The Science Journal of the American Association for Respiratory Care

2008 OPEN FORUM Abstracts


Robert Gillette1, Robert DiGeronimo1, Stephen Messier1

Background: HFOV may be lung-protective for critically ill neonates and can often support those failing other modes, but cannot be used in transport. The Bronchotron� is a small, lightweight, pneumatically driven HFPV that is gaining favor for transport but is not well studied. The equivalence of gas exchange by the two devices is unknown.

Objectives: Compare HFOV to HFPV matched for mean airway pressure (MAP), tidal volume (TV), and frequency (F) in oxygenating/ventilating piglets with acute lung injury.

Methods: Twelve healthy piglets (3.4±0.6 kg) were intubated, placed on conventional support (FiO2 1.0), and underwent repeated saline lavage until pO2<60 mmHg. They were then randomized to the Sensormedics® 3100A HFOV or Bronchotron® HFPV with settings adjusted to maintain pCO2 of 45-60 mmHg. After stabilization, TV, F, MAP, pressure amplitude (PA), pCO2 and pO2 were tracked every 5 min for 30 min. TV was measured with a previously validated Florian® hot wire anemometer. Animals were then switched to the other device at matched TV, F, and MAP for 30 min, tracking the same parameters. MAP was then increased by 5 cmH2O and the experiment repeated. Repeated measures ANOVA was used for continuous data. All results are mean ± SD

Results: After injury, the oxygenation index was 10.4±4.0 and the modified ventilatory index was 111±35. TV and F to produce the specified pCO2 were 3.1±0.7 ml/kg and 7.2±0.6 Hz, there was no difference in TV (p=0.88), F (p=0.97), or MAP (p=0.89) between devices, and these matched tightly for each anmial. As in our previous bench studies, the PA needed to generate this TV on HFPV (36±5 cmH2O ) was higher vs. the HFOV (31±6 cmH2O), but here not quite to statistical significance (p=0.09). When matched for TV, F, and MAP, there was no difference in ventilation (pCO2=50±11 vs. 46±10 mmHg, p=0.22) or oxygenation (pO2=150±74 vs. 149±106 mmHg, p=0.57) between the HFPV and HFOV, respectively. Results at the higher MAP were analagous. The pO2 but not pCO2, impedance (Z), or PA, differed between MAP levels on each device.

Conclusion: In this model, HFPV provided gas exchange equivalent to HFOV at matched TV, F, and MAP. HFPV may require higher PA than HFOV to generate equivalent TV/gas exchange. Raising MAP level affected pO2