2004 OPEN FORUM Abstracts
The Effects of High Frequency Chest Wall Oscillation on TIDAL Volume and Paco2 in a Swine Model of Acute Lung Injury
Michael
A Gentile RRT, Donna S Hamel RRT, Damian M Craig MS, George A
Quick, Ira M Cheifetz MD, Duke University Medical Center, Durham, NC
Background: The Vest™ airway clearance
system (Hill Rom, St. Paul, MN) compresses and releases the chest
wall through an inflation-deflation cycle that results in high
frequency chest wall oscillation (HFCWO). This compression exerts
pressure to the chest at a rapid frequency and may interfere with
tidal volume (Vt) delivery while used in conjunction with
Pressure Control Ventilation (PCV). We hypothesized that the
external pressure exerted to the chest during PCV would not adversely
affect PaCO2.
Methods: Twelve swine (10.3 ± 1.1 kg)
with acute lung injury induced by saline lavage were ventilated with
a Viasys Avea ventilator (Viasys Critical Care, Palms Springs, CA).
Ventilator settings in the pressure control mode included: PIP
adjusted to achieve Vt 10 ml/kg, respiratory rate 25, FiO2
0.6, PEEP 8 cmH2O, inspiratory time 0.50 seconds. Animals
were randomized to either treatment with Vest +PCV or PCV alone. The
Vest System was placed on animals at a pressure setting of 0.5 and
frequency of 5Hz. All animals were ventilated for four hours. Tidal
volumes were measured by a flow sensor (NICO; Respironics-Novametrix,
Wallingford, CT) at the circuit wye. Data were analyzed by ANOVA
with repeated measures.
Results: HFCWO + PCV resulted in lower delivered tidal volumes than PCV alone
(p=0.0001). PaCO2 did not significantly differ
(p=0.76).
| PaCO2 (torr) | Tidal Volume (ml) | |
| Vest | 57 ± 15 | 4.7 ± 0.8 |
| Control | 47 ± 19 | 10 ± 1.8 |
| p | 0.76 | 0.0001 |
Conclusion: Despite the reduction in delivered
tidal volume, PaCO2 remained stable during HFCWO. HFCWO
in conjunction with PCV may enhance ventilation by allowing for
acceptable CO2 elimination at lower delivered tidal
volumes.