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Table 2 Overview of properly seated blood pressure measurement using smartwatch device

From: Smartphone / smartwatch-based cuffless blood pressure measurement : a position paper from the Korean Society of Hypertension

Critical steps for proper BP measurements Specific introductions
Step 1: Properly prepare the position and the autonomic BP measurement device for the calibration 1. Have the patient relax, sitting in a chair with feet flat on the floor and back supported. The patient should be seated for 3–5 min without talking or moving around. Arm and wrist should be dry and free of excessive perspiration or skin lotion.
2. The patient should avoid caffeine, exercise, and smoking for at least 30 min before measurement.
3. Ensure that the patient has emptied his/her bladder.
4. Neither the patient nor the observer should talk during the rest period or the measurement.
5. Sit in the chair with the back well-supported, legs uncrossed, and feet flat on the ground. Support the user’s arm (e.g., resting on a desk). The patient should not be holding his/her arm because the isometric exercise will affect the BP levels. During the measurement, the user should breathe normally, avoiding deepen or slow down the breath.
6. Use an upper-arm, cuff-based BP monitoring device validated and ensured that it is calibrated periodically.
8. Use the correct cuff size such that the bladder encircles 75–100% of the arm.
Step 2: Calibration 1. Wear the smartwatch on the wrist, not too tight.
2. Position the middle of the cuff on the patient’s upper arm (wearing smartwatch) at the level of the right atrium (midpoint of the sternum).
3. Acquire the pulse wave by the smartwatch
4. Acquire the reference blood pressure by the upper-arm, cuff-based BP monitoring device. At the first measurement, record BP in both arms. If the systolic blood pressures between two arms are different by 10 mmHg, visit the hospital and check the cause of the inter-arm difference.
5. Then, enter the cuff-based blood pressure monitor reading on the smartphone. Repeat steps 3–5 two more times (for a total of three measurements).
Step 3: Measurement Keep the step 1–5 in Step 1.
Step 4: Regular recalibration Recalibrate regularly to keep the BP value correctly. If the wearer of the smartwatch is changed or the wearing position is changed to the other arm, the watch must be recalibrated.