The Effect of Water Carbonation on Orthostatic Tolerance

Study Overview
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Brief Summary
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The primary purpose of this investigation is to determine whether water carbonation can improve orthostatic tolerance in healthy control volunteers. Orthostatic tolerance refers to the ability to maintain an adequate blood pressure when standing. In some individuals blood pressure can fall when standing, predisposing to dizzy spells or fainting episodes. Drinking water can boost blood pressure and making fainting episodes less likely. However, it is not clear whether the carbonation of the water has any further impact on the blood pressure response. This is important because it may be that carbonated water expands the stomach (gastric distension), provoking an increase in sympathetic activity. The increase in sympathetic nervous system activity boosts blood pressure. Resolving this question would have important implications for patients with syncope. This study will test whether carbonated water will have any further impact on blood pressure than the already known effect of non-carbonated water.

Detailed Description
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The primary purpose of this investigation is to determine whether water carbonation can improve orthostatic tolerance in healthy control volunteers. Orthostatic tolerance refers to the ability to maintain an adequate blood pressure when standing [1]. In some individuals blood pressure can fall when standing, predisposing to dizzy spells or fainting episodes [1]. Drinking water can boost blood pressure and making fainting episodes less likely [2-8]. However, it is not clear whether the carbonation of the water has any further impact on the blood pressure response [9,10]. This is important because it may be that carbonated water expands the stomach (gastric distension), provoking an increase in sympathetic activity. The increase in sympathetic nervous system activity boosts blood pressure. Resolving this question would have important implications for patients with syncope. This study will test whether carbonated water will have any further impact on blood pressure than the already known effect of non-carbonated water. Volunteers (n=25) will be asked to undergo a tilt test to assess cardiovascular reflex control and orthostatic tolerance (measured as time to presyncope, or near fainting, in minutes). It has been previously shown that this technique to be reproducible, reliable, and to have high sensitivity and specificity for differentiating persons with differing orthostatic tolerance, or for examining the effects of interventions aimed at improving orthostatic tolerance [4,6,11-18]. Volunteers will undergo this test on three separate days. On each day participants will be asked to drink a glass of water: either a 50ml drink of room temperature water (control condition), a 500ml drink of flat (non-carbonated) room temperature water, or a 500ml drink of carbonated room temperature water. The study will be conducted in a randomised, single-blind fashion. The investigator responsible for terminating the test will be blinded as to the water condition on each test day, rendering the study single blind. It will not be possible to blind participants as to the carbonation of the water, however, participants will not be informed as to the hypothesised impact of the water conditions.

Official Title
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The Effect of Water Carbonation on Orthostatic Tolerance

Conditions
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Orthostatic Hypotension, Syncope, Vasovagal Syncope

Intervention / Treatment
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* Other: 500mL carbonated water
* Other: 500mL still water
* Other: 50mL still water


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: healthy, English-speaking Exclusion Criteria: pregnancy or suspected pregnancy, history of cardiovascular disease, history of neurological disease, history of recurrent fainting (≥ 2 episodes of fainting with loss of consciousness in the prior 6 months)

