Inspired oxygen concentrations using a humidifier/tracheostomy t-piece system

Abstract

Summary: This study examines the inspired oxygen concentrations achieved using a humidifier driven by oxygen under pressure and a standard T-piece connection fitted to the tracheostomy tube. Since the expiratory ports provided in the T-piece were considered to be a possible source of entrainment from outside this connection, the inspired oxygen concentration was compared to the oxygen concentration delivered from the humidifier. This comparison was used as an indication of dilution. Using controlled patterns of respiration, as measured by a pneumotachograph, in thirty subjects it was found that the humidifierflow was diluted by outside air when the inspiratory flow rate exceeded the humidifier flow. To avoid gross contamination of the pneumotachograph, the delivered gases were not humidified in the experiment. With the system described, lower inspired oxygen levels were found than anticipated and dilution of humidification was also presumed to occur. © 1972 John Sherratt and Son Ltd.