Question

What are the volumes and capacities that can and cannot be measured by spirometry?

Answer 1

The lung volumes that can be measured by spirometry are inspiratory reserve volume, tidal volume, expiratory reserve volume. It can also measure inspiratory capacity nd vital capacity as inspiratory capacity is a sum of inspiratory reserve volume and tidal volume, while vital capacity is the sum of inspiratory reserve volume, tidal volume and expiratory reserve volume.

Spirometer cannot measure residual volume as well as the functional residual capacity and total lung capacity as these require the measure of residual volume. These volumes must be calculated by methods such as gas dilution or body plethysmography. Spirometer measures the lung volumes and capacities by measuring the airflow in and out of the lungs and hence, residual volume cannot be measured.