A Mathematical Approach To Factors Affecting Blood Flow
Jean Louis Marie Poiseuille was a French physician and physiologist who devised a mathematical equation describing blood flow and its relationship to known parameters. The same equation also applies to engineering studies of the flow of fluids. Although understanding the math behind the relationships among the factors affecting blood flow is not necessary to understand blood flow, it can help solidify an understanding of their relationships. Please note that even if the equation looks intimidating, breaking it down into its components and following the relationships will make these relationships clearer, even if you are weak in math. Focus on the three critical variables: radius , vessel length , and viscosity .
- is the Greek letter pi, used to represent the mathematical constant that is the ratio of a circles circumference to its diameter. It may commonly be represented as 3.14, although the actual number extends to infinity.
- P represents the difference in pressure.
- r4 is the radius of the vessel to the fourth power.
- is the Greek letter eta and represents the viscosity of the blood.
- is the Greek letter lambda and represents the length of a blood vessel.
One of several things this equation allows us to do is calculate the resistance in the vascular system. Normally this value is extremely difficult to measure, but it can be calculated from this known relationship:
If we rearrange this slightly,
Conflict Of Interest Statement
AM has no conflict of interest. BS collaborates with Pulsion Medical Systems SE as a member of the medical advisory board and received honoraria for giving lectures and refunds of travel expenses from Pulsion Medical Systems SE. BS received research support from Edwards Lifesciences . BS received institutional research grants, unrestricted research grants, and refunds of travel expenses from Tensys Medical Inc. . BS received honoraria for giving lectures and refunds of travel expenses from CNSystems Medizintechnik AG .
Complications Of High Blood Pressure
Untreated or poorly managed high blood pressure can cause serious and even life threatening issues. It can damage your blood vessels as well as your organs. The longer your hypertension goes untreated, the more it can damage your body and affect your health.
Potential complications of high blood pressure include:
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What Is Measured In An Arterial Blood Gas Test
An arterial blood gas test usually includes the following measurements:
- Oxygen content : This measures the amount of oxygen in your blood.
- Hemoglobin: This measures the amount of hemoglobin, the protein responsible for carrying oxygen to your cells, in your blood.
- Oxygen saturation : This measures how much hemoglobin in your blood is carrying oxygen. Hemoglobin is a protein in your red blood cells that carries oxygen from your lungs to the rest of your body.
- Partial pressure of oxygen : This measures the pressure of oxygen dissolved in your blood. It helps show how well oxygen moves from your lungs to your bloodstream.
- Partial pressure of carbon dioxide : This measures the amount of carbon dioxide in your blood and how well carbon dioxide can move out of your body.
- pH: This measures the balance of acids and bases in your blood, known as your blood pH level. The pH of blood is usually between 7.35 and 7.45. If its lower than that, your blood is considered too acidic. If its higher than that range, your blood is considered too basic .
- Bicarbonate : This is calculated using the measured values of pH and PaCO2 to determine the amount of the basic compound made from carbon dioxide
Mean Arterial Pressure Significance
As mentioned earlier, a normal range for mean arterial pressure is 70 to 110 mm Hg. A mean arterial pressure in the high range could be an indication that the heart has to work much harder than it should. This is causing stress on the heart. High MAP can result in advanced heart disease, blood clots, heart attack, and stroke. When high mean arterial pressure is ongoing, heart muscles will enlarge and grow thicker, and jeopardize life expectancy. When MAP goes up quickly in a short period of time, organs can fail. A mean arterial pressure in the high range isnt the only concern though, low is also problematic.
Low MAP can also be fatal if left untreated. Pressure readings less than 60 mm Hg must be addressed. In this case, when organs are not getting the blood they need, you can go into shock and organs can fail. Low MAP can be caused by sepsis, hemorrhaging, stroke, or some sort of trauma.
