Lung volumes

Lung Physiology Workshop
LUNG VOLUMES

Muhammad Amin Ibrahim
KPJ Selangor Specialist Hospital, Shah Alam, Selangor, Malaysia

Lung volumes refer to the volume of air in the lungs at different phases of the respiratory cycle, which consist of movable and non-movable volumes. The later volumes cannot be measured directly using a spirometer. Determination of the non-movable volumes, namely fractional residual volume (FRV) and residual volume (RV) is more difficult as it is impossible to "completely '' breathe out. Therefore, measurement of these volumes has to be done via indirect methods such as radiographic planimetry, body plethysmography, closed circuit dilution (including the helium dilution technique) and nitrogen washout. Among these four methods, body plethysmography and nitrogen washout are the two most common clinical tests used in Malaysia. In this presentation, we will discuss the physical laws, indications/contra-indications and technical aspects of these two methods.