Paradoxical response to nebulised salbutamol in wheezy infants, assessed by partial expiratory flow-volume curves.

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Abstract
Lower airway responses to nebulised bronchodilators were studied in 18 chronically or recurrently wheezy infants, aged 3-15 months, by means of partial forced expiratory flow-volume manoeuvres performed with an inflatable jacket. Maximum flow at functional residual capacity (FRC) (VmaxFRC) was used as the index of intrathoracic airways function. Peak expiratory flow rate was also measured. Baseline airways resistance and lung volume were determined during quiet breathing in an infant whole body plethysmograph. Measurements were made on separate days before and after nebulised salbutamol 2.5 mg with nebulised saline as control. The results were paradoxical: there was no change in VmaxFRC after saline, but a significant decline in VmaxFRC was found after salbutamol. Peak expiratory flow remained unchanged. These observations suggest that under conditions of forced expiration intrathoracic airways function may be further impaired by nebulised bronchodilator treatment in wheezy infants. When nebulised bronchodilator drugs are used to treat severe airways obstruction in infancy, careful monitoring is essential.