Phasic Pressure Research Articles

The Spectrum Of Symptoms In Older Patients With Severe Orthostatic Hypotension

Abstract Background Orthostatic Hypotension (OH) is an important cause of falls in older people, with patients typically presenting with postural dizziness/light-headedness. However, while we recognise clinically that in older patients with OH, symptoms are often absent or atypical, little work to date has captured this spectrum of OH symptoms. The aim of this study therefore was to examine symptom profiles in a large cohort of older people with severe OH and ascertain the prevalence of ‘asymptomatic’ OH. Methods We included a consecutive cohort of older patients (aged ≥60 years) with severe OH attending a tertiary referral falls unit. OH, was identified during an active stand using a Finometer® measuring beat-to-beat phasic blood pressure. Patients were asked to report any symptoms during the test and each symptom was recorded. Severe OH was defined as failure of recovery of BP to within 20 mmHg systolic/10mmHg diastolic of baseline value within 3 minutes of standing. Results 71% of patients (n=393) reported symptoms during the active stand, with two thirds of these reporting ≥2 symptoms. The most frequent reported symptoms were dizziness (52%) and poor balance (52%), followed by weakness (38%), visual disturbance (28%), light-headedness (21%), fatigue (6%), nausea (4%), feeling warm (4%) and palpitations (1%). Nurses reported pallor in 13% of patients, while 3% needed to lie down due to hypotension/presyncope. Average time to symptom reporting was 16 seconds (compared to 11 seconds in patients who did not have severe OH). Conclusion Almost one third with severe OH reported no symptoms during an active stand, while only half reported ‘typical’ OH symptoms of dizziness/light-headedness. Atypical symptoms such as fatigue, and generalised weakness are relatively common. Atypical symptomatology is therefore frequent in older patients with severe OH. These findings have important implications for the clinical assessment of older people with falls.

Effects of virtual reality on psychophysical measures of pain: superiority to imagination and nonimmersive conditions.

Virtual reality (VR) has been shown to be effective in pain management. However, to date, little is known about the mechanisms by which immersive experiences influence pain processing. The aim of this study was to investigate the direct effects of an immersive VR environment on the perception of experimental pain in individuals with chronic pain and pain-free controls. The immersion in a VR landscape was compared with mental imagery and a nonimmersive control condition. Using a randomized within-crossover design, pressure pain detection and tolerance thresholds, spatial and temporal summation (SSP, TSP), and conditioned pain modulation (CPM) were measured in 28 individuals with chronic pain and 31 pain-free controls using phasic cuff pressure on the legs. Direct comparison between the groups showed that although individuals with pain had significantly lower pain thresholds, reduced CPM effects, and increased TSP, the VR condition had the same pain-inhibitory effect on pain thresholds as in pain-free controls. Conditioned pain modulation effects were reduced by all conditions compared with baseline. There were no significant differences between conditions and baseline for TSP and SSP. Overall, pain modulatory effects were largest for VR and smallest for imagery. These results demonstrate that immersion in a VR environment has an increasing effect on pain thresholds, reduces pain inhibition in a CPM paradigm, and has no effects on TSP. This applies for participants with chronic pain and pain-free controls. These VR effects exceeded the effects of mental imagery on the nonimmersive control condition. This indicates that VR effectively modulates pain perception in both patients and controls irrespective of differences in pain perception.

The Maximal Urethral Pressure at Rest and during Normal Bladder Filling Is Only Determined by the Activity of the Urethral Smooth Musculature in the Female

The aim of this opinion paper is to determine the entities that define the maximal urethral pressure (MUP) during rest and during bladder filling that is needed to guarantee continence in females. For the development of this opinion, the literature was searched for via the Pubmed database and historic sources. Animal studies indicate that the maximal urethral pressure is determined by the smooth muscle activity in the mid-urethra. Additionally, during increased smooth muscle tone development, the largest sympathetic responses are found in the middle part of the urethra. This could be confirmed in human studies that are unable to find striated EMG activity in this area. Moreover, the external urethral striated sphincter is situated at the distal urethra, which is not the area with the highest pressure. The external urethral sphincter only provides additional urethral pressure in situations of exertion and physical activity. From a physics point of view, the phasic pressure of the external striated sphincter at the distal urethra cannot be added to the tonic pressure generated by the smooth muscle in the mid-urethra. The assertion that mid-urethral pressure is the result of different pressure forces around the urethra, including that of the external striated sphincter, is not supported by basic research evidence combined with physical calculation and should therefore be considered a misconception in the field of functional urology.

