghai Pudong New Area People's Hospital, Shanghai 201200, China.

Address correspondence to: Zui Zou, School of Anesthesiology, Naval Medical University, 168 Changhai Road, Yangpu District, Shanghai 200433, China. E-mail: zouzui@smmu.edu.cn.

Received October 26, 2024; Accepted January 7, 2025; Published June 30, 2025

Difficult airways are a common concern for physicians in the department of anesthesiology,  emergency medicine, and critical care medicine. SEEK^flex (Safe Easy Endotracheal kit-flexible) is a novel multifunctional introducer developed by our team to address difficult airways.  It has been registered as a medical device in  China (Zhejiang Medical Device Registration  Approval No. 20232081322).

The SEEK^flex system features a dual-component  design, consisting of a primary introducer and a  supplementary adapter. With an outer diameter  of 4.0 mm and an inner diameter of 2.4 mm, it  is compatible with tracheal tubes of an internal  diameter exceeding 4.5 mm. The introducer, extending from 43 to 81 cm, is equipped with  a flexible steel core for guidance and a smooth  polyvinyl chloride (PVC) sheath. This assembly  can be securely fastened using a blue locking  mechanism, as depicted in Figure 1A-B [1]. 

SEEK^flex can be bent at an appropriate angle  due to the malleability of its inner core, allowing it to be easily inserted into the trachea just  under the epiglottis in cases of unpredicted  difficult airway (Cormack-Lehane Grade III).  This procedure is facilitated by a video laryngoscope. The endotracheal position of SEEK^flex is  confirmed by connecting it to an EtCO₂ monitor  via the adapter after removing the inner core  (Figure 1C). The endotracheal tube can be easily advanced into the trachea using the Seldinger technique, with the guidance of reconnected,  post-stretching SEEK^flex. In addition, we have  developed a “12-step” approach for awake  tracheal intubation using SEEK^flex and a video  laryngoscope, which has yielded satisfactory  clinical results [2].

At the distal end of the outer catheter, there is  one vent at the top and 4 rows of lateral vents.  After removing the inner core and attaching the  adapter, local anesthetic can be administrated, and oxygenation can be maintained using  a ventilator, like a slender tracheal tube. The  original version of this introducer was used for  reintubation of COVID-19 patients, and the outer catheter could be left in place for subglottic  oxygenation after extubation [3]. This feature is  also used for oxygenation maintenance and tracheal intubation in emergency situations during  bronchoscopic balloon dilation [4]. 

Several randomized controlled studies, approved by the Ethics Committee of the Naval  Medical University and currently in the process  of data collection, may further provide robust  evidence of its safety and efficacy. We believe  that this new multifunctional introducer can be  widely adopted by anesthesiologists due to its  versatility across multiple clinical scenarios.