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Physiologic Evidence for the Efficacy of Positive Expiratory Pressure as an Airway Clearance Technique in Patients With Cystic Fibrosis

JC Darbee, PT, PhD, is Assistant Professor, Department of Rehabilitation Sciences, Division of Physical Therapy, College of Health Sciences, University of Kentucky, 900 S Limestone St, Lexington, KY 40536 (USA) (darbee{at}uky.edu).
PJ Ohtake, PT, PhD, is Associate Professor, Department of Rehabilitation Sciences, University of Buffalo, The State University of New York
BJB Grant, MD, is Professor, Departments of Medicine, Physiology and Biophysics, and Social and Preventive Medicine, University of Buffalo, The State University of New York. Dr Grant is also Division Head of Pulmonary, Critical Care and Sleep Medicine, University of Buffalo, The State University of New York, and Veteran Affair's Medical Center, Buffalo, NY
FJ Cerny, PhD, is Chair and Associate Professor, Department of Physical Therapy, Exercise and Nutrition Sciences, University of Buffalo, The State University of New York

Address all correspondence to Dr Darbee. Dr Darbee was a doctoral candidate in the Department of Physical Therapy, Exercise and Nutrition Sciences, University of Buffalo, The State University of New York, Buffalo, NY, at the time of this study

Background and Purpose. Individuals with cystic fibrosis (CF) have large amounts of infected mucus in their lungs, which causes irreversible lung tissue damage. Although patient-administered positive expiratory pressure (PEP) breathing has been promoted as an effective therapeutic modality for removing mucus and improving ventilation distribution in these patients, the effects of PEP on ventilation distribution and gas mixing have not been documented. Therefore, this preliminary investigation described responses in distribution of ventilation and gas mixing to PEP breathing for patients with moderate to severe CF lung disease. Subjects and Methods. The effects of PEP breathing on ventilation distribution, gas mixing, lung volumes, expiratory airflow, percentage of arterial blood oxyhemoglobin saturation (SpO₂), and sputum volume were studied in 5 patients with CF (mean age=18 years, SD=4, range=13–22) after no-PEP, low-PEP (10–20 cm H₂O), and high-PEP (>20 cm H₂O) breathing conditions. Single-breath inert gas studies and lung function tests were performed before, immediately after, and 45 minutes after intervention. Single-breath tests assess ventilation distribution homogeneity and gas mixing by observing the extent to which an inspired test gas mixes with gas already residing in the lung. Results. Improvements in gas mixing were observed in all PEP conditions. By 45 minutes after intervention, the no-PEP group improved by 5%, the low-PEP group improved by 15%, and the high-PEP group improved by 23%. Slow vital capacity increased by 1% for no PEP, by 9% for low PEP, and by 13% for high PEP 45 minutes after intervention. Residual volume decreased by 13% after no PEP, by 20% after low PEP, and by 30% after high PEP. Immediate improvements in forced expiratory flow during the middle half of the forced vital capacity maneuver (FEF_25%–75%) were sustained following high PEP but not following low PEP. Discussion and Conclusion. This study demonstrated the physiologic basis for the efficacy of PEP therapy. The results confirm that low PEP and high PEP improve gas mixing in individuals with CF, and these improvements were associated with increased lung function, sputum expectoration, and SpO₂. The authors propose that improvements in gas mixing may lead to increases in oxygenation and thus functional exercise capacity.

Key Words: Airway clearance • Chest physical therapy • Cystic fibrosis • Gas mixing • Ventilation distribution

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				J. C Darbee, J. F Kanga, and P. J Ohtake Physiologic Evidence for High-Frequency Chest Wall Oscillation and Positive Expiratory Pressure Breathing in Hospitalized Subjects With Cystic Fibrosis Physical Therapy, December 1, 2005; 85(12): 1278 - 1289. [Abstract] [Full Text] [PDF]