Abstract
Drug delivery from a Dry Powder Inhaler (DPI) is dependent on the peak inspiratory flow rate (PIFR) generated. Currently available methods for estimating PIFR from most DPIs are limited and mainly rely on subjective assessment. We aim to show that spirometric and Diskus™ PIFR and Inspiratory Vital Capacity (IVC) are related to the underlying respiratory condition and that spirometric PIFR can be used to assess whether Diskus™ PIFR will be adequate when using this DPI. Healthy volunteers and patients with asthma, COPD, neuromuscular disease and non-respiratory disorders were recruited (n = 85). Demographics and baseline lung function by spirometry were recorded. Flow and volume readings were taken while patients used a Diskus™ DPI, housed in an airtight container connected to a spirometer. T-tests were performed to compare mean spirometric and Diskus™ PIFR/ IVC between groups. Stepwise regression analysis of Diskus™ PIFR versus spirometric PIFR, spirometric IVC, age, gender, condition, BMI, FEV1 and FVC was performed.The Diskus™ PIFR for the COPD and Neuromuscular Disease group was more than 10 L/min lower than the Healthy or Asthma groups (p < 0.05). The mean spirometric and Diskus™ IVC of the Healthy group was significantly (>0.75 L) higher than the mean for the other three groups (p < 0.05). Diskus™ PIFR was moderately correlated with spirometric PIFR and age (Adjusted R2 = 0.58, p < 0.0001). PIFR generated using a Diskus™ DPI is dependent on the underlying disease and age. A spirometric PIFR of less than 196 L/min should prompt further investigation into the suitability of a patient for a Diskus™ DPI, with possible consideration of alternate devices.Electronic supplementary materialThe online version of this article (doi:10.1186/2193-1801-3-496) contains supplementary material, which is available to authorized users.
Highlights
Inhaled bronchodilators and steroids have been the mainstay of treatment of obstructive airways disease for at least 20 years (Hanania et al 2012)
The mean spirometric peak inspiratory flow rate (PIFR) was significantly lower for the chronic obstructive pulmonary disease (COPD) and Neuromuscular disease groups compared to the Asthma or Healthy/ Non-respiratory condition groups (p ≤ 0.001)
The DiskusTM PIFR for the COPD and Neuromuscular Disease groups was more than 10 L/min lower than the Healthy or Asthma groups and was significantly lower than 60 L/min (p < 0.05)
Summary
Inhaled bronchodilators and steroids have been the mainstay of treatment of obstructive airways disease for at least 20 years (Hanania et al 2012). Plavec et al investigated the proportion of patients with asthma or chronic obstructive pulmonary disease (COPD) with significant broncho-obstruction who do not have inspiratory flows necessary for the adequate use of dry powder inhaler (DPI) devices DiskusTM and Turbuhaler. They found that significant proportions of patients with both asthma and COPD failed to achieve an appropriate flow rate for drug delivery and the proportion of patients who could not generate a high flow rate increased during exacerbations (Plavec et al 2012). Another study done by Al-Showair et al found that PIF from a DiskusTM inhaler was affected by the severity of COPD; there were small but significant improvements in the PIF achieved by some patients after training (Al-Showair et al 2007)
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