Question

What is the functional residual capacity if the expiratory reserve volume is 1100 mL, the residual volume is 1200 mL, and the tidal volume is 500 mL?

• A. 1200 mL
• B. 1600 mL
• C. 2300 mL
• D. 3200 mL

Answer 1

The correct option is C

2300 mL

The correct option is C.

Explanation of the correct option:

1. Functional residual capacity (FRC) refers to the volume of air that is left in the lungs after a typical exhalation process.
2. The FRC is about 3L in a normal person.
3. Expiratory reserve volume (ERV) is the maximum amount of extra air that can be forcefully expired after a normal expiration.
4. Tidal volume (TV) refers to the volume of air inhaled or exhaled in a normal breathing process.
5. Residual volume (RV) refers to the volume of air that is left after a forceful exhalation.

Calculation of FRC:

Step 1: Given Data

$$\begin{gathered} \mathrm{ERV}=1100\mathrm{mL} \\ \mathrm{RV}=1200\mathrm{mL} \\ \mathrm{TV}=500\mathrm{mL} \end{gathered}$$

Step 2: Applying the formula

Formula used: $\mathrm{FRC}=\mathrm{ERV}+\mathrm{RV}$

Step 3: Solving the equation

Given: $\mathrm{ERV}=1100\mathrm{mL}\mathrm{and}\mathrm{RV}=1200\mathrm{mL}$

$$\begin{gathered} \mathrm{FRC}=1100\mathrm{mL}+1200\mathrm{mL} \\ \mathrm{FRC}=2300\mathrm{mL} \end{gathered}$$

Final Answer: The functional residual capacity is 2300 mL.