Nasal-CPAP の High Frequency Oscillation 特性

抄録

High frequency oscillatory (HFO) is an artificial ventilation method that allows adequate gas exchange by supplying an oscillating flow with a high ventilation rate of 5 to 30Hz through the tracheal tube into the airway at a single tidal volume (TV_HFO：2～3ml/Kg) smaller than the dead space capacity. The authors have developed a small-sized generator for Nasal-CPAP (HNCPAP) using an air-curtain and entrainment that can control MAP (Mean Airway Pressure) and HFO separately. This paper describes Nasal-HFO characteristics of HNCPAP. Experiments were conducted using the simulating healthy lungs breathing mode of a spontaneous breathing simulator for neonates, with constant MAP, and with and without HFO at three tidal volumes (TV), respectively. In the experiment, the following parameters are measured: alveolar pressure (Palv) just before the test lung, airway pressure (Paw) after passing HNCPAP, CPAP pressure (Cpap), and sub pressure (Sub) and inhalation and exhalation flow (Flow). The experimental conditions are MAP500Pa, respiratory rate 50breaths/min, HFO frequency 15Hz, stroke volume 15ml, tidal volume 2ml, 5ml, and 7ml. The following results were obtained. (1)ΔPaw_HFO on inhalation increased in dependence on TV and reached the alveoli without halving in the airway. (2) The entrainment effect was significantly halved when HFO was added in the first half of exhalation, and (3) TV_HFO on inhalation increased in a TV-dependently and was about half that of HFO in the case of tracheal tube. Finally, we were able to clarify the Nasal-HFO characteristics and fluid device properties when HFO was added to HNCPAP.