Biology · Breathing and Exchange of Gases · NEET
A spirometer (spirometer/respirometer). The person breathes through a mouthpiece connected to the instrument, and it records how much air is moved in and out. NCERT says the pulmonary volumes and capacities 'can be estimated by using a spirometer,' which helps in clinical diagnosis of lung health.
No. Residual Volume (about 1100-1200 mL) is the air that stays in the lungs even after a forceful expiration. Since you can never breathe this air out through the tube, a spirometer cannot detect it. RV is measured by indirect methods (like helium dilution or body plethysmography), not simple spirometry. This single point is the most common NEET trap on this topic.
Any capacity that contains Residual Volume: Functional Residual Capacity (FRC = ERV + RV) and Total Lung Capacity (TLC = RV + ERV + TV + IRV). Because RV is unmeasurable by the spirometer, these two also cannot be found by it directly. Vital Capacity (VC), Inspiratory Capacity (IC) and Expiratory Capacity (EC) do NOT include RV, so they CAN be measured.
For NEET, treat them as the same instrument for measuring lung volumes. Spirometry is the test; the graph it produces is a spirogram. The exam expects you to know it is the tool used to estimate respiratory volumes and capacities for clinical diagnosis.
Reduced Vital Capacity or reduced volumes can signal disorders. For example, in emphysema the alveolar walls are damaged and elastic recoil falls, changing the volumes; in asthma the airways narrow. So measuring these values helps doctors detect and monitor respiratory disease — the practical reason NCERT links volumes to clinical diagnosis.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
To measure respiratory volumes (like Tidal Volume, IRV, ERV) and capacities (like Vital Capacity). NCERT states these can be estimated with a spirometer and used in clinical diagnosis of lung function.
Because Residual Volume is air trapped in the lungs that can never be breathed out, even after the most forceful expiration. A spirometer only records air that actually moves through the tube, so RV is invisible to it.
Functional Residual Capacity (FRC = ERV + RV) and Total Lung Capacity (TLC = RV + ERV + TV + IRV). Both contain RV, so both cannot be measured directly by a spirometer.
Yes. Vital Capacity (ERV + TV + IRV) does not include Residual Volume, so it can be measured directly by asking the person to breathe out fully after a maximum inspiration.
Yes, as a short factual and trap-based point: know it is the instrument for measuring volumes/capacities, and that RV, FRC and TLC cannot be measured directly by it. NEET often frames questions around which value the spirometer cannot read.
