Question

Which of the following relations is/are CORRECT in terms of various lung volume measurements?

• A. Vital capacity minus expiratory reserve volume equals inspiratory capacity.
• B. Vital capacity plus expiratory reserve volume equals inspiratory capacity.
• C. Total lung capacity equals the sum of inspiratory capacity and functional residual capacity.
• D. Functional residual capacity is the difference between expiratory reserve volume and residual volume.

Hint:

- Vital capacity represents the maximum air exhaled after maximum inhalation. - Functional residual capacity is always a sum of ERV and RV. - Total lung capacity can be expressed as \(TLC = IC + FRC\).

Answer 1

The Correct Option is A, C

Step 1: Recall lung volume definitions. \begin{itemize} \item Tidal Volume (TV): Volume of air inhaled/exhaled during normal breathing. \item Inspiratory Reserve Volume (IRV): Extra volume inhaled after normal inspiration. \item Expiratory Reserve Volume (ERV): Extra volume exhaled after normal expiration. \item Residual Volume (RV): Volume left after maximal expiration. \end{itemize} From these we define: \[ \text{Vital Capacity (VC)} = TV + IRV + ERV \] \[ \text{Inspiratory Capacity (IC)} = TV + IRV \] \[ \text{Functional Residual Capacity (FRC)} = ERV + RV \] \[ \text{Total Lung Capacity (TLC)} = VC + RV \] Step 2: Verify each option. - (A) \(VC - ERV = (TV + IRV + ERV) - ERV = TV + IRV = IC\). True. - (B) \(VC + ERV = (TV + IRV + ERV) + ERV = TV + IRV + 2ERV \neq IC\). False. - (C) \(TLC = VC + RV\). Also, \(IC + FRC = (TV+IRV) + (ERV+RV) = TV + IRV + ERV + RV = VC + RV = TLC\). True. - (D) FRC is the sum \(ERV + RV\), not the difference. False. Final Answer: (A) and (C)