title: Comparison of settings used for high-frequency chest-wall compression in cystic fibrosis.
abstract: BACKGROUND
  Cystic fibrosis (CF) patients commonly use a high-frequency chest-wall compression (HFCWC) device for airway clearance that generates oscillatory flow with a sine-wave configuration. Typical HFCWC settings combine a lower Vest inflation pressure setting (eg, 5 on the Vest's arbitrary 1-10 scale for the setting that controls the background pressure of the inflatable vest) with mid-range frequency (14-16 Hz) (lower-pressure/mid-frequency HFCWC).
  
  
  OBJECTIVE
  To determine whether HFCWC with higher pressure settings (6-10 on the Hill-Rom Vest's arbitrary 1-10 scale) combined with variable mid-frequencies (8, 9, and 10 Hz, plus 18, 19, and 20 Hz) (higher-pressure/variable-frequency HFCWC) results in greater sputum expectoration than lower-pressure/mid-frequency HFCWC.
  
  
  METHODS
  This was a controlled randomized crossover study. Sixteen clinically stable, adult CF patients participated. Patients performed airway clearance with HFCWC, once each with lower-pressure/mid-frequency HFCWC and higher-pressure/variable-frequency HFCWC, on separate occasions. All sputum produced during each session was collected. Patients completed pulmonary function tests before and after each session.
  
  
  RESULTS
  Median sputum wet weight was greater with higher-pressure/variable-frequency HFCWC than with lower-pressure/mid-frequency HFCWC (6.4 g, range 0.49-22.0 g, versus 4.8 g, range 0.24-15.0 g, P = .02). Dry sputum weight differences did not reach statistical significance (higher-pressure/variable-frequency HFCWC 0.20 g, range 0.009-0.62 g, lower-pressure/mid-frequency HFCWC 0.12 g, range 0.0001-1.0 g, P = .23). Higher-pressure/variable-frequency HFCWC and lower-pressure/mid-frequency HFCWC resulted in similar increases in FEV(1) (70 mL vs 90 mL, P = .21) and forced vital capacity (80 mL vs 80 mL, P = .94). Post-therapy sputum viscoelastic properties did not differ. Patients perceived the 2 regimens as equally comfortable and effective (P = .35 and P = .35, respectively).
  
  
  CONCLUSIONS
  In adult CF patients, single-session higher-pressure/variable-frequency HFCWC resulted in greater sputum expectoration by wet weight, but not other differences, compared to the commonly used lower-pressure/mid-frequency settings. Longer-term comparisons are needed in a larger, more diverse population to determine whether sustained use of the higher-pressure/variable-frequency settings results in clinically important differences in outcomes.
authors.affiliation: Department of Medicine, Hennepin County Medical Center, University of Minnesota School of Medicine, Mail Stop G-5, 701 Park Avenue, Minneapolis, MN 55415, USA. kempa001@umn.edu
authors.forename: Robert R
authors.initials: RR
authors.lastname: Kempainen
authors.forename: Carlos
authors.initials: C
authors.lastname: Milla
authors.forename: Jordan
authors.initials: J
authors.lastname: Dunitz
authors.forename: Kay
authors.initials: K
authors.lastname: Savik
authors.forename: Ann
authors.initials: A
authors.lastname: Hazelwood
authors.forename: Cynthia
authors.initials: C
authors.lastname: Williams
authors.forename: Bruce K
authors.initials: BK
authors.lastname: Rubin
authors.forename: Joanne L
authors.initials: JL
authors.lastname: Billings
mesh_terms: D000328:Adult; D035641:Chest Wall Oscillation / Q000295:instrumentation / Q000379:methods*; D018592:Cross-Over Studies; D003550:Cystic Fibrosis / Q000628:therapy*; D005260:Female; D006801:Humans; D008297:Male; D013183:Sputum; D016896:Treatment Outcome