Critical care medicine
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Critical care medicine · Sep 1984
Comparative StudyHemodynamic effects of continuous positive-pressure ventilation and high-frequency jet ventilation with positive end-expiratory pressure in normal dogs.
The hemodynamic effects of high-frequency jet ventilation (HFJV) at 60, 120, 240, and 480 breath/min, and conventional ventilation at 15 breath/min were compared in 6 anesthetized, paralyzed dogs, at 0, 10, and 20 cm H2O of positive end-expiratory pressure (PEEP). On HFJV at the same inspired oxygen, PaCO2, and PEEP levels, hemodynamic function improved significantly. ⋯ When PEEP was applied, hemodynamic function improved even when mean airway pressure was maintained constant. The findings suggest that lung volume was smaller during HFJV, and/or that lung volume changes during each respiratory cycle contributed to differences in venous return and ventricular function.
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As the treatment of respiratory failure becomes more sophisticated and technical, the critical care nurse is faced with many challenges. High-frequency ventilation is a modality of respiratory support employing principles different from those of conventional ventilation. For these reasons, the nurse must be familiar with the indications for its use and the practical management of the ventilated patient. This paper addresses those aspects of respiratory support which have the greatest impact on nursing care.
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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.
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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.
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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.