(viii.) blood pressure in men (ix.) non-invasive methods
TRANSCRIPT
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(VIII.) Blood pressure in men(IX.) Non-invasive methods of blood pressure
measurement
Physiology I – practicals
Dep. of Physiology, Fac. of Medicine, MU 2015 © Jana Svačinová
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Arterial blood pressure during heart cycle
SBP
DBP
MBP
Cardiac cycle
Mean BP (MBP): calculated MBP in the course of one heart cycle (integral of pressure curve)
PBPPulse bloodpressure
PBP = SBP – DBP
MBP DBP + 1/3 PBP
Blood pressure (BP): pressure of blood on arterial wall(arterial BP: portion of energy of LV contraction transformed into lateral pressure is put on arterial wall)
Systolic BP - the highest value of BP during cardiac cycle
Diastolic BP – the lowest value of BP during cardiac cycle
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Blood pressure depends on cardiac output and peripheral resistance
• Systolic BP depends mainly on CO
• Diastolic BP depends mainly on TPR
Arterial Blood Pressure(BP)
Total peripheral resistance(TPR)
Heart Rate(HR)
Systolic Volume(SV)
=
*
*Cardiac output(CO)
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• Short-term – baroreflex
• Medium-term – renin-angiotensin-aldosterone system (RAAS)
• Long-term – excretion of Na+ via kidneys
Regulation of blood pressure
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Baroreceptors – carotid sinus + aortic archAfferent nerve: vagus nerves, n.XI.
Cardiac branch of baroreflex: Decrease of BP induces increase of HR and vice versaEfferent nerve: vagus nerves (to SA node)
Peripheral branch of baroreflex: Decrease of BP induces increase of TPR
• Vasoconstriction of small arteries
• Venoconstriction – redistribution of blood volume
Efferent nerve: sympathetic nerve fibers to peripheral vessels
Regulation of blood pressure – baroreflexAutonomic nervous system
Sympathetic NS ( BP, HR, SV, TPR) X Parasympathetic NS ( BP, HR, SV, TPR)
Function: regulation of short-term changes of BP via modulation of HR and TPR
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Short-term effects• Amount of blood – affects SV (haemorrhage, dehydration)• External pressure on arteries – intrathoracic a intraabdominal pressure (coughing,
defecation, childbirth, ventilation)• Body position – orthostatic and clinostatic reaction• Mental conditions – emotions, stress, …• Physical activity• External temperature• Drugs, alcohol,…
Long-term effects• Age (lower BP in small children than in elderly people• Gender (higher BP in men)
Changes of BP
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Methods of BP measurement
24-hours measurement
Photopletysmography (volume-clamp method – Prof. Peňáz)
Palpatory method (tonometer + pulse palpation)
Auscultatorymethod(tonometer +stethoscope)
Oscillometric method
Other possibilities:
Invasive vs. Non-invasiveDirect vs. Indirect
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Laminar / turbulent flow, Korotkow sound
𝑅𝑒 =𝑣 ∙ 𝑆 ∙ 𝜌
𝜂Reynold´s number Re: probability of turbulent flowv: velocity of blood flowS: area of cross-section of artery (.r2): density of blood: viscosity of blood(increase viscosityin case of anaemia/erythrocytopenia)
S1 < S2 Re1 < Re2
Laminar flow Re < 2000Turbulent flow Re > 3000
r1r2
CuffBrachial a.
Laminar flow Turbulent flow
Re1
Re2
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Korotkow sounds(Auscultatory m.)
Contitual measurement
Pressure in cuff
Pressure oscillationsin cuff(Oscillometric m.)
SBP
DBP
SBP MBP DBP
Blood flow
Pri
nci
ple
of
BP
me
asu
rem
en
t
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24-hours monitoring of BP
Decrease of BP (10 - 15%) at night
8 9 1110 12 13 14 1615 17 18 19 2120 22 23 24 21 3 4 5 76
120
140
100
80
60
[mmHg]
SBPDBPHeart rate
Awake state Sleep
BP
hour
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Rules for BP measurement
• Examined person is sitting for a few minutes before the measurement
• Only validated apparatus must be used• Perform at least two measurements in the course of 1 – 2
minutes• Use cuff of standard size (12 – 13 cm width and 35 cm long) • Smaller or bigger cuffs must be available for patients with
smaller or bigger size of arm• Cuff must be always at the level of heart of examined person• Pressure in the cuff must be decreased slowly (2 mmHg/s)
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Methods Benefits Disadvantages BP value
Auscultatory • Accurate estimate of SBP/DBP• Simple, No electric supply is
required
• Subjective, for accurate measurement practices is required
• Accurate cuff is required
SBP + DBP
Oscillometric • Accurate estimate of MBP• Automatic, fast• Low cost of device, good for
measurements at home
• DBP/SBP is calculated• Inaccurate in case of arrhythmias
MBP
24 – hours monitoring
• Monitoring during whole day• Exclusion of white coat
hypertension
• Disturbance by cuff inflation (especially at night)
Photoplethys-mography
• Continual BP record• Analysis of BP variability
• Measurement on finger• Cost of device
Continually
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Physiological values of BP, hypertension
BP SBP[mmHg]
DBP[mmHg]
No
rmal Optimal <120 <80
Normal 120 – 129 80 – 84
Higher normal 130 – 139 85 – 90
Hyp
erte
nsi
on 1. degree 140 – 159 90 – 99
2. degree 160 – 179 100 – 109
3. degree > 180 > 110
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Changes of BP during and after physical activity
• Increased of BP depends on character of physical activity• Blood is distributed in the body according to metabolic needs – re-distribution during
physical activity
• Increased CO increased SBP• Vasodilatation in working muscle, vasoconstriction in skin, GIT Stability or light change of DBP during rhythmic work Increase of DBP during and after isometric muscle contraction (e.g. weightlifting)
Vasoconstriction in skin is temporary – vasodilatation in skin due to heat production as a thermoregulatory mechanism
• After the physical activity BP decreases on/slightly under the previous level, blood flow through skeletal muscles may remain increased.
• Time required for recovery depends on parasympathetic activity (it is possible to improve it by training)