title: Effects of changes in lung volume on oscillatory flow rate during high-frequency chest wall oscillation.
abstract: BACKGROUND
  The effectiveness of high-frequency chest wall oscillation (HFCWO) in mucolysis and mucous clearance is thought to be dependant on oscillatory flow rate (Fosc). Therefore, increasing Fosc during HFCWO may have a clinical benefit.
  
  
  OBJECTIVE
  To examine effects of continuous positive airway pressure (CPAP) on Fosc at two oscillation frequencies in healthy subjects and patients with airway obstruction.
  
  
  METHODS
  Five healthy subjects and six patients with airway obstruction underwent 12 randomized trials of HFCWO (CPAP levels of 0 cm H2O, 2 cm H2O, 4 cm H2O, 6 cm H2O, 8 cm H2O and 10 cm H2O at frequencies of 10 Hz and 15 Hz) within a body plethysmograph, allowing measurements of changes in lung volume. Fosc was measured by reverse plethysmography using a 20 L isothermic chamber near the mouth. At the end of each randomized trial, an inspiratory capacity manoeuvre was used to determine end-expiratory lung volume (EELV).
  
  
  RESULTS
  EELV increased significantly (P<0.05) with each level of CPAP regardless of oscillation frequency. Fosc also significantly increased with CPAP (P<0.05) and it was correlated with EELV (r=0.7935, P<0.05) in obstructed patients but not in healthy subjects (r=0.125, P=0.343). There were no significant differences in perceived comfort across the levels of CPAP.
  
  
  CONCLUSIONS
  Significant increases in Fosc with CPAP-induced increases in lung volume were observed, suggesting that CPAP may be useful as a therapeutic adjunct in patients who have obstructive airway disease and who require HFCWO.
authors.affiliation: Department of Medicine University of Alberta, Edmonton, Alberta.
authors.forename: Scott J
authors.initials: SJ
authors.lastname: Butcher
authors.forename: Michal P
authors.initials: MP
authors.lastname: Pasiorowski
authors.forename: Richard L
authors.initials: RL
authors.lastname: Jones
mesh_terms: D000328:Adult; D000368:Aged; D035641:Chest Wall Oscillation; D045422:Continuous Positive Airway Pressure; D005260:Female; D006801:Humans; D008176:Lung Volume Measurements; D008297:Male; D008875:Middle Aged; D010991:Plethysmography; D029424:Pulmonary Disease, Chronic Obstructive / Q000628:therapy*