Adobe Systems
Department of Physiology, Faculty of Medicine, Masaryk University
1
Blood pressure
Physiology II – practice
Spring, weeks 7th-9th
Study materials were supported by the project: MUNI/FR/1474/2018

Adobe Systems
Department of Physiology, Faculty of Medicine, Masaryk University
2
Arterial blood pressure curve
̶Blood pressure (BP): pressure of blood on the vessel wall
(arterial BP – part of the energy of systole converted into lateral pressure on the vascular wall)
̶Mean arterial pressure (MAP): mean value of blood pressure in the inter-beat interval (IBI) –
integral of the BP curve; area above MAP = area below MAP
(MAP is an additional quantity, it is not the arithmetic mean of the systolic (SBP) and diastolic
(DBP) pressure values, because the duration of systole and diastole during the cardiac cycle is
different)
aproximation: MAP = DBP + 1/3 PP (PP = SBP – DBP)
̶Definition:
̶SBP (systolic BP)
maximal of BP in the inter-beat interval
̶DBP (diastolic BP)
minimal BP in the inter-beat interval
̶Attention: Values of SBP and DBP vary in
   different parts of the cardiovascular system
SBP
DBP
MAP
Inter-beat interval
PP
pulse pressure
Dicrotic notch

Adobe Systems
Department of Physiology, Faculty of Medicine, Masaryk University
3
Blood pressure
MAP is a function of cardiac output (CO) and total peripheral resistance
•SBP is determined mainly by CO
•DBP is determined mainly by TPR

̶
̶
Arterial blood pressure
(BP)
Total peripheral resistance
(TPR)
Heart rate
(HR)
Stroke volume
(SV)
 =
*
*
Cadiac output
(CO)

Adobe Systems
Department of Physiology, Faculty of Medicine, Masaryk University
4
Blood pressure regulation
̶Short-term – neural control, mainly baroreflex
̶Middle-term – hormonal regulation, renin-angiotensin-aldosterone system (RAAS)
̶Long-term – hormonal regulation of blood volume

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5
Short-term BP control – baroreflex
̶Cardiac branch of baroreflex:
̶Parasympathetic efferentation: rami cardiaci n. vagus to SA node - ↓ HR and cardiac contractility
̶Sympathetic efferentation: n.cardiaci to SA node - ↑ HR and cardiac contractility
̶Peripheral branch of baroreflex:
̶Only sympathetic efferentation: sympathetic vascular innervation (mainly of arterioles)
↑ BP → ↓ TPR due to vasodilation in peripheral circulation and vice versa (↑TPR due to
vasoconstriction)
̶
(notice: vasoconstriction of small arteries and arterioles, venoconstriction – blood
redistribution)
̶Autonomic nervous system:  sympathetic nerves (↑ BP, HR, SV, TPR) X parasympathetic nerves (↓ BP,
HR, SV, TPR)
̶Function: rapid regulation of BP via changes in HR and TPR
̶baroreceptors – sinus caroticus + sinus aorticus;  afferentation: n. vagus, n. glossopharyngeus

Adobe Systems
Department of Physiology, Faculty of Medicine, Masaryk University
6
Blood pressure changes
̶Short-term influences
̶blood volume – influence on cardiac output (bleeding, dehydration)
̶external pressure to the vessels – intrathoracic and intraabdominal pressure (cough, defecation,
childbirth, artificial ventilation)
̶position – orthostasis/clinostasis: redistribution of blood due to gravity
̶CNS – emotions, mental stress, …
̶physical exercise – BP changes depend on intensity, duration and type of exercise
̶heat (↓ TPR), cold (↑ TPR)
̶alcohol, medicaments,…
̶Long-term influences
̶age (the fastest changes during childhood and adolescence, in adults slow increase in SBP)
̶sex (men have higher BP)
̶genetics

Adobe Systems
Department of Physiology, Faculty of Medicine, Masaryk University
7
Methods of the arterial BP measurement
24-hour blood pressure monitoring
Photoplethysmografic (volume-clamp method, Peňáz)
Palpatory
(sphygmomanometer)
Auscultatory
(sphygmomanometer,
stethoscope)
Oscillometric
In practicals
Another methods:

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8
Basic principle: Laminar / turbulent flow
 (Korotkoff sounds in auscultatory method; oscillation in oscilometric method).
Reynolds number Re: predicts the transition from laminar to turbulent of flow
v: velocity of blood flow
S: area of vascular lumen (p.r2)
r: density of blood
h: viscosity of blood
     (lower in anemia)
S1 < S2 a v1≈ v2  → Re1 < Re2 → turbulent flow
laminar flow Re < 2000
turbulent flow Re > 3000
r1
r2
cuff
a. brachialis
laminar flow
turbulent flow
Re1
Re2
v1
v2
closely behind narrowing of the artery:

Adobe Systems
Department of Physiology, Faculty of Medicine, Masaryk University
9
Principles of BP measurement
Korotkoff sound
(auscultatory method)
Continually measured BP
Pressure in the cuff
Pressure oscillations in the cuff
(oscillometric method)
SBP
DBP
SBP
MAP
DBP
Blood flow in the artery

