Simultaneous Pressure Recordings Research Articles

Application of transcranial transmission ultrasound in the detection of vasospasm in patients with aneurysmal subarachnoid hemorrhage: illustrative cases.

Effective management of patients with aneurysmal subarachnoid hemorrhage (aSAH) demands vigilant monitoring and treatment, given the risks of complications such as cerebral vasospasm and delayed ischemic neurological deficits (DINDs). Transcranial transmission ultrasound (TTUS) is a well-established technique for assessing brain pulsatility. This pilot study aims to explore the utility of TTUS in detecting impaired intracerebral blood flow associated with DINDs. The authors examined 2 male patients, ages 45 and 52 years, with aSAH Hunt and Hess grades 4 and 2, respectively, who developed DINDs during their clinical course. Simultaneous recordings of arterial blood pressure, heart rate, and TTUS measurements were obtained in the intensive care unit. TTUS analysis revealed abnormal arrhythmic wave patterns during DIND episodes, whereas baseline measurements on DIND-free days showed no abnormalities. Following endovascular spasmolysis, TTUS demonstrated a normalization of abnormal waves, returning to baseline levels, alongside the resolution of neurological symptoms. TTUS, a noninvasive method for assessing brain pulsatility, shows promise as a novel tool for monitoring aSAH patients, potentially aiding in prompt diagnostics and additional therapeutic interventions. Its capacity to provide further insights for individuals at risk of delayed cerebral ischemia warrants further investigation in clinical studies. https://thejns.org/doi/10.3171/CASE24146.

Predictive value of cerebrovascular time constant for delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage

Time constant of the cerebral arterial bed (τ) is a transcranial Doppler (TCD) based metric that is expected to quantify the transit time of red blood cells from the insonation point to the arteriole-capillary boundary during a cardiac cycle. This study aims to assess the potential of τ as an early predictor of delayed cerebral ischemia (DCI). Consecutive patients (56 ± 15 years) treated for aneurysmal subarachnoid haemorrhage were included in the study. τ was assessed through a modelling approach that involved simultaneous recordings of arterial blood pressure and cerebral blood flow velocity (CBFV) from TCD's first recordings. 71 patients were included. 17 patients experienced DCI. τ was significantly shorter in patients who later developed DCI: 187 ± 64 ms vs. 249 ± 184 ms; p = 0.040 with moderate effect size (rG = 0.24). Logistic regression showed that there was a significant association between increased CBFV, shortened τ, and the development of DCI (χ2 = 11.54; p = 0.003) with AUC for the model 0.75. Patients who had both shortened τ and increased CBFV were 20 times more likely to develop DCI (OR = 20.4 (2.2–187.7)). Our results suggest that early alterations in τ are associated with DCI after aSAH. The highest performance of the model including both CBFV and τ may suggest the importance of both macrovascular and microvascular changes assessment.

Ascending aortic impedance in young endurance athletes: a time-resolved phase-contrast MRI study.

Ventricular-vascular coupling in endurance athletes remains incompletely understood. The purpose of this study was to determine the ascending aortic impedance in endurance athletes and explore its associations with traditional cardiovascular measurements. In 15 young male endurance runners and 19 young healthy men, time-resolved (CINE) two-dimensional (2-D) phase-contrast MRI quantified the ascending aortic flow while the pressure waveform was simultaneously collected via a generalized transfer function. The aortic impedance modulus and phase were calculated in the frequency domain while characteristic impedance (ZcF) was calculated by averaging moduli between the 4th and 8th heart rate (HR) harmonics. Stroke volume (SV), left ventricular (LV) morphometry, double product, aortic compliance, and total peripheral resistance (TPR) were also measured. Endurance athletes had higher SV, slower HR, greater LV end-diastolic volume and mass, and lower double product than sedentary participants (all P < 0.05). ZcF was significantly lower in athletes than in sedentary participants (73.3 ± 19.2 vs. 93.4 ± 19.0 dyn·s/cm5, P = 0.005). Furthermore, ZcF was negatively correlated with SV (r = -0.691) and aortic compliance (r = -0.601) but was positively correlated with double product (r = 0.445) and TPR (r = 0.458; all P < 0.05). Multivariate analysis revealed that ZcF was the strongest predictor of SV followed by TPR and HR (adjusted R2 = 0.788, P < 0.001). Therefore, our findings collectively suggest that LV afterload quantified by aortic ZcF is significantly lower in endurance athletes than in sedentary adults. The lower pulsatile LV afterload may contribute to greater SV in endurance athletes.NEW & NOTEWORTHY This is the first study to investigate aortic impedance with the noninvasive, simultaneous recordings of aortic pressure using SphygmoCor XCEL and flow using phase-contrast MRI. We found that the characteristic impedance (Zc) is significantly lower in endurance athletes than sedentary adults, is the strongest predictor of stroke volume (SV), and is inversely associated with aortic compliance. These findings suggest that aortic impedance is a key determinant of the ventricular-vascular coupling adapted to long-term training in endurance athletes.

First description and validation of a new method for estimating aortic stenosis burden and predicting the functional response to TAVI.

