title: Controlled delivery of krypton-81m boli in normal subjects: results and implications.
abstract: Interregional sequential filling potentially affects lung ventilation imaging, depending on the distribution of the tracer within the inspired volume. We investigated its importance quantitatively under near tidal breathing conditions in the upright lung using a short-lived radioactive tracer. Ten normal volunteers performed two runs of 900-ml breaths (from functional residual capacity) in which 100 ml of 81mKr boli were delivered "early" or "late" in inspiration, i.e., 50 ml or 450 ml volumetric depth. Apex-to-base gradients in the vertical profile were -106 +/- 22 (s.e.) counts/cm (early) and -187 +/- 24 (s.e.) counts/cm (late). Ratios of upper-to-lower regional ventilation (U/L) were 0.88 +/- 0.01 (s.e.) (early) and 0.81 +/- 0.01 (s.e.) (late). Simulations with a compartment model show that a simple pattern of sequential filling can by itself account for the experimental results observed. Control over 81mKr delivery can be important to physiologically accurate assessment of ventilation-perfusion matching. Controlled delivery techniques could also modify effectiveness and targeting of other inhaled agents including therapeutic aerosols.
authors.affiliation: Medical Physics Department, Royal Free Hospital and School of Medicine, London, United Kingdom.
authors.forename: S
authors.initials: S
authors.lastname: Verbanck
authors.forename: S
authors.initials: S
authors.lastname: Koneru
authors.forename: M
authors.initials: M
authors.lastname: Cohen
authors.forename: S W
authors.initials: SW
authors.lastname: Clarke
authors.forename: J E
authors.initials: JE
authors.lastname: Agnew
mesh_terms: D000280:Administration, Inhalation; D000328:Adult; D003198:Computer Simulation; D005541:Forced Expiratory Volume; D005652:Functional Residual Capacity; D006801:Humans; D007727:Krypton Radioisotopes / Q000008:administration & dosage*; D008168:Lung / Q000000981:diagnostic imaging*; D011877:Radionuclide Imaging; D012115:Residual Volume; D014109:Total Lung Capacity; D014692:Ventilation-Perfusion Ratio
chemical_list: D007727:Krypton Radioisotopes