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Inspiratory gas temperature in the endotracheal tube when ventilated with a heated humidifier

International Organization of Standardization recommends that inspiratory gas should possess absolute humidity of more than 33 mg/l. In this study we measured the temperature in the endotracheal tube (ETT) with a hypothesis that actual temperature of inspiratory gas is lower than that set by heated humidifier resulting in an inadequate humidification.

Methods

A lung model (TTL, Michigan Instruments) was ventilated using a PB840 ventilator (Puritan-Bennett) via an 8 mm ETT. A heated humidifier (MR290, Fisher & Paykel) was set in the inspiratory limb of a standard ventilator circuit with a target temperature of 37°C. The ventilator settings were: volume control mode, rate 10/min, PEEP 0 cmH2O with various tidal volumes (VT). The temperature of inspiratory gas was measured at 22 cm, 27 cm and 32 cm from the distal end of the ETT using a thin wire thermocouple thermometer.

Results

Mean inspiratory temperatures (°C) are shown in Table 1.

Table 1

Conclusion

The actual mean inspiratory gas temperature was lower than the target temperature set by the humidifier, especially with low VT, which may result in an inadequate humidification.

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Fujino, Y., Uchiyama, A., Miyoshi, E. et al. Inspiratory gas temperature in the endotracheal tube when ventilated with a heated humidifier. Crit Care 7, P158 (2003). https://doi.org/10.1186/cc2047

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  • DOI: https://doi.org/10.1186/cc2047

Keywords

  • Endotracheal Tube
  • Target Temperature
  • Ventilator Setting
  • Thin Wire
  • Absolute Humidity