CVR biophysics terms (week 13)

just terms + definitions from CVR week 13 pre-work

Flow (Q)

volume of fluid (blood or air) passing through a vessel or airway per unit of time, usually expressed in liters per minute (L/min)

Resistance (R)

opposition to flow through a vessel or airway, often influenced by the diameter of the vessel or airway + the viscosity of the fluid; measured in units such as dyn·s·cm⁻⁵

Pressure (P)

force exerted by the fluid per unit area within the cardiovascular or respiratory systems; blood pressure is measured in mm of mercury (mmHg), while respiratory pressures are often measured in cm of water (cmH₂O)

Ohm's Law for Fluid Flow

principle that relates flow (Q), pressure (P), and resistance (R) in a system, expressed as: 𝑄 = 𝑃/𝑅; helps clinicians understand how changes in resistance + pressure affect blood flow & can guide treatment strategies in conditions like shock or heart failure

Laminar Flow

smooth, orderly flow pattern in which fluid moves in parallel layers with minimal mixing; characterized by Reynolds number less than 2000; in smaller airways + blood vessels & causes disruptions to laminar flow can indicate pathology, such as turbulent flow in stenotic arteries

Turbulent Flow

chaotic, disordered flow pattern where fluid moves irregularly, often with vortices + eddies; occurs when Reynolds number exceeds 2000; in large airways or major blood vessels & is often associated with pathological conditions like atherosclerosis or valvular heart disease

Reynolds Number (Re)

dimensionless number that predicts flow patterns in different fluid flow situations; calculated as: 𝑅𝑒 = 𝜌𝑣𝑑/𝜂, where ρ is fluid density, 𝑣 is velocity, 𝑑 is diameter, & 𝜂 is viscosity; determines whether the flow is laminar or turbulent, which is crucial for diagnosing/managing cardiovascular + respiratory conditions

Compliance (C)

ability of a hollow organ (like the lungs or blood vessels) to stretch + expand in response to pressure; calculated as: 𝐶 = 𝛥𝑃/𝛥𝑉, where ΔV is the change in volume & ΔP is the change in pressure; high compliance indicates flexible vessels or lungs, while low compliance can signify stiffness, as seen in conditions like pulmonary fibrosis or arteriosclerosis

Poiseuille's Law

describes resistance to the flow of a fluid through a cylindrical vessel, expressed as: 𝑅 = (8 𝜂 𝐿)/𝜋𝑟4, where R is resistance, r is radius (to the fourth (4th) power, 𝜂 is viscosity, & L is length; highlights the significant impact of vessel or airway radius on resistance to the blood flow, which is crucial for treating conditions like asthma or vascular occlusions

Bernoulli's Principle

an increase in the speed of a fluid occurs simultaneously with a decrease in pressure or potential energy of the fluid; helps explain phenomena like the drop in blood pressure across stenotic heart valves or the airflow patterns in obstructive lung diseases

Starling's Law of the Heart

heart's stroke volume increases in response to an increase in the volume of blood filling the heart (the end-diastolic volume), assuming other factors remain constant; essential for understanding heart function & managing conditions like heart failure, where preload + afterload must be carefully balanced

Mean Arterial Pressure (MAP)

average pressure in a patient’s arteries during one cardiac cycle, calculated as: MAP = 1/3 SBP + 2/3 DBP, where SBP is systolic blood pressure & DBP is diastolic blood pressure; important indicator of overall cardiovascular health & tissue perfusion; abnormal MAP can signal conditions like shock or hypertension

Blood Pressure (BP)

pressure exerted by circulating blood upon the walls of blood vessels; part of the clinical variables to monitor the health of an animal's cardiovascular system; can be measured as systolic (pressure during heart contraction or maximal pressure) & diastolic (pressure during heart relaxation or minimum pressure) in mmHg

Blood Flow

movement of blood through the circulatory system, which delivers oxygen + nutrients to tissues & removes waste products; in volume per unit time (ex: mL/min or L/min)

Blood Perfusion

passage of blood through the blood vessels to a tissue or organ, ensuring oxygen + nutrient delivery at the cellular level; in mL/min per gram of tissue

Cardiac Output (CO)

volume of blood pumped by the heart per minute; critical parameter in determining how well the heart is performing & delivering blood to the tissues; 𝐶𝑂=𝐻𝑅×𝑆𝑉; in L/min or mL/min

Stroke Volume (SV)

amount of blood ejected by the left ventricle of the heart in one contraction; in mL/beat

Contractility

intrinsic ability of the heart muscle (myocardium) to contract & generate force (Inotropism); influenced by calcium levels, autonomic nervous system activity, etc.; increased contractility enhances cardiac output, while decreased contractility can lead to heart failure

Heart Rate (HR)

number of heart beats per minute (Chronotropism); in beats per minute (bpm)

Systolic Blood Pressure (SBP)

pressure in the arteries during the contraction of the heart muscle (systole); often used to define hypertension in veterinary medicine, especially in cats & dogs

