Pulse pressure

Key takeaways

Pulse pressure belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Pulse pressure to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Pulse pressure from memory before moving on to harder problems.

Reference excerpt

Pulse pressure is the difference between systolic and diastolic blood pressure. It is measured in millimeters of mercury (mmHg). It represents the force that the heart generates each time it contracts. Healthy pulse pressure is around 40 mmHg. A pulse pressure that is consistently 60 mmHg or greater is likely to be associated with disease, and a pulse pressure of 50 mmHg or more increases the risk of cardiovascular disease. Pulse pressure is considered low if it is less than 25% of the systolic. (For example, if the systolic pressure is 120 mmHg, then the pulse pressure would be considered low if it were less than 30 mmHg, since 30 is 25% of 120.) A very low pulse pressure can be a symptom of disorders such as congestive heart failure.

Calculation Pulse pressure is calculated as the difference between the systolic blood pressure and the diastolic blood pressure. The systemic pulse pressure is approximately proportional to stroke volume, or the amount of blood ejected from the left ventricle during systole (pump action) and inversely proportional to the compliance (similar to elasticity) of the aorta.

Systemic pulse pressure (most commonly measured at the brachial artery in the upper arm using a Sphygmomanometer) = Psystolic − Pdiastolic e.g. normal 120 mmHg – 80 mmHg = 40 mmHg low: 100 mmHg − 80 mmHg = 20 mmHg high: 160 mmHg − 80 mmHg = 80 mmHg Pulmonary pulse pressure is normally much lower than systemic blood pressure due to the higher compliance of the pulmonary system compared to the arterial circulation. It is measured by right heart catheterization or may be estimated by transthoracic echocardiography. Normal pulmonary artery pressure is 8 mmHg–20 mmHg at rest. e.g. normal 15mmHg – 8mmHg = 7mmHg high 25mmHg – 10mmHg = 15mmHg

Values and variation

Low (narrow) pulse pressure A pulse pressure is considered abnormally low if it is less than 25% of the systolic value. If the pulse pressure is extremely low, i.e. 25 mmHg or less, it may indicate low stroke volume, as in congestive heart failure. The most common cause of a low (narrow) pulse pressure is a drop in left ventricular stroke volume. In trauma, a low or narrow pulse pressure suggests significant blood loss. A narrow pulse pressure is also caused by aortic stenosis. This is due to the decreased stroke volume in aortic stenosis. Other conditions that can cause a narrow pulse pressure include blood loss (due to decreased blood volume), and cardiac tamponade (due to decreased filling time). In the majority of these conditions, systolic pressure decreases, while diastolic pressure remains normal, leading to a narrow pulse pressure. In the Postural Orthostatic Tachycardia Syndrome it is postulated that declining venous return reduces stroke volume and frequently results in low pulse pressure. In extreme cases, patients experience a drop in pulse pressure to 0 mm Hg upon standing, rendering them practically pulseless while upright. This condition leads to significant morbidity, as many affected individuals struggle to remain standing.

High (wide) pulse pressure

Consistently high A pulse pressure of 50 mmHg or more can increase the risk of heart disease, heart rhythm disorders, stroke and other cardiovascular diseases and events. Higher pulse pressures are also thought to play a role in eye and kidney damage from diseases such as diabetes. There are currently no drugs approved to lower pulse pressure, but some antihypertensive drugs have been shown to modestly lower pulse pressure, while other drugs used for hypertension can actually have the counterproductive side effect of increasing resting pulse pressure. The aorta has the highest compliance in the arterial system due in part to a relatively greater proportion of elastin fibers versus smooth muscle and collagen. This serves to dampen the pulsatile ejection fraction of the left ventricle, thereby reducing the initial systolic pulse pressure, but slightly raising the subsequent diastolic phase. If the aorta becomes rigid, stiff and inextensible because of disorders, such as arteriosclerosis, atherosclerosis or elastin defects (in connective tissue diseases), the pulse pressure would be higher due to less compliance of the aorta. In hypertensive patients, a high pulse pressure can often be an indicator of conduit artery stiffness (stiffness of the major arteries). When the arterial walls are stiffer (less compliant), the heart has to beat harder to overcome the resistance from the stiff arteries, resulting in an increased pulse pressure. Other conditions that can lead to a high pulse pressure include aortic regurgitation, aortic sclerosis, severe iron-deficiency anemia (due to decreased blood viscosity), arteriosclerosis (due to loss of arterial compliance), and hyperthyroidism (due to increased systolic pressure), or arteriovenous malformation, among others. In aortic regurgitation, the aortic valve insufficiency results in the backward flow of blood (regurgitation) that is ejected during systole, and its return to the left ventricle during diastole. This increases the systolic blood pressure, and decreases the diastolic blood pressure, leading to a widened pulse pressure. A high pulse pressure combined with bradycardia and an irregular breathing pattern is associated with increased intracranial pressure, a condition called Cushing's triad seen in people after head trauma with increased intracranial pressure. Common causes of widening pulse pressure include:

Anemia Aortic dissection Atherosclerosis Arteriovenous fistula Chronic aortic regurgitation Aortic root aneurysm Aortic root dilation Beri beri Distributive shock Endocarditis Fever Heart block Increased intracranial pressure Patent ductus arteriosus Pregnancy Thyrotoxicosis

From exercise For most individuals, during aerobic exercise, the systolic pressure progressively increases while the diastolic pressure remains about the same, thereby widening the pulse pressure. These pressure changes facilitate an increase in stroke volume and cardiac output at a lower mean arterial pressure, enabling greater aerobic capacity and physical performance. The diastolic drop reflects a reduced systemic vascular resistance of the muscle arterioles in response to the exercise.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Pulse pressure

Start with the simplest possible case. Write down what Pulse pressure claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Pulse pressure before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Pulse pressure ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Pulse pressure

In research: Pulse pressure appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Pulse pressure in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Pulse pressure is common in secondary-school and first-year university syllabi. It links to neighbouring topics Blood pressure, Cardiovascular physiology, Medical signs, so understanding it makes those chapters shorter.
In everyday life: Look for Pulse pressure outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Pulse pressure in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Pulse pressure means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Pulse pressure out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Pulse pressure in simple terms?

Pulse pressure is the difference between systolic and diastolic blood pressure. It is measured in millimeters of mercury (mmHg).

Why does Pulse pressure matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Pulse pressure?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Pulse pressure.