title: Regional lung function in children: the accuracy of nitrogen-13 inhalation and infusion studies.
abstract: The assumptions made in 13N lung function tests in children with pulmonary or cardiac disorders have been examined. The index of lung function employed was the height/area (H/A) of the lung curves obtained following either bolus inhalation or infusion of 13N. Three aspects were considered: (1) the accuracy of H/A values with count rates obtained in typical patients; (2) the effect on perfusion H/A values of prolonged arrival of isotope in the lungs; and (3) the effect on perfusion H/A values of recirculation of isotope through the lungs due to a right-to-left intracardiac shunt. It was found that, for inhalation studies, the index H/A was sufficiently accurate to distinguish localised from generalised disease. For perfusion studies, prolonged arrival of isotope in the lungs caused a reduction in measured H/A values of up to 15%. In the presence of a right-to-left shunt recirculation of isotope could prevent the detection of a small, poorly-ventilated lung component. It is concluded that the use of 13N for measurement of ventilation/perfusion balance is not a sensitive method for monitoring the progress of generalised pulmonary disease.
mesh_terms: D002648:Child; D002675:Child, Preschool; D006801:Humans; D008168:Lung / Q000502:physiology* / Q000503:physiopathology; D008171:Lung Diseases / Q000503:physiopathology*; D009590:Nitrogen Radioisotopes; D014692:Ventilation-Perfusion Ratio
chemical_list: D009590:Nitrogen Radioisotopes