What does the term 'respirable fraction' describe in aerosol therapy?

What does the term 'respirable fraction' describe in aerosol therapy?

• A. The portion of aerosol that deposits in the mouth
• B. The portion of aerosol in the size range typically 1-5 micrometers capable of reaching the lower respiratory tract
• C. The portion exhaled unchanged
• D. The total emitted dose

Answer: (B)

Respirable fraction refers to the part of the aerosol that is small enough to reach the lower respiratory tract. In practice, this means particles about 1 to 5 micrometers in diameter. These particles can bypass the mouth and trachea and deposit in the bronchioles and alveoli by mechanisms like sedimentation and diffusion. Larger particles tend to impact and deposit in the mouth-throat region, while very tiny particles may be exhaled without depositing. So the respirable fraction is the size-dependent portion of the dose that actually has the potential to reach the lungs, not the portion deposited in the mouth, not the portion exhaled unchanged, and not the total emitted dose.

Respirable fraction refers to the part of the aerosol that is small enough to reach the lower respiratory tract. In practice, this means particles about 1 to 5 micrometers in diameter. These particles can bypass the mouth and trachea and deposit in the bronchioles and alveoli by mechanisms like sedimentation and diffusion. Larger particles tend to impact and deposit in the mouth-throat region, while very tiny particles may be exhaled without depositing. So the respirable fraction is the size-dependent portion of the dose that actually has the potential to reach the lungs, not the portion deposited in the mouth, not the portion exhaled unchanged, and not the total emitted dose.