Question

An important "vital sign" for monitoring human health is blood pressure. In particular, doctors want to know what the pressure of a patient's blood is as it passes through the heart. Use the energy density model with energy- density-system representation to logically respond to these FNT prompts.

(a) What are the two separate fluid systems when a cuff is used measure a person’s blood pressure. Are the two systems connected, and if so, how?
(b) Why is blood pressure normally measured with a cuff around the upper arm with the person sitting upright?
(c) Suppose you want to measure the blood pressure of a person and for whatever reason (perhaps due to injury), you are not able to use an upper arm of the person to measure the blood pressure, so you have to use a leg instead. In what position would you place the person before making the measurement? Why?
(d) Given that you want to find the pressure at heart level, and if you knew what the normal blood pressure at that level should be, show how you could calculate the percent error you would get if you measured a patient’s blood pressure on the patient’s leg while the patient was sitting up?

Answer 1

To measure blood pressure, a sphygmomanometer with an inflatable cuff and a mercury manometer is used. Blood pressure is typically measured at the upper arm level with the heart, and if the arm is unavailable, the cuff can be placed on the leg while the patient is lying down. To determine percent error in this position, compare the leg reading to the expected heart-level reading, accounting for the hydrostatic pressure difference.

Step-by-step explanation:

Understanding Blood Pressure Measurements

An important vital sign in monitoring human health is blood pressure, often measured with a sphygmomanometer. This device includes an inflatable cuff placed on the upper arm at the same level as the heart to restrict blood flow, and a manometer, typically filled with mercury, to measure the pressure.

(a) Two Fluid Systems in Blood Pressure Measurement

When measuring blood pressure using a cuff, there are two separate fluid systems involved: the blood in the arteries and the air in the cuff. These two systems are connected via the pressure that the cuff applies to the artery. The cuff inflates to restrict blood flow, and as it deflates, the pressure at which blood begins to flow again is the systolic pressure. When blood flows without interruption, it indicates the diastolic pressure.

(b) Positioning for Blood Pressure Measurement

Blood pressure is usually measured with a cuff around the upper arm while the person is sitting upright to ensure that the cuff is at the same level as the heart, minimizing the effects of gravity on blood flow and pressure readings.

(c) Alternative Measurement Position

If an upper arm cannot be used, the cuff can be placed on a leg. In this case, the person should be lying down with the leg elevated to the level of the heart to ensure accurate readings, considering the effects of hydrostatic pressure.

(d) Calculating Percent Error in Blood Pressure Measurement

To find the percent error when measuring blood pressure on the leg of a sitting patient, you'd compare the expected pressure at the heart level (e.g., 120/80 mm Hg) to the reading from the leg, accounting for the hydrostatic pressure difference due to the height difference between the heart and the leg. The formula for percent error is |(Experimental value - Theoretical value) / Theoretical value| x 100%.

Answer 2

A.

Step-by-step explanation:

The force that is applied by the blood against the arterial walls refers to the blood pressure. It is a reflection of the work done by the heart. It is dependent on the volume of the blood and the resistance of the blood vessels.