Adobe Systems
Department of Physiology, Faculty of Medicine, Masaryk University
10
Rules for BP measurement
̶Environment: pleasant room temperature, quiet surroundings
̶Position: the patient sits with his back leaning backwards, both legs are on the floor, forearm
rests on a surface
̶Reasonable cuff size, correct positioning at heart level
̶The measurement happens at rest and starts after 5 – 10 minutes of sitting down
̶Measurement by auscultatory method
̶Inflate the cuff to a pressure 30 mmHg higher than the pressure at which the radial pulse
disappeared
̶The pressure reduction rate in the cuff is 2 – 3 mmHg/s
̶The pressure value is determined with 2 mmHg accuracy
̶The BP should be measured 3 times at least five minutes apart and the final BP value is a mean
value of the last two measurements

Adobe Systems
Department of Physiology, Faculty of Medicine, Masaryk University
11
24-hour blood pressure monitoring
BP decrease during night: 10-15%
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120
140
100
80
60
[mmHg]
SBP
DBP
heart rate
awake
sleeping
blood pressure
hours

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method
advantages
disadvantages
measured value
auscultatory
•exact estimation of SBP/DBP
•easy, it doesn´t require electricity
•subjective, experience is necessary
•SBP/DBP from different IBI
SBP and DBP
oscillometry
•exact estimation of MAP
•automatic, fast
•BP can be measured by layman, cheap (home measurement)
•DBP/SBP is calculated (dependence on model, influenced by a shape of pulse wave)
•SBP/DBP from different IBI
•false values during arrhythmia
MAP, sometimes SBP
(it depends on a device)
24-hour BP monitoring
•BP record from whole day
•diagnosis of white-coat hypertension
•disruptive influence of measuring  (during sleeping)
•SBP/DBP from different IBI
BP is measured each
15–60 min
photople-thysmography (Peňáz)
•continual BP record
•possibility of beat-to beat SBP/DBP calculation (BP variability analysis)
•measurement on a finger, brachial BP is calculated
•expensive device
continual BP record

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Diagnosis of hypertension
̶Isolated systolic hypertension: SBP> 140 and DBP <90 mmHg
̶High normal BP – annual monitoring recommended
̶Home measurement to exclude white coat hypertension
̶Hypertension is diagnosed when:
̶average BP from 4–5 examinations is > 140/90 mmHg
̶BP during a home measurement repeatedly > 135/80 mmHg
̶mean BP from 24-hour monitoring is > 130/80 mmHg

Adobe Systems
Department of Physiology, Faculty of Medicine, Masaryk University
14
Changes in blood pressure during exercise
̶Increase in BP depends on the type, intensity and duration of the exercise
̶Sympathetic activation: changes in the cardiovascular system serve to satisfy the metabolic needs
of working muscle
̶Impact of exercise on blood pressure:
̶Increased cardiac output → ↑ SBP
̶Redistribution of blood in the body – metabolic vasodilation in muscle (increased blood flow in
the muscle), vasoconstriction in the GIT, skin and kidneys → maintaining or slight change in DBP
(depending on the extent of the TPR decrease)
̶Vasoconstriction in the skin is temporary, till thermoregulatory mechanisms dominate
̶DBP increases during isometric muscle work (e.g. weightlifting)
̶After exercise: decrease in BP to resting values or slightly lower values, the blood flow in the
muscle remains elevated until recovery
̶Recovery interval is determined by the parasympathetic tone (can be increased by training)

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In addition


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Boron and Boulpaep, Medical physiology

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Arteries – „garden“ analogy
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Heart
cardiac output
Carotids
perfusion pressure in the brain
Arteries, arterial BP
Resistance vessels
total peripheral resistance
The primary purpose of BP neural regulation is to maintain constant perfusion pressure in the
brain.
Baroreflex
-A decrease in arterial pressure leads to sympathetic activation → an increase in heart rate (and
cardiac output) and peripheral resistance
An increase in arterial pressure leads to activation of the parasympathetic nervous system → a
decrease in heart rate (and cardiac output) and, indirectly, in peripheral resistance

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Changes in cardiovascular system during exercise
•Muscles can take up to 80% of CO (cardiac output)
After the sudden termination of heavy exercise without slowing down – "bleeding out into the
muscle" – the heart has already decreased CO, but the vessels of the muscle are still dilated –
blood redistribution to the muscle – strong drop in BP – fainting
문 문호 개방 잠금 디자인 - Pixabay의 무료 이미지 Fototapeta Zavřené dveře • Pixers® • Žijeme pro změnu Lidské
srdce: víc než jen pumpa - Blog Eugenika
Working muscle
Gastrointestinal tract: MedlinePlus Medical Encyclopedia Image Natažení, natržení, přetržení svalu
GIT, skin
↑ Venous return
↑ Sympathicus→ ↑ R(resistence – peripheral)
↑ Sympathicus → ↑CO due to ↑HR  → ↑BP
Metabolic autoregulation → ↓R