A seven-equation diffused interface method for resolved multiphase flows

The seven-equation model is a compressible multiphase formulation that allows for phasic velocity and pressure disequilibrium. These equations are solved using a diffused interface method that models resolved multiphase flows. Novel extensions are proposed for including the effects of surface tension, viscosity, multi-species, and reactions. The allowed non-equilibrium of pressure in the seven-equation model provides numerical stability in strong shocks and allows for arbitrary and independent equations of states. Whereas, the allowed non-equilibrium of velocity allows the method to be useful even for unresolved particles where a finite-rate velocity relaxation is observed. A discrete equations method (DEM) models the fluxes. We show that even though stiff pressure- and velocity-relaxation solvers have been used, they are not necessarily needed for all the tests with DEM because the non-conservative fluxes are accurately modeled. An interface compression scheme controls the numerical diffusion of the interface, and its effects on the solution are discussed. Test cases are used to validate the computational method and demonstrate its applicability. They include multiphase shock tubes, shock propagation through a material interface and a dispersed particle curtain, a surface-tension-driven oscillating droplet, an accelerating droplet in a viscous medium, and shock–detonation interacting with a deforming droplet. Simulation results are compared against exact solutions and experiments when possible.

Use of a Pressure Wire for Automatically Correcting Artifacts in Phasic Pressure Tracings From a Fluid-Filled Catheter

Background/purposeMatching phasic pressure tracings between a fluid-filled catheter and high-fidelity pressure wire has received limited attention, although each part contributes half of the information to clinical decisions. We aimed to study the impact of a novel and automated method for improving the phasic calibration of a fluid-filled catheter by accounting for its oscillatory behavior. Methods/materialsRetrospective analysis of drift check tracings was performed using our algorithm that corrects for mean difference (offset), temporal delays (timing), differential sensitivity of the manifold transducer and pressure wire sensor (gain), and the oscillatory behavior of the fluid-filled catheter described by its resonant frequency and damping factor (how quickly oscillations disappear after a change in pressure). ResultsAmong 2886 cases, correcting for oscillations showed a large improvement in 28 % and a medium improvement in 41 % (decrease in root mean square error >0.5 mmHg to <1 or 1-2 mmHg, respectively). 96 % of oscillators were underdamped with median damping factor 0.27 and frequency 10.6 Hz. Fractional flow reserve or baseline Pd/Pa demonstrated no clinically important bias when ignoring oscillations. However, uncorrected subcycle non-hyperemic pressure ratios (NHPR) displayed both bias and scatter. ConclusionsBy automatically accounting for the oscillatory behavior of a fluid-filled catheter system, phasic matching against a high-fidelity pressure wire can be improved compared to standard equalization methods. The majority of tracings contain artifacts, mainly due to underdamped oscillations, and neglecting them leads to biased estimates of equalization parameters. No clinically important bias exists for whole-cycle metrics, in contrast to significant effects on subcycle NHPR.

Standard CPR versus interposed abdominal compression CPR in shunted single ventricle patients: comparison using a lumped parameter mathematical model

