Regional lung function: physiology and clinical applications.

The current status of tests of regional lung function has been reviewed from the physiological and clinical standpoint. Recent technical innovations include the use of single photon and positron emission computerized tomography (SPECT and PET). For PET work, neon-19 (t 1/2 17 sec) has been introduced as a ventilation tracer, and fluorine-18 deoxyglucose as a marker of glucose metabolism. Indium-111 labelled neutrophils have been studied. Physiological measurements of the distribution of blood flow and ventilation are concentrating on non-gravitational influences such as the pattern of force generation by the respiratory muscles and vasomotor tone. Ventilation and perfusion imaging of the lung with the gamma camera has established itself as an essential screening test for the diagnosis of pulmonary embolic disease. Inhalation of a radio-labelled aerosol of small particle size (1 micron) may be an acceptable substitute for a radioactive gas ventilation scan. Mucociliary clearance has been investigated with radionuclide techniques. Measurements of regional lung water have been replaced by tracers sensitive to alterations of epithelial (inhaled 99Tcm-DTPA) or endothelial (i.v. 113Inm-transferrin) permeability. New techniques using positron emission tomography, such as measurements of extravascular lung density, regional ventilation (19Ne) and regional glucose metabolism (18F-deoxyglucose) have been discussed briefly.