Lung Volumes PDF

Anna Rees Lung Volumes Intended Identify the normal lung volumes with values obtained from spirometry, including TV, IRV, Learning ERV, VC, FRC, RV, IC and TLC, FEV1. Outcome Lung Volumes The gas held by the lungs can be thought of in terms of subdivisions, or specific lung...

Anna Rees Lung Volumes Intended Identify the normal lung volumes with values obtained from spirometry, including TV, IRV, Learning ERV, VC, FRC, RV, IC and TLC, FEV1. Outcome Lung Volumes The gas held by the lungs can be thought of in terms of subdivisions, or specific lung volumes. These volumes can be measured through pulmonary Loading… function testing, one of which is spirometry Lung Volume Trace Descriptions of Lung Volumes and Loading… Capacities Think – how easy is it to blow up a completely deflated balloon?  After breathing out, the lungs are not completely emptied of air. This is useful physiologically, as a completely deflated lung requires significantly more energy to inflate it than one in which the alveoli have not completely collapsed. Even following a maximum respiratory effort (forced expiration), some air remains within the lungs. This occurs because as the expiratory muscles contract during forced expiration, all the structures within the lungs (including the airways) are compressed by the positive intrapleural pressure. Consequently, the smaller airways collapse before the alveoli empty completely, meaning some air remains within the Residual lungs; this is known as the residual volume (RV). During normal breathing (quiet breathing), the lung volume oscillates between Volume and inhalation and exhalation. In quiet breathing, after the tidal volume has been expired: Functional Pressure outside the chest is equal to pressure inside the alveoli (i.e., atmospheric pressure). Elastic forces tending to collapse the lung are balanced by the elastic recoil Residual trying to expand the chest. This creates a subatmospheric (negative) pressure in the intrapleural space. Capacity The lung volume at this point is known as functional residual capacity (FRC). Both RV and FRC can be measured using nitrogen washout, helium dilution and plethysmography (NOT spirometry) Conclusion – check your learning Can you draw and label a lung volume trace? Can you define each lung volume and give a value for tidal volume? What is the physiological significance of residual volume?