Comparison of a novel humidifier with two conventional humidifiers during high-frequency oscillatory ventilation

Introduction

During high-frequency oscillatory ventilation (HFOV), drying of the airways and mucous plug formation can be complications associated with inadequate humidification. This study compares water vapor delivery of a standard passover humidifier and a conchatherm humidifier typically used during HFOV with a novel humidifier that employs the principle of capillary force vaporization.

Methods

The Sensormedics 3100B oscillatory ventilator (Cardinal Health, Yorba Linda, CA, USA) was connected to a test lung at the following settings: mean airway pressure, 30 cmH₂O; power, 6.0; inspiratory time percentage, 33%; frequency of 6 Hz and bias flow 30 l/min on room air. The 3100B was run at the above settings first using five different MR850 passover humidifiers (Fisher & Paykel, Auckland, New Zealand), followed by five different Hydrate OMNIs (Hydrate Inc., Midlothian, VA, USA) and then five different ConchaTherm Neptunes (Teleflex Medical, Research Triangle Park, NC, USA). The gas temperature and relative humidity were recorded continuously using an electronic hygrometer/thermometer (SHT75; Sensirion, Staefa, Switzerland) in two circuit configurations: (1) between the test lung/patient wye (triangular plastic connector that connects the inspiratory and expiratory limbs of the circuit with the patient endotracheal tube) and (2) distal to a condensation tube placed between the test lung/patient wye. The condensation tube served to approximate the upper airways in our lung model and collect the condensate. Water condensate was collected over a 30-minute test period for each run. All humidifiers were set to 37°C.

Results

See Table 1.

Table 1 abstract P29

Conclusion

In this model, the Hydrate OMNI provided the highest absolute humidity during HFOV. The difference was amplified at the end of the condensation tube. Further study on humidification during HFOV is warranted.