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An experimental model for the measurement of inspired gas temperatures in ventilated neonates
Author(s) -
Jardine Luke Anthony,
Dunster Kimble Robert,
Davies Mark William
Publication year - 2008
Publication title -
pediatric pulmonology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.866
H-Index - 106
eISSN - 1099-0496
pISSN - 8755-6863
DOI - 10.1002/ppul.20731
Subject(s) - thermocouple , medicine , temperature measurement , anesthesia , repeated measures design , mechanics , nuclear medicine , thermodynamics , materials science , mathematics , composite material , statistics , physics
Objective To determine the inspired gas temperature at points from the endo‐tracheal tube (ETT) circuit manifold to the tip of the ETT in a model neonatal lung. Design A model lung attached to standard ventilator circuit, autofeed chamber and humidifier was ventilated using typical pressure‐limited, time cycled settings. Temperatures were measured at various distances along the ETT using a K‐type thermocouple temperature probe. Results The inspired gas temperature dropped from the circuit temperature probe site (40°C) to the proximal end of the ETT (37°C). The temperature dropped further as it passed through the exposed part of the ETT (34°C) but then warmed again on entering the lung model so that the inspired gas at the distal end of the ETT was 37°C. Statistically significant differences were found with a one‐way ANOVA P ‐value of <0.0001. The differences between each pair of mean temperatures were statistically significant (all P < 0.001) except when comparing the proximal end of the ETT with midway down the ETT (Bonferroni's Multiple Comparison Test, P > 0.05). Conclusions Inspired gas temperature drops as it passes through the circuit temperature probe site, the proximal end of the ETT and the exposed part of the ETT. The inspired gas rewarms on entering the model lung and exits the ETT at the desired temperature. The effect of measuring temperature closer to the patient, setting the circuit temperature higher and/or increasing the ambient temperature through which the circuit passes, need to be evaluated. Pediatr Pulmonol. 2008; 43:29–33. © 2007 Wiley‐Liss, Inc.