Method of deflection corrected tonometry with phantom vessel experiments.

Background: The Continuous Non-Invasive measurement of arterial Blood Pressure [CNIBP] is possible via the method of arterial tonometry and the arterial volume clamp methods. Arterial tonometry successfully measures continuous arterial pressure but requires large vessel deformation and a highly miniaturized pressure sensor to obtain a direct calibration of pressure. A properly designed tonometer is capable of achieving pressure accuracy of less than 5% error at the radial artery.

Tonometric arterial pulse sensor with noise cancellation.

Arterial tonometry provides for the continuous and noninvasive recording of the arterial pressure waveform. However, tonometers are affected by motion artifact that degrades the signal. An arterial tonometer was constructed using two piezoelectric transducers centered within a solid base.

Measurement and monitoring of electrocardiogram belt tension in premature infants for assessment of respiratory function.

Background: Monitoring of the electrocardiogram (ECG) in premature infants with conventional adhesive-backed electrodes can harm their sensitive skin. Use of an electrode belt prevents skin irritation, but the effect of belt pressure on respiratory function is unknown. A strain gauge sensor is described which measures applied belt tension.

Cardiac force and muscle shortening in regional ischemia: asynchronization and possible uncoupling.

Acute myocardial ischemia affects both cardiac muscle force development and shortening in the affected regions. The exact mechanisms are unclear. We investigated myocardial function during ischemia and reperfusion both experimentally and with a muscle fiber model.

Experimental evaluation of the elastic determinants of myocardial function in vivo.

Shortening of myocardial fibers occurs following force development in those fibers. The extent, speed and timing of shortening are determined by kinetics and extent of force. However, shortening is also influenced by the elastance/viscosity of the muscle tissue, because that determines the coupling between force and shortening.

Characteristic dysfunction of stunned myocardium induced by 2,3-butanedione monoxime without ischaemia.

1. In the present study, we tested the hypothesis that, even in the absence of prior ischaemia, 2,3-butanedione monoxime (BDM), an inhibitor of contraction at the actin-myosin level, could produce the postischaemic dysfunction characteristic of stunned myocardium. 2,3-Butanedione monoxime was injected directly into the left anterior descending coronary artery (LAD) before and again after myocardial stunning produced by 15 min occlusion of the LAD followed by 30 min reperfusion.

Elongation as a new shape index for the left ventricle.

Objectives: This study was done to quantify the shape of the left ventricle (LV). It was proposed that the shape of the LV is intimately related to its performance and that its elongation (ELO) is a sensitive measure of this performance. The performance was tested against classical cardiovascular parameters.

Effects of partial ischaemia and volume loading on myocardial efficiency and cardiac performance in dogs.

Aims And Methods: To determine whether volume loading may be beneficial for the performance of ischaemic heart, myocardial ischaemia was created by partial occlusion of the left anterior descending coronary artery (LAD) to reduce the blood flow to 30 approximately 40% of basal level in 11 open chest anaesthetised dogs. Global left ventricular function as well as regional performance were studied under four different levels of volume loading, euvolemia (EUVO), hypervolemia (HYPER), normovolemia and hypovolemia.

Results: Left ventricular dP/dt(max) and cardiac output were decreased significantly during partial occlusion (3511.

Hypervolaemia improves global and local function and efficiency in postischaemic myocardium.

1. In the present study, we investigated the effects of blood volume on postischaemic function and efficiency. In 14 anaesthetized dogs, following recovery from a period of 15 min occlusion of the left anterior descending coronary artery, the effects of hypervolaemia (HYPER; 15% increased volume produced by fast infusion of Hespan; B Braun Medical, Irvine, CA, USA), normovolaemia (NORMO) and hypovolaemia (HYPO) were studied.

Noninvasive measurement of the human brachial artery pressure-area relation in collapse and hypertension.

A noninvasive method to obtain pressure-lumen area (P-A) measurements of the human brachial artery is introduced. The data obtained from this method are analyzed using a mathematical model of the relationship between vessel pressure and lumen area including vessel collapse and hypertension. An occlusive arm cuff is applied to the brachial artery of ten normal subjects.

Beta-adrenergic stimulation of reperfused myocardium after 2-hour ischemia.

Postischemic myocardium possesses considerable contractile and metabolic reserves, but their mobilization could result in increased cell death. We tested the hypothesis that beta-adrenergic stimulation of reperfused myocardium would increase segment work more than O2 consumption, thereby improving efficiency without increased cell death. In 16 open-chest anesthetized dogs, the left anterior descending coronary artery (LAD) was ligated for 2 h; during the reperfusion period, isoproterenol (ISO; 0.

Vessel growth and collapsible pressure-area relationship.

The role that the pattern of vessel wall growth plays in determining pressure-lumen area (P-A) and pressure-compliance curves was examined. A P-A vessel model was developed that encompasses the complete range of pressure, including negative values, and accounts for size given the fixed length, nonlinear elastic wall properties, constant wall area, and collapse. Data were obtained from excised canine carotid and femoral arteries, jugular veins, and elastic tubing.

Novel design of a regional myocardial force transducer.

A novel force transducer was designed to measure the circumferential regional force developed in the ventricular myocardium in vivo. The transducer is composed of a frame, a carrier bar, and a cantilever spring. Two resistance strain gauges embedded on the spring serve as force-sensing elements.

Modeling of mechanical dysfunction in regional stunned myocardium of the left ventricle.

