Mechanism of bronchoconstrictive effects of aerosolized buffered saline in asthmatics

Bronchoconstriction, measured by spirometry and body plethysmography, has been reported with deep breaths of air and of aerosolized buffered saline (ABS) (0.5% sodium chloride and phosphate buffer), in some stable asthmatics. To investigate the mechanisms of this phenomenon, we measured airway resistance (Raw) and functional residual capacity (FRC) in ten asthmatics after deep breaths of ABS, tidal breaths of ABS, tidal breaths of unbuffered normal saline (0.9% sodium chloride) and tidal breaths of 0.5% sodium chloride (ABS without phosphate) on different days. Raw and FRC increased with deep breaths and tidal breaths of ABS in all asthmatics, but not with tidal breaths of normal saline and unbuffered 0.5% sodium chloride. Thus the phosphate buffer rather than the hypoosmolarity of aerosolized buffered saline causes bronchoconstriction in asthmatics.