Albuterol metered dose inhaler performance under hyperbaric pressures.

Area of Science:

• Pharmacology
• Aerosol Science
• Hyperbaric Medicine

Background:

• Metered dose inhalers (MDIs) are crucial for delivering medications like albuterol.
• Understanding MDI performance under altered atmospheric pressures is important for specific patient populations.

Purpose of the Study:

• To investigate the effects of hyperbaric environments on albuterol MDI actuation weight, aerosol particle size, and particle number.
• To compare the performance of chlorofluorocarbon (CFC) and hydrofluoroalkane (HFA) powered MDIs with different canister types.

Main Methods:

• Albuterol MDIs (CFC, short HFA, long HFA) were tested in a multiplace hyperbaric chamber.
• Pressures ranged from 1 ATA (sea level) to 3 ATA (66 fsw).
• Weight change per actuation, aerosol particle size (geometric mean diameter), and particle number were measured.

Main Results:

• Weight per actuation decreased at 3 ATA for CFC and long HFA MDIs but not for short HFA MDIs.
• Nanoparticle size decreased with pressure for CFC and short HFA MDIs.
• Particle numbers significantly reduced at 3 ATA for CFC and long HFA MDIs (4-7% of 1 ATA), but less so for short HFA MDIs (26% of 1 ATA).

Conclusions:

• Albuterol MDI performance, including weight delivered and aerosol characteristics, is significantly affected by hyperbaric conditions.
• The impact of pressure varies depending on the MDI's propellant (CFC vs. HFA) and canister type (short vs. long).
• Short canister HFA MDIs demonstrated more consistent performance across tested pressures compared to CFC and long HFA MDIs.