Usually, when they mention a term like that in a textbook, the answer is to be found in the next sentence or two or in the index. What have you found out about it? If something about what you read confused you, explain, and we'll try to help.
Think about what would cause your systolic and diastolic pressures to either be closer together or farther apart. It could be a neuro cause like in "Cushing's Triad," (bradycardia, widening pulse pressure and irregular respirations). Or it could be a cardiac cause such as cardiac tamponade where you get a narrowing pulse pressure do to the impaired filling ability of the heart. Anytime you see blood pressures that are not normal you want to look for a reason why.
We are happy to help with homework and explain things.....but we want you to tell us what you think first. It isn't just WHAT causes these phenomenons to occur.......why do these phenomenons occur? what is the pathophysiology. It isn't enough just to know what causes a situation you need to know why this occurs to you can critical think/problem solve how to treat/intervene.
I suppose in the past I've always thought of BP as shifting to an either high or low state, so this concept of widening or narrowing pulse pressure is interesting to me. The definition is explained in the text, but I was more curious whether there are any key causes that are associated with either of these two. I understand that widening PP would be indicative of a slower overall heart contraction and relaxation and a narrowing PP would conversely be related to a faster contraction and relaxation. I was curious to see if either of these states trigger a common cause to all of you experienced nurses?
Widening pulse pressure that is associated with head trauma.
The Cushing reflex (not to be confused with Cushing's triad is a hypothalamic response to ischemia, usually due to poor perfusion (delivery of blood) in the brain.
The Cushing reflex consists of an increase in sympathetic outflow to the heart as an attempt to increase arterial blood pressure and total peripheral resistance, accompanied by bradycardia.
The ischemia activates the sympathetic nervous system, causing an increase in the heart's output by increasing heart rate and contractility along with peripheral constriction of the blood vessels. This accounts for the rise in blood pressure, ensuring blood delivery to the brain. The increased blood pressure also stimulates the baroreceptors (pressure sensitive receptors) in the carotids, leading to an activation of the parasympathetic nervous system, which slows down the heart rate, causing the bradycardia.
The Cushing reflex is usually seen in the terminal stages of acute head injury.
A pulse pressure is considered abnormally low if it is less than 25% of the systolic value. 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 (insufficient preload leading to reduced cardiac output).
If the pulse pressure is extremely low, i.e. 25 mmHg or less, the cause may be low stroke volume, as in Congestive Heart Failure and/or shock.
A narrow pulse pressure is also caused by aortic valve stenosis and cardiac tamponade.
Low pulse pressure in tamponade is caused by the inability of the heart to fill fully because the pericardium is full of fluid or blood or tumor, so each beat is low in pressure. The pulse pressure is decreased because the systolic is so low. Aortic stenosis obstructs output and has the same result. Bradycardia, whether as part of Cushing's triad, complete heart block, or toxic effects on the heart, or many other things, widens the pulse pressure because the diastolic pressure has such a long time to run off into the capillary bed before the next booming systole.
Good thinking, OP. Pulse pressure, as you can see, is a sign but not a diagnosis. Many different diagnoses can account for changes, so it's only one piece of the puzzle.