The Science Journal of the American Association for Respiratory Care

2008 OPEN FORUM Abstracts

GAS EXCHANGE WITH HIGH FREQUENCY OSCILLATORY (HFOV) VS. PERCUSSIVE (HFPV) VENTILATION IN AN ANIMAL LUNG INJURY MODEL

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