Y-Piece Temperature and Humidification During Mechanical Ventilation
BACKGROUND: Practitioners often presume there is adequate humidification in the ventilator circuit if the Y-piece is at a specified temperature, but control of Y-piece temperature may be inadequate to ensure adequate humidification. METHODS: In an in vitro bench model we measured water-vapor
delivery with several heated humidification setups and a wide range of minute volume (VE) values. The setup included a condenser, hygrometry, and thermometer. First, we calibrated the system with a point-source humidifier and water pump. Then we tested the water-vapor delivery during
non-heated-wire humidification and during heated-wire humidification with a temperature gradient of 3°C, 0°C, and 3°C between the humidifier and the Y-piece. We compared the results to 2 recommended humidification values: 100% saturated (absolute humidity 44 mg H2O/L)
gas at 37°C (saturated/37°C); and 75% saturated (absolute humidity 33 mg H2O/L), which is the humidity recommended by the International Organization for Standardization (the ISO standard). In all the experiments the setup was set to provide 35°C at the Y-piece. RESULTS:
Our method for measuring water-vapor delivery closely approximated the amount delivered by a calibrated pump, but slightly underestimated the water-vapor delivery in all the experiments and the whole VE range. At all VE values, water-vapor delivery during non-heated-wire
humidification matched or exceeded saturated/37°C and was significantly greater than that during heated-wire humidification. During heated-wire humidification, water-vapor delivery varied with the temperature gradient and did not reach saturated/37°C at VE > 6 L/min.
Water-vapor delivery with the negative temperature gradient was below the ISO standard. CONCLUSIONS: Maintaining temperature at one point in the inspiratory circuit (eg, Y-piece), does not ensure adequate water-vapor delivery. Other factors (humidification system, VE, gradient setting)
are critical. At a given temperature, humidification may be significantly higher or lower than expected.
Document Type: Research Article
Department of Pulmonary and Critical Care Medicine, Stony Brook University Medical Center, State University of New York at Stony Brook
Department of Pulmonary and Critical Care Medicine, Stony Brook University Medical Center, State University of New York at Stony Brook, HSC T 17–040, Stony Brook NY 11794;, Email: firstname.lastname@example.org
Publication date: April 1, 2009
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