Lung volumes and capacities, Functional residual capacity Helium dilution method
By ProfDr Samia Jawed Student spirometer. THE GRAPHICAL RELATIONSHIP AMONG VARIOUS LUNG VOLUME AND CAPACITIES. Spirogram What are the advantages of residual volume, FRC, dead space air? Clinical measurementsof specific volumes and capacities provide insights into lung function and origin of disease processes. These tests are screening and not diagnostic. The VC is the maximum volume of air that an individual can move in a single breath.
The most useful assessment of VC is to expire as quickly and forcefully as possible. This way we get timed vital capacity or forced vital capacity.(FVC). During the FVC maneuver ,volume of air exhaled in the first second is FEV1. From 0-20 years vital capacity increases
From years it remains stable if there is no pathology With more aging elasticity of lungs decreases and residual volume increases Pathology affects vital capacity Like neuromuscular disorders,lower motor neuron diseases,myasthenia gravis, kyphosis, scoliosis, Lung infections, collapse, pleural effusion, bronchial Asthma, emphysema, chronic Brochitis etc.
Males have more VC.Why? VC decreases in pregnancy and while lying down. Flow volume curves in different conditions Helium dilution method FRC and its measurement. What is the difference between hyperventilation, hyperpnoea, tachypnoea?