The effect of altitude on inhaler performance

Area of Science:

• Pharmaceutical technology
• Respiratory medicine
• Aerosol science

Background:

• Pressurized metered dose inhalers (pMDIs) and dry powder inhalers (DPIs) are crucial for delivering medication to the lungs.
• Inhaler performance can be affected by environmental factors, including altitude, which influences air density and pressure.
• Understanding these effects is vital for ensuring consistent therapeutic delivery across different geographical locations and altitudes.

Purpose of the Study:

• To investigate the impact of varying altitudes on the performance of selected pMDIs and DPIs.
• To quantify changes in in vitro lung dose, device resistance, shot weight, and spray duration under simulated high-altitude conditions.

Main Methods:

• Developed a specialized testing apparatus with the Alberta Idealized Throat to simulate consistent breathing patterns.
• Tested five pMDIs and two DPIs at four distinct altitudes (670m, 2450m, 3260m, 4300m).
• Employed gravimetric and chemical assays for in vitro lung dose determination; measured device resistance, spray duration, and shot weight.

Main Results:

• No significant alterations in the in vitro lung dose were observed for any of the tested pMDIs.
• pMDI shot weight and spray duration remained unaffected by altitude changes.
• DPI device resistance decreased with increasing altitude, correlating with ambient pressure; DPI lung dose was consistent at 4 kPa pressure drop, but one DPI showed reduced dose at baseline flow rates.

Conclusions:

• Pressurized metered dose inhalers demonstrate consistent lung dose delivery across tested altitudes.
• Dry powder inhaler resistance is significantly affected by altitude, though lung dose remains largely stable under standard operating conditions.
• Specific inspiratory flow rates may influence DPI performance at higher altitudes, warranting consideration for patient use in mountainous regions.