Similarity between the suprasystolic wideband external pulse wave and the first derivative of the intra-arterial pulse wave

Wideband External Pulse Recorded During Cuff Blood Pressure Measurement: A New Technique for Cardiovascular Assessment

Introduction

The wideband external pulse (WEP) recorded during blood pressure measurement reveals three components (K1, K2, K3). K1 is recorded with cuff pressure (CP) above systolic (SP).

Aim

To assess whether the K1 pattern contains information about the functional and structural properties of the cardiovascular system.

Methods

WEP analysis, echocardiography, carotid artery (CA) ultrasonography and applanation tonometry were conducted on 178 hypertensives. K1R, a feature of K1, was defined to provide a measure between the arterial incident and backward reflective waves.

Results

K1R was strongly correlated to vascular functional and structural parameters compatible with vascular effects of aging and hypertension. ANOVA analysis (K1R < 0 vs K1R > 0) showed that K1R < 0 participants: (1) were older, shorter, weighed less, had a smaller body surface area; (2) had higher SP, pulse (PP) and mean (MP) pressure, lower heart rate (HR), greater total peripheral resistance (TPR), lower cardiac output (CO), and a stiffer arterial system; (3) had a greater left ventricular (LV) relative wall thickness (LVRWT), carotid artery (CA) relative wall thickness (CARWT), CA far-wall intima-media thickness at end diastole (CIMTd) and CA cross-sectional area (CSA) (all p < 0.001). Regressions revealed that age, TPR, SP, gender, and HR predicted K1R (R² = 0.64) and that PP and K1R predicted CARWT (R² = 0.14). Logistic regression revealed that age, TPR, SP and aortic diameter differentiated K1R < 0 from K1R > 0 (Nagelkerke R² = 0.77).

Conclusions

K1R is related to vascular functional properties, with suggestive evidence that K1R is also related to vascular structural properties and perhaps subsequent cardiovascular risk.

Design of a Continuous Blood Pressure Measurement System Based on Pulse Wave and ECG Signals

With increasingly fierce competition for jobs, the pressures on people have risen in recent years, leading to lifestyle and diet disorders that result in significantly higher risks of cardiovascular disease. Hypertension is one of the common chronic cardiovascular diseases; however, mainstream blood pressure measurement devices are relatively heavy. When multiple measurements are required, the user experience and the measurement results may be unsatisfactory. In this paper, we describe the design of a signal collection module that collects pulse waves and electrocardiograph (ECG) signals. The collected signals are input into a signal processing module to filter the noise and amplify the useful physiological signals. Then, we use a wavelet transform to eliminate baseline drift noise and detect the feature points of the pulse waves and ECG signals. We propose the concept of detecting the wave shape associated with an instance, an approach that minimizes the impact of atypical pulse waves on blood pressure measurements. Finally, we propose an improved method for measuring blood pressure based on pulse wave velocity that improves the accuracy of blood pressure measurements by 58%. Moreover, the results meet the american medical instrument promotion association standards, which demonstrate the feasibility of our measurement system.

Non-invasive model-based estimation of aortic pulse pressure using suprasystolic brachial pressure waveforms

Elevated central arterial (aortic) blood pressure is related to increased risk of cardiovascular disease. Methods of non-invasively estimating this pressure would therefore be helpful in clinical practice. To achieve this goal, a physics-based model is derived to correlate the arterial pressure under a suprasystolic upper-arm cuff to the aortic pressure. The model assumptions are particularly applicable to the measurement method and result in a time-domain relation with two parameters, namely, the wave propagation transit time and the reflection coefficient at the cuff. Central pressures estimated by the model were derived from completely automatic, non-invasive measurement of brachial blood pressure and suprasystolic waveform and were compared to simultaneous invasive catheter measurements in 16 subjects. Systolic blood pressure agreement, mean (standard deviation) of difference was -1 (7)mmHg. Diastolic blood pressure agreement was 4 (4)mmHg. Correlation between estimated and actual central waveforms was greater than 90%. Individualization of model parameters did not significantly improve systolic and diastolic pressure agreement, but increased waveform correlation. Further research is necessary to confirm that more accurate brachial pressure measurement improves central pressure estimation.

Noninvasive assessment of arterial pressure

PURPOSE OF REVIEW

To briefly review recent advances in the noninvasive assessment of arterial pressure (indirect methods) in the field of critical care.

RECENT FINDINGS

Automated oscillometric measurements underestimate intraarterial systolic blood pressure. Digital photoplethysmography has led to conflicting results, although the obtained respiratory pulse pressure variation correlates with the fluid-challenge-induced changes in stroke volume. The pulse oximetry photoplethysmographic signal recorded at the digital or ear level may be useful in monitoring respiratory arterial pressure variations, although technical improvements and clarifications are needed. Arterial tonometry is increasingly used in the cardiovascular field to reconstruct central aortic pressure. A recent study has shown that radial artery tonometry is feasible in hemodynamically stable patients and that peripheral pulse pressure reflects the combined influences of arterial stiffness and stroke volume, especially in elderly patients. The limitations of this technique include the potential bias related to the use of a generalized transfer function and the difficulty in obtaining reliable recordings in hemodynamically unstable patients.

SUMMARY

Intraarterial blood pressure must be preferred over noninvasive blood pressure recordings when critical decisions are required. In hemodynamically stable patients, valuable information may be obtained by using noninvasive techniques, amongst which arterial tonometry seems especially promising.