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Effects of Positive End-Expiratory Pressure on Oscillated Flow Rate During High-Frequency Chest Compression FREE TO VIEW

Ryan J. Perry; Godfrey C. W. Man; Richard L. Jones
Author and Funding Information

From the University of Alberta, Edmonton, Alberta, Canada

1998 by the American College of Chest Physicians

Chest. 1998;113(4):1028-1033. doi:10.1378/chest.113.4.1028
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Objective: To investigate the effects of positive end-expiratory pressure (PEEP) on end-expiratory lung volume (EELV) and mean oscillated flow rate (VOSC) during high-frequency chest compression (HFCC) in normal subjects and patients with severe COPD.

Design: Comparative study.

Setting: Pulmonary function and lung mechanics laboratory, University of Alberta Hospitals.

Participants: Six normal subjects (five male; one female) and six patients with clinically stable COPD (five male; one female) with hypercapnia.

Interventions: A pneumatic vest system was operated at 10 Hz with a mean chest wall pressure of 16 cm H2O to provide the HFCC. A closed-circuit spirometer system permitted measurement of HFCC- and PEEP-induced changes in EELV that were expressed as per cent baseline functional residual capacity (FRC). An isothermic chamber connected near the mouthpiece permitted measurement of VOSC.

Results: For the normal subjects, HFCC caused a significant decrease in EELV to 82.0% of FRC (p≤0.01) and the addition of 4.8±0.5 cm H2O of PEEP during HFCC increased EELV to 97.5% FRC. In the COPD patients, HFCC decreased EELV to 92.3% of FRC (p≤0.01), and the addition of 3.7±1.0 cm H2O of PEEP increased EELV to 98.4% FRC. For the normal subjects, increasing EELV to near FRC caused VOSC during expiration to increase 14.6% (p≤0.01), but there was no significant effect on VOSC during inspiration (5.1% increase). In the COPD patients, PEEP increased VOSC during both inspiration (30.5%) and expiration (57.0%) (both, p≤0.01).

Conclusions: Addition of a modest amount of PEEP during HFCC prevents the decrease in EELV and increases VOSC during both phases of spontaneous breathing in COPD patients. This higher VOSC during HFCC+PEEP may improve the effectiveness of HFCC in clearing mucus from the lungs of patients with airway disease.




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