Diastolic Blood Pressure (DBP)

pressure in the arteries when the heart rests between beats (diastole); important in assessing overall cardiovascular health & for detecting hypotension or hypertension

Hypotension

abnormally low blood pressure, generally defined as systolic BP <80 mmHg in dogs & <90 mmHg in cats; causes include shock, blood loss, heart failure, or sepsis; can result in poor perfusion of organs & tissues

Hypertension

abnormally high blood pressure, typically defined as systolic BP > 160 mmHg in both cats & dogs; associated with damage to vital organs such as the kidneys, eyes, brain, & heart; commonly secondary to other conditions like kidney disease or hyperthyroidism

Systemic Vascular Resistance (SVR)

resistance to blood flow within all of the blood vessels in the body, except the pulmonary circulation; increases in SVR can contribute to hypertension, while decreases can lead to hypotension

Renin-Angiotensin-Aldosterone System (RAAS)

hormone system that regulates blood pressure and fluid balance; renin converts angiotensinogen to angiotensin I, which is then converted to angiotensin II, leading to vasoconstriction + aldosterone release; overactivity of the RAAS can result in hypertension, while inhibition can lower blood pressure, potentially leading to hypotension

Vasoconstriction

narrowing of blood vessels due to contraction of the muscular walls of the vessels; increases systemic vascular resistance, contributing to hypertension

Vasodilation

widening of blood vessels caused by relaxation of the muscular walls of the vessels; decreases systemic vascular resistance, which can lead to hypotension

Baroreceptors

specialized stretch receptors located primarily in the carotid sinuses + aortic arch that detect changes in blood pressure; help regulate blood pressure by signaling the brain to adjust heart rate & vessel dilation/constriction

Sympathetic Nervous System (SNS)

part of the autonomic nervous system that controls the body's fight-or-flight response, including increasing heart rate & blood vessel constriction; overactivation can lead to hypertension, while its inhibition may cause hypotension

Hypovolemia

decreased volume of circulating blood in the body; often a cause of hypotension, particularly in cases of dehydration, blood loss, or severe trauma

Hypervolemia

increased volume of circulating blood in the body; can contribute to hypertension by increasing the pressure on blood vessel walls

Renal Perfusion

flow of blood to the kidneys; decreased renal perfusion can trigger the RAAS, leading to hypertension, while excessive renal perfusion can lead to hypotension in certain cases

End Organ Damage

damage to vital organs, such as the heart, kidneys, brain, & eyes, caused by prolonged high blood pressure (hypertension); chronic hypertension can lead to serious complications, including kidney failure, retinal damage, & heart disease

Pulmonary Hypertension

elevated blood pressure in the arteries of the lungs; although distinct from systemic hypertension, it is an important condition to monitor, especially in dogs, as it can lead to right-sided heart failure

Shock

life-threatening condition in which blood pressure drops dangerously low, leading to inadequate blood flow to tissues; key cause of hypotension in both cats & dogs, requiring immediate medical intervention

Hyperthyroidism

condition in which the thyroid gland produces too much thyroid hormone, leading to increased metabolism & often elevated blood pressure; common cause of secondary hypertension in cats

Chronic Kidney Disease (CKD)

long-term, irreversible damage to the kidneys, affecting their ability to filter blood properly; major cause of secondary hypertension in both cats + dogs due to increased RAAS activity & fluid retention

Primary Hypertension

high blood pressure with no identifiable underlying cause (idiopathic); less common in veterinary medicine compared to secondary hypertension, but still important in older or predisposed animals

Secondary Hypertension

high blood pressure caused by an underlying disease or condition, such as kidney disease, hyperthyroidism, or diabetes; most cases of hypertension in dogs + cats are secondary & treatable by addressing the underlying condition

Myocardial Contractility

strength of the heart's contraction; poor myocardial contractility can contribute to hypotension by reducing cardiac output, while increased contractility may exacerbate hypertension

Preload

amount of blood in the ventricles at the end of diastole (filling phase); increased preload stretches the myocardium and affects contractility → CHF may result from excessive preload, leading to volume overload

Afterload

resistance that the heart must overcome to eject blood during systole (contraction); influenced by systemic vascular resistance (SVR) & the compliance of the aorta & other large arteries

Crystalloids

type of intravenous fluid solution that contains small molecules, such as electrolytes (sodium, chloride, potassium), which can easily move across cell membranes; commonly used in veterinary medicine for fluid therapy to replace lost fluids, correct electrolyte imbalances, & maintain hydration

Edema

abnormal accumulation of fluid in the interstitial spaces of tissues or body cavities, leading to swelling

Interstitial Space

space between cells + capillaries where fluid exchange occurs

Hydrostatic Pressure

static pressure a fluid (blood) exerts simply due to its presence against the walls of the capillaries due to gravity and the fluid's weight; pressure exerted by fluids in the blood vessels promotes fluid movement out into tissues

