Effect of age on the sensitivity of upper airway reflexes.

We have recorded the threshold concentration of inhaled ammonia vapour required to elicit reflex glottic closure (NH3TR) in 102 healthy, nonsmoking volunteers (39 female) aged 17-96 yr in order to assess the effect of age upon upper airway reflex sensitivity. A single measurement of sensitivity was made in each subject using a system delivering small concentrations of ammonia vapour for single intermittent breaths to the upper airway and recording glottic closure using an inspiratory pneumotachograph. We found a strong positive correlation between age and NH3TR, indicating a decrease in upper airway reflex sensitivity with increasing age.