Performance of heated wire humidifiers: an in vitro study

Area of Science:

• Respiratory care
• Biomedical engineering
• Mechanical ventilation

Background:

• Heated humidifiers (HHs) are crucial for conditioning inspired gases during mechanical ventilation.
• Water condensation in breathing circuits can lead to complications like airway occlusion and infection.
• Heated wire humidifiers (HWHs) were developed to minimize or eliminate circuit condensation.

Purpose of the Study:

• To assess the performance of three HWHs (MR850, CONCHATHERM IV, DAR HC 2000) in terms of gas temperature and absolute humidity (AH).
• To compare the efficiency of HWHs against a standard heated humidifier (MR730 HH).
• To evaluate the impact of different temperature settings and gradients on HWH performance.

Main Methods:

• Evaluated three HWH models and one standard HH using a test lung.
• Measured gas temperature and AH at the Y-piece under varying ventilation volumes (5 and 15 L/min).
• Tested different temperature settings (35°C, 37°C, 39°C) and temperature gradients (-2°C, 0°C, +2°C).

Main Results:

• All HWHs successfully eliminated water condensation in the inspiratory circuit.
• MR850 and CONCHATHERM IV delivered lower gas temperature and AH compared to DAR HC 2000 and MR730 HH at a 0°C gradient.
• Increasing temperature gradients increased AH in all HWHs and gas temperature in the CONCHATHERM IV.

Conclusions:

• HWHs effectively prevent circuit condensation.
• Significant variations exist in the gas temperature and AH delivered by different HWH models.
• The actual gas temperature and AH delivered by HWHs may be lower than intended settings.