Abstract

Development of supraglottic airway device avoiding impairment of carotid artery blood flow

Yoon Ha Joo
Interdisciplinary Program in Bioengineering
Seoul National University Graduate School

The supra-glottic airway(SGA) is a device that have one or two cuffs attached to the end or middle of the tube to cover the larynx. SGA has the advantages of simple configuration and relatively low skill required. So, this is the most popular alternative to endotracheal intubation(E-tube intubation) and has already been widely introduced in medical practice. However, recent large-scale studies of patients with cardiac arrest in out of hospital have reported that SGA intubation have worse spontaneous circulation recovery, survival rate, and neurological prognosis than E-tube intubation. It is presumed that the pressure of the laryngeal lumen which occurs when the cuff inflated on the glottis is closely attached to the airway entrance obstructs the blood flow of the carotid artery but not proved yet. The purpose of this study is to identify what differences are occurring and analyze the causes of various types of SGAs and E-tube on hemodynamic aspects and develop of new SGAs that is most advantageous in terms of brain survival in patients with cardiac arrest.
In order to compare with the effects of e-tube and three types of SGAs, laryngeal mask airway(LMA), i-gel and combitube on cerebral blood flow and pressure, pre-clinical studies were conducted using total of 12 pigs weighing about 40kg cardiac arrest models.
We analyzed the factors affecting the physiological parameters using computed tomography(CT) images of pigs intubated with e-tube and three types of SGAs. First, the 3D model of the SGAs / carotid artery / upper respiratory tract before and after intubation was prepared by Seg3D program , Meshmixerprogram . Second, SGAs after intubation and upper respiratory tract before intubation were output to the FDM 3D printer for detailed appearance analysis. Third, we calculated the volume per unit length of the carotid artery and analyzed whether the carotid artery was pressured by SGAs cuff expansion.
New-LMA and new-combitube were created to reduce the pressure on the carotid artery. This is based on the patent of Earplug US005957136 US4867149, and a plug and plug cuff with thin wings is fabricated using silicone, which is an elastic polymer material. First, a mold was designed to fabricate a cuff using the Inventor program, Seg3D, Meshmixer and outputs using FDM 3D Printer 3DP-110F(Single). Second, a new cuff is fabricated by casting silicon into the mold.
The air-leakage in-vitro test was performed on new SGAs manufactured by using the manikin in the gating system. Preclinical study was conducted on 8 pigs weighing about 42.5kg cardiac arrest model. There was a decrease in carotid artery blood flow in the new-SGA. However, it is confirmed that the decrease is smaller than that of existing products. This allows the new gateways to demonstrate improved performance over existing products.