Pulse transit time

Poyares D, Guilleminault C, Rosa A, Ohayon M, Koester U. Arousal, EEG spectral power and pulse transit time in UARS and mild OSAS subjects. Clin Neurophysiol 2002 113 1598-1606. 

To study the skin-core effects in more detail, ultrasonic measurements were made on a sample as it was machined progressively thinner from alternate sides, with the removed layer being 0.4 mm thick. Results from successive experiments were compared to obtain the pulse transit times for the layer of material which had been removed. Analyses of these transit times gave the profiles of 3 and for sample 1 shown in Figures 14.8 and 14.9, respectively. Besides the peak in the modulus in the skin region there is another peak about 1.2 mm from the surface of the plaque. This peak has also been observed in static modulus experiments on other injection molded plaques and has been attributed... 

C. C.Y. Poon and Y. T. Zhang, Cuff-less and noninvasive measurements of arterial blood pressure by pulse transit time, in Proceedings of the 27th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, China, pp. 5877-5880, 2005. 

C. C. Y. Poon, Y. T. Zhang and Y. B. Liu, Modeling of pulse transit time under the effects of hydrostatic pressure for cuffless blood pressure measurements, in Proceedings of the 3rd lEEE-EMBS International Summer School and Symposium on Medical Devices and Biosensors, U.S.A., pp, 65-68,2006. 

X, F. Teng and Y. T. Zhang, Theoretical study on the effect of sensor contact force on pulse transit time, IEEE Transactions on Biomedical Engineering, Vol. 54, no. 8, pp. 1490-1498, Aug. 2007. 

R. Payne, C. Symeonides, D. Webb et al., "Pulse transit time measured from the EGG An unreliable marker of beat-to-beat blood pressure," Journal of Applied Physiology, vol. 100, no. 1, pp. 136-141, 2006. 

B. McGarthy, C. Vaughan, B. O Flynn et al, "An examination of calibration intervals required for accurately tracking blood pressure using pulse transit time algorithms," Journal of Human Hypertension, vol. 27, no. 12, pp. 744-750, Dec 2013. 

Q. Liu, B. P. Yan, C. Yu et al., "Attenuation of systolic blood pressure and pulse transit time hysteresis during exercise and recovery in cardiovascular patients," IEEE Transactions on Biomedical Engineering, vol. 61, no. 2, pp. 346-352, Feb 2014. 

HDO and Pulse Transit Time Measurement The Next Generation... 

HDO can be upgraded with a specific cuff. The extra features of this cuff (see Fig. 15a, b) allow for an additional optic blood fiow evaluation and further pulse transit time (PTT) measurements while evaluating blood pressure and PWA. This cuff has three sensors that allow for accurate investigation of the PTT leading to additional information regarding arterial stiffness and how drugs may affect this... 

HDO is a reliable and accurate method for non-invasive blood pressure measurement. The use of this technology allows for blood pressure and cardiovascular information to be more frequently assessed and thus included into safety pharmacology and toxicology studies. Early detection of impaired vascular resistance can be added as a key parameter in the detectirm and assessment of heart and kidney disease as well as for use in metabolic research such as diabetes. Visualisation and analysis of single pulse waves, pulse pressure, the opening behaviour of the artery and in particular also pulse transit time might open new dimensions in the overall cardiovascular and metabolic evaluation of drugs for use in patients. 

If 0 < V < 2.592 the fiber is single moded. The pulse transit time of Eq. (11-36) is inversely proportional to the group velocity, and pulse spreading due to waveguide dispersion is proportional to VAD = A/where D is the scalar distortion parameter. The expression for D in Table 15-2 is plotted as the solid curve in Fig. 15-1 (d). Compared with the dashed curve, calculated numerically, the maximum relative error is 9.6% at F = 2.9, while at K = this error is 9.4%. There is no zero of waveguide dispersion. 

