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Inhaler technique, Dry powder inhaler, Aerosol delivery, Peak inspiratory flow rate


Health Rerearch Board Ireland


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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.


Medicine and Health Sciences


Jansen N Seheult, Simon Costello, Kee Chun Tee, Tariq Bholah, Hasan Al Bannai, Imran Sulaiman, Richard W Costello. Investigating the relationship between peak inspiratory flow rate and volume of inhalation from a Diskus™ Inhaler and baseline spirometric parameters: a cross-sectional study. SpringerPlus 2014;3:496

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Additional file..docx (231 kB)
Demographics and baseline lung function tests for patients by disease category. Table S2. Number of patients in each disease group with a DiskusTM PIFR greater than or equal to 60 L/min and less than 60 L/min. Results from Chi-squared test are shown. The null hypothesis is that the proportions of patients with a Diskus™ PIF value less than or equal to sixty is independent of their diagnosis.As the test statistic is greater than the critical value, we can reject the null hypothesis. Figure S1. Receiver Operating Characteristic Curve for spirometric PIFR versus binary Diskus™ PIFR based on threshold of 60 L/min. The solid line represents an AUC of 0.5. Figure S2. Receiver Operating Characteristic Curve for spirometric PIFR versus binary Diskus™ PIFR based on threshold of 30 L/min. The solid line represents an AUC of 0.5.