The resistance to airflow of tracheostomy tubes, connections, and heat and moisture exchangers

Abstract

Studies have been made of the resistance to airflow of tracheostomy tubes, connections, and heat and moisture exchangers. Two commercially available humidifying devices (viz., aluminium foil type with funnel-shaped ends) were unacceptable in this respect though modifications to the end pieces would probably correct the defect. The multilayered guaze type device is found to have the least resistance to airflow. Resistance to airflow of tracheostomy tubes (rubber and silver) increases sharply as the flow rate is increased or the internal diameter is decreased. For a given internal diameter the resistance offered by a silver tracheostomy tube is less than the resistance in a James rubber tube-due to shorter and smoother curve of the former. The total resistance of a system (e.g., tracheostomy tube, connector and humidifying device connected in series) is unpredictable and is not necessarily the sum of the resistances of its component parts. © 1965 John Sherratt and Son Ltd.