1. Sphygmomanometer Gauges
Unit 31
Sphygmomanometer Gauges

2. Basic Principles of Reading Sphygmomanometer Gauges
A sphygmomanometer is an instrument calibrated for measuring blood pressure (BP) in millimeters (mm) of mercury (Hg).
There are two main types of sphygmomanometer gauges, mercury and aneroid.

3. Basic Principles of Reading Sphygmomanometer Gauges
The mercury sphygmomanometer as shown on the next slide has a long column of mercury.
Each line on the gauge represents two millimeters of mercury (mm Hg). If it is calibrated correctly, the level of mercury should be at zero when viewed at eye level.
Because blood pressure is recorded as the pressure drops in the gauge, it is best to learn to read the gauge in a backward direction.

4. Basic Principles of Reading Sphygmomanometer Gauges
Mercury sphygmomanometer gauge. 4

5. Basic Principles of Reading Sphygmomanometer Gauges
The aneroid sphygmomanometer gauge as shown on the next slide does not have a column of mercury. It is calibrated equivalent to mm Hg, and each line represents 2 mm Hg.
Note that long lines represent a multiple of 10.
Because readings are recorded as the pressure drops, it is best to learn to read the gauge in a backward direction.

6. Basic Principles of Reading Sphygmomanometer Gauges
Aneroid sphygmomanometer gauge.

7. Basic Principles of Recording Blood Pressure
Blood pressure (BP) is a measurement of the pressure that the blood exerts on the walls of the arteries during the various stages of heart activity.
There are two types of BP measurements: systolic and diastolic.

8. Basic Principles of Recording Blood Pressure
Systolic pressure occurs in the walls of the arteries when the left ventricle of the heart is contracting and pushing blood into the arteries.
A normal range for systolic pressure is 100 to 120 mm Hg.
Diastolic pressure is the constant pressure in the walls of the arteries when the left ventricle of the heart is at rest, or between contractions.
A normal range for diastolic pressure is 60 to 80 mm Hg.

9. Sphygmomanometer Gauges
Example: On the aneroid sphygmomanometer gauge shown on the next slide (calibrated equivalent to mm Hg; each line represents 2 mm Hg), a reading 4 lines below 160 would be what?

10. Sphygmomanometer Gauges
A reading 4 lines below the 160 mark equals:
160 – 2 – 2 – 2 – 2
= 152 mm Hg
- The correct reading would be 152 mm Hg.

11. Practical Problem
When using an aneroid sphygmomanometer as shown on the next slide, what is the correct reading 2 lines below the 120 mark?

12. Practical Problem

13. Practical Problem Each line equals 2 mm Hg, so subtract:
120 – 2 – 2 = 116
The correct reading is 116 mm Hg.