(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 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) PBP Pulse blood pressure 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 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) • Short-term – baroreflex • Medium-term – renin-angiotensin-aldosterone system (RAAS) • Long-term – excretion of Na+ via kidneys Regulation of blood pressure Baroreceptors – carotid sinus + aortic arch Afferent nerve: vagus nerves, n.XI. Cardiac branch of baroreflex: Decrease of BP induces increase of HR and vice versa Efferent 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 – baroreflex Autonomic 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 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 Methods of BP measurement 24-hours measurement Photopletysmography (volume-clamp method – Prof. Peňáz) Palpatory method (tonometer + pulse palpation) Auscultatory method (tonometer + stethoscope) Oscillometric method Other possibilities: Invasive vs. Non-invasive Direct vs. Indirect Laminar / turbulent flow, Korotkow sound 𝑅𝑒 = 𝑣 ∙ 𝑆 ∙ 𝜌 𝜂 Reynold´s number Re: probability of turbulent flow v: velocity of blood flow S: area of cross-section of artery (.r2) : density of blood : viscosity of blood (increase viscosity in case of anaemia/ erythrocytopenia) S1 < S2 Re1 < Re2 Laminar flow Re < 2000 Turbulent flow Re > 3000 r1 r2 Cuff Brachial a. Laminar flow Turbulent flow Re1 Re2 Korotkow sounds (Auscultatory m.) Contitual measurement Pressure in cuff Pressure oscillations in cuff (Oscillometric m.) SBP DBP SBP MBP DBP Blood flow PrincipleofBPmeasurement 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] SBP DBP Heart rate Awake state Sleep BP hour 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) 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 Physiological values of BP, hypertension BP SBP [mmHg] DBP [mmHg] Normal Optimal <120 <80 Normal 120 – 129 80 – 84 Higher normal 130 – 139 85 – 90 Hypertension 1. degree 140 – 159 90 – 99 2. degree 160 – 179 100 – 109 3. degree > 180 > 110 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)