Effect of amplitude and inspiratory time in a bench model of non-invasive HFOV through nasal prongs.
OBJECTIVE
Non-invasive high frequency oscillatory ventilation through nasal prongs (nHFOV) has been proposed to combine the advantages of oscillatory pressure waveform and non-invasive interface. We studied the effect of oscillation amplitude and inspiratory time on the pressure transmission and tidal volume delivery through different nasal prongs.


METHODS
In vitro mechanical study on a previously described bench model of nHFOV. The model was built connecting SM3100A tubings to a neonatal lung model, via two differently sized binasal prongs. A circuit with no nasal prongs was used as control. Tidal volume (T(v) ), oscillatory pressure ratio (ΔP(dist) /ΔP(prox) ), and ventilation (DCO(2) ) were measured across a range of amplitudes and inspiratory times (I(T) ). Measurements were performed with a low-dead space hot wire anemometer coupled with a pressure transducer.


RESULTS
Using both nasal prongs, T(v) , ΔP(dist) /ΔP(prox) , and DCO(2) were 83%, 40%, and 71%, respectively, of those provided with the control circuit. No differences were noticed between small and large prongs. T(v) and ΔP(prox) were linked by a quadratic relationship. T(v) plateaus for amplitude values >65 cmH(2) O. ΔP(dist) /ΔP(prox) shows same tendency. Same results were obtained with both types of prongs and with increasing I(T) . On the whole, mean T(v) was higher with I(T) at 50% than at 33% (2.4 ml vs. 1.4 ml; P < 0.001).


CONCLUSIONS
Changing oscillation amplitude and I(T) has a significant effect on ventilation. Varying these two parameters provides a theoretical T(v) within the ideal values for HFOV also using the smallest nasal prongs.
Pediatric Intensive Care Unit, Dept of Emergency and Intensive Care, University Hospital A.Gemelli, Catholic University of the Sacred Heart, Rome, Italy. dm.deluca@fastwebnet.it
Daniele
D
De Luca
Marco
M
Piastra
Domenico
D
Pietrini
Giorgio
G
Conti
D000281:Administration, Intranasal; D057785:Catheters; D006612:High-Frequency Ventilation / Q000295:instrumentation* / Q000379:methods; D006801:Humans; D007231:Infant, Newborn; D008168:Lung / Q000502:physiology; D008954:Models, Biological; D063087:Noninvasive Ventilation / Q000295:instrumentation* / Q000379:methods; D013990:Tidal Volume / Q000502:physiology