Wrist measurement of blood pressure: some critical remarks to oscillometry

Cuff-Less Blood Pressure Prediction Based on Photoplethysmography and Modified ResNet

Cardiovascular disease (CVD) has become a common health problem of mankind, and the prevalence and mortality of CVD are rising on a year-to-year basis. Blood pressure (BP) is an important physiological parameter of the human body and also an important physiological indicator for the prevention and treatment of CVD. Existing intermittent measurement methods do not fully indicate the real BP status of the human body and cannot get rid of the restraining feeling of a cuff. Accordingly, this study proposed a deep learning network based on the ResNet34 framework for continuous prediction of BP using only the promising PPG signal. The high-quality PPG signals were first passed through a multi-scale feature extraction module after a series of pre-processing to expand the perceptive field and enhance the perception ability on features. Subsequently, useful feature information was then extracted by stacking multiple residual modules with channel attention to increase the accuracy of the model. Lastly, in the training stage, the Huber loss function was adopted to stabilize the iterative process and obtain the optimal solution of the model. On a subset of the MIMIC dataset, the errors of both SBP and DBP predicted by the model met the AAMI standards, while the accuracy of DBP reached Grade A of the BHS standard, and the accuracy of SBP almost reached Grade A of the BHS standard. The proposed method verifies the potential and feasibility of PPG signals combined with deep neural networks in the field of continuous BP monitoring. Furthermore, the method is easy to deploy in portable devices, and it is more consistent with the future trend of wearable blood-pressure-monitoring devices (e.g., smartphones and smartwatches).

Validation of the A&D wrist-cuff UB-511 (UB-512) device for self-measurement of blood pressure

OBJECTIVES

To determine the accuracy of the A&D UB-511 (UB-512) oscillometric wrist-cuff device for self-measurement of blood pressure, the only difference between the two devices being the size of storage memory.

METHODS

Device evaluation was performed according to the modified British Hypertension Society protocol released in 1993. Eighty-five study participants with characteristics outlined in the British Hypertension Society protocol were recruited among those attending our out-patient clinic. The device was evaluated according to the various steps of the protocol. The non-dominant arm was used for blood pressure measurement. To maintain the wrist at cardiac level during validation, the arm was kept horizontal at the mid-sternum level and supported by a soft table. The wrist was kept extended. Sequential readings were taken for the main validation test. Outcome was classified according to the criteria of the British Hypertension Society recommendations, which are based on four strata of accuracy differing from the mercury standard by 5, 10 and 15 mmHg, or more.

RESULTS

The device achieved a British Hypertension Society grade B for systolic and a grade B for diastolic blood pressure. The device tended to overestimate arm blood pressure, the mean difference (+/-1 SD) between device and observers being 4.3+/-8.7 mmHg for systolic blood pressure and 3.7+/-8.1 mmHg for diastolic blood pressure for observer 2, and 4.4+/-8.6 mmHg for systolic blood pressure and 3.8+/-7.9 mmHg for diastolic blood pressure for observer 1. In a logistic regression analysis, age was the sole predictor of an achieved difference between device and mercury column by 5 mmHg or less (hazard ratio 1.020; 95% confidence interval 1.003-1.04; P=0.024).

CONCLUSIONS

These data show that the A&D UB-511 (UB-512) device satisfies the British Hypertension Society recommendations with a grade B/B. The device tends to overestimate cuff blood pressure and its accuracy increases with age.

Short-Term Effects of a Single Exercise Bout at Moderate Altitude on Blood Pressure

Context:

Effects of a single bout of exercise at moderate altitude on blood pressure (BP) are largely unknown.

Objective:

To evaluate the effect of a single exercise bout at moderate altitude on BP.

Design:

Prospective, observational.

Setting:

Field study, Alpine mountains.

Participants:

127 men, 71 women (138 normotensive, 60 hypertensive).

Intervention:

Exercise duration: 2.5 ± 0.4 h; 650-m difference in altitude.

Main Outcome Measures:

BP and heart rate (HR).

Results:

Hypertensives had (1) higher systolic BP (SBP) and diastolic BP (DBP) before exercise (P< .01), whereas this difference was lost during exercise; (2) increased HR during the entire duration of exercise; and (3) significantly decreased SBP and DBP (P< .05) throughout the entire period of exercise.

Conclusions:

Exposure to a single exercise bout at moderate altitude is associated with a transient decrease in SBP and DBP, which is more pronounced in hypertensives.

Comparison of wrist blood pressure measurement with conventional sphygmomanometry at a cardiology outpatient clinic

OBJECTIVE

Oscillometric measurement of blood pressure at the wrist is becoming a widely used method for detection of hypertension and its control by treatment. The objective of the present study was to evaluate accuracy and suitability of wrist measurement in a clinical routine setting.

PATIENTS AND METHODS

A series of 333 consecutive patients admitted to our cardiology outpatient clinic were included. Blood pressure was measured at both upper arms according to World Health Organization-International Society of Hypertension guidelines. Oscillometric measurement was performed at the contralateral wrist simultaneously. Blood pressure readings were taken by an oscillometric device applied at the wrist ('Klock'; Industrielle Entwicklung Medizintechnik, Stolberg, Germany) and a conventional mercury sphygmomanometer applied at the upper arm.

RESULTS

Seventy-eight patients were excluded due to differences in blood pressure > 5 mmHg between both upper arms or due to 'error' messages of the wrist device. The data of the remaining 255 patients (149 males; mean age, 65 +/- 13 years; range, 18-95 years) are presented. Mean conventional blood pressure was significantly lower compared with the wrist device (137 +/- 20/80 +/- 11 mmHg versus 153 +/- 28/87 +/- 18 mmHg; P < 0.001 and P < 0.001). The mean difference was 16 +/- 25/6 +/- 17 mmHg. In clinical terms, differences in blood pressure exceeding +/-20/+/-10 mmHg reflecting classification of hypertension are considered important. Measurements of 101 (40%) patients were within these limits. Systolic readings of 110 (43%) and diastolic readings of 117 patients (46%) were beyond this scope.

CONCLUSION

Due to low reliability of wrist blood pressure measurement, it cannot compete with the upper arm standard procedure. If ever, it should only be used if test readings in an individual comparing wrist and upper arm measurement show differences within a range of +/-20/+/-10 mmHg.