Abstract
We have measured lung volume (FRC), tidal volume delivered (VT), and alveolar pressures (PA) during jet ventilation of rabbits. The rabbits were ventilated with room air using the Healthdyne jet ventilator at a driving pressure of 4 psi and frequencies from 2 to 15 Hz. The 0.98 mm ID jet cannula was inserted 2 cm into a 3.5 mm endotracheal tube. Pressure was measured in the trachea (Ptr) just distal to the endotracheal tube tip, and in the alveoli. Alveolar pressure was measured by gluing an adapter to the pleural surface which had been exposed through a thoracotomy. After closing the thoracotomy, pleural punctures were made through the adapter and a pressure transducer was inserted. Volume was measured with a pressure plethysmograph. The animals were ventilated at 2, 5, 10 and 15 Hz, with inspiratory times (TI) of 10, 30 and 50%. There was a marked increase in FRC during jet ventilation, to 80% or more of total lung capacity at 50% TI. The increase in FRC was related to mean expiratory flow rate. Mean PA and Ptr were equal and exceeded mean pressure at the airway opening. Tidal volume diminished with increasing frequency, and was greatest at 30% TI at any frequency. VT exceeded estimated dead space below 10 Hz. PA swings were equal to Ptr swings, fell with increasing frequency and were least at 10% TI. We conclude that dangerously large increases in FRC may occur during jet ventilation, and that measurement of pressure at the airway opening is an inadequate means of monitoring airway pressures during jet ventilation. (Supported in part by HL 27372.)
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Frantz, I., Close, R. LUNG VOLUME, TIDAL VOLUME, AND ALVEOLAR PRESSURE DURING JET VENTILATION. Pediatr Res 18 (Suppl 4), 391 (1984). https://doi.org/10.1203/00006450-198404001-01791
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DOI: https://doi.org/10.1203/00006450-198404001-01791