Breathing pattern alterations with aerosolized buffered saline--effects of topical airway anesthesia

Bronchoconstriction, measured by spirometry and body plethysmography, may occur with inhalation of aerosolized buffered saline (ABS) (0.5% sodium chloride and phosphate buffer) in asymptomatic patients with bronchial asthma. To estimate the prevalence and mechanism of this phenomenon, we employed continuous non-invasive monitoring of the breathing pattern to estimate changes of end-expiratory level, minute ventilation and mean inspiratory flow, which may be more sensitive albeit less specific indicators of bronchoconstriction. We studied normal and asymptomatic asthmatic subjects before and after ABS inhalation. Deep breaths of ABS had no effect on the breathing pattern in normals, but in all of the asthmatics increases of end-expiratory level, minute ventilation, tidal volume and mean inspiratory flow lasted at least 15 minutes. On another day, prior topical airway anesthesia in the asthmatic subjects prevented the changes in breathing pattern after ABS inhalation. Thus analysis of the breathing pattern suggests that bronchoconstriction or irritation of vagal airway receptors after inhalation of aerosolized buffered saline occurs to a high degree in asymptomatic asthmatic subjects because changes in breathing pattern are prevented by prior airway anesthesia which probably inactivates vagal afferent pathways.