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

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ClinicalTrials.gov Identifier: NCT02083029
Recruitment Status : Completed
First Posted : March 11, 2014
Last Update Posted : March 11, 2014
Sponsor:
Information provided by (Responsible Party):
Prof A H Morice, Hull University Teaching Hospitals NHS Trust

Brief Summary:
The investigators' hypothesis is that dysregulation of autonomic function, as revealed during a simulated dive reflex, may result in an attenuation of the heart rate response to a greater degree in asthmatics who collapse during exacerbations of asthma than that seen in healthy individuals and in asthmatics without a history of syncope. The investigators will test this by assessing autonomic function through a dive reflex protocol.

Condition or disease Intervention/treatment Phase
Asthma Syncope Procedure: Simulated dive reflex Not Applicable

Detailed Description:
Tests of autonomic function are notoriously difficult to evaluate. Here the investigators required a well validated test of the dynamic cardiovascular response to an abrupt stimulus and considered the diving reflex the most reliable and practical. In man, the diving reflex acts as a vestigial reflex aimed at conserving oxygen storage during apnoeic facial immersion. Facial immersion activates a vagally-induced bradycardia and a sympathetically activated alpha-adrenergic peripheral vasoconstriction and hypertension. There are two triggers of the diving reflex, facial immersion in water and breath hold, both of which can impact on heart rate attenuation. Facial immersion can be further delineated into exposure to cold, wetness and pressure.

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Study Type : Interventional  (Clinical Trial)
Actual Enrollment : 24 participants
Allocation: Non-Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)
Primary Purpose: Basic Science
Official Title: Vagal Nerve Stimulation Assessed by the Diving Reflex: An Investigation Into Mechanisms of Asthma Death
Study Start Date : January 2013
Actual Primary Completion Date : January 2014
Actual Study Completion Date : January 2014

Resource links provided by the National Library of Medicine

MedlinePlus related topics: Asthma Fainting

Arm Intervention/treatment
Experimental: Syncopal Asthmatic
All subject undergo simulated dive reflex, with 30s facial immersion and continuous HR and BP monitoring with Nexfin over a period of 6 minutes.
Procedure: Simulated dive reflex
All subjects undergo simulated dive reflex, with 30s facial immersion and continuous HR and BP monitoring with Nexfin over a period of 6 minutes.

Experimental: Non Syncopal Asthmatic
All subject undergo simulated dive reflex, with 30s facial immersion and continuous HR and BP monitoring with Nexfin over a period of 6 minutes.
Procedure: Simulated dive reflex
All subjects undergo simulated dive reflex, with 30s facial immersion and continuous HR and BP monitoring with Nexfin over a period of 6 minutes.

Experimental: Normal Volunteers
All subject undergo simulated dive reflex, with 30s facial immersion and continuous HR and BP monitoring with Nexfin over a period of 6 minutes.
Procedure: Simulated dive reflex
All subjects undergo simulated dive reflex, with 30s facial immersion and continuous HR and BP monitoring with Nexfin over a period of 6 minutes.




Primary Outcome Measures :
  1. Change in heart rate from baseline [ Time Frame: 2 minutes prior to facial immersion in water and in 10 second epochs continuously until 3 minutes after facial immersion ]
    Nexfin and ECG monitoring continuously measuring subject heart rate during dive protocol, over a period of 6 minutes. Beat to beat data is converted into mean HR per 10-second epoch and compared to a baseline value for each subject.


Secondary Outcome Measures :
  1. Change in blood pressure from baseline [ Time Frame: 2 minutes before facial immersion and continuously throughout dive protocol, over a period of 6 minutes ]
    Nexfin monitoring continuously measuring subject blood pressure (systolic, diastolic and mean arterial pressure) during dive protocol, over a period of 6 minutes. Beat to beat data is converted into mean blood pressure values per 10-second epoch and compared to a baseline value for each subject



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Ages Eligible for Study:   18 Years to 85 Years   (Adult, Older Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   Yes
Criteria

Inclusion Criteria:

  • Syncopal Asthmatics: Asthmatic patients with a history of syncope during asthma exacerbations
  • Normal Asthmatics: Asthmatic patients on BTS Step 3 treatment (LABA/ICS) with no history 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 be excluded.
    • No test will be performed on any subject during an acute worsening of asthma or upper airway infection. If the subject has had an upper airway infection in the last three weeks. Another appointment should be made unless the subject is unwilling to come back, in which case testing should continue. The number of days elapsed since the end of the airway infection should be recorded.
    • If the subject smokes: citric acid or capsaicin challenges must be performed at least one hour after the last cigarette has been smoked.
    • Subjects taking beta-blockers and calcium antagonists will be excluded from this study. 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 last twelve hours: If the subject is willing to come back another time for challenge testing, another appointment should be made. If the subject is unwilling to return another time, testing should proceed and the medication used recorded.
    • If the subject has had any food or drink products containing caffeine or menthol within the last hour. If the subject is unwilling to wait for 1 hour before starting the test, the subject should return another time. If the subject is unwilling to return another time, testing should proceed and the medication used recorded.
    • If the participant is currently involved in research, or within 3 months of participation in any type of research, they will be excluded from this study.

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT02083029


Locations
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United Kingdom
Hull Clinical Trials Unit, Respiratory academic department
Cottingham, Yorkshire, United Kingdom, HU16 5JQ
Sponsors and Collaborators
Hull University Teaching Hospitals NHS Trust
Investigators
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Principal Investigator: Alyn Morice, MD Head Cardiorespiratory Studies Hull York Medical School University of Hull Castle Hill Hospital Cottingham
Publications automatically indexed to this study by ClinicalTrials.gov Identifier (NCT Number):
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Responsible Party: Prof A H Morice, Head Cardiorespiratory Studies Hull York Medical School University of Hull Castle Hill Hospital Cottingham, Hull University Teaching Hospitals NHS Trust
ClinicalTrials.gov Identifier: NCT02083029    
Other Study ID Numbers: CTU070813
First Posted: March 11, 2014    Key Record Dates
Last Update Posted: March 11, 2014
Last Verified: March 2014
Keywords provided by Prof A H Morice, Hull University Teaching Hospitals NHS Trust:
Asthma
Death
Mechanism
Syncope
Dive reflex
Additional relevant MeSH terms:
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Asthma
Syncope
Bronchial Diseases
Respiratory Tract Diseases
Lung Diseases, Obstructive
Lung Diseases
Respiratory Hypersensitivity
Hypersensitivity, Immediate
Hypersensitivity
Immune System Diseases
Unconsciousness
Consciousness Disorders
Neurobehavioral Manifestations
Neurologic Manifestations
Nervous System Diseases