Cardiopulmonary resuscitation (CPR) in the shunted single-ventricle population is associated with poor outcomes. Interposed abdominal compression-cardiopulmonary resuscitation, or IAC-CPR, is an adjunct to standard CPR in which pressure is applied to the abdomen during the recoil phase of chest compressions. A lumped parameter model that represents heart chambers and blood vessels as resistors and capacitors was used to simulate blood flow in both Blalock-Taussig-Thomas and Sano circulations. For standard CPR, a prescribed external pressure waveform was applied to the heart chambers and great vessels to simulate chest compressions. IAC-CPR was modelled by adding phasic compression pressure to the abdominal aorta. Differential equations for the model were solved by a Runge-Kutta method. In the Blalock-Taussig-Thomas model, mean pulmonary blood flow during IAC-CPR was 30% higher than during standard CPR; cardiac output increased 21%, diastolic blood pressure 16%, systolic blood pressure 8%, coronary perfusion pressure 17%, and coronary blood flow 17%. In the Sano model, pulmonary blood flow during IAC-CPR increased 150%, whereas cardiac output was improved by 13%, diastolic blood pressure 18%, systolic blood pressure 8%, coronary perfusion pressure 15%, and coronary blood flow 14%. In this model, IAC-CPR confers significant advantage over standard CPR with respect to pulmonary blood flow, cardiac output, blood pressure, coronary perfusion pressure, and coronary blood flow. These results support the notion that single-ventricle paediatric patients may benefit from adjunctive resuscitation techniques, and underscores the need for an in-vivo trial of IAC-CPR in children.

Positive affect and distraction enhance whereas negative affect impairs pain modulation in patients with recurrent low back pain and matched controls.

Pathophysiological causes of low back pain (LBP) remain generally unclear, so focus has shifted to psychosocial features and central pain processing. Effects of attentional and affective manipulation on conditioned pain modulation and tonic pain perception were examined in 30 patients with recurrent LBP in 2 sessions, one with and one without clinical pain, and compared with healthy participants. Phasic cuff pressure on one leg, scored on a Numerical Rating Scale, was used for test stimuli, and contralateral tonic cuff pain rated on an electronic Visual Analogue Scale was the conditioning stimulus (CS). Test stimuli were assessed before and during (1) control with no manipulation or CS, (2) 3 attentional manipulations (Flanker with or without CS or CS-Only), and (3) 3 affective manipulations (positive, neutral, and negative images) with CS. Greater inhibition of test stimuli Numerical Rating Scale scores was observed in CS-only (P = 0.028), combined CS&attention (P = 0.026), and CS&Positive (P = 0.006) than control paradigms, and greater in CS&Positive (P = 0.019) than CS&Negative paradigms. Electronic Visual Analogue Scale scores of CS pain increased throughout all paradigms with CS (P < 0.05), except the CS&Positive paradigm, and greater facilitation was observed in the CS-Only paradigm than all others (P < 0.02), and lower facilitation was additionally observed in the CS&Positive paradigm compared with CS&Attention and CS&Negative paradigms (P < 0.01). Flanker effects and interruptive effects of CS pain on attention were observed consistent with prior findings, and affective manipulation produced less shift in valence among people with recurrent LBP than controls (P < 0.05). Attention and positive affect with CS pain evoked conditioned pain modulation, and all attentional or affective tasks, especially positive affect, reduced facilitation of CS pain.

The Sphincter of O'Beirne - Part 1: Study of 18 Normal Subjects.

Gastroenterologists have ignored or emphasized the importance of the rectosigmoid junction in continence or constipation on and off for 200years. Here, we revisit its significance using high-resolution colonic manometry. Manometry, using an 84-channel water-perfused catheter, was performed in 18 healthy volunteers. The rectosigmoid junction registers as an intermittent pressure band of 26.2 ± 7.2mmHg, or intermittent phasic transient pressure increases at a dominant frequency of 3cpm and an amplitude of 28.6 ± 8.6mmHg; or a combination of tone and transient pressures, at a single sensor, 10-17cm above the anal verge. Features are its relaxation or contraction in concert with relaxation or contraction of the anal sphincters when a motor pattern such as a high-amplitude propagating pressure wave or a simultaneous pressure wave comes down, indicating that such pressure increases or decreases at the rectosigmoid junction are part of neurally driven programs. We show that the junction is a site where motor patterns end, or where they start; e.g. retrogradely propagating cyclic motor patterns emerge from the junction. The rectosigmoid junction is a functional sphincter that should be referred to as the sphincter of O'Beirne; it is part of the "braking mechanism," contributing to continence by keeping content away from the rectum. In an accompanying case report, we show that its excessive presence in a patient with severe constipation can be a primary pathophysiology.

The effect of colonic tissue electrical stimulation and celiac branch of the abdominal vagus nerve neuromodulation on colonic motility in anesthetized pigs.

