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Study Title and Description

Acute effects of caffeine and tobacco on arterial function and wave travel.



Key Questions Addressed
1 For [population], is caffeine intake above [exposure dose], compared to intakes [exposure dose] or less, associated with adverse effects on cardiovascular outcomes?
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Primary Publication Information
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TitleData
Title Acute effects of caffeine and tobacco on arterial function and wave travel.
Author J Swampillai,F Rakebrandt,K Morris,CJ Jones,AG Fraser,
Country
Year 2006
Numbers

Secondary Publication Information
There are currently no secondary publications defined for this study.


Extraction Form: Cardiovascular Design
Design Details
Question... Follow Up Answer Follow-up Answer
What outcome is being evaluated in this paper? Cardiovascular
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What is the objective of the study (as reported by the authors)? The aim of this study was to investigate the acute haemodynamic effects of changes in arterial stiffness and wave travel induced by caffeine and tobacco on left ventricular loading in healthy subjects.
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Provide a general description of the methods as reported by the authors. Information should be extracted based on relevance to the SR (i.e., caffeine related methods) All the study subjects were healthy volunteers with no history of cardiovascular disease and none took any regular medication. They abstained from caffeine, nicotine, food and alcohol for 12 h before each study. The effects of caffeine were studied in 17 subjects (eight men, nine women; aged 42 +/- 13 years) and compared with 10 controls (five men, five women; aged 42 +/- 13 years). All the subjects and controls were non-smokers and regular caffeine drinkers (> 100 mg/day). After baseline investigations, the subjects took 100 mg caffeine in tablet form with 30 mL of water, while controls took 30 mL of water alone. Arterial stiffness and wave intensity were re-measured 60 min later. Non-invasive vascular studies were performed with a SSD 5500 ultrasound machine (Aloka, Tokyo, Japan) using a 7·5-MHz linear array probe incorporating a 5-MHz Doppler transducer. All studies were carried out in a darkened, quiet room with the ambient temperature maintained at 23oC. Subjects rested supine for 10 min before the baseline scan and a single observer recorded all measurements. The longitudinal view of the right common carotid artery 1 cm proximal to the carotid bulb was used for standard measurements. The change in vessel diameter was calculated using high-resolution on-line wall tracking. Once a suitable image was obtained and the cursors set as above, a 20-s recording was taken and stored on a computer for later off-line analysis. After calibration, the computer calculated the pressure within the vessel from its change in diameter and the Doppler measured the velocity of blood flow within the artery. Arterial pressure waveforms were obtained by measuring diameter change within the common carotid artery using wall-tracking and calibrating peak and bottom values with systolic and diastolic blood pressure measured with sphygmomanometry. Using both pressure and velocity, the wave intensity was calculated and displayed in graphical form using the continuous electrocardiogram as a time reference. Blood pressure (BP) was recorded in the upper right arm immediately before each scan (Omron 750CP; Omron, Kyoto, Japan) and the electrocardiogram was continuously monitored. Wave intensity was calculated as [(dP/dt) x (dU/dt)], where dP/dt is the change in arterial pressure and dU/dt is the change in velocity of arterial blood flow. Changes in arterial pressure were estimated from changes in carotid arterial diameter, calibrated by measured arterial pressure. The initial positive peak of wave intensity represented a forward compression wave (FCW) produced during early systole which accelerated the aortic flow and increased the pressure. The second peak in late systole was a forward expansion wave (FEW) which decelerated the flow and closed the aortic valve. In mid-systole, the negative net wave intensity represents backward travelling waves reflected towards the heart from the periphery (wave reflections, WR). Pressure-velocity loops in early systole were obtained using customised wave intensity software (Matlab®; The Math Works, Natick, MA) by an application of the water-hammer equation. The beta index is a measure of local arterial stiffness represented by: β = ln{(Ps/Pd)/[(Ds−Dd)/Dd]}where, Ps and Pd are systolic and diastolic blood pressure, respectively, and Ds and Dd are the maximum and minimum arterial diameters measured by wall tracking of the intima-media borders of the carotid artery. The Peterson’s pressure-strain elastic modulus (epsilon, Ep) of a vessel is another measure of local arterial elasticity calculated as Ep = [(Ps−Pd)/(Ds−Dd)] x Dd. Data were analyzed using SPSS software, version 11 (SPSS Inc, Chicago, IL). Values are presented as means +/- SD. The mean values were compared between interventions and within each group using Student’s paired t-test and P < 0·05 was considered statistically significant.
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How many outcome-specific endpoints are evaluated? 3
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What is the (or one of the) endpoint(s) evaluated? (Each endpoint listed separately) Blood pressure (SBP and DBP)
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List additional health endpoints (separately). 2 Heart rate
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List additional health endpoints (separately).3 Aortic stiffness (forward compression wave [FCW], forward expansion wave [FEW], wave reflections [WR], beta [beta index of stiffness], epsilon [Peterson's pressure-strain elastic modulus], wave speed [WS])
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List additional health endpoints (separately).4
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List additional health endpoints (separately).5
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List additional health endpoints (separately).6
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Clinical, physiological, other Physiological
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What is the study design? Controlled Trial
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Randomized or Non-Randomized? NCT
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What were the diagnostics or methods used to measure the outcome? Objective
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Optional: Name of Method or short description Non-invasive vascular studies were performed with a SSD 5500 ultrasound machine (Aloka, Tokyo, Japan) using a 7·5-MHz linear array probe incorporating a 5-MHz Doppler transducer. Blood pressure (BP) was recorded in the upper right arm immediately before each scan (Omron 750CP; Omron, Kyoto, Japan) .
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Caffeine (general) Caffeine (general)
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Coffee, Chocolate, energy drink, gum, medicine/supplement, soda, tea, other?
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Measured or self reported? Measured
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Children, adolescents, adults, or pregnant included? Adults
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What was the reference, comparison, or control group(s)? (e.g. high vs low consumption, number of cups, etc.) Non-exposed controls
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What were the listed confounders or modifying factors as stated by the authors? (e.g. multi-variable components of models.  Copy from methods) None
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What conflicts of interest were reported? No information provided
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Refid 17087778
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What were the sources of funding? No information provided
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Results & Comparisons

No Results found.