Tracheostomy Tube Type and Inner Cannula Selection Impact Pressure and Resistance to Air Flow

Abstract

BACKGROUND: Advancements in tracheostomy tube design now provide clinicians with a range of options to facilitate communication for individuals receiving ventilator assistance through a cuffed tube. Little is known about the impact of these modern design features on resistance to air flow. METHODS: We undertook a bench model test to measure pressure-flow characteristics and resistance of a range of tubes of similar outer diameter, including those enabling subglottic suction and speech. A constant inspiratory ؎ expiratory air flow was generated at increasing flows up to 150 L/min through each tube (with or without optional, mandatory, or interchangeable inner cannula). Driving pressures were measured, and resistance was calculated (cm H 2 O/L/s). RESULTS: Pressures changed with increasing flow (P < .001) and tube type (P < .001), with differing patterns of pressure change according to the type of tube (P < .001) and direction of air flow. The singlelumen reference tube encountered the lowest inspiratory and expiratory pressures compared with all double-lumen tubes (P < .001); placement of an optional inner cannula increased bidirectional tube resistance by a factor of 3. For a tube with interchangeable inner cannulas, the type of cannula altered pressure and resistance differently (P < .001); the speech cannula in particular amplified pressure-flow changes and increased tube resistance by more than a factor of 4. CONCLUSIONS: Tracheostomy tube type and inner cannula selection imposed differing pressures and resistance to air flow during inspiration and expiration. These differences may be important when selecting airway equipment or when setting parameters for monitoring, particularly for patients receiving supported ventilation or during the weaning process.

Tracheostomy insertion in COVID-19: insertion practice and factors leading to unplanned tube exchange

“…These differences are important, as the ID of a tracheostomy has significant implications on airflow, resistance, and work of breathing (73)(74)(75). The Hagen-Poiseuille equation dictates that laminar flow is proportional to the radius of the vessel to the power of 4.…”

How design characteristics of tracheostomy tubes affect the cannula and tracheal flows

“…In vitro studies have been performed to study the airflow characteristics of endotracheal and tracheostomy tubes. in vivo studies have also been performed to study the airflow characteristics for tracheostomy and endotracheal tubes following intubation.…”

“…Experimental studies indicated that over‐ or underinsertion of tracheostomy tubes into the airway can increase airway resistance . Differences in airflow among the various tube designs have been described as important factors in the selection of the tracheostomy tube for patients requiring ventilator‐assisted breathing …”

“…5 Mortality resulting from vascular injury has also been reported in a small number of patients. 6 In vitro studies have been performed to study the airflow characteristics of endotracheal 7,8 and tracheostomy [9][10][11][12] tubes. in vivo studies have also been performed to study the airflow characteristics for tracheostomy 13 and endotracheal tubes 8 following intubation.…”

“…10 Differences in airflow among the various tube designs have been described as important factors in the selection of the tracheostomy tube for patients requiring ventilatorassisted breathing. 11 Advances in computational fluid dynamics (CFD) have enabled simulations of airflow in rigid 14,15 and compliant models 16 of anatomically accurate healthy and diseased tracheas. The effect of various airway surgeries performed to correct obstructive sleep apnea, expressed as a change in the work of breathing, were evaluated preoperatively using CFD modeling.…”