Knowledge on optimal electrical stimulation (ES) modalities and region-specific functional effects of colonic neuromodulation is lacking. We aimed to map the regional colonic motility in response to ES of (a) the colonic tissue and (b) celiac branch of the abdominal vagus nerve (CBVN) in an anesthetized porcine model. In male Yucatan pigs, direct ES (10Hz, 2ms, 15mA) of proximal (pC), transverse (tC), or distal (dC) colon was done using planar flexible multi-electrode array panels and CBVN ES (2Hz, 0.3-4ms, 5mA) using pulse train (PT), continuous (10min), or square-wave (SW) modalities, with or without afferent nerve block (200Hz, 0.1ms, 2mA). The regional luminal manometric changes were quantified as area under the curve of contractions (AUC) and luminal pressure maps generated. Contractions frequency power spectral analysis was performed. Contraction propagation was assessed using video animation of motility changes. Direct colon ES caused visible local circular (pC, tC) or longitudinal (dC) muscle contractions and increased luminal pressure AUC in pC, tC, and dC (143.0±40.7%, 135.8±59.7%, and 142.0±62%, respectively). The colon displayed prominent phasic pressure frequencies ranging from 1 to 12cpm. Direct pC and tC ES increased the dominant contraction frequency band (1-6cpm) power locally. Pulse train CBVN ES (2Hz, 4ms, 5mA) triggered pancolonic contractions, reduced by concurrent afferent block. Colon contractions propagated both orally and aborally in short distances. In anesthetized pigs, the dominant contraction frequency band is 1-6cpm. Direct colonic ES causes primarily local contractions. The CBVN ES-induced pancolonic contractions involve central neural network.

Regional Colonic Motility Response to Colon Tissue, Celiac vagus and Sacral Nerve Electrical Stimulation

BackgroundThe colon has distinct proximal (pC), transverse (tC), distal (dC) and colorectal regions. The different colonic regions response to neuromodulation is not well known. Interest in neuromodulation, as an alternative therapy to refractory gut motility disorders is increasing, although efficacy and optimal stimulation parameters remain elusive.AimDetermine the effect of neuromodulation (direct colon tissue or autonomic nerves) on the colonic regional phasic contractions in a porcine model.MethodsAnesthetized male Yucatan pigs (6 months old, 25–30 kg) were used. Following laparotomy, still manometry catheters (Millar) were placed in the pC, tC, dC and the anal canal (AC). The colonic luminal phasic pressure changes were monitored under basal conditions, during and after electrical stimulation (ES). Direct colon tissue ES was done using planar flexible multi‐electrode array panels (10Hz, 2ms, 15mA). In separate groups, the celiac branch of the vagus nerve (CBVN, 2 Hz, 5mA, 0.3–4ms, pulse train) or sacral nerve roots (S2, 30Hz, 0.3ms, 0.5mA) was electrically stimulated with or without concurrent afferent anodal nerve block (200Hz, 0.1ms, 2mA, for CBVN). Phasic pressure changes were analyzed using area under the curve of contraction (AUC) and fast Fourier transform (FFT) to obtain the frequency spectra. Contraction frequency power changes were analyzed using repeated measures 2‐way ANOVA and Sidak’s post hoc test.ResultsIn anesthetized male pigs, the basal activity of the colon is characterized by prominent phasic pressure frequencies (1–12cpm) with dominant frequency power of the 1–6cpm in all the 3 regions monitored (pC, tC, dC). Direct colon tissue ES at all regions increased area AUC however only pC and tC increased the respective region’s dominant frequency band power (1–6cpm) (pC: 1cpm p&lt;0.05, 2 cpm p&lt; 0.001, 3 cpm p&lt;0.01 vs baseline; tC: 2 cpm, p&lt;0.05 vs baseline). CBVN ES triggered pancolonic increase in AUC and caused a significant increase in the 1–3cpm power at the tC (2 cpm p&lt;0.01, 3 cpm p&lt;0.01 vs baseline). S2 stimulation selectively increased AUC at dC and the anal canal (Fig. 1). Afferent block reduced the CBVN‐induced increased AUC in the pC and tC and the power at tC.ConclusionBoth direct colon tissue and celiac branch of the vagus nerve ES increase AUC and power of the dominant frequency band (1–6cpm). S2 stimulation selectively increased AUC of the dC and the anal canal. The physiological significance of the region specific increase in the colonic AUC and power of dominant contraction frequency band in response to neuromodulation warrants further studies in non‐anesthetized state.Support or Funding InformationNIH SPARC grant #OT2OD24899Heat map of colonic luminal pressure area under the curve of contraction in response to sacral S2 nerve stimulation in anesthetized adult male Yucatan pigs. Heat map (percentage of baseline) is generated from 3 pigs at baseline (30 min), during stimulation (10 min) and post stimulation (30 min) periods.Figure 1

