Circulation Ch 14 PDF

Circulation Physiology Chapters 14-19 Dr. Barbara T. Alexander Office: G359 [email protected] Circulation Physiology Why Circulation Physiology is Important to Health Care Professionals America’s Health Ranking Cardiovascular Disease 2022 America’s Health Ranking High Blood Pressure 2022...

Circulation Physiology Chapters 14-19 Dr. Barbara T. Alexander Office: G359 [email protected] Circulation Physiology Why Circulation Physiology is Important to Health Care Professionals America’s Health Ranking Cardiovascular Disease 2022 America’s Health Ranking High Blood Pressure 2022 Physical Inactivity 2021 Percentage of adults who reported being physically inactive. Mississippi, 2021 Physical Inactivity 3% State Rank 49 Diabetes 2021 Percentage of individuals with diabetes Mississippi, 2021 Adult diabetes, 14.6% State Rank 48 Release date September 21, 2023 Obesity Starting in 1990, The precentage of Individuals with obesity is increasing In the USA. What is the Leading Causes of Death in Women? Heart Disease Currently in the US, 3 million women are living with breast cancer, which causes one in 31 deaths. Almost 50 million women have cardiovascular disease, which encompasses heart disease and strokes and causes one in three deaths. In 2021, 9.9% of the women in MS reported being told by a health professional that they have heart disease. Circulation Physiology: Your peers Circulation Physiology: Your patient population About 10,000 people are turning 65 every day Circulation Physiology: Your patient population Dental Students: Did you know that the heart and mouth are connected? Periodontal Infection may be a risk factor for Cardiovascular Disease Periodontal Infection may be a risk factor for Cardiovascular Disease Maintaining oral hygiene is an important part of your overall health. Cleveland Clinic Inflammation CV Risk Gum Disease Bacteria Blood stream Plaque Oral health and heart disease Dental care and heart disease: Special precautions AHA Recommendations: Special recommendations are important for people with: • prosthetic heart valves • a previous history of endocarditis • certain congenital heart defects including those with shunts, with prosthetic material or device. For someone with heart disease, they have three responsibilities: 1. Establish and maintain a healthy mouth. 2. Practice good oral hygiene and visit their dentist regularly. 3. Make sure their dentist knows they have a heart problem. Anticoagulant medications and dental procedures Should dentists offer health screenings? Each year, nearly 20 million men, women and children in the United States fail to see a family physician or similar health care professional, but they do pay at least one visit to the dentist. U.S. Department of Health & Human Services' 2008 National Health Interview Survey Chapter 14: Introduction to the circulation and the mechanics of vessels: pressure, flow and resistance Function: Components: To service the Systemic or peripheral needs of the body tissues. circulation Pulmonary circulation Blood flow route: Pulmonary circulation £ Right heart Left heart £ ¤ Vena cava Aorta £ ¤ Large veins large arteries £ ¤ small veins small arteries £ ¤ arterioles ¢ capillaries ¢ venules Figure 14-1 Slide 1 Pulmonary circulation: Dr. William Harvey, 1628 Right heart ¢ pulmonary artery ¢ pulmonary capillaries ¢pulmonary veins ¢ left heart Characteristics of the vascular tree components Vessel Characteristics Aorta Cross-sectional Area (cm2) 2.5 Arteries high pressure thick muscular wall 20 Arterioles thinner, but still muscular wall “blood flow control conduits“ 40 Capillaries nutrient exchange very thin wall 2500 Venules low pressure thin muscle wall collect blood from capillaries 250 Veins low pressure conduit for blood transport back to heart major reservoir for extra blood Slide 2 80 Systolic Pulsatile Diastolic Pulsatile Low pressureAll needed for exposure to O2 and gas exchange Ave ~17 mmHg Prevent leakage of plasma But allow nutrient diffusion ~0 mmHg Figure 14-2 Volume 16% Arterial System High pressure Low volume Low compliance (∆V/∆P) Slide 3 4% 64% Venous System Low pressure High volume High compliance 4% Where is most of the blood volume? Where is the site of most vascular resistance? Where is the pressure lowest? Why? Why is the venous system high compliance (capacitance)? Basic Theory of Circulatory Function Goal of the circulatory system: deliver nutrients and remove wastes. At the same time, blood flow to each organ/tissue is precisely controlled and arterial pressure is controlled independently. 1. Rate of blood flow to each tissue is almost always precisely controlled in relation to tissue need. (BF = volume of blood that flows past a certain point during a specified amount of time) 2. Cardiac output is controlled mainly by the sum of all the local tissue flows. (CO = volume of blood pumped by the heart) 3. Generally, arterial pressure is controlled independently of either local blood flow control or cardiac output. Slide 4 (BP = force that drives the blood throughout the body) Pressure, Flow and Resistance #1 Figure 14-3 ∆P = P1 - P2 Ohms Law ∆P = F x R or F = ∆P/R #2 Blood Flow through a vessel is determined by: # 1. Pressure difference (∆P) between 2 ends F = blood flow ∆P = pressure difference R = resistance # 2. Impediment of flow through vessel (Resistance) Friction •Pressure, flow, and resistance are related. •Pressure drops along a resistance vessel. Slide 5 Pressure, Flow and Resistance #1 Figure 14-3 ∆P = P1 - P2 Ohms Law ∆P = F x R or F = ∆P/R #2 F = blood flow ∆P = pressure difference R = resistance •Pressure, flow, and resistance are related. •Pressure drops along a resistance vessel. Figure 14-2 Slide 6 Blood Flow: Quantity of blood that passes a certain point at a given period of time. (ml/min) Laminar Flow – when blood flows at a steady rate: flows in streamline. • Each layer of blood remains the same distance from wall. • Type of flow = laminar or streamline. Turbulent Flow – blood flowing in all directions, continually mixing. No flow Laminar Turbulent Figure 14-6 Slide 7 “Parabolic”- molecules in contact with wall barely move, next layers slip over preceding layers. Thus, center layer flows most rapidly. Can occur with obstruction, turn, rough surface. Flow no longer linear or streamline. Develop eddy currents which will increase resistance to flow. Resistance to Blood Flow F = ∆P/R Resistance: Impediment to blood flow in a vessel. Cannot be measured directly. R = ∆P/F Resistance of the entire circulatory system is called total peripheral resistance (TPR). Conductance: Measure of pressure difference. blood conductance = 1 / resistance Slide 8 flow through a vessel for a given Blood Flow Reynolds’ number (Re): measure of the tendency for turbulence to occur. Low Re = laminar flow Re = (flow velocity)(diameter)(density) / viscosity Re = v d p / n Density: amount of mass that can be contained in a volume Viscosity: a liquid’s resistance to flow Re decreases as blood viscosity increases. Anemia or ↓ blood viscosity can contribute to turbulence. Slide 9 Resistance to Blood Flow BF: Resistance most sensitive to changes in radius/diameter. 4th power Law: Different Blood Flows Arterioles control blood flow Arteriole Slight change in diameter can cause tremendous changes in ability to conduct blood. • A 4 fold increase in diameter leads to a 256fold decrease in resistance and a 256 increase in flow (44 = 256). (2 fold = 16 fold) • A 4 fold increase in vessel length leads to a 4-fold increase in resistance and a 4-fold decrease in flow. Figure 14-8 (2 fold = 2 fold) Poiseuille Law F = p ∆P r4 / 8 h L F = blood flow L = length ∆P = pressure difference h = viscosity r = radius Slide 10 Organization of Resistance Beds Determines Total Resistance (Rtotal ) Total peripheral resistance (Rtotal): Series Equals sum of resistance of entire peripheral circulation. Parallel Figure 14-9 Summation of Resistances: Independent regulation of blood flow. Total R is less than the vessel with the lowest resistance. Series: R1 + R2 = Rtotal Parallel: 1/R1 + 1/R2 + 1/R3 + 1/R4 = 1/Rtotal •Resistance beds in parallel offer less resistance vs. beds in series. •Loss of a resistance bed for a parallel circuit leads to an increase in total resistance. Slide 11 Parallel provides another pathway for conductance. Hematocrit and viscosity Hematocrit •percentage of cells in blood, typically RBCs •Anemia - too few •Polycythemia - too many Figure 14-10 Normal 38 (F) - 42 (M) Slide 12 Anemia Polycythemia Hematocrit and viscosity Poiseuille Law F = p ∆P r4 / 8 h L Hematocrit is an important determinant of viscosity. £ Hematocrit ¢ £ viscosity 4 fold viscosity of water Figure 14-11 £Viscosity ¢ less flow in vessel Normal 38 (F) - 42 (M) Slide 13 if all other factors are constant. Viscosity: force to make a fluid move Anemia and Dental Care Anemia can increase the risk of infection with a dental procedure. Antibiotic prophylaxis may be indicated before any invasive dental procedures to prevent possible infection risk. Because anemia reduces the number of red blood cells present, one common symptom is paleness in the gums, which some have come to consider anemia gums. Instead of a normal, healthy pink, they begin to take on a faded or even whiter shade of their normal color. Clinical Correlation Methods for Measuring Blood Flow Electromagnetic flowmeter- electrical voltage proportional to rate of flow of vessel placed in a magnetic field. Utilizes the generation of electromotive force in blood moving through a magnetic field. Ultrasonic doppler flowmeter – transmission of ultrasound frequency with the sound wave reflected off a moving blood cell proportional to flow. Slide 14 Systolic Pulsatile Diastolic Pulsatile Low pressureAll needed for exposure to O2 and gas exchange Ave ~17 mmHg Prevent leakage of plasma But allow nutrient diffusion ~0 mmHg Figure 14-2 Volume 16% Arterial System High pressure Low volume Low compliance (∆V/∆P) Slide 15 4% 64% Venous System Low pressure High volume High compliance 4% Where is most of the blood volume? Where is the site of most vascular resistance? Where is the pressure lowest? Why? Why is the venous system high compliance (capacitance)? Arterial pressure, vascular resistance and blood flow. 7 Ohms Law Blood flow (ml/min) 6 5 ∆P = F x R or F = ∆P/R 4 3 2 1 Distend 0 20 40 60 80 100 120 140 160 200 Arterial pressure (mm Hg) Slide 16 F = blood flow ∆P = pressure difference R = resistance Effect of pressure on vascular resistance and blood flow. The relationship between pressure and flow is not linear as one might expect based on the P = F x R equation. Dilates vessels and £ blood flow. Vessels are not rigid. Constricts vessels and ˜ blood flow. Figure 14-13 Slide 17 Increases in P increases the driving force for flow, but also distends vessels at the same time which decreases Resistance (R). Changes in flow can be caused by changes in sympathetic nerve stimulation. At a given P, increased stimulation decreases flow due to vasoconstriction.