Mark W Nagel1, Jason A Suggett 1 & Jolyon P Mitchell2
1 Trudell Medical International, 725 Baransway Drive, London, Ontario, N65 5G4, Canada
2 Jolyon Mitchell Inhaler Consulting Services Inc., 1154 St. Anthony Rd., London, Ontario, N6H 2R1, Canada
Summary
It has been claimed that an adequate lung dose should be received above a threshold pressure drop of 10 cm H2O with any DPI, based on the negative pressure generated by the patient’s inspiratory effort. We report first the validation of a volumetric flow sensor/recorder simulating adult inhalation in accordance with a standard sinus flow rate-time waveform. We then used this sensor as validated to record flow profiles from 5 patients with varying severity of COPD familiar with the Turbuhaler* DPI, inhaling from a placebo Turbuhaler*, representing a DPI having medium flow resistance. Maximum inspiratory pressures were 19.2, 11.5, 12.7, 33.3 and 50.0 cm H2O for patients A to E. In the laboratory, we recreated each inhalation profile via the breathing simulator-anatomical model oropharynx coupled to the mouthpiece of a Symbicort* Turbuhaler* DPI. The simulator was located distal to a microbial collection filter, positioned at the exit of a model adult oropharynx, to capture medication likely to have deposited at the carina and therefore potentially available for lung delivery. The corresponding mass of budesonide and formoterol components (n = 3 replicates, mean ± SD) recovered from the model mimicking these inspiratory flow rate-time profiles varied widely from 13.6 ± 3.3 to 35.3 ± 1.4 μg budesonide and from 0.7 ± 0.1, to 1.8 ± 0.1 μg formoterol. These findings highlight the value in discussion around what is an ‘adequate’ lung dose and what other factors, in addition to pressure drop, may be involved.
Key Message
This laboratory simulation re-created previously generated inhalation profiles from COPD patients to assess medication delivery from the same medium resistance DPI via a model oropharynx to a collection filter with highly variable outcomes that were related to inhalation duration and maximal inspiratory pressure.