Phasic pressure measurements for coronary and valvular interventions using fluid-filled catheters: Errors, automated correction, and clinical implications.

ObjectivesWe sought to develop an automatic method for correcting common errors in phasic pressure tracings for physiology‐guided interventions on coronary and valvular stenosis.BackgroundEffective coronary and valvular interventions rely on accurate hemodynamic assessment. Phasic (subcycle) indexes remain intrinsic to valvular stenosis and are emerging for coronary stenosis. Errors, corrections, and clinical implications of fluid‐filled catheter phasic pressure assessments have not been assessed in the current era of ubiquitous, high‐fidelity pressure wire sensors.MethodsWe recruited patients undergoing invasive coronary physiology assessment. Phasic aortic pressure signals were recorded simultaneously using a fluid‐filled guide catheter and 0.014″ pressure wire before and after standard calibration as well as after pullback. We included additional subjects undergoing hemodynamic assessment before and after transcatheter aortic valve implantation. Using the pressure wire as reference standard, we developed an automatic algorithm to match phasic pressures.ResultsRemoving pressure offset and temporal shift produced the largest improvements in root mean square (RMS) error between catheter and pressure wire signals. However, further optimization <1 mmHg RMS error was possible by accounting for differential gain and the oscillatory behavior of the fluid‐filled guide. The impact of correction was larger for subcycle (like systole or diastole) versus whole‐cycle metrics, indicating a key role for valvular stenosis and emerging coronary pressure ratios.ConclusionsWhen calibrating phasic aortic pressure signals using a pressure wire, correction requires these parameters: offset, timing, gain, and oscillations (frequency and damping factor). Automatically eliminating common errors may improve some clinical decisions regarding physiology‐based intervention.

Assessment of numerical schemes for complex two-phase flows with real equations of state

Some accidental scenarii studied in the framework of the nuclear safety analysis involve liquids undergoing strong pressure drops at high temperature. In order to perform realistic simulations of such situations, a code based on a model that can handle both the thermodynamical disequilibrium between liquid and vapor and complex equations of state is required. We propose herein to test a homogeneous model built on the basis of the Euler system of equations and complemented by a mixture pressure law. The latter is defined in accordance with the Gibbs relation on the basis of the phasic pressures which are defined through a look-up table based on the IAPWS-97 formulation. A wide range of verification problems (Riemann problems) is then studied to assess the behavior of the numerical schemes for this complex equation of state. The tested relaxation scheme is the best compromise between accuracy and stability. At last, a simple test case of vaporization near a wall is investigated in order to test some return to thermodynamical-equilibrium time-scale based on the nucleation theory.

