Abstract
HFJV, unlike high frequency oscillation, relies on passive elastic properties of the lung for exhalation. I:E can be adjusted to allow time for exhalation and prevent inadvertent PEEP. To determine which I:E affords maximal cardiopulmonary function we varied I:E from 1:1 to 1:5 at 600 BPM and measured PaO2, PaCO2, calculated alveolar-arterial O2 differences (AaDO2) and estimated systemic blood flow (Q) using Fick's principle (assuming constant oxygen consumption) in surfactant depleted cats (lungs lavaged 6 times). Mean airway pressure (MAP) was held constant at 6 cm H2O, inspiratory pressure was 9 to 10 cm H2O, PEEP 4 cm H2O, and FiO2 1.0. Results (meanĀ±SE) show highest PaO2 and PaCO2, and lowest AaDO2 and Q were at 1:1. PaO2 increased as ratios changed from 1:3 to 1:5 (p<0.01). It is interesting that oxygenation varied even though MAP, rate and FiO2 were constant. Q at 1:5 was less than 1:4 (P<0.01). We conclude: the combination of best oxygenation and ventilation with least cardiovascular effects was obtained when an I:E of 1:4 was used.
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Johnston, J., Richardson, P. & Carlstrom, J. THE INSPIRATORY: EXPIRATORY TIME (I:E) DURING HIGH FREQUENCY JET VENTILATION (HFJV) OF AN RDS MODEL. Pediatr Res 18 (Suppl 4), 402 (1984). https://doi.org/10.1203/00006450-198404001-01855
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DOI: https://doi.org/10.1203/00006450-198404001-01855