Vagal Nerve Stimulation Assessed by the Diving Reflex: An Investigation Into Mechanisms of Asthma Death

Inclusion Criteria:

• Syncopal Asthmatics: Asthmatic patients with a history of syncope during asthmaexacerbations

• Normal Asthmatics: Asthmatic patients on BTS Step 3 treatment (LABA/ICS) with nohistory of syncope during exacerbations

• Normal volunteers: no history of airways disease or syncope

Exclusion Criteria:

• • Subjects who are pregnant, or have pacemakers in situ are excluded from this study.

• Subjects with significant cardiovascular disease are excluded from this study.

• Those who are non-English speakers and special groups (i.e. mentally ill,children under 16 years of age, and those suffering from dementia) will beexcluded.

• No test will be performed on any subject during an acute worsening of asthma orupper airway infection. If the subject has had an upper airway infection in thelast three weeks. Another appointment should be made unless the subject isunwilling to come back, in which case testing should continue. The number of dayselapsed since the end of the airway infection should be recorded.

• If the subject smokes: citric acid or capsaicin challenges must be performed atleast one hour after the last cigarette has been smoked.

• Subjects taking beta-blockers and calcium antagonists will be excluded from thisstudy. No beta agonists should be taken within 6 hours of starting this study.

• If the subject has taken any over the counter (OTC) cough mixture within the lasttwelve hours: If the subject is willing to come back another time for challengetesting, another appointment should be made. If the subject is unwilling toreturn another time, testing should proceed and the medication used recorded.

• If the subject has had any food or drink products containing caffeine or mentholwithin the last hour. If the subject is unwilling to wait for 1 hour beforestarting the test, the subject should return another time. If the subject isunwilling to return another time, testing should proceed and the medication usedrecorded.

• If the participant is currently involved in research, or within 3 months ofparticipation in any type of research, they will be excluded from this study.