Abstract
This study was undertaken to ascertain whether the use of a valved holding chamber (VHC) during bronchial provocation testing might increase lung deposition and repeatability of the test relative to the tidal breathing method. The 2-min tidal breathing results were compared to five inhalations from a VHC device in patients using the Pari-provoII nebulizer (MMD = 2.1mkm). Lung and mouth deposition, losses though the exhaled air and losses before aerosol delivery to the patient's mouth were measured in patients using a radiolabeled 99Tc-DTPA solution and gamma camera. The study revealed that lung deposition was 67% with the VHC method, and losses with exhaled air were 29% of the inhaled amount. The tidal breathing method resulted in lung deposition of 20.9 ± 3.4%, and losses with exhaled air were 77.5 ± 3.5%. Mouth deposition did not differ significantly between methods. Variability in lung deposition was 15.3% for the VHC and 32.0% for the tidal breathing method. In addition to greater lung deposition and reproducibility, the VHC method allows easier calculation of the inhaled dose.
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