Hydraulic Pressure

pressure generated by fluid flow through a confined space, reflecting the dynamic component of fluid movement; refers to the pressure exerted as blood moves through capillaries under the force of the heart's pumping action; contributes to shear stress on the endothelial cells lining the capillaries, influencing vascular function & health

Oncotic (Colloid Osmotic) Pressure

pressure exerted by plasma proteins (ex: albumin) to retain fluid within blood vessels by drawing it back from tissues

Lymphatic System

network of vessels that drains excess interstitial fluid & returns it to the circulatory system

Inflammatory Edema

caused by increased vascular permeability & fluid leakage due to inflammation (ex: in response to infection or tissue injury)

Non-inflammatory Edema

results from mechanical or metabolic dysfunction, without inflammation, such as due to heart failure or hypoproteinemia

Increased Vascular Permeability

key mechanism in inflammatory edema where endothelial cells become more permeable, allowing plasma & proteins to leak into tissues

Increased Hydrostatic Pressure

cause of non-inflammatory edema where high blood pressure in capillaries pushes excess fluid into tissues (ex: during heart failure)

Decreased Oncotic Pressure

results from a drop in plasma proteins (ex: in liver disease or protein-losing conditions), reducing fluid reabsorption into capillaries

Lymphatic Obstruction

occurs when the lymphatic system cannot drain fluid properly, leading to localized edema (ex: in tumors or infections)

Endothelial Dysfunction

impaired function of endothelial cells lining blood vessels, leading to abnormal fluid leakage

Congestive Heart Failure

condition that increases hydrostatic pressure, often leading to non-inflammatory edema in the lungs, abdomen, or extremities

Liver Cirrhosis

condition impairs the production of plasma proteins, reducing oncotic pressure & leading to edema (ascites in the abdomen)

Protein-losing Enteropathy

disorder where proteins are lost through the gastrointestinal tract, reducing oncotic pressure

Hypoalbuminemia

abnormally low albumin levels in the blood, often causing non-inflammatory edema

Sepsis

severe systemic infection that can cause inflammatory edema through cytokine-induced vascular permeability

Pitting Edema

form of non-inflammatory edema where pressure leaves a temporary indentation in the swollen tissue

Non-pitting Edema

typically associated with inflammatory edema; the tissue remains firm despite pressure

Effusion

accumulation of fluid in body cavities (ex: pleural effusion, pericardial effusion, ascites)

Anascara

severe, generalized edema affecting the entire body

Histamine

chemical released by mast cells that increases vascular permeability & promotes edema during allergic reactions

Cytokines

proteins such as interleukins and TNF-α that promote inflammation & increase vascular permeability

Prostaglandins/Leukotrienes

lipid-derived molecules that enhance vasodilation & vascular permeability

Neutrophils

type of white blood cell that accumulates in tissues during acute inflammation, contributing to inflammatory edema

Dilated Cardiomyopathy (DCM)

heart's chambers (primarily the ventricles) enlarge, & the myocardial walls become thin and weak, reducing the heart's ability to pump blood effectively; common in large breed dogs (ex: Doberman Pinschers)

Hypertrophic Cardiomyopathy (HCM)

characterized by thickening (hypertrophy) of the heart muscle, particularly the left ventricle, which impairs the heart's ability to relax & fill appropriately during diastole; common in cats (ex: Maine Coons & Ragdolls)

Backward Failure

inability of the heart to adequately empty during systole, leading to venous congestion & fluid accumulation (ex: pulmonary edema, ascites)

Forward Failure

inadequate blood supply to tissues due to reduced cardiac output, leading to poor perfusion (ex: hypotension, weakness)

Pulmonary Edema

fluid accumulation within the lungs, typically due to left-sided heart failure; clinical signs are coughing + dyspnea (difficulty breathing)

Ascites

fluid accumulation within the abdominal cavity, often associated with right-sided heart failure

Pleural Effusion

fluid accumulation in the pleural cavity (space surrounding the lungs); seen in cats with CHF

Endocardiosis

degenerative condition of heart valves, especially the mitral valve, leading to regurgitation & CHF; common in older small-breed dogs

Ventricular Remodeling

structural changes in the heart in response to chronic stress, including dilation or hypertrophy; can progress to CHF over time

Cardiogenic Shock

severe form of heart failure with a critical reduction in cardiac output, leading to inadequate perfusion of vital organs

Furosemide

diuretic used to manage pulmonary edema by reducing fluid overload; commonly used in the emergency management of CHF

Pimobendan

inodilator (positive inotrope & vasodilator) that improves heart contractility & reduces afterload; cornerstone drug in the management of CHF in dogs

Beta-Blockers

medications that reduce sympathetic nervous system activation & heart rate (ex: atenolol, often used in feline HCM)

ACE Inhibitors (ex: Enalapril, Benazepril)

drugs that block RAAS activation, reducing vasoconstriction & fluid retention in CHF patients

Tachypnea

abnormally rapid breathing, often seen in animals with CHF & pulmonary edema

Syncope

temporary loss of consciousness due to reduced cerebral perfusion; often seen in animals with advanced heart disease