Here are some situations where perfusion of organs might come into play and impact MAP:
- Head injuries
- Abdominal aneurysm
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What Is The Windkessel Effect
During systole, the left ventricle ejects around 70 mL of blood into the aorta . The elastic aortic walls expand to accommodate the SV, moderating the consequent increase in intra-aortic pressure from a diastolic blood pressure of 80 mmHg to a systolic blood pressure of 120 mmHg. The ejected blood possesses kinetic energy, whilst there is storage of potential energy in the stretched aortic wall. In diastole, recoil of the aortic wall converts the stored potential energy back into kinetic energy. This maintains the onward flow of blood during diastole, thereby maintaining DBP this is known as the Windkessel effect. This effect, along with the cardiac valves, converts the sinusoidal pressure wave generated in the heart into a positive and constant pressure at the tissues, much like converting AC to DC electricity. With advancing age, there is degeneration of elastin in the wall of the aorta. The aortic wall becomes less compliant, and its ability to accommodate SV without a large increase in pressure reduces. This accounts for the development of systolic hypertension in the elderly.
Systemic Arterial Pressure And Age
Fetal blood pressure
In pregnancy, it is the fetal heart and not the mother’s heart that builds up the fetal blood pressure to drive blood through the fetal circulation. The blood pressure in the fetal aorta is approximately 30 mmHg at 20 weeks of gestation, and increases to approximately 45 mmHg at 40 weeks of gestation.
The average blood pressure for full-term infants:
- Systolic 6595 mmHg
In children, the normal ranges for blood pressure are lower than for adults and depend on height. Reference blood pressure values have been developed for children in different countries, based on the distribution of blood pressure in children of these countries.
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How Is An Unusual Map Treated
An unusual MAP is usually a sign of an underlying condition or problem in the body, so the treatment depends on the cause. causes may include heart conditions, Sepsis, stroke, internal bleeding, and more.
For a low MAP, treatment may focus on safely raising blood pressure quickly to avoid organ damage. This is usually done with:
- intravenous fluids or blood transfusions to increase blood flow
- medications called vasopressors that tighten blood vessels, which can increase blood pressure and make the heart beat faster or pump harder
Depending on the cause, treating a high MAP may also require quick action, in this case, to reduce overall blood pressure. This can be done with oral or intravenous nitroglycerin . This medication helps to relax and widen blood vessels, making it easier for blood to reach the heart.
Once the blood pressure is under control, the doctor can continue treating the underlying cause. This may involve:
- breaking up a stroke-causing blood clot
- inserting a stent into a coronary artery to keep it open
What Do Blood Pressure Numbers Mean
Blood pressure is measured using two numbers:
The first number, called systolic blood pressure, measures the pressure in your arteries when your heart beats.
The second number, called diastolic blood pressure, measures the pressure in your arteries when your heart rests between beats.
If the measurement reads 120 systolic and 80 diastolic, you would say, 120 over 80, or write, 120/80 mmHg.
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What Is A Blood Pressure Measurement
Each time your heart beats, it pumps blood into your arteries. A blood pressure measurement is a test that measures the force in your arteries as your heart pumps. Blood pressure is measured as two numbers:
- Systolic blood pressure measures pressure inside your arteries when the heart beats.
- Diastolic blood pressure measures the pressure inside the artery when the heart rests between beats.
High blood pressure, also known as hypertension, affects tens of millions of adults in the United States. It increases the risk of life-threatening conditions including heart attack and stroke. But high blood pressure rarely causes symptoms. A blood pressure measurement helps diagnose high blood pressure early, so it may be treated before it leads to serious complications.
Other names: blood pressure reading, blood pressure test, blood pressure screening, sphygmomanometry
Enhancing Healthcare Team Outcomes
Several guidelines exist to prevent intravascular catheter-related infections. One is available through the CDC. Emphasis is placed on choosing sites with lower rates of infection. In adults, this would be the radial, brachial, and dorsalis pedis. In children, it is more appropriate to use the radial, dorsalis pedis, posterior tibial arteries. Other points of emphasis are clinician attire of mask and cap, proper hand hygiene, adequate cleansing of patient skin, and placement of drapes to create a sterile field.
