Leah-Jane Hopkins1, Riccardo Brini1, Marissa Gotsell1, Diego Copelli2 & Richard Friend1
1Chiesi Ltd, Units T1-T3, Bath Road industrial Estate, Bath Road, Chippenham, SN14 0AB
2Chiesi Farmaceutici SPA, Largo Francesco Belloli, 11a Parma, Italy
Summary
The cold freon effect is an involuntary response to a cold sensation hitting the throat. This can sometimes occur when administering a pressurised metered dose inhaler (pMDI). Plume temperature is typically measured using a plume temperature tester comprising of a dose collection tube with temperature probes sited at four set intervals. The probes are usually located in the centre of the plume tester, thereby measuring the temperature at the centre of the plume. The cold freon effect, if experienced by the patient, will be triggered by temperature at the edge of the plume. The aim of this study was to investigate the effect of the different probe locations on the plume temperature response.
Two different probe locations were identified. The first location is on the internal walls and the other, is in the centre of the plume tester tube. A difference in plume temperature was observed between probes positioned at the two locations described above. This temperature difference is greatest at the first two thermocouples (25mm and 50mm from the tester inlet). The effect is reduced at probes situated 75mm and 100mm from the tester inlet, which represents the distance between the device and the patient’s throat.
When testing plume temperature, the probe location plays a pivotal role in providing the most representative results. To understand the impact that plume temperature could have on a patient due to the cold freon effect, readings should be taken with the probes positioned on the sidewall of the plume tester apparatus.