Arterial Pressure Regulation Part 1 تفريغ PDF

Arterial pressure regulation | Doctor explanation Key information If you have any Abbreviation questions or concerns regard...

Arterial pressure regulation | Doctor explanation Key information If you have any Abbreviation questions or concerns regarding Explanation this document. Writer : Fatimah Ali Almubarak 219-220 notes Writer : Ali Alnajim Mnemonic Book Deleted References Dr Shuja Kazi MBBS, M.Phil (Physiology) Department of Biomedical Sciences [email protected] § Describe the relationship between blood pressure, blood flow and vascular resistance § Explain different methods of measuring blood pressure § Describe the factors that affect the mean arterial pressure It’s an easy lecture Finish it fast! Blood pressure (BP): Force exerted by the blood against the vessel wall It’s a pressure produced when the blood is flowing against the wall of the vessel It has to recordings: systolic record : when the heart contracts and the pressure increases Diastolic record : when the heart relaxes Pulse Pressure (PP): The difference between systolic and diastolic pressure (~ 40 mmHg) The average DBP: diastolic blood pressure SBP: systolic blood Mean arterial pressure (BP): The averaged arterial pressure over the pressure cardiac cycle (~ 90-100 mmHg) It’s the average pressure required to propel (push) the blood in forward direction. = 93mmHg on average , The way to calculate it : To help u https://youtu.be/XiVpku0vjLU Blood flow (F): Quantity of blood that passes a given point in the circulation in a given period of time. How much blood is the passing from point A to point B at a given period of time Resistance: Tendency of the vascular system to oppose flow When the heart pumps the blood in the circulation > the blood moves forward > striking against the wall in the vascular system So the vascular system creates resistance ( make resistance to the function of the heart , oppose the flow of the blood ) Cardiac output: Amount of blood pumped into the aorta by the heart each minute (~ 5000 ml/min). It depends on Definition Example Stroke volume The amount of blood pumped from ( end diastolic volume) – ( end systolic the ventricles in one beat volume) CO (Cardiac output) Heart rate Number of beats or contractions each Normal value 60-100bpm SV ( stroke volume minute So the formula CO = SV*HR = ml\min HR ( heart beats) Deliver blood to all parts of the body through different types of vessels attached to a pulsatile pump Starting from when the heart pumps > the blood is pumping to various types of vessels Note* Depending On histology lecture, the Elastic arteries should be first § Muscular arteries § Elastic arteries § Arterioles § Capillaries § Venules § Veins  VOLUMES OF BLOOD IN DIFFERENT PARTS OF THE CIRCULATION Total distribution of the blood in the body Two third (64%) of total blood in the body is accumulated in the systemic veins and venules This is because the walls of their vessels are thin and they have valves and they are under low pressure. So they have more blood than arteries  Relationship Between Pressure, Flow & Resistance The blood flow is: 1- directly proportional to the pressure gradient or difference. 2- inversely proportional to the resistance of the vessel. F = ∆P This means: R Greater pressure gradient, greater blood flow Greater resistance, lesser blood flow F = Blood Flow ∆P = Pressure Difference R = Resistance  Blood flow (F)through a blood vessel is determined by 2 factors Pressure Difference & Resistance. (1) Pressure difference (∆P) of blood between the two ends of the vessel (Driving force) 219 note The driving force of the blood flow is NOT the pressure at the start point or the end point. The main driving force of the blood flow is the pressure gradient (difference) between the two points ( start and the end point). End Start P1 PRESSURE GRADIENT (∆P) P2 point point We have two vessels, the pressure difference in the first one is : 100 – 75 = 25 At the second one is : 40– 15 = 25 So they have the same pressure difference, so also they have the same value of blood flow Blood F is directly proportional to ∆P, The absolute value of the pressure is not important to flow, but the difference in pressure is important which determining the flow of blood  The vessel below because more Which Vessel have greater tendency of pressure gradient = more blood flow Blood Flow?  