Predictors of Peak Inspiratory Flow Rate (PIFR) in Advanced COPD.

SESSION TYPE: New Insights into COPDPRESENTED ON: Monday, October 22, 2012 at 04:00 PM - 05:30 PMPURPOSE: Clinical efficacy of dry-powder inhalers (DPIs) in COPD is predicated on adequate de-aggregation of drug pellets into respirable particles by inspiratory flow generated through a delivery device. Peak inspiratory flow rate (PIFR) ≥60 l/min against the internal resistance (resist) of a DPI is optimal. In a previous study, we found that 37 of 200 (18.5%) patients exhibited PIFR <60 l/min against the simulated resistance of the Diskus® device (PIFRresist). This study was conducted to identify factors that predicted PIFRresist.METHODS: PIFRresist was measured in 204 patients (113 women, 93 men) with advanced COPD (FEV1 ≤50% predicted) using an In-Check DIAL® (Clement Clerke International, Ltd; Harlow, UK). The In-Check DIAL® accurately replicates the internal resistance of specific inhaler devices. Spirometric and anthropometric data were collected.RESULTS: Data are presented as means and standard deviations. Subject age was 70.1±6.9 years. Percent-predicted FEV1 (PFEV1) and percent-predicted FVC (PFVC) were 37.1±8.5% and 74.8±16.5%, respectively. PIFRresist measurements were 65.9±16.8 l/min and 78.5±17.3 l/min for women and men, respectively. Multivariate regression analysis demonstrated that age, gender, height, PFVC, and percent-predicted inspiratory capacity (PIC) yielded an R2-adjusted of 0.357 with PIFRresist as the dependent variable and a significance level <0.05 for stepwise entry of variables. Zero-order coefficients for each of these terms were -0.27, 0.35, 0.40, 0.37, and 0.36, respectively. Weight and PFEV1 were not accepted into the regression model.CONCLUSIONS: In patients with advanced COPD, approximately 36% of the variance in PIFRresist was explained by age, gender, height, PFVC, and PIC. Future evaluations of PIFRresist in patients with advanced COPD should consider these variables.CLINICAL IMPLICATIONS: 1) Patients with advanced COPD may not derive optimal therapeutic benefit from a bronchodilator delivered by DPI device if PIFRresist is <60 l/min; 2) When assessing efficacy of bronchodilator therapy administered by DPI device, health care providers should consider specific patient characteristics, including older age, female gender, shorter stature, and reduced lung volumes (PFVC and PIC).DISCLOSURE: The following authors have nothing to disclose: Alex Gifford, Laurie Waterman, Joseph Ward, Louis Milanesi, Donald Tomlinson, Donald MahlerNo Product/Research Disclosure InformationDartmouth-Hitchcock Medical Center, Section of Pulmonary and Critical Care Medicine, Lebanon, NH.