Inspiratory flow rate and dynamic lung function in cystic fibrosis and chronic obstructive lung diseases.

STUDY OBJECTIVES The peak inspiratory flow rates (PIFRs) generated by cystic fibrosis (CF) and COPD patients through a range of clinically relevant resistances have not yet been reported (to our knowledge). The objectives of this study were to (1) explore a relevant range of resistive loads and address whether patients with stable CF and COPD can generate the PIFR sufficient to disperse dry-powder inhalants (DPI) and (2) determine whether the optimal inspiratory flow rate effective for delivery of aerosolized pharmacologic therapeutic agents can be attained with a comfort rating acceptable to subjects. DESIGN Prospective, controlled, subject-blinded study. SETTING Pulmonary function laboratory at the VA Palo Alto Health Care System. PATIENTS OR PARTICIPANTS Thirty-six subjects, including 12 healthy volunteers, 12 subjects with CF, and 12 subjects with COPD were studied. MEASUREMENTS Studies of dynamic lung function and PIFR without and with varying resistances were obtained at a single laboratory visit. RESULTS Dynamic lung function and PIFR varied inversely with the resistive load for all patient groups and did not correlate with the disease severity, as indicated by FEV1 of percent predicted. The average subjective comfort rating for any given resistive load was similar for subjects with CF and COPD. CONCLUSIONS These results support the conclusion that subjects with stable CF and COPD of varying severity can comfortably generate the necessary flow rates to operate new and currently available DPIs over a wide range of inspiratory resistances.