One aspect that cannot be overlooked is the importance of nursing care in managing catheter-associated infections. While nurses are typically not placing these catheters, they are at the front-line when it comes to infection prevention. This is because they are usually the ones accessing the ports for lab draws in addition to performing dressing changes and routine skincare. Through proper education of nursing staff on how to maintain sterility of arterial pressure monitoring circuit and continued care of the skin around the cannulation site, the infection rate associated with arterial catheters can be minimized.
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Whats Considered Elevated Blood Pressure
Blood pressure numbers that are higher than 120/80 mm Hg are a warning sign. It means you need to pay attention to your blood pressure and focus on heart-healthy habits.
Although these numbers arent technically considered high blood pressure, youve moved out of the normal range. Elevated blood pressure may turn into high blood pressure, which puts you at an increased risk of heart disease and stroke.
Elevated blood pressure
When your systolic pressure is between 120 and 129mm Hgand your diastolic pressure is less than 80mm Hg, it means you have elevated blood pressure.
No medications are necessary for elevated blood pressure. But your doctor may talk with you about the importance of a healthy lifestyle, such as getting regular exercise, eating a balanced diet, and managing your weight.
You may receive a diagnosis of stage 1 hypertension if:
- your systolic blood pressure is between 130 and 139 mm Hg, or
- your diastolic blood pressure is between 80 and 89 mm Hg
However, the AHA notes that if you get only one reading this high, you may not truly have stage 1 hypertension. What determines the diagnosis of hypertension at any stage is the average of your blood pressure numbers over a period of time.
Your doctor can help you measure and track your blood pressure to confirm whether its too high.
Stage 1 hypertension
If your systolic blood pressure is 130 to 139 mm Hgor your diastolic blood pressure is 80 to 89 mm Hg, its considered stage 1 hypertension.
Most People With Hypertension Feel Okay
Hypertension usually does not produce any symptoms, because the organs of the body can resist high blood pressure for a long time. Thats why its important to have regular medical examinations to make sure your blood pressure isnt creeping up as you grow older.High blood pressure over a period of time can contribute to many illnesses, including:
- heart attack
The effects of high blood pressure on the arteries are worsened by:
- cigarette smoking
- high levels of saturated fat in the diet
- high blood cholesterol
Responses to some types of stress may affect both blood pressure and changes in the arteries, but this remains scientifically uncertain.
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When Is An Arterial Blood Gas Test Performed
Healthcare providers frequently order arterial blood gas tests for the following settings or areas of medicine:
- Emergency medicine: Emergency medicine is the area of medicine thats concerned with the care of illnesses or injuries requiring immediate medical attention.
- Anesthesiology: Anesthesiology is the area of medicine thats concerned with the care of people before, during and after surgery. It encompasses anesthesia, intensive care medicine, critical emergency medicine and pain medicine.
- Pulmonology: Pulmonology is the area of medicine that deals with diseases involving your respiratory system.
Healthcare providers evaluate several conditions using an ABG, including:
Your provider may also perform an arterial blood gas test if you have any of the following lung conditions to make sure your treatment is working properly:
Can Pulmonary Arterial Hypertension Be Cured
Pulmonary hypertension cannot be cured, but treatments can reduce your symptoms and help you manage your condition. If the cause is identified and treated early, it may be possible to prevent permanent damage to your pulmonary arteries, which are the blood vessels that supply your lungs.
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How Is High Blood Pressure Controlled
These steps can help you control your blood pressure:
Take prescribed medicine exactly as directed by your healthcare provider
Choose foods that are low in sodium
Choose foods low in calories and fat
Choose foods high in fiber
Maintain a healthy weight, or losing weight if overweight
Limit serving sizes
Increase physical activity
Reduce or omit alcoholic beverages
Sometimes daily medicine is needed to control high blood pressure. If you have high blood pressure, have your blood pressure checked routinely and see your healthcare provider to monitor the condition.
