Iodine-123 metaiodobenzylguanidine (123I-MIBG) radioaerosol is of potential use in the investigation of the neuroadrenergic function of the lungs; however, before the method can be successfully employed the following issues need to be clarified: (1) Does the nebulization affect the radiochemical purity of 123I-MIBG? (2) Is the pulmonary distribution of inhaled 123I-MIBG homogeneous in normal subjects? (3) Does the pulmonary clearance of inhaled 123I-MIBG reflect the functional status of the neuroadrenergic system of the lungs? In this study we performed: (1) a chromatographic study of nebulized 123I-MIBG; (2) a quantitative evaluation of the lung distribution of 123I-MIBG radioaerosol in normal subjects as compared with that of technetium-99m diethylene triamine penta-acetic acid (99mTc-DTPA) and (3) an assessment of 123I-MIBG lung clearance both under control conditions and after pharmacologically induced beta-blockade, again compared with 99mTc-DTPA. For these purposes, eight normal subjects were divided randomly into an "MIBG group" and a "DTPA group" (four subjects each) and submitted to three scintigraphic studies each: a baseline study, and studies after the administration of a low (80 mg) and a high (160 mg) dose of propranolol. Radiochemical purity of nebulized 123I-MIBG ranged between 97.18% and 98.70%. The lung distribution of 123I-MIBG, as judged by the aerosol penetration index, was identical to that of 99mTc-DTPA under all study conditions. The 123I-MIBG clearance rate was slower than that of 99mTc-DTPA under baseline conditions (135+/-32 min vs 69+/-27 min, P<0.01) and increased significantly after propranolol administrations, while the 99mTc-DTPA clearance did not change. The following conclusions were drawn: (1) the nebulization does not affect the radiochemical purity of 123I-MIBG; (2) the lung distribution of 123I-MIBG is homogeneous in normal subjects; (3) the pulmonary clearance of 123I-MIBG reflects the functional status of the neuroadrenergic system of the lungs. Thus this scintigraphic method is suitable for research and perhaps for future clinical use.

E Ef ff fe ec ct ts s o of f a a f fi il lt te er r a at t t th he e m mo ou ut th h o on n p pu ul lm mo on na ar ry y f fu un nc ct ti io on n t te es st ts sL. Fuso*, D. Accardo*, G. Bevignani*, E. Ferrante**, A. Della Corte*, R. Pistelli* Effects of a filter at the mouth on pulmonary function tests. L. Fuso, D. Accardo, G. Bevignani, E. Ferrante, A. Della Corte, R. Pistelli. ERS Journals Ltd 1995. ABSTRACT: The aim of this study was to verify whether the increase of resistance to airflow using a filter at the mouth could determine significant systematic errors of measurement or change the diagnostic performance in a respiratory physiology laboratory.The effect of the new filter Spirobac (DAR Spa, Italy) was assessed on out-patients referred to our laboratory for routine functional evaluation. The following tests were performed: maximal expiratory flow-volume curve, plethysmographic lung volume and airway resistance, bronchodilator test, and methacholine challenge test. Each test was performed randomly, twice with the filter and twice without.Significant differences between measurements with and without filter were found for forced vital capacity, forced expiratory volume in one second, airway resistance, and specific airway conductance (sGaw). These differences were unrelated to the average values of the measurements, except for sGaw. The limits of agreement were within the range of intraindividual short-term repeatability for almost all of the function indices. The overall concordance between tests performed with and without filter was 78% for bronchodilator test and 53% for methacholine test. However, in all the cases but one, the concordance of the methacholine test was inside the short-term repeatability.We conclude that the filter Spirobac has a statistically significant effect on the results of some pulmonary function tests. However, this is not considered to be clinically significant, since the changes due to the filter were within the intraindividual variability of repeated measurements for almost all the function indices and no appreciable classification error was found in diagnostic tests.