Effect of High-Frequency Jet Ventilation on Airway Temperature

Abstract

The effect of high-frequency jet ventilation (HFJV) on airway temperature was studied experimentally. A jet ventilator (MERA-S HFO Jet Ventilator^®) and a test lung (21) were assembled similar to when used clinically, and temperature in the test lung was measured using a thermister. The working pressure and frequency of the jet of the HFO ventilator were set at 0.25 to 3.00kg/cm² and from 3 to 40Hz, respectively. Each temperature measurement was carried out using dry gas only and during humidification with normal saline solution 5 or 10ml/hr via a special double-needle. In the dry gas group, the temperature in the test lung increased in the presence of all combinations of working pressure and frequency. The increment in temperature was caused by friction heat produced by intermittent jet gas flow passing through the conducting tube from the HFO ventilator. The maximal temperature increment was 7°C, measured at a frequency of 10Hz and working pressure of 3kg/cm². In the humidified gas group, the temperature decreased 3.1°C at an infusion rate of 5ml/hr and 5.2°C at an infusion rate of 10ml/hr. These result suggest that airway temperature monitoring be recommended during HFJV.