Human Cardiovascular Function

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Department of Physiology

PHY2042

Body Systems Physiology

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Human Cardiovascular Function
Worksheet

Pre-prac reading: Vander’s Human Physiology, 13th Edition

Chapter 12, sections A, B, C, D & E

Due by:

Noon (12 pm) Friday September 23

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Observations of Human Cardiovascular Function

Part 1                The Arterial Pulse

1.        Why is it possible to feel the arterial pulse in a superficial artery?

The superficial artery is located close to the surface of the skin. Pressure can be applied at this point to feel the arterial pulse.

Part 2                Indirect Measurement of Human Blood Pressure

1.        Record in the table below the systolic and diastolic blood pressure determined by the auscultatory method in three group members.

        Also record in the table the pulse pressure and mean arterial pressure for each subject

2.        Record in the table below the systolic and diastolic blood pressure determined using the cardiomicrophone in the same group members as for question 1.

        Also record in the table the pulse pressure and mean arterial pressure for each subject

3.        List below the systolic blood pressure determined using the finger pulse transducer in the same group members as for question 1.

4.        In one subject from your group, list below the systolic blood pressure determined with the hand hanging loosely down by the side (below heart), on the desk or chair arm (heart level) and above the head (above heart).

5.        Suggest two possible sources of error or variation in the auscultatory technique for blood pressure measurement?

The observer may not have heard the initial point at which the sounds began, This would result in a lower systolic blood pressure measurement. Secondly, the observer may have had difficulty distinguishing precisely where the Korotkoff sounds stop. This would result in an inaccurate dialstolic blood pressure measurement.

6.        Explain the underlying cause of the Korotkoff sounds that you detected with the cardiomicrophone as the cuff pressure was decreased.

The Korotkoff sounds are cause by turbulent blood flow. The usual laminar flow in the arteries causes little vibration in the arterial walls and the blood vessels are not constricted – this is why we do not normally hear the Korotkoff sounds. Partial constriction of the artery causes turbulent blood flow and the artery produces more  vibrations and sounds. In this instance, turbulent blood flow occurred as the cuff pressure was greated than the diastolic and less than the systolic pressure. Increased resistance of blood flow causes turbulent flow which results in Korotkoff noises – detected by the cardiomicrophone.

7.        Why does the finger pulse transducer, which operates on the same principle as the palpatory method (Riva Rocci), tend to give systematically low estimates of systolic blood pressure?

Sounds are detectable at the point of systolic blood pressure i.e. when blood starts to go through the compressed point of artery.         In this instance, the cuff is too tight at the point of systolic blood pressure resulting in restricted blood flow. This decreases wall expansion and how detectable the pulse is. The pulse transducer is delayed in determining systolic blood pressure which produces lower estimates.

8.        Do you think that pulse measurement can replace the stethoscope in determining diastolic pressure? Why?

No. Pulse measurement only produces an estimate of systolic blood pressure – detects pulse. Even when the cuff is reduced to diastolic, the pulse is present indicating that the absence of Korotkoff sounds cannot be detected. Thus, diastolic pressure cannot be estimated.

9        Briefly explain why the arterial pressure measured using the finger pulse is different with the arm in different positions.