The sum of residual volume and expiratory reserve volume is:

Appeared in: NVS- 2025

Explanation

Functional Residual Capacity (FRC) is defined as the volume of air remaining in the lungs at the end of a normal, passive expiration.
It is calculated by adding the Expiratory Reserve Volume (ERV) and the Residual Volume (RV).
FRC represents the equilibrium point where the outward elastic recoil of the chest wall is balanced by the inward elastic recoil of the lungs.
This volume of air acts as a crucial buffer, preventing drastic fluctuations in alveolar oxygen and carbon dioxide levels with each breath.

Option A: Vital Capacity is the total amount of air that can be forcibly exhaled after a maximal inhalation, not the air remaining after a normal breath.
Option B: Total Lung Capacity is the entire volume of air the lungs can possibly hold, including the air taken in during a maximal inhalation.
Option D: Inspiratory Capacity is the maximum amount of air that can be inhaled starting from the end of a normal exhalation.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Definitions and components of pulmonary lung capacities as background academic context rather than a clinical decision trigger.
FRC is a key parameter in assessing respiratory function. A decreased FRC, seen in conditions like obesity, ascites, or restrictive lung diseases (e.g., fibrosis), can lead to airway closure and impaired gas exchange.
An increased FRC is a hallmark of obstructive lung diseases like emphysema and chronic bronchitis, where air trapping occurs due to loss of elastic recoil or airway obstruction.
In critical care, nurses manage ventilator settings, particularly Positive End-Expiratory Pressure (PEEP), to optimize a patient's FRC, which helps improve oxygenation and prevent ventilator-induced lung injury.

How to Approach the Question

First, identify the keywords in the question: 'sum', 'residual volume', and 'expiratory reserve volume'.
This is a factual recall question requiring knowledge of respiratory physiology definitions.
Recall the definitions of the four main lung capacities: Vital Capacity, Total Lung Capacity, Functional Residual Capacity, and Inspiratory Capacity.
Mentally formulate the equation for each capacity. For example, FRC = ERV + RV.
Match the combination given in the question ('Residual Volume + Expiratory Reserve Volume') to its corresponding capacity.
Select the option that correctly names this combination.

Concept Tested & Keywords

QNTbPChxXn5xq_mo6ORtVb

E6 Physiology Guyton 4SAE Part 2A p. 56-58

Practise the full NVS- 2025

Attempt every question from this paper in a timed mock, then review the full solution for each one.