Effect of Amplitude and Inspiratory Time in a Bench Model of Non-Invasive High Frequency Oscillatory Ventilation Through Nasal Prongs

Abstract

Background and Aims: Nasal high frequency oscillatory ventilation (nHFOV) has been proposed to combine the advantages of oscillatory pressure waveform and of non-invasive interface. We studied the effect of oscillation amplitude and inspiratory time on the pressure transmission and stroke volume delivered through different nasal prongs.Methods: A bench model of nHFOV was built connecting SM3100A oscillator tubings via two differently sized nasal prongs, to a neonatal lung model carrying mechanical properties of recovering RDS. A standard circuit with no nasal prongs was used as control. Tidal volume (Tv), oscillatory pressure ratio (?Pdist/△Pprox) and ventilation (DCO2) were measured across a range of amplitudes and with inspiratory time (IT) set at 33% and 50%. Measurements were performed with a low-dead space hot wire anemometer coupled with a pressure transducer, specifically validated for neonatal ventilation.Results: Tv, Pdist/△Pprox and DCO2 were 83%, 40% and 71%, respectively, of those provided with the control circuit. No differences were noticed between small and large prongs. Tv and △Pprox were linked by a quadratic relationship and Tv plateaus for amplitude values > 65 cmH2O. △Pdist/△Pprox shows the same tendency. Same results were obtained with both types of prongs and with increasing IT. On the whole, mean Tv was higher with IT at 50% than at 33% (2.4 mL vs 1.4 mL;p < 0.001).Conclusions: Changing oscillation amplitude significantly affect ventilation during nHFOV and this effect seems greater than that obtained by varying the frequency. 50% IT always provides an higher Tv delivery and ventilation.

DOI: 10.1038/pr.2011.732

Cite this paper

@article{Luca2011EffectOA, title={Effect of Amplitude and Inspiratory Time in a Bench Model of Non-Invasive High Frequency Oscillatory Ventilation Through Nasal Prongs}, author={Daniele De Luca and Marco Piastra and Giulia Conti}, journal={Pediatric Research}, year={2011}, volume={70}, pages={507-507} }