2771 Acute Gastric Dilatation: A Cause for Concern

INTRODUCTION: Gastroparesis in diabetics can be worsened by hyperglycemia. Acute elevations in blood glucose suppress the frequency and contraction amplitude of antral pressure waves while stimulating phasic pyloric pressure waves, which can result in Acute Gastric Dilatation (AGD). Though an unusual occurrence, it requires a high degree of suspicion to avoid its rare but life-threatening complications. We present our experience of two patients with AGD. CASE DESCRIPTION/METHODS: Case 1: A 30-year-old male presented to the ER with nausea, vomiting and abdominal pain. His comorbidities included type 1 diabetes and end-stage renal disease. On examination, his abdomen was notably distended and bowel sounds were sluggish. No guarding or rigidity was appreciated. He was hypotensive (76/49 mmHg) and hypoxic. Lab values were significant for blood glucose of 1155 mg/dL and a pH of 6.97. He was emergently intubated and started on IV insulin and Epinephrine. An abdominal plain film x-ray showed acute gaseous distention of the stomach. An NG tube was passed which drained 500cc of brownish gastric content. A repeat x-ray 4 hrs later revealed resolution of gastric dilatation which was confirmed by CT-abdomen. Patient's abdominal symptoms improved thereafter and he made a full recovery in time. Case 2: 59-year-old male was brought to the ER with an altered mental status. As per EMS, he had “very high” blood sugar levels. His comorbidities included diabetes mellitus and chronic hepatitis C. His abdomen was distended with decreased bowels sounds. His vital signs were stable. Lab values were significant for hyperglycemia (649 mg/dL), and a blood pH of 7.29. He underwent an abdominal x-ray which showed marked distention of the stomach. A follow-up CT abdomen confirmed the finding, with no mechanical cause of obstruction identified. He was started on IV Insulin, IV antibiotics and was planned for endoscopic workup, however, his conditioned rapidly deteriorated and he required pressors with mechanical ventilation. The patient eventually suffered a cardiac arrest and was unable to be revived. DISCUSSION: AGD presents with nausea, vomiting, succussion splash, and abdominal distension. Acute hyperglycemia in uncontrolled diabetics is the precipitating factor. If intragastric pressures exceed 20 cmH20 (lower limit of gastric venous pressure), it can cause mucosal ischemia and necrosis. This may be followed by perforation, which has a high mortality rate. Emergency decompression with NG tube seems to be the treatment of choice.

A three-phase flow model with two miscible phases

The paper concerns the modelling of a compressible mixture of a liquid, its vapor and a gas. The gas and the vapor are miscible while the liquid is immiscible with the gaseous phases. This assumption leads to non symmetric constraints on the void fractions. We derive a three-phase three-pressure model endowed with an entropic structure. We show that interfacial pressures are uniquely defined and propose entropy-consistent closure laws for the source terms. Naturally one exhibits that the mechanical relaxation complies with Dalton’s law on the phasic pressures. Then the hyperbolicity and the eigenstructure of the homogeneous model are investigated and we prove that it admits a symmetric form leading to a local existence result. We also derive a barotropic variant which possesses similar properties.

Effects of intraduodenal administration of lauric acid and L-tryptophan, alone and combined, on gut hormones, pyloric pressures, and energy intake in healthy men

The fatty acid, lauric acid ('C12'), and the amino acid, L-tryptophan ('Trp'), modulate gastrointestinal functions including gut hormones and pyloric pressures, which are important for the regulation of energy intake, and both potently suppress energy intake. We hypothesized that the intraduodenal administration of C12 and Trp, at loads that do not affect energy intake individually, when combined will reduce energy intake, which is associated with greater modulation of gut hormones and pyloric pressures. Sixteen healthy, lean males (age: 24±1.5 y) received 90-min intraduodenal infusions of saline (control), C12 (0.3 kcal/min), Trp (0.1 kcal/min), or C12+Trp (0.4 kcal/min), in a randomized, double-blind, cross-over study. Antropyloroduodenal pressures were measured continuously, and plasma cholecystokinin (CCK), ghrelin, and glucagon-like peptide-1 (GLP-1) concentrations, appetite perceptions, and gastrointestinal symptoms at 15-min intervals. Immediately after the infusions, energy intake from a standardized buffet meal was quantified. C12+Trp markedly reduced energy intake (kcal; control: 1,232±72, C12: 1,180±82, Trp: 1,269±73, C12+Trp: 1,056±106), stimulated plasma CCK (AUC(area under the curve)0-90 min, pmol/L*min; control: 21±8; C12: 129±15; Trp: 97±16; C12+Trp: 229±22) and GLP-1 (AUC0-90 min, pmol/L*min; control: 102±41; C12: 522±102; Trp: 198±63; C12+Trp: 545±138), and suppressed ghrelin (AUC0-90 min, pg/mL*min; control: -3,433±2,647; C12: -11,825±3,521; Trp: -8,417±3,734; C12+Trp: -18,188±4,165) concentrations, but did not stimulate tonic, or phasic, pyloric pressures, compared with the control (all P<0.05), or have adverse effects. C12 and Trp each stimulated CCK (P<0.05), but to a lesser degree than C12+Trp, and did not suppress energy intake or ghrelin. C12, but not Trp, stimulated GLP-1 (P<0.05) and phasic pyloric pressures (P<0.05), compared with the control. The combined intraduodenal administration of C12 and Trp, at loads that individually do not affect energy intake, substantially reduces energy intake, which is associated with a marked stimulation of CCK and suppression of ghrelin. The study was registered as a clinical trial at the Australian and New Zealand Clinical Trial Registry (www.anzctr.org.au,) as 12613000899741.

