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."