Recently, I encountered a postoperative patient with apnea and routinely received oxygen on the ECG monitor. The family members of the patient were nervous and asked the author to explain to him what the values on the ECG monitor screen represent and what the normal range is. After explaining everything from blood pressure to blood oxygen to the family and preparing to leave, suddenly the family pointed to the number in parentheses behind the blood pressure value and asked the author what is this? But the author fell down.

　　 went back to the nurse's station and immediately consulted the instruction manual of the ECG monitor. The instruction manual did not explain the values in parentheses. But after reading the blood pressure setting menu, the author initially estimated that the value in brackets is the average pressure, that is, the average arterial pressure.

　　So what is the mean arterial pressure?

　　The explanation in the book "Basic Nursing" is: in a cardiac cycle, arterial blood pressure fluctuates regularly with the contraction and relaxation of the ventricle. When the ventricles contract, the arterial blood pressure rises to the highest value called systolic blood pressure. At the end of ventricular diastole, the lowest value of arterial blood pressure drop is called diastolic blood pressure. The difference between systolic and diastolic blood pressure is called pulse pressure. In a cardiac cycle, the average value of arterial blood pressure is called mean arterial pressure, which is equal to diastolic blood pressure plus 1/3 pulse pressure or 1/3 systolic blood pressure plus 2/3 diastolic blood pressure. Mean arterial pressure is related to cardiac output and systemic resistance, and is one of the indicators of good organ tissue perfusion. That is, the calculation formula of mean arterial pressure is as follows: mean arterial pressure = 1/3 systolic pressure + 2/3 diastolic pressure, or mean arterial pressure = diastolic pressure + 1/3 pulse pressure. Then the average arterial pressure of blood pressure 118/73mmHg=118*1/3+73*2/3=88. Therefore, the value in brackets behind the blood pressure value on the ECG monitor screen is indeed the mean arterial pressure. It is worth noting that some papers pointed out that there is a certain difference between the average arterial pressure obtained by the calculation formula and the actual average arterial pressure.

　　In order to reduce the difference, what should I pay attention to when using an ECG monitor to measure non-invasive blood pressure?

　　1. Before starting the measurement, confirm whether the selected monitoring method is suitable for the patient. Choose the appropriate armband for the patient. If you choose an inappropriate armband, you will not get the correct measurement value.

　　2. Non-invasive blood pressure measurement should not be performed on patients suffering from sickle cell disease and any skin damage or expected damage.

　　3. Do not take non-invasive blood pressure measurement on the arm that has undergone mastectomy.

　　4. Do not install armbands on limbs with intravenous infusion or catheterization. During the inflation of the cuff, when the infusion slows down or becomes blocked, it may cause injury around the catheter.

　　5. The inflatable tube connecting the blood pressure cuff and the monitor should be unobstructed and not entangled in the arm or other parts. If the air in the armband cannot be exhausted, it will cause peripheral dysfunction due to limb ischemia.

　　6. If the non-invasive pressure measurement time in continuous measurement mode is too long, the limbs rubbing with the armband may be accompanied by purpura, ischemia and nerve damage. When monitoring patients, always check the color, warmth and sensitivity of the distal limbs. Once any abnormality is observed, place the armband in another place or stop blood pressure measurement immediately.

　　7. Blood pressure cannot be measured in patients with extreme pulse rates (less than 40 beats/min or greater than 240 beats/min) or patients who are connected to a heart-lung machine. In the following situations, the measurement may be inaccurate or impossible:

　　1) If it is difficult to detect regular arterial pressure pulsations

　　2) Suffer from arrhythmia

　　3) Excessive and continuous patient movement

　　4) Rapid changes in blood pressure

　　5) Severe shock or hypothermia, reducing blood flow to the surrounding area

　　6) Because of obesity, the thick fat layer around the limbs attenuates the concussion from the arteries

　　7) On the edema limb