2004 OPEN FORUM Abstracts
High Frequency Chest Wall Oscillation does not adversely affect Cardiac Output in a Swine Model of Pediatric Acute Lung Injury
DS Hamel, MA
Gentile, DM Craig, G Quick; IM Cheifetz, Pediatric Critical Care
Medicine, Duke Children’s Hospital, Durham, NC.
Background: The Vest Airway Clearance System (Hill Rom, St. Paul, MN), an air-pulse generator with a vest interface, compresses and releases the chest wall through an inflation-deflation cycle. This compression exerts pressure to the chest at a rapid frequency. In a preliminary study, we demonstrated that high frequency chest wall oscillation (HFCWO) provided by the Vest System effectively augmented conventional mechanical ventilation (CMV) by allowing for comparable CO2 elimination at lower delivered tidal volumes.
Hypothesis: We hypothesized that the external pressure exerted to the chest during HFCWO would not adversely affect cardiac output (CO).
Methods: Eight swine (10.3-19 kg) with acute lung injury induced by saline lavage were ventilated with a Servo 300 ventilator (Siemens Corp.). Ventilator settings in the pressure control mode included: Vt 10 cc/kg, respiratory rate 20, FiO2 1.0, PEEP 7 cm H2O, inspiratory time 0.60 seconds. CO was measured by the thermodilution technique with a pulmonary artery catheter. The Vest System was placed on the animal and set at a pressure setting of 0.5. For each frequency setting (5, 10, and 15 Hz), CO was measured without HFCWO (10 minute stabilization period) and during HFCWO (10 minute oscillation period). The frequencies were re-randomized, and the study was repeated for each animal. Data were analyzed by ANOVA with repeated measures.
Results: HFCWO at a pressure setting of 0.5, did not alter CO (p=0.67, frequency difference p=0.97).
Conclusion: Despite the application of intermittent external positive pressure to the thorax, CO remained stable during HFCWO. Thus, HFCWO may be effective as an adjunct therapy during CMV to augment gas exchange without compromising hemodynamic stability."