Ages Eligible for Study
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Minimum Age: 19 Years
Maximum Age: 50 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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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Crossover Assignment
Interventional Model Description: Each participant will complete the test for every condition (3 tests per participant, order of treatment randomized).
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: 500mL carbonated water first, then 500mL of still water, then 50mL of still water<br>Participants will undergo this test on three separate days. On each day participants will be asked to drink a glass of water: either a 50mL drink of still water (control condition), a 500mL drink of still (non-carbonated) water, or a 500mL drink of carbonated water. In this arm of the study, participants will receive 500mL carbonated water on the first test day, 500mL still water on the second test day, then 50mL still water on the third day. | Other: 500mL carbonated water<br>* Drink 500mL carbonated water immediately prior to head-up tilt test<br>Other: 500mL still water<br>* Drink 500mL still water immediately prior to head-up tilt test<br>Other: 50mL still water<br>* Drink 50mL still water immediately prior to head-up tilt test<br>|
| Experimental: 500mL still water first, then 500 mL carbonated water, then 50mL still water<br>Participants will undergo this test on three separate days. On each day participants will be asked to drink a glass of water: either a 50mL drink of still water (control condition), a 500mL drink of still (non-carbonated) water, or a 500mL drink of carbonated water. In this arm of the study, participants will receive 500mL still water on the first test day, 500mL carbonated water on the second test day, then 50mL still water on the third day. | Other: 500mL carbonated water<br>* Drink 500mL carbonated water immediately prior to head-up tilt test<br>Other: 500mL still water<br>* Drink 500mL still water immediately prior to head-up tilt test<br>Other: 50mL still water<br>* Drink 50mL still water immediately prior to head-up tilt test<br>|
| Experimental: 500mL carbonated water first, then 50mL of still water, then 500mL of still water<br>Participants will undergo this test on three separate days. On each day participants will be asked to drink a glass of water: either a 50mL drink of still water (control condition), a 500mL drink of still (non-carbonated) water, or a 500mL drink of carbonated water. In this arm of the study, participants will receive 500mL carbonated water on the first test day, 50mL still water on the second test day, then 500mL still water on the third day. | Other: 500mL carbonated water<br>* Drink 500mL carbonated water immediately prior to head-up tilt test<br>Other: 500mL still water<br>* Drink 500mL still water immediately prior to head-up tilt test<br>Other: 50mL still water<br>* Drink 50mL still water immediately prior to head-up tilt test<br>|
| Experimental: 500mL still water first, then 50mL still water, then 500 mL carbonated water<br>Participants will undergo this test on three separate days. On each day participants will be asked to drink a glass of water: either a 50mL drink of still water (control condition), a 500mL drink of still (non-carbonated) water, or a 500mL drink of carbonated water. In this arm of the study, participants will receive 500mL still water on the first test day, 50mL still water on the second test day, then 500mL carbonated water on the third day. | Other: 500mL carbonated water<br>* Drink 500mL carbonated water immediately prior to head-up tilt test<br>Other: 500mL still water<br>* Drink 500mL still water immediately prior to head-up tilt test<br>Other: 50mL still water<br>* Drink 50mL still water immediately prior to head-up tilt test<br>|
| Experimental: 50mL still water first, then 500mL still water, then 500 mL carbonated water<br>Participants will undergo this test on three separate days. On each day participants will be asked to drink a glass of water: either a 50mL drink of still water (control condition), a 500mL drink of still (non-carbonated) water, or a 500mL drink of carbonated water. In this arm of the study, participants will receive 50mL still water on the first test day, 500mL carbonated water on the second test day, then 500mL carbonated water on the third day. | Other: 500mL carbonated water<br>* Drink 500mL carbonated water immediately prior to head-up tilt test<br>Other: 500mL still water<br>* Drink 500mL still water immediately prior to head-up tilt test<br>Other: 50mL still water<br>* Drink 50mL still water immediately prior to head-up tilt test<br>|
| Experimental: 50mL still water first, then 500mL carbonated water, then 500 mL still water<br>Participants will undergo this test on three separate days. On each day participants will be asked to drink a glass of water: either a 50mL drink of still water (control condition), a 500mL drink of still (non-carbonated) water, or a 500mL drink of carbonated water. In this arm of the study, participants will receive 50mL still water on the first test day, 500mL still water on the second test day, then 500mL still water on the third day. | Other: 500mL carbonated water<br>* Drink 500mL carbonated water immediately prior to head-up tilt test<br>Other: 500mL still water<br>* Drink 500mL still water immediately prior to head-up tilt test<br>Other: 50mL still water<br>* Drink 50mL still water immediately prior to head-up tilt test<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Orthostatic tolerance | The time, in minutes, to presyncope (near-fainting) after the initiation of head-up tilt | 0-50 minutes | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Tilt table, Osmopressor reflex, Gastropressor reflex