2000 OPEN FORUM Abstracts
DETERMINING THE EFFECT OF FREQUENCY AND AMPLITUDE ON THE TIDAL VOLUME DELIVERED DURING HIGH FREQUENCY OSCILLATION
Khaled A. Sedeek MD, Muneyuki Takeuchi MD, Robert M. Kacmarek PhD RRT, Respiratory Care, Massachusetts General Hospital and Harvard Medical School, Boston, MA
Background: HFO has been shown advantageous in the management of Infant Respiratory Distress Syndrome and has been proposed for use in Adult Respiratory Distress Syndrome. However, limited data on the effect of pressure amplitude (
Methods: In six sheep (29±2 kg) severe lung injury was induced by repeated saline lung lavage until the PaO2 decreased to less than 100 mm Hg (65±14 mm Hg) during VC (FiO2 1.0, PEEP 5 cmH2O, VT 12 ml/kg and RR 15). After stabilization HFO was initiated at a MAP equal to the point of maximum curvature (PMC) on the expiratory limb of the P-V curve (27±2.4 cmH2O) (S Goddon: AJRCCM. 159:A77, 1999). VT at all combinations of rates 4, 6, 8, and 10 Hz, and pressure amplitudes of 30, 40, 50, and 60 cmH2O with an FiO2 of 1.0 and an Inspiratory time of 50% using the Sensomedics adult HFO was measured. Flow was measured by a pneumotachometer calibrated with a 400 ml/sec flow delivered by precision flowmeter (Brooks Instruments), Flow was amplified and digitized using a computerized graphics program (WINDAQ; Dataq Instruments Inc.) at 1000 Hz and recorded by using WINDAQ. Data was continuously recorded for one minute and three breaths were analyzed at each rate and
Results: Results (see table): VT was directly proportional to Amplitude (P<0.0001) and inversely proportional to the Frequency (P<0.0001). At 60 cm H2O
| AMPLITUDE | FREQUENCY | |||
| 10 Hz | 8 Hz | 6 Hz | 4 Hz | |
| 60 cmH2O | 35±11 ml | 49±14 ml | 75±21 ml | 131±34 ml |
| 50 cmH2O | 30±10 ml | 43±12 ml | 64±16 ml | 108±30 ml |
| 40 cmH2O | 24±9 ml | 34±11 ml | 52±13 ml | 87±24 ml |
| 30 cmH2O | 18±6 ml | 26±8 ml | 40±10 ml | 64±18 ml |
Conclusion: At low rates and high