Abstract
Background: pMDI inserts include the mouthpiece instruction: close around/hold firmly between the lips. The perfect seal for laboratory testing may not, however, be representative of patient use.
Aim: To determine gap-effects on salbutamol delivery from low (LR) and high resistance (HR), and breath-actuated (BA)/training pMDIs.
Methods: Sealed and 0.18cm2gap adapters, and modified actuators to mimic low and high pMDI resistances were made. The four combinations were tested with Ventolin® Evohaler® (+standard actuator=Control), using a Next Generation Impactor™ operated to pharmacopoeial standard. The effect of sealed, small and large gaps (0.18 and 0.45 cm2) on the activation flow rate of salbutamol Autohaler®, Easi-Breathe® and the pMDI trainer Trainhaler®+Flo-Tone® were tested using a 1L/min/step waveform generator (MH Custom Design & Mfg LC, USA).
Results: Pairwise comparisons of calculated lung dose % (stages 3-5, Table 1) indicated that resistance and gap significantly influenced lung dose; resistance more so. Activation flow rates were significantly larger (P<0.05) for gapped than sealed devices (Table 2).
Conclusion: The sealed-lips instruction particularly affected non-BA pMDI lung dose from low resistance devices, but is unlikely to be detectable clinically. The instruction is critical for BA devices, and may impact clinically where patients use both types of device. Sealed lips should remain the default instruction.
- © 2014 ERS