A hyperbolic phase-transition model with non-instantaneous EoS-independent relaxation procedures

This article deals with the thermodynamic equilibrium recovery mechanisms in two-phase flows and their numerical modeling. The two phases, initially at different pressures, temperatures and chemical potentials, are supposed to be driven towards equilibrium conditions by three relaxation processes. First, a mechanical process applies to relax phasic pressures, then a thermal process, to allow the sensible heat transfer between the phases at different temperatures, and, lastly, a chemical process that is responsible for the mass transfer.The two-phase flow model is composed of six partial differential equations with source terms that allow the description of mixtures at full thermodynamic disequilibrium. Its homogeneous portion is hyperbolic and it is solved by a second-order accurate finite volume scheme that uses a HLLC-type approximate Riemann solver. The source terms modeling the relaxation processes are separately integrated as three systems of ordinary differential equations.The main contributions of this paper are: the capability of describing the possibly non-instantaneous time delay of equilibrium recover in a novel way, the equation of state independence of the numerical scheme, and the possibility to take into account the morphology of the flow pattern by using the interfacial area between phases.

Coronary Hemodynamics in Patients With Severe Aortic Stenosis and Coronary Artery Disease Undergoing Transcatheter Aortic Valve Replacement: Implications for Clinical Indices of Coronary Stenosis Severity

ObjectivesIn this study, a systematic analysis was conducted of phasic intracoronary pressure and flow velocity in patients with severe aortic stenosis (AS) and coronary artery disease, undergoing transcatheter aortic valve replacement (TAVR), to determine how AS affects: 1) phasic coronary flow; 2) hyperemic coronary flow; and 3) the most common clinically used indices of coronary stenosis severity, instantaneous wave-free ratio and fractional flow reserve. BackgroundA significant proportion of patients with severe aortic stenosis (AS) have concomitant coronary artery disease. The effect of the valve on coronary pressure, flow, and the established invasive clinical indices of stenosis severity have not been studied. MethodsTwenty-eight patients (30 lesions, 50.0% men, mean age 82.1 ± 6.5 years) with severe AS and coronary artery disease were included. Intracoronary pressure and flow assessments were performed at rest and during hyperemia immediately before and after TAVR. ResultsFlow during the wave-free period of diastole did not change post-TAVR (29.78 ± 14.9 cm/s vs. 30.81 ± 19.6 cm/s; p = 0.64). Whole-cycle hyperemic flow increased significantly post-TAVR (33.44 ± 13.4 cm/s pre-TAVR vs. 40.33 ± 17.4 cm/s post-TAVR; p = 0.006); this was secondary to significant increases in systolic hyperemic flow post-TAVR (27.67 ± 12.1 cm/s pre-TAVR vs. 34.15 ± 17.5 cm/s post-TAVR; p = 0.02). Instantaneous wave-free ratio values did not change post-TAVR (0.88 ± 0.09 pre-TAVR vs. 0.88 ± 0.09 post-TAVR; p = 0.73), whereas fractional flow reserve decreased significantly post-TAVR (0.87 ± 0.08 pre-TAVR vs. 0.85 ± 0.09 post-TAVR; p = 0.001). ConclusionsSystolic and hyperemic coronary flow increased significantly post-TAVR; consequently, hyperemic indices that include systole underestimated coronary stenosis severity in patients with severe AS. Flow during the wave-free period of diastole did not change post-TAVR, suggesting that indices calculated during this period are not vulnerable to the confounding effect of the stenotic aortic valve.

