Question

To determine the effect of breath holding on the deposition of particles, the sedimentation efficiency, S, is defined as

• A. S = (Distance the particle falls during breath holding) (Mean regional airway diameter)
• B. S = (Distance the particle falls during breath holding) × (Half the mean regional airway diameter)
• C. S = (Distance the particle falls during breath holding) + (Twice mean regional airway diameter)
• D. S = (Distance the particle falls during breath holding) - (Mean regional airway diameter)

Answer 1

The Correct Option is A

To solve this question, we need to understand what is being asked regarding the particle deposition during breath holding and how it relates to the sedimentation efficiency, \( S \). The correct formula for \( S \) must logically relate the distance a particle falls during breath holding and the regional airway dimensions.

Let's examine the given options one by one: 

1. \(S = (\text{Distance the particle falls during breath holding}) \times (\text{Mean regional airway diameter})\)
2. \(S = (\text{Distance the particle falls during breath holding}) \times \left(\frac{1}{2} \times \text{Mean regional airway diameter}\right)\)
3. \(S = (\text{Distance the particle falls during breath holding}) + (2 \times \text{Mean regional airway diameter})\)
4. \(S = (\text{Distance the particle falls during breath holding}) - (\text{Mean regional airway diameter})\)

The correct approach requires understanding how the deposition of particles is influenced by both the falling distance and the airway diameter. Sedimentation efficiency is typically a product of these two factors because the effectiveness of deposition increases with the length of the path available for sedimentation and the airway size.

Option 1 provides this product in a straightforward form:

\(S = (\text{Distance the particle falls during breath holding}) \times (\text{Mean regional airway diameter})\)

Let's reason through the other options:

• Option 2 reduces the diameter effect unnecessarily, which does not align with typical models of deposition.
• Option 3 introduces an addition term, which would not logically constitute efficiency as a product of relevant factors.
• Option 4 subtracts the diameter effect, which makes it less intuitive in modeling increase in deposition efficiency.

Thus, the most logical and straightforward model of sedimentation efficiency, \( S \), is option 1, where the distance and airway diameter are multiplicative factors.

Therefore, the correct answer is:

Option 1: \( S = (\text{Distance the particle falls during breath holding}) \times (\text{Mean regional airway diameter}) \)