Lung Function testing

Objectives
? explain common tests of lung function including simple spirometry ? describe the measurement of forced vital capacity (FVC) and forced expiratory volume in one second (FEV1.0)
? explain obstructive and restrictive patterns of spirometry
? explain expiratory and inspiratory flow volume loops and how they are affected by upper and lower airway obstruction
? describe in principle the measurement of residual volume and transfer factor ? explain the nitrogen washout curve
Lung Volumes

Simple spirometry
Vital capacity is particularly significant. Tables can be used to predict the
vital capacity of an individual of known age, height and sex
GOALS of spirometry ? To predict the presence of pulmonary dysfunction ?To know the functional nature of disease (obstructive or restrictive. ) ?To assess the severity of disease ?To assess the progression of disease ?To assess the response to treatment ?To identify patients at increased risk of morbidity and mortality, undergoing pulmonary resection.
Measurements Obtained from the FVC Curve • FEV1---the volume exhaled during the first second of the FVC maneuver
• FEF 25-75%---the mean expiratory flow during the middle half of the FVC maneuver; reflects flow through the small (<2 mm in diameter) airways
• FEV1/FVC---the ratio of FEV1 to FVC X 100 (expressed as a percent); an important value because a reduction of this ratio from expected values is specific for obstructive rather than restrictive diseases