Effects of changes in lung volume on oscillatory flow rate during high-frequency chest wall oscillation

BACKGROUND: The effectiveness Of high-frequeny chest wall oscillation (HFCWO) in mucolysis and MUCOUS clearance is thought to be dependant on oscillatory flow rare (Fosc). Therefore, increasing Fosc during HFCWO may have a clinical benefit. OBJECTIVES: To examine effects Of Continuous Positive airway I-M-CSSUre (CPAP) on Fosc at two oscillation frequencies in healthy subjects and patients with airway obstrucrion. METHODS: Five health 7 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 cin H2O, 8 cm H2O and 10 cm H2O at frequencies of 10 Hz and 15 Hz) within a hody plethysmograph allowing Of Chan, CS ill lung volumc. Fosc was measured by reverse plethysmography using a 20 L isothermic chamber near the mouth. At the end of each randoiriized trial, an inspiratly 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 EFLV (r=0.7935, P < 0.05) in obstructed patients but not in heathy subjects (r=0.125, P=0.343). There were no significant differences in per, ceived comfort across the levels of CPAR CONCLUSIONS: Significant increases in Fosc with CPAP-induced increases in lung volume were Observed, suggesting that CPAP may be ueful as a therat)C36C adjunct In patients who have obstructive airway disease and who require HFCWO.