The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Pulse transit time (PTT) has been reported correlated with heart rate (HR) and blood pressure (BP), however, the results are not consistent in different investigations. Towards a better understanding of the underlying mechanisms of the PTT changes, this study compares the power spectrum density of the variability in PTT with that in HR and BP under rest and post-exercise physiological conditions....
This paper investigates the specific contributions of the pre-ejection period (PEP) and pulse transit time (PTT) for blood pressure estimation based on the pulse wave methodology. We show that in short-term physical stress tests, PEP dominates PTT variations raising the question of a suitable blood pressure calibration. A model using a generalized pulse wave velocity achieves acceptable accuracy for...
Real time left ventricular (LV) pressure-volume (P-V) loops have provided a framework for understanding cardiac mechanics in experimental animals and humans. Conductance measurements have been used for the past 25 years to generate an instantaneous left ventricular (LV) volume signal. The standard conductance method yields a combination of blood and ventricular muscle conductance; however, only the...
The mean of cardiovascular pressure signals is an important metric in patient monitoring applications for many types of diseases and injuries. It is typically calculated with a moving average of 3-8 s of the pulsatile signal. This method of calculating the mean introduces a delay of 1.5-4 s. We demonstrate that an FIR filter with coefficients calculated with a least squares error (LSE) estimator can...
This study aims to examine the presence of a possible third renal autoregulatory mechanism in the very low frequency (VLF) band (~10 mHz) using a high-resolution time- frequency spectral method. Blood pressure and renal blood flow data were measured from conscious and anesthetized Sprague-Dawley and spontaneously hypertensive rats, at the level of the whole kidney (via ultrasound flow probe) and local...
A new method of measuring blood pressure (BP) is presented. This technique involves automatic analysis of the wideband external pulse (WEP) recorded by a pressure sensor positioned over the brachial artery during standard BP cuff deflation. Three distinct components of this "K" or "WEP" signal can be defined: K1, K2, and K3 [1]. Each component has a different shape and "appearance/disappearance"...
A truly wearable non-invasive blood pressure (NIBP) sensor- light-weight, compact, unobstrusive, and essentially unnoticeable to the patient-could revolutionize healthcare delivered beyond the traditional walls of medical facilities, offering new ways to care for patients in their everyday surroundings. This paper presents results from our work towards the development of a self-contained, wearable...
We introduce a novel technique for continuous (i.e., automatic) monitoring of cardiac output (CO) and left atrial pressure (LAP) by mathematical analysis of a pulmonary artery pressure (PAP) waveform. To obtain an initial evaluation of the technique, we applied it to PAP waveforms obtained from nine critically ill patients and compared the resulting CO and LAP estimates with standard operator- dependent...
The onset of second heart sound is triggered by the closure of aortic valve due to the interaction of left ventricle and arterial system. Noninvasive experiments found that RS2 defined by the time delay from the peak of ECG R wave to the onset of the second heart sound had a close inverse correlation with arterial systolic blood pressure. However, no theoretical study has been carried out to investigate...
We describe a novel algorithm to estimate the pulse pressure variation index (PPV) from arterial blood pressure signals (ABP). PPV has been shown to be one of the best predictors of fluid responsiveness in mechanically ventilated subjects. Our PPV algorithm uses a non-linear technique for envelope estimation, eliminating the need for automatic beat detection. Additionally, the algorithm makes use...
Maintaining intracranial pressure (ICP) below 20-25 mmHg is an important clinical goal in the treatment of patients with traumatic brain injury (TBI). It is well known that the partial pressure of arterial CO2 (PaCO2) can affect cerebral blood flow, cerebral blood volume, and therefore ICP. The end-tidal CO2 (ETCO2) is usually monitored by clinicians as a proxy for PaCO2. We show examples where subclinical...
Preceding studies have shown photoplethysmographic (PPG) signal resembles blood pressure (BP) wave and varies. Some investigators also have studied this relationship to explain complex hemodynamic characterization. The purpose of this study is to make a trial of finding arterial BP (ABP) using PPG signal. This new attempt is based on the theory that BP consists of the change of blood volume (BY) and...
A novel long-term less-invasive blood pressure monitoring system with fluid-filled cuff is proposed for advanced biological research. The system employs an instrumented elastic cuff attached with a rigid isolation ring on the outside wall of the cuff. The cuff is wrapped around a blood vessel for real-time blood pressure monitoring. The elastic cuff is made of bio-compatible soft silicone material...
Continuous and non-invasive monitoring of blood pressure (BP) is important to prevent hypertensive patients from stroke and heart attack. However, most of the prevalent BP devices can provide solely intermittent measurements. In this study, a novel parameter RS2 , defined as the time interval from the R wave of electrocardiographic (ECG) signal to the peak of second heart sound of phonocardiographic...
The three-element Windkessel model is widely used and accepted for analyzing blood flow and pressure in arterial system and cerebral circulation. In most studies, changes in mean arterial blood pressure data is used as input to estimate the model parameters. However, estimation of linear model parameters, using input-output data, requires that the input be persistently exciting. This study examined...
An arterial stiffness index based on the transmission line model is defined. The parameters of the transmission line model are initially estimated using measured pressure, flow and aortic root diameter. Pressure is measured at the carotid using applanation tonometry. Flow is measured using Doppler at the ascending aorta. Aortic root diameter is measured using 2-D echocardiography. The initial estimates...
Pulse arrival time and the amplitude of the finger photoplethysmogram were used to track blood pressure continuously over 10-minute intervals. The measures were recorded with a holter-oximeter from a sample of 8 young, healthy human subjects in the supine and standing positions. Results indicate that, with individual calibration, systolic and diastolic blood pressure can be estimated with an average...
This paper presents an adaptive multi-channel (AMC) approach for the reconstruction of the central aortic blood pressure (BP) waveform from multiple peripheral BP measurements. In contrast to most of the previously developed single-channel methods for estimating central aortic BP waveform, the key merit of the AMC algorithm is its ability to be individualized without any prior model training or parameter...
A hidden semi-Markov model is proposed to describe a trend signal for non-invasive mean blood pressure. Based on the model, a Viterbi beam search algorithm working with an adaptive cumulative sum test is proposed to detect change points and recognize change patterns online. Testing results on the simulated signals and clinical signals demonstrate that the algorithm has improved performance over the...
Left ventricular ejection fraction (EF) is perhaps the most clinically significant index of global ventricular function. EF is measured in clinical practice via imaging methods such as echocardiography. However, these methods generally require a well-trained operator and expensive capital equipment. Thus, EF measurements are only obtained in the clinical setting and are usually made few and far between...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.