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Comparison of High-Frequency Chest Wall Oscillation With Differing Waveforms for Airway Clearance in Cystic Fibrosis^*

^* From the Minnesota Cystic Fibrosis Center (Dr. Kempainen, Ms. Williams, and Ms. Hazelwood), Department of Medicine, University of Minnesota School of Medicine, Minneapolis, MN; Department of Pediatrics and Biomedical Engineering (Dr. Rubin), Wake Forest University School of Medicine, Winston-Salem, NC; and Center for Excellence in Pulmonary Biology (Dr. Milla), Department of Pediatrics, Stanford University School of Medicine, Stanford, CA.

Correspondence to: Carlos E. Milla, MD, Center for Excellence in Pulmonary Biology, Department of Pediatrics, Stanford University School of Medicine, 770 Welch Rd, Suite 350, Stanford, CA 94304; e-mail: cmilla{at}stanford.edu

Abstract

Background: High-frequency chest wall oscillation (HFCWO) is commonly used by cystic fibrosis (CF) patients for airway clearance. The primary objective of this study was to determine whether the use of a newer HFCWO device that generates oscillations with a triangular waveform results in greater sputum production than a commonly used device that generates oscillations with a sine waveform.

Methods: This was a controlled, randomized, double-blind, crossover study. Fifteen clinically stable, adult CF patients participated. Patients performed airway clearance with each device once and at matched oscillation frequencies and pressures. All sputum produced during each session was collected. Patients completed pulmonary function tests before and after each session, and rated the comfort of the two devices.

Results: Mean sputum wet and dry weight produced during sine waveform and triangular waveform HFCWO sessions did not differ (p = 0.11 and p = 0.2, respectively). Mean changes in FEV₁ and FVC following HFCWO therapy were also comparable (p = 0.21 and p = 0.56, respectively). However, there was a significant reduction in air trapping by residual volume/total lung capacity ratio following triangular waveform HFCWO (p = 0.01). In addition, in vitro cough transportability was 10.6% greater following therapy with the triangular waveform device (p = 0.05). Patients perceived the two devices as equally comfortable (p = 0.8).

Conclusions: Single-session sputum production is comparable with sine and triangular waveform HFCWO devices. Longer term comparisons are needed to determine whether sustained use of the devices results in clinically important differences in outcomes.

Registered at: clinicaltrials.gov (NCT 00308958).

Key Words: airway clearance techniques • bronchial drainage • cystic fibrosis • high-frequency chest wall oscillation