REGIONAL PULMONARY FUNCTION STUDIED WITH XENON133 IN PATIENTS WITH BRONCHIAL ASTHMA*

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Abstract
Twelve patients with bronchial asthma in spontaneous or medically maintained remission have been studied by routine pulmonary function tests and the xenon133 technique. In spite of a somewhat wider scatter of data, the xenonl33 static distribution indexes for ventilation and perfusion in asthmatic subjects showed, in general, close agreement with the previously reported findings in normal subjects. In some cases, slight zonal abnormalities of the ventilation indexes after a single tidal breath indicated minor local reductions of ventilation. The perfusion distribution appeared to be normal. A development of the xenon133 technique is described whereby the time course of gas distribution during equilibration with a closed circuit can be followed over six lung zones simultaneously. In six of the twelve patients studied, the residual impairment of gas distribution was found to follow a zonal rather than a diffuse uniform pattern. The patients showing this defect had a significantly greater degree of impairment of forced expiratory volume, maximal mid-expiratory flow rate, and helium mixing efficiency than did those not showing this abnormality. These findings indicate that the residual ventilatory impairment in patients with bronchial asthma in remission must be seen as a zonal or possibly lobar phenomenon. Such regional ventilatory impairment does not seem to be accompanied by a corresponding reduction in perfusion.