Healthy And Unhealthy Blood Pressure Ranges
Learn whats considered normal, as recommended by the American Heart Association.
|SYSTOLIC mm Hg||and/or||DIASTOLIC mm Hg|
|HIGH BLOOD PRESSURE STAGE 1||130 139|
|HIGH BLOOD PRESSURE STAGE 2||140 OR HIGHER|
|HYPERTENSIVE CRISIS||HIGHER THAN 180||and/or||HIGHER THAN 120|
Note: A diagnosis of high blood pressure must be confirmed with a medical professional. A doctor should also evaluate any unusually low blood pressure readings.
The five blood pressure ranges as recognized by the American Heart Association are:
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What Is The Significance Of Mean Arterial Pressure
Written byBel Marra HealthPublished onMarch 2, 2017
Mean arterial pressure, or MAP, is something that tells a doctor how well the body is processing oxygenated blood that is delivered to the tissues and organs. It is used to explain average blood pressure in a person during a single cardiac cycle. If MAP is low, a person can go into shock, but a high MAP can also have negative implications.
Most people are familiar with the term systolic blood pressure, but it isnt an adequate measure of perfusion . Mean arterial pressure can help determine actual pressure of blood against the arterial walls. The arteries are fibrous and muscular vessels that carry blood from the heart to other structures throughout the human body.
Fortunately, the majority of blood pressure machines in hospitals will calculate mean arterial pressure for us. In intensive care situations, MAP is often monitored with invasive tools, such as an arterial line, which is a thin catheter inserted into an artery.
Diagnosis And Therapy Of Arterial Hypertension
In order to diagnose arterial hypertension, blood pressure must be measured. 140/90 mmHg in a single measurement is not sufficient for a diagnosis. Only when elevated values are measured in at least three measurements within a few weeks can we be sure that there is elevated blood pressure. However, it is not always trivial to make the diagnosis, as some patients’ blood pressure is only too high or fluctuates greatly under certain circumstances. In such situations, it is best to invest more time in clarification. An example of this is the so-called “practice or white coat hypertension“. Some patients are nervous during a doctor’s visit, which can manifest itself in short-term high blood pressure. In order to detect this temporary increase, patients can measure their blood pressure themselves at home or a long-term blood pressure measurement can be arranged.
The basis of the therapy is a change in lifestyle: heart-healthy diet, sufficient exercise, adequate sleep, weight reduction, smoking cessation, minimising the consumption of alcohol, sugar, salt, saturated fats and stress reduction.
Drug therapy is usually used for severely elevated blood pressure. There are many different active substances available, which are often combined with each other. If patients have side effects from the medication, it is almost always possible to find an active substance that is well tolerated.
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What Is Mean Arterial Pressure
Automatic blood pressure monitors give you a systolic and diastolic blood pressure reading. Many of them also include a small number in parentheses underneath or beside your standard blood pressure reading. This number in parentheses is the mean arterial pressure .
MAP is a calculation that doctors use to check whether theres enough blood flow to supply blood to all your major organs. Too much resistance and pressure may impede that flow.
Resistance refers to the way the width of a blood vessel impacts blood flow. For example, its harder for blood to flow through a narrow artery. As resistance in your arteries increases, blood pressure also increases while the flow of blood decreases.
You can also think of MAP as the average pressure in your arteries throughout one cardiac cycle, which includes the series of events that happen every time your heart beats.
Keep reading to learn more about the normal, high, and low ranges of MAP and what they mean.
In some cases, in the hospital, a doctor may place a central line in a person and use that to determine the values of cardiac output, central venous pressure, and systemic vascular resistance. They may then use these other values to calculate a persons MAP. However, an actual calculation is not always necessary as there is typically a machine that also provides the MAP reading automatically.
You can also calculate a MAP value automatically here.