Mercury sphygmomanometer principle explained

Introduction: Before the advent of electronic sphygmomanometers, people used traditional mercury sphygmomanometers. Mercury sphygmomanometer operation is more difficult, only people with certain medical experience can master the use of method. In the current medical people measuring blood pressure method is generally indirect method, sphygmomanometer respectively by the balloon, check pressure meter, cuff composition, in the medical cuff of the rubber capsule two tubes were connected with the check pressure machine and balloon. Here is a detailed knowledge of the principle of mercury sphygmomanometer.

Classification of traditional sphygmomanometers

There are two kinds of desktop, vertical, vertical sphygmomanometers can be adjusted to any height.

The working principle of the mercury sphygmomanometer

Measurement of blood pressure with a balloon to the cuff wrapped in the upper arm of the inflatable pressure, the pressure through the soft tissues of the role of the brachial artery. When the pressure is higher than the systolic pressure, the balloon is slowly deflated outward, and the pressure inside the cuff is then lowered, when the pressure inside the cuff is lower than the systolic pressure, the pressure inside the cuff is lowered. Then fell, when the pressure in the cuff is equal to or slightly lower than the cardiac contraction pressure, with the cardiac contraction ejection, the blood can be rushed away from the blocked blood vessels to form a vortex, with a stethoscope will begin to hear the sound of the beat, at this time, the pressure value indicated by the manometer is equivalent to the systolic pressure.

Continue to slowly deflate, so that the pressure in the cuff is gradually reduced, when the pressure in the cuff is lower than the systolic blood pressure, but higher than the diastolic blood pressure of this period of time, the heart every contraction, can be heard once. When the pressure in the cuff is lowered to a level equal to or slightly lower than the diastolic pressure, the blood flow is unimpeded, and the sound accompanying the heartbeat suddenly weakens or disappears, at which time the pressure indicated by the manometer is equivalent to the diastolic pressure. Blood pressure measured by the indirect method is an approximation, and its accuracy is somewhat related to the measurement technique. During measurement, the cuff should be stretched out so that the zero point of the upper arm, heart and mercury detector (or spring detector) are kept at the same level as far as possible, and the deflation should not be too fast, otherwise there will be a large error.

Poor sensitivity is manifested in the uniform pressurization or depressurization, the mercury column rises and falls sluggishly, and there is a jumping phenomenon.

The main reason for the difference in sensitivity is the mercury oxide generated by the oxidation of mercury, hindering the rise and fall of the mercury column;?

In addition to the upper end of the oscillometric tube ventilation holes are blocked will also cause this failure. The solution; repeated filtration of mercury to remove the mercury oxide; clean the tube; keep the vent open.

Mercury sphygmomanometer calibration method is how

Because of its frequent use, poor maintenance, easy to fail. Then? Mercury sphygmomanometer in the use of common failures are:

1, the mercury column broken line or bubble: the use of pressure, mercury sphygmomanometer mercury column broken line or bubble phenomenon, the main reason for the storage of mercury vials in the amount of mercury is too small caused; in addition, the mercury column in the middle of the air, the display tube wall or storage of mercury vials is too dirty as well as storage vials of mercury vials at the mouth of the wind there is also a gap in the reason;

2, the mercury Leakage: mercury leakage is also one of the common failures of the mercury sphygmomanometer, its causes: mercury storage poor cracks or mercury storage vials glued at the cracks; mercury storage valve is damaged; mercury leakage will lead to mercury sphygmomanometer can not work properly, only after the repair can be used.

3, zero misalignment: the causes of zero misalignment is; the amount of mercury is too much or too little; mercury storage bottle on the lid of the air permeability is poor; mercury or mercury storage bottle is too dirty; mercury storage bottle bottom bore channel is not smooth.

4, poor sensitivity: poor sensitivity is manifested in the uniform pressurization or depressurization, the mercury column rise and fall sluggishly, there is a jump phenomenon.

The main reason for the poor sensitivity is the mercury in the oxidation of mercury oxide generated by dirtying the wall of the tube, hindering the sensitive rise and fall of the mercury column; in addition to the upper end of the tube is clogged with air holes will also cause this failure.

Solution of the method; repeated filtration of mercury, remove the mercury oxide; cleaning of the tube; to keep the ventilation holes smooth. Then when encountered the above problems, how should be calibrated when the mercury sphygmomanometer encountered quality problems, should be replaced in a timely manner, and the mercury sphygmomanometer generally need to be calibrated once a year, you need to monitor the Technical Supervision Bureau, the use of is to open the switch, the mercury flat zero or open the switch to tilt the mercury gradually and uninterruptedly to reach 180 mmHg or more uninterrupted is the standard.

What you should pay attention to the use of

1, rationalize the rubber skin tube, to prevent knots, entanglement and so on, to keep the airway open.

2, after opening the mercury pot, the mercury level should reach the zero line, if less than, be sure to send for repair. This situation is due to the amount of mercury is not enough, will cause the measurement results inaccurate, mercury stratification and even splash out and other consequences.

3, when the mercury level rises to a higher position, be sure to slow down the pumping speed, to prevent for some reason caused by the liquid surface shock, so that the mercury splash out.

4, if you find that when pumping, the liquid level stops rising, be sure to stop pumping and check whether the air circuit is smooth.

5, do not raise the mercury to the highest place, to meet the clinical needs.

6, after use, remember to tilt to the right at least 45 °, wait for the mercury to flow back to the mercury pot, close the mercury pot switch.

7, once the mercury leaks out, remember to immediately sprinkle a large amount of sulfur powder to oxidize the mercury to mercury sulfide.

In the process of mercury use often appear zero out of alignment, caused by the amount of mercury in the sphygmomanometer is too much or too little, the specific solution is to adjust the amount of mercury in the sphygmomanometer, so that the zero calibration. Sometimes the mercury will also appear rubber cushion cushion blockage, when this situation will lead to the rise of the mercury becomes slow, which affects the measurement results, you can use a needle to make the rubber cushion usually. I hope that my explanation can bring you harvest oh. The above is about the principle of mercury sphygmomanometer content, I hope it can help you!

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