Reversible mechanical dysfunction of the myocardium after a single or multiple episode(s) of coronary artery occlusion has been observed in previous studies and is termed myocardial stunning. The hypothesis that stunning could be represented by a decrease in maximum available muscle force in the stunned region was examined by means of a mathematical model that incorporates series viscoelastic elements. A canine experimental model was also employed to demonstrate depressed contractility and a consistent delay of shortening in the stunned region.

Analysis of effect of two concurrent ischaemic zones on left ventricular function.

Left ventricular (LV) function due to two concurrent ischaemic zones (IZs) is investigated using a cardiovascular system model. The model comprises a three-compartment LV, the venous return and the arterial system. Haemodynamic responses of the LV to changes in the IZ size and myocardial contraction timings are explored.

Amyloid beta-mediated oxidative and metabolic stress in rat cortical neurons: no direct evidence for a role for H2O2 generation.

H2O2 and free radical-mediated oxidative stresses have been implicated in mediating amyloid beta (1-40) [A beta (1-40)] neurotoxicity to cultured neurons. In this study, we confirm that addition of the H2O2-scavenging enzyme catalase protects neurons in culture against A beta-mediated toxicity; however, it does so by a mechanism that does not involve its ability to scavenge H2O2. A beta-mediated elevation in intracellular H2O2 production is suppressed by addition of a potent H2O2 scavenger without any significant neuroprotection.

Computer modeling of non-adjacent regional ischemic zones on ventricular function.

Multiple regional myocardial ischemia that leads to depressed left ventricular (LV) function is commonplace. Quantitative analysis of the hemodynamic consequences, however, has been limited. We investigated this aspect using a novel computer model of the cardiovascular system.

Linear hydraulic pressure-pulse actuator (LHPA): a versatile instrument that produces a simulated blood pressure pulse wave for small sized vessels.

An instrument is presented which produces a simulated circulatory pulsatile pressure wave for small sized vessels. The linear hydraulic pressure-pulse actuator (LHPA) is designed to be extremely versatile, that is, a blood pressure wave source of any shape, amplitude, offset and frequency can be simulated. In addition, the LHPA can reproduce accurately a real pulse pressure wave by simply imputting an actual data record of a circulatory pressure pulse.

Impairment of integrin-mediated cell-matrix adhesion in oxidant-stressed PC12 cells.

Oxidants are believed to play an important and complex role in neuronal injury and death in the aging process and various neurode generative diseases. We studied the effect of oxidative stress on integrin-mediated cell-extracellular matrix (ECM) interactions using the PC12 neuronal cell line. In assays in which attachment was measured between 30 and 90 min, addition of hydrogen peroxide (H2O2) to the attachment medium resulted in a dose-dependent inhibition of initial cell attachment to collagen.

Human cortical neuronal (HCN) cell lines: a model for amyloid beta neurotoxicity.

Human cortical neuronal cell lines HCN-1A and HCN-2 are killed for following exposure of the differentiated cells to amyloid beta-peptide(1-40), a component of senile plaques and other amyloid deposits in brains from Alzheimer's patients. We present a model of A beta toxicity uncomplicated by the presence of other cell types that can be used to address the mechanism of A beta neurotoxicity. This model will be useful in the evaluation of neuroprotective compounds which may attenuate cortical neuronal loss in Alzheimer's disease.

Theory of the oscillometric maximum and the systolic and diastolic detection ratios.

It is proposed that the maximum in cuff pressure oscillations during oscillometry is due to the buckling of the brachial artery under a cuff. This theory is investigated by means of a mathematical model of oscillatometry that includes the mechanics of the occlusive arm cuff, the arterial pressure pulse waveform, and the mechanics of the brachial artery. A numerical solution is provided for the oscillations in cuff pressure for one cycle of cuff inflation and deflation.

Real-time left ventricular volume of the canine heart from ultrasonic dimension data.

A real-time (instantaneous) system is presented to measure the dynamic volume of the left ventricle. This system uses the invasive measurement of long axis diameter, short axis diameter, and wall thickness of the cardiac left ventricle. Three pairs of pulse-transit ultrasonic dimension transducers are used to obtain these measurements.

Mechanics of the occlusive arm cuff and its application as a volume sensor.

Although a common medical instrument, the mechanical function of an occlusive arm cuff has not been fully described in an engineering sense. The occlusive arm cuff is examined here using a mathematical mechanics model and experimental measurements. Cuff stretch was modeled by a nonlinear pressure-volume function.

Ascorbic acid-enhanced antiproliferative effect of flavonoids on squamous cell carcinoma in vitro.

We examined the effects of flavone and two polyhydroxylated plant flavonoids (quercetin and fisetin), either singly or in combination with ascorbic acid, on the growth of a human squamous cell carcinoma cell line (HTB 43) in vitro. Fisetin and quercetin significantly impaired cell growth in the presence of ascorbic acid. Exposure of cells to ascorbic acid (2 micrograms/ml) and 2 micrograms/ml of either fisetin or quercetin resulted in 61 and 45% inhibition of cell growth, respectively, in 72 h, while treatment with ascorbic acid alone had no effect on cellular proliferation.

Peripheral vascular effects on auscultatory blood pressure measurement.

Experiments were conducted to examine the accuracy of the conventional auscultatory method of blood pressure measurement. The influence of the physiologic state of the vascular system in the forearm distal to the site of Korotkoff sound recording and its impact on the precision of the measured blood pressure is discussed. The peripheral resistance in the arm distal to the cuff was changed noninvasively by heating and cooling effects and by induction of reactive hyperemia.