An alternative perspective is as follows. A 5-frmction pulse in time has an infinitely broad frequency range. Thus, the pulse promotes transitions to all the excited-state vibrational eigenstates having good overlap (Franck-Condon factors) with the initial vibrational state. The pulse, by virtue of its coherence, in fact prepares a coherent superposition of all these excited-state vibrational eigenstates. From the earlier sections, we know that each of these eigenstates evolves with a different time-dependent phase factor, leading to coherent spatial translation of the wavepacket. 

The technique just described requires the porous medium to be sealed in a cell, so It cannot be used with pellets of irregular shape or granular material. For such materials an alternative technique Introduced by Eberly [64] is attractive. In Eberly s method the porous pellets or granules are packed into a tube through which the carrier gas flows steadily. A sharp pulse of tracer gas is then injected at the entry to the tube, and Its transit time through the tube and spreading at the exit are observed. A "chromatographic" system of this sort is very attractive to the experimenter,... 

A variation on the transit time method is the frequency-difference or sing-around method. In this technique, pulses are transmitted between two pairs of diagonally mounted transducers. The receipt of a pulse is used to trigger the next pulse. Alternatively this can be done using one pair of transducers where each acts alternately as transmitter and receiver. The frequency of pulses in each loop is given by... 

In most ultrasonic tests, the significant echo signal often is the one having the maximum ampHtude. This ampHtude is affected by the selection of the beam angle, and the position and direction from which it interrogates the flaw. The depth of flaws is often deterrnined to considerable precision by the transit time of the pulses within the test material. The relative reflecting power of discontinuities is deterrnined by comparison of the test signal with echoes from artificial discontinuities such as flat-bottomed holes, side-drilled holes, and notches in reference test blocks. This technique provides some standardized tests for sound beam attenuation and ultrasonic equipment beam spread. 

Typical current pulses observed for x-cut quartz, z-cut lithium niobate, and y-cut lithium niobate are shown in Fig. 4.3. Following a sharp rise in current to an initial value (the initial rise time is due to tilt, misalignment of the impacting surfaces), the wave shapes show either modest increases in current during the wave transit time for quartz and z-cut lithium niobate... 

Fig. 4X When x-cut quartz is subjected to impact loading whose duration is less than wave transit time, an anomalous current pulse can be observed after the stress release. The diagram shows locations at which experiments were conducted and delineates the region of normal and anomalous response (after Graham and Ingram ([72G03]).

The whole sequence of successive pulses is repeated n times, with the computer executing the pulses and adjusting automatically the values of the variable delays between the 180° and 90° pulses as well as the fixed relaxation delays between successive pulses. The intensities of the resulting signals are then plotted as a function of the pulse width. A series of stacked plots are obtained (Fig. 1.40), and the point at which the signals of any particular proton pass from negative amplitude to positive is determined. This zero transition time To will vary for different protons in a molecule. 

Figure 23 shows screenshots of the data processing at various stages performed in order to design the actively compensated pulse that results in the RF field profile displayed in Figure 23A. Here, the leading and trailing edges have a cosine shape40 with a transition time of 1.25 ps. This interval was divided into 50 steps, so that each step has a width of 25 ns,...

Figure 23 Calculation of the shape of the actively compensated pulse can be carried out on the software. (A) shows the real (red line) and the imaginary (green line) component of an example of the target pulse shape t>,(f). Its leading and the trailing edges have a cosine shape with a transition time of 1.25 xs in 50 steps, and the width of the plateau is 5 ps. (B) Laplace transformation B(s) multiplied by the Laplace transformed step function U(s). (C) It was then divided by the Laplace transformation Y(s) of the measured step response y(t) of the proton channel of a 3.2-mm Varian T3 probe tuned at 400.244 MHz to obtain V(s). (D) Finally, inverse Laplace transformation was performed on V(s) to obtain the compensated pulse that results in the RF pulse with the target shape. Time resolution was 25 ns, and o = 20 was used for the Laplace and inverse Laplace transformations.

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