STANDARDIZATION OF INHALATION PROVOCATION TESTS - 2 TECHNIQUES OF AEROSOL GENERATION AND INHALATION COMPARED

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Abstract
Comparison of methods of aerosol generation and inhalation is required to improve standardization of inhalation provocation tests. Two widely used methods were compared in 10 asthmatics, by measuring the dose and distribution of radiolabeled aerosol deposited in the throat and lung, and the provocation concentration of inhaled histamine required to reduce the FEV1 [1 s forced expiratory volume] by 20% (PC20). In 1 method aerosol was generated by a Wright nebulizer and inhaled by tidal breathing for 2 min. In the other aerosol was generated by a DeViibiss 646 nebulizer attached to a dosimeter, and was inhaled by 5 inspiratory capacity breaths. The measurements with each method were repeated once to determine the reproducibility of results. Both methods deposited the same dose in the lung, but the distribution of the dose was different; the dosimeter method deposited more aerosol in the throat and central airways. The PC20 obtained with each method was the same. The reproducibility of all measurements in the same subject was similar. The lung dose deposited by each method in different subjects varied to the same degree. Bronchial response to inhaled histamine can be measured as reliably, using a nebulizer and tidal breathing, as by a more complex dose-metering device. When the methods are regulated as described, the PC20 will have the same clinical significance.