title: Age-related reduction in 99Tcm-DTPA alveolar-capillary clearance in normal humans.
abstract: Age is known to reduce the efficacy of body organs and systems, even in the absence of disease. The alveolar-capillary clearance (ACC) rate is representative of the alveolar-capillary barrier's functional state. We studied 29 healthy non-smokers, who were selected after clinical and radiographic evaluation. The patients were divided into three groups based on age: Group I, < or = 30 years (n = 10); Group II, 31-55 years (n = 9); Group III, > or = 56 years (n = 10). Each patient inhaled 750 MBq 99Tcm-diethylenetriamine pentaacetate (99Tcm-DTPA) aerosol generated by a Venticis nebulizer (particles with a mean diameter of 1.1 microns) for 5 min. Forty frames of 30 s duration each were acquired and the ACC rates for the right and left lungs determined using a computer program. The mean ACC rates for the three groups were as follows: Group I, 1.31% min-1; Group II, 1.08% min-1; Group III, 0.76% min-1. The differences between Groups I and III (P < 0.001) and Groups II and III (P = 0.03) were shown to be significant. There was no significant difference between Groups I and II. Possible explanations for an age-related reduction in ACC rates include a reduction in the internal alveolar surface, the closure of the small airways, a reduction in the lung blood capillaries and a reduction in cardiac output. We conclude that there appears to be an age-related reduction in ACC rates in healthy non-smokers, even in the absence of clinically and radiographically detectable lung disease. However, larger studies are required.
authors.affiliation: Centre of Image Sciences and Medical Physics, Ribeirão Preto School of Medicine, University of São Paulo, Brazil.
authors.forename: F J
authors.initials: FJ
authors.lastname: Braga
authors.forename: J C
authors.initials: JC
authors.lastname: Manço
authors.forename: J F
authors.initials: JF
authors.lastname: Souza
authors.forename: E
authors.initials: E
authors.lastname: Ferrioli
authors.forename: J
authors.initials: J
authors.lastname: De Andrade
authors.forename: N
authors.initials: N
authors.lastname: Iazigi
mesh_terms: D000280:Administration, Inhalation; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D002196:Capillaries; D005260:Female; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging* / Q000254:growth & development / Q000502:physiology; D008297:Male; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D009330:Nebulizers and Vaporizers; D011650:Pulmonary Alveoli / Q000098:blood supply / Q000000981:diagnostic imaging / Q000502:physiology*; D011877:Radionuclide Imaging; D012016:Reference Values; D016284:Technetium Tc 99m Pentetate / Q000008:administration & dosage / Q000493:pharmacokinetics*
chemical_list: D016284:Technetium Tc 99m Pentetate