The association between antidepressant use and orthostatic hypotension in older people: a matched cohort study

Orthostatic hypotension (OH) is often reported as a significant potential adverse effect of antidepressant use but the association between phasic blood pressure (BP) and antidepressants has not yet been investigated. This cross-sectional study compares continuously measured phasic BP and prevalence of OH in a cohort of antidepressant users ≥50 years compared with an age- and sex-matched cohort not taking antidepressants. OH was defined as a drop in systolic BP ≥ 20 mm Hg or in diastolic BP ≥ 10 mm Hg at 30 seconds after standing, measured using continuous beat-to-beat finometry. Multilevel time × group interactions revealed significantly greater systolic and diastolic BP drop in antidepressant users than nonusers at 30 seconds after stand. The prevalence of OH among antidepressant users was 31% (63/206), compared with 17% in nonusers (X2 = 9.7; P = .002). Unadjusted logistic regression models demonstrated that selective serotonin reuptake inhibitor use was associated with OH at an odds ratio of 2.11 (95% confidence interval: 1.25–3.57); P = .005, and this association was not attenuated when covariates including cardiac disease and depressive symptom burden were added. There was no statistically significant association between serotonin noradrenaline reuptake inhibitor or tricyclic antidepressant use and OH in unadjusted models although the study was not powered to detect changes within these subgroups. Older people taking antidepressants have a two-fold higher prevalence of OH than nonusers, highlighting the importance of screening the older antidepressant user for OH and dizziness and rationalizing medications to reduce the risk of falls within this vulnerable cohort.

Cannabinoids and gastrointestinal motility: Pharmacology, clinical effects, and potential therapeutics in humans.

Cannabinoid agents and cannabis are frequently used for relief of diverse gastrointestinal symptoms. The objective of this article is to increase the awareness of gastroenterologists to the effects of cannabinoids on gastrointestinal motility, as gastroenterologists are likely to encounter patients who are taking cannabinoids, or those with dysmotility that may be associated with cannabinoid mechanisms. The non-selective cannabinoid agonist, dronabinol, retards gastric emptying and inhibits colonic tone and phasic pressure activity. In addition to the well-recognized manifestations of cannabinoid hyperemesis, cannabinoid mechanisms result in human and animal models of gastrointestinal and colonic dysmotility. Decreased enteric FAAH activity is associated with colonic inertia in slow transit constipation and, conversely, the orphan G protein-coupled receptor, GPR55, is overexpressed in streptozotocin-induced gastroparesis, suggesting it is involved in inhibition of antral motility. Experimental therapies in gastrointestinal motility and functional disorders are focused predominantly on pain relief mediated through cannabinoid 2 receptors or inhibition of DAGLα to normalize colonic transit. In summary, cannabinoid mechanisms and pharmacology are relevant to the current and future practice of clinical gastroenterology.

Studies on the subcooled boiling in a fuel assembly with 5 by 5 rods using an improved wall boiling model

An improved wall boiling model with consideration of thin film heat transfer was employed with the Eulerian two-fluid model to investigate the three-dimensional flow boiling characteristics in a fuel assembly with 5 by 5 rod bundle and a vaned grid. Models were validated by using the experimental data for subcooled boiling, post-dryout heat transfer and critical heat flux. The calculated results agreed well with experimental data. Thermohydraulics in the rod bundle were obtained, including temperature, velocity, phasic volume fraction and pressure, based on which, the effects of mixing vane on the localized thermohydraulics were studied. Mixing vane can significantly reduce the cross section averaged vapor fraction and increase the heat transfer capacity due to the swirl effects on two-phase flow; however, it will increase the localized vapor fraction on the heated surface, which may result in the anticipation of boiling crisis, i.e., reach the critical heat flux. Besides, influences of heat flux profile on the flow and heat transfer characteristics were also obtained by comparing two cases with uniform and cosine heat flux distribution along the axial direction. Finally, the impacts of thin film heat transfer on the wall heat partition were investigated, proving that thin film heat transfer played an essential role in the modeling of wall boiling when the vapor fraction at heated surface exceeding 0.25.