Study the following equations w.r.t. pulmonary volumes and capacities. The (-) indicates a minus sign.

• (a) TLC - (ERV + IRV + RV)
• (b) EC - ERV
• (c) VC - (ERV + IRV)
• (d) FRC - RV
• (e) IC - RV

How many of the above equations represent tidal volume?

• (1) Two
• (2) Three
• (3) Four
• (4) Five

To determine how many of the given equations represent tidal volume, we first need to understand what tidal volume (TV) is. Tidal volume is the amount of air inhaled or exhaled during normal breathing. Let's analyze each equation:

Equations Breakdown

• (a) TLC - (ERV + IRV + RV): This equation represents tidal volume because it simplifies to TV.
• (b) EC - ERV: This does not represent tidal volume.
• (c) VC - (ERV + IRV): This also simplifies to tidal volume.
• (d) FRC - RV: This does not represent tidal volume.
• (e) IC - RV: This simplifies to tidal volume as well.

Summary of Findings

From the analysis, equations (a), (c), and (e) represent tidal volume. Therefore, the answer is:

Three