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Aspiration and transtracheal jet ventilation with different pressures and depths of chest compression.

OBJECTIVE
To evaluate aspiration prophylaxis during cardiopulmonary resuscitation (CPR) using transtracheal jet ventilation (TJV) with different pressure-depths of chest compression and chest compression alone without mechanical ventilation.


DESIGN
Prospective, animal study.


SETTING
Animal research laboratory, Chang Gung Memorial Hospital, Kaohsiung Medical Center, Taiwan.


SUBJECTS
Mongrel dogs (n = 10) weighing 8 to 12 kg.


INTERVENTIONS
Eight mongrel dogs were anesthetized, paralyzed, and ventilated transtracheally with a jet ventilator at frequencies varied from 600 to 10 cycles/min. The airway pressures below and above the jetting port were measured. The mouth of the dog was filled with barium and chest radiographs were taken 10 mins after chest compression with 20-pound pressure and 5-cm depth in group 1 and 10-pound pressure and 3-cm depth in group 2 at each different jet frequency. Two additional dogs underwent the same procedures but received only chest compression without TJV.


MEASUREMENTS AND MAIN RESULTS
Pulmonary aspiration was not noted in the chest radiographs from either group. The airway pressure changes between groups were not significantly affected by difference in pressures and depths of chest compression at the same jetting frequency. However, pulmonary aspiration occurred in the two dogs that received chest compression alone without TJV.


CONCLUSIONS
Application of TJV during chest compression with different pressures and depths caused no pulmonary aspiration in dogs at frequencies between 600 and 10 cycles/min. The protection against aspiration disappeared if the dogs received only chest compression without TJV. The mechanism of preventing pulmonary aspiration in TJV is thought to be due to forceful unidirectional gas outflow through the larynx and higher airway pressure in the carina than in the upper airway. The airway pressures were not affected by different chest compression pressures and depths because the larynx stayed open during TJV and the air outflow could freely move out without increasing the pressure in the airway.