Critical care medicine
-
Critical care medicine · Sep 1984
Comparative StudyHigh-frequency positive-pressure ventilation with the MA-1 ventilator.
A conventional, low-frequency ventilator was modified to ventilate dogs at high frequencies of 85 to 185 cycle/min while cardiovascular and pulmonary variables were monitored. Although gas transport was adequate, cardiac output was diminished when compared to low-frequency ventilation. The addition of an in-line pneumotachograph markedly increased PaCO2 during high-frequency ventilation. Carbon dioxide transport was primarily dependent upon the magnitude of the tidal volume at all high frequencies tested.
-
Critical care medicine · Sep 1984
Effect of continuous positive airway pressure on lung mechanics during high-frequency jet ventilation.
Six mongrel dogs were studied in a body plethysmograph to ascertain the effects of continuous positive airway pressure (CPAP) during high-frequency jet ventilation (HFJV), using an open system allowing gas entrainment. Increases in CPAP significantly reduced tidal volume. ⋯ At constant CPAP, tidal volume correlated well with the difference between peak airway pressure and CPAP, while the FRC change was correlated with the difference between end-expiratory pressure and CPAP. The relationship between end-expiratory airway pressure and total change in FRC was predictable from lung compliance at all levels of CPAP.
-
Critical care medicine · Sep 1984
Measuring gas leakage from bronchopleural fistulas during high-frequency jet ventilation.
A simple volumetric system can be used to measure leakage from bronchopleural fistulas even when inspiratory volumes are unknown or when constant suction is required.
-
Critical care medicine · Sep 1984
Airway pressure as a measure of gas exchange during high-frequency jet ventilation.
Airway pressure during high-frequency jet ventilation (HFJV) reflects safety, ventilator performance, and gas exchange. The value of airway pressure as a monitoring and control variable for predicting the effectiveness of gas exchange was examined in 2 studies using healthy dogs. In the first study, HFJV was delivered to the airway via an extra lumen in the wall of an endotracheal tube, at a frequency of 150 cycle/min and 30% inspiratory time. ⋯ The airway pressure difference correlated strongly with efficiency of gas exchange for both CO2 elimination and oxygenation. Mean and end-expiratory pressures showed little influence over moderate ranges, but use of 15 cm H2O of PEEP decreased efficiency of both CO2 elimination and oxygenation, presumably due to increased dead space because of lung overdistension. We conclude that the airway pressure difference, measured as far distal in the airway as is safe and practical, can be useful for monitoring and controlling HFJV.