Effect of Fire Suppression and Emergency Duties on Vascular Function

Study Overview
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Brief Summary
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Firefighters are at increased risk of death from heart attacks when compared to other emergencyy service professionals whose jobs involve similar components such as emergency call-outs and shift work. In the largest analysis of cause of death amongst on-duty firefighters, firefighter deaths were classified according to the duty performed during the onset of symptoms or immediately prior to any sudden death. The majority of deaths due to a cardiovascular cause (i.e. heart attack) occurred during fire suppression whilst this activity represented a relatively small amount of a firefighters professional time. There was also a risk of death associated with other duties such as emergency non-fire response and physical exertion. The investigators hypothesize that participation in active fire-fighting duties impairs blood vessel function and increases blood clot formation when compared with non-fire-fighting activities. In this study, healthy career firefighters will be assessed after three periods of duty: fire-suppression, emergency response without fire suppression and following a sedentary shift. The investigators will take blood samples to measure platelet activity (platelets are the particles in blood that help blood clot) and will examine how blood clots outside of the body. The investigators will then perform studies placing small needles in the arm to assess blood vessel function following these duties. By undertaking this comprehensive assessment of blood, blood vessel and heart function the investigators hope to understand the mechanisms whereby the risk of a heart attack, fatal or otherwise, is posed throughout these distinct duties that firefighters undertake on a daily basis.

Official Title
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Effect of Fire Suppression and Emergency Duties on Vascular Function in Firefighters

Conditions
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Vascular Function, Atherothrombosis

Intervention / Treatment
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* Procedure: Forearm Vascular Study
* Procedure: Badimon Chamber


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Non-smoking healthy firefighters Exclusion Criteria: Current smoker History of lung or ischaemic heart disease Malignant arrhythmia Systolic blood pressure >190mmHg or <100mmHg Renal or hepatic dysfunction Previous history of blood dyscrasia Unable to tolerate the supine position Blood donation within the last 3 months Recent respiratory tract infection within the past 4 weeks Routine medication including aspirin and NSAIDs

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 60 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Fire suppression<br>Firefighters will attend for vascular assessments following a night shift where they have performed fire suppression | Procedure: Forearm Vascular Study<br>* Forearm venous occlusion plethysmography to measure forearm blood flow during intra-arterial infusion of the vasodilators Verapamil (10-100 µg/min), bradykinin (100-1000 pmol/min), sodium nitroprusside (2-8 µg/min) and Acetylcholine (5-20 µg/min).<br>* Other names: VP;Procedure: Badimon Chamber<br>* Ex-vivo assessment of thrombus formation using the Badimon Chamber<br>|
| Non-fire emergency duty<br>Firefighters will attend for vascular assessments following a night shift where they have had an emergency response without fire suppression eg. road traffic collision. | Procedure: Forearm Vascular Study<br>* Forearm venous occlusion plethysmography to measure forearm blood flow during intra-arterial infusion of the vasodilators Verapamil (10-100 µg/min), bradykinin (100-1000 pmol/min), sodium nitroprusside (2-8 µg/min) and Acetylcholine (5-20 µg/min).<br>* Other names: VP;Procedure: Badimon Chamber<br>* Ex-vivo assessment of thrombus formation using the Badimon Chamber<br>|
| Sedentary shift<br>Firefighters will attend for vascular assessments following a night shift where they have remained sedentary throughout the shift. | Procedure: Forearm Vascular Study<br>* Forearm venous occlusion plethysmography to measure forearm blood flow during intra-arterial infusion of the vasodilators Verapamil (10-100 µg/min), bradykinin (100-1000 pmol/min), sodium nitroprusside (2-8 µg/min) and Acetylcholine (5-20 µg/min).<br>* Other names: VP;Procedure: Badimon Chamber<br>* Ex-vivo assessment of thrombus formation using the Badimon Chamber<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Forearm blood flow measured by venous occlusion plethysmography in response to infused vasodilators |  | up to 12 hours after exposure | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Ex-vivo thrombus formation using the Badimon chamber |  | up to 12 hours after exposure | 
| Plasma t-PA and PAI concentrations following infusion of bradykinin |  | During forearm study, up to 12 hours after exposure | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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firefighters, myocardial infarction, endothelial function, thrombosis, fire suppression, non-fire emergency duty, sedentary shift