Noninvasive investigation of blood pressure changes using the pulse wave transit time: a novel approach in the monitoring of hemodialysis patients

Abstract

Severe blood pressure changes are well known in hemodialysis. Detection and prediction of these are important for the well-being of the patient and for optimizing treatment. New noninvasive methods for this purpose are required. The pulse wave transit time technique is an indirect estimation of blood pressure, and our intention is to investigate whether this technique is applicable for hemodialysis treatment. A measurement setup utilizing lower body negative pressure and isometric contraction was used to simulate dialysis-related blood pressure changes in normal test subjects. Systolic blood pressure levels were compared to different pulse wave transit times, including and excluding the cardiac preejection period. Based on the results of these investigations, a pulse wave transit time technique adapted for dialysis treatment was developed and tried out on patients. To determine systolic blood pressure in the normal group, the total pulse wave transit time was found most suitable (including the cardiac preejection period). Correlation coefficients were r = 0.80 +/- 0.06 (mean +/- SD) overall and r = 0.81 +/- 0.16 and r = 0.09 +/- 0.62 for the hypotension and hypertension phases, respectively. When applying the adapted technique in dialysis patients, large blood pressure variations could easily be detected when present. Pulse wave transit time is correlated to systolic blood pressure within the acceptable range for a trend-indicating system. The method's applicability for dialysis treatment requires further studies. The results indicate that large sudden pressure drops, like those seen in sudden hypovolemia, can be detected.

A new approach for detecting sudden hypotension in hemodialysis by using dual-channel optical system

“…The results of Ahlstrom's study showed that pressure was estimated with a higher correlation with PTT. 26 Our results were in good agreement with the aforementioned report while we did not use ECG for continuous BP. In studies that calculate PTT based on QRS complex extraction from the ECG as a time reference, this may not be the optimum reference to use as stated by the previous studies.…”

An examination of calibration intervals required for accurately tracking blood pressure using pulse transit time algorithms

“…These results support findings by other authors that using PTT alone is not enough and other cardiac parameters such as pre-ejection period should be included in the algorithms. 17,18 Other authors have also investigated using different methods of relating PTT to BP. Fung et al 19 derived a relation using the kinetic energy of the pulse wave as a basis and incorporated various body measurements, as well as an estimation for pre-ejection period in their algorithm.…”

Beat-to-beat blood pressure measurement from instantaneous harmonic phase-shifts in non-invasive photoplethysmographic signals

“…The correlation coefficients found were at least |r| = 0.85 for SBP and |r| = 0.61 for DBP [1][2][3][4][5]. Even though, the estimation of the PTT has some disadvantages: (i) the dependency on the measuring location and the length of measuring distance, (ii) the choice and method to find minima, maxima and saddle points within the photoplethysmography (PPG) and electrocardiography (ECG) signals, (iii) appearance of undetermined fluctuations in the time delay between the pressure wave and the ECG Rpeak during blood ejection of the left ventricle and (iv) the influences of auto-regulation on arterial stiffness that produce undetermined drifts of the PTT values over time [6][7][8][9][10].…”