Vagal sensitivity in intrinsic and allergic asthma

In 20 intrinsic and 25 allergic asthmatic patients with active disease, vagal baroreflex sensitivity was assessed by use of the phenylephrine test, and vagal blockade effects on airways were measured by the response to intravenous atropine. For a given phenylephrine-induced increase in blood pressure, bradycardia was more marked in patients with intrinsic asthma than in those with allergic asthma. Intravenous atropine caused a similar spirometric improvement in both groups. It is suggested that: 1) an inverse relationship exists between vagal sensitivity and the allergic state in asthma; 2) antigenic related stimulation modulated by a low vagal tone and non-antigenic related stimuli with high tone modulation result in similar cholinergic discharges.