The Science Journal of the American Association for Respiratory Care
BACKGROUND: Clinicians who treat patients suffering from cold water near-drowning or hypothermia routinely warm inspire gases greater than body temperature in accordance with care guidelines promulgated by the various organizations. However, humidifiers are designed to prevent heating gases beyond 41
Methods: The maximum temperature that a circuit could achieve was measured after varying tubing lengths (1.5 feet, 3 feet, and 6 feet), gas flow (opening or closing a venturi receiving a fixed flow rate of 10 L/min), and the size of the heat source (one or two heated humidifiers in aerosol circuit). A total of ten runs were made in each of the possible twelve combinations.
Results: Univariate statistics showed significant differences for Venturi open/close (p=.0001) and the number of heaters (p=.0001) but not the tubing length (p=0.19). However, the multivariate analysis revealed significance for tubing length, number of heaters, and venturi open/closed (p=.01). CONCLUSION: All factors (tubing length, number of heaters, and tubing length) were important determinants of maximum gas temperature. The effect of tubing length can be overwhelmed by higher gas flows.