Vascular resistance is a term used to define the resistance to flow that must be overcome to push blood through the circulatory system (2) Vascular resistance (R) -Blood Flow (F) is inversely proportional to R Resistance of a vessel is influenced by three main factors: § length of the tube (L) Directly § radius of the tube (r^4) Inversely § viscosity of the blood (h) Directly Thickness or ‫ﻟزوﺟﺔ‬  Radius means the half of the diameter of the lumen. Radius is directly proportional to the blood flow and inversely proportional to the resistance. It states that if we are increasing (doubling) the radius (*2), we are increasing the blood flow 16 times and decreasing the resistance 16 times and. ‫ التدفق راح يتضاعف‬،‫يعني اذا تضاعف القطر‬ All the factors discussed are applied in Poiseuille`s law equation. Blood flow is directly proportional to: 1- pressure gradient 2- fourth power of the radius Blood flow is inversely proportional to: 1- blood viscosity 2- vessel length § Blood viscosity: is a measure of the thickness of blood. § Viscosity of blood is ~ 3 times as great as that of water The greater blood viscosity > greater resistance > less blood flow § The greater the blood viscosity (hematocrit) the less the blood flow The viscosity of the blood is measured by Hematocrit (normally 45%). This thickness is made up of the blood elements: RBCs, proteins. In the case of polycythemia ( high hematocrit), - the blood viscosity will be high - more resistance - Less blood flow In the case of anemia ( low hematocrit), - Anemic patient have less viscosity - less resistance - more blood flow.  Laminar flow or streamline flow of blood Blood flows in streamlines with each layer of blood There are 2 types of blood flow: remaining the same distance from the vessel wall 1- laminar flow: Is the flow of blood in a streamline - at the same direction - it doesn’t produce any sound. 2- turbulent flow: Turbulent flow Blood flowing in all directions in the vessel - When the cells striking against the wall of the vessel - It produces a sound so we can hear it ( we can see it in arteries, Also Whenever there is bifurcation (branching) of the great vessels) Turbulent flow Blood flowing in all directions in the vessel Use of Sphygmomanometers 1. Manual sphygmomanometers 2. Digital sphygmomanometers Manual Digital  NO blood flow Inflatable cuff NO sound Pressure gauge Turbulent blood flow Korotkoff sounds Stethoscope Streamline blood flow NO sound Brachial artery Figure 15-7: Measurement of arterial blood pressure Explanation in the next slide  NO blood flow How does it measure the blood -pressure? 1- apply the cuff over the brachial artery on NO sound cubital fossa area 2-Inflate the pressure to 30-40 mm Turbulent blood flow Korotkoff sounds then release it slowly until the pulse returns, you will hear a sound, this sound is created because the blood is trying to move in a narrow opening ( hear it by stethoscope) Streamline blood flow When the sound is disappeared that means all NO sound the vessel is dilated and the type of flow changed from Turbulent to Streamline § Easy to operate by anyone without training § May use manual or automatic inflation § Can be used in noisy environments § Measure systolic and diastolic pressures, using a electric pressure sensor and electronic components including a microprocessor. § Most display pulse The disadvantages: - Less accurate § Less accurate - It depends on the battery - It has margins of errors § Direct measurement of BP § Insertion of a thin catheter into an artery (eg. Brachial, radial, femoral) § Cannula must be connected to a sterile, fluid-filled system § This system includes a transducer connected to an electronic patient monitor or computer. This type is : § Requires very close supervision - Direct invasion into artery - Used during cardiothoracic surgery (severe bleeding IF disconnected) - It couldn’t be used routinely because  Systolic & Diastolic BP Notch If the MAP changed > altered the regulated Systolic pressure caused by system so the senses of the When the heart body monitoring the MAP contracts closer of Normal value : 110-140 aortic When the heart valve relaxes Normal value : Mean 60 - 90 pressure Diastolic pressure Another way to calculate the MAP : Clinically arterial BP is expressed as systolic P over diastolic P 120/80 (read 120 over 80) Mean arterial pressure = Diastolic + 1/3 pulse pressure =80+(1/3)40=93 mm Hg § Pulse pressure is the strength of the pulse wave. § Pulse pressure (PP) = Systolic–Diastolic PP is affected by: stroke volume and compliance of the vessel wall § Mean arterial pressure is the main driving force for blood flow. 219 Compliance is rigidity or flexibility of the vessels. If the vessel wall starts losing its compliance pulse pressure would be high (Less compliance= more rigid vessel) If compliance of the lung reduces, it will be difficult to breath. Similarly, if the compliance of vessels reduces pulse pressure would be more. arteriosclerosis: Condition occur in old people, the blood vessels would be more rigid and hard and they will have a high pulse pressure  The pressure is much greater in large arteries The greatest drop at the Mean arterial pressure occur But the greater at the level of arterioles drop in MAP is in Because Arterioles are the arterioles regulator of the flow of the blood of each organ, Because they contain the sphincters to exchange the gases to the organ..  Chapters 14 (Guyton & Hall 14th edition) Q1) the amount of blood the ventricles Q2) all of the following influence pump it per contraction ( or beat) vascular resistance of blood flow A. Cardiac output except B. Stroke volume A. Viscosity C. End systolic B. Length D. End diastolic C. Pressure gradient QB 220, slide 5 D. Radius QB 220, slide 12 1)-B 2)-C Answers: 04/02/2022 R 28