Up to one-fifth of patients continue to have poor quality of life after transcatheter aortic valve implantation (TAVI), with an additional similar proportion not surviving 1 year after the procedure. We aimed to assess the value of a new method based on an integrated analysis of left ventricular outflow tract flow velocity and aortic pressure to predict objective functional improvement and prognosis after TAVI. In a cohort of consecutive patients undergoing TAVI, flow velocity-pressure integrated analysis was obtained from simultaneous pressure recordings in the ascending aorta and flow velocity recordings in the left ventricular outflow tract by echocardiography. Objective functional improvement 6 months after TAVI was assessed through changes in a 6-min walk test and NT-proBNP levels. A clinical follow-up was conducted at 2 years. Of the 102 patients studied, 82 (80.4%) showed objective functional improvement. The 2-year mortality of these patients was significantly lower (9% vs. 44%, p = 0.001). In multivariate analysis, parameter "(Pressure at Vmax - Pressure at Vo)/Vmax" was found to be an independent predictor for objective improvement. The C-statistic was 0.70 in the overall population and 0.78 in the low-gradient subgroup. All echocardiographic parameters and the valvuloarterial impedance showed a C-statistic of <0.6 for the overall and low-gradient patients. In a validation cohort of 119 patients, the C-statistic was 0.67 for the total cohort and 0.76 for the low-gradient subgroup. This new method allows predicting objective functional improvement after TAVI more precisely than the conventional parameters used to assess the severity of aortic stenosis, particularly in low-gradient patients.

Operando swelling measurement of silicon carbon composite based anode in pouch cell: Effect of external pressure, balancing and anode initial porosity

Silicon lithiation induces a high material expansion, leading to significant swelling and mechanical pressure at the anode and cell levels. In this study, the swelling behaviour of a bilayer pouch cell with high-performance silicon carbon graphite (Si-C/G) anode material was measured, considering the effect of external pressure on the pouch and the cell design parameters such as the balancing and the anode initial porosity. Operando swelling was measured by using an in-house high precision (< 0.1 μm) compression set-up involving simultaneous pressure and thickness recording as well as dynamic pressure regulation system. Results show that a minimum level of pressure is mandatory to obtain a reversible swelling, and that the anode porosity is directly linked to the pressure applied on the cell after particles dynamic rearrangement. The impact on capacity retention is also discussed.

Abstract 9: Autoregulation-based Blood Pressure Targets After Endovascular Thrombectomy

Background: Optimal level blood pressure (BP) targets in acute stroke remain elusive. Tailored hemodynamic management after endovascular thrombectomy (EVT) may reduce the risk of reperfusion injury and promote penumbral recovery. Our study aimed to evaluate the relationship between personalized autoregulation-based BP targets, secondary brain injury, and functional outcomes. Methods: We prospectively enrolled 200 patients with acute ischemic stroke who underwent EVT. Autoregulatory function was continuously measured for &gt;=24 hours using simultaneous recordings of near-infrared spectroscopy and mean arterial pressure (MAP). The resulting autoregulatory index was used to calculate and trend the BP range at which autoregulation was most preserved. Percent time and “dose” that MAP exceeded the upper limit or dropped below the lower limit of autoregulation (ULA, LLA) were calculated for each patient. Hemodynamic parameters were correlated with short-term clinical endpoints (symptomatic ICH), biomarkers of secondary brain injury (net water uptake, hemorrhagic transformation (HT), infarct progression), and 90-day functional outcomes. Results: Personalized BP targets were successfully computed in 195 patients (mean age 70 ± 16, 45% female, mean NIHSS 14, mean monitoring time 31 ± 28 hours). Time above the ULA was associated with worse functional outcomes at 90-days after adjusting for age, sex, NIHSS, ASPECTS and TICI (adjusted OR per 10% increase 1.4, 95% CI 1.1-1.6, P=0.004). The burden of hyperperfusion was significantly greater among patients with HT (median 2.7 vs. 3.2 mmHg*min, p=0.01) and sICH (median 2.8 vs. 4.8 mmHg*min, p=0.05) than in those without it. Furthermore, time spent above the ULA was significantly correlated with net water uptake at 72 hours (r=0.37, p=0.03). Among patients with unsuccessful reperfusion, there was a non-significant correlation between time below the LLA and infarct progression (r=0.35, p=0.064). Conclusions: In the largest study conducted to date, deviations from personalized BP targets were associated with an increased risk of secondary brain injury and worse functional outcomes. Autoregulation-oriented BP management represents a promising strategy for maximizing recovery after ischemic stroke.

Historical view onto the contribution of phlebodynamometry to the knowledge of venous hemodynamics in the lower extremity

Contribution of phlebodynamometry to the knowledge of the venous hemodynamics in the lower extremity is assessed from the historical point of view. Höjensgard, Stürup, and Arnoldi yielded in the 50's and 60's of the last century substantial information concerning changes of venous pressure in superficial and deep veins of the lower extremity arising during calf pump activity. They confirmed the previous finding that the venous pressure in the quiet standing position corresponds to the column of blood extending from the point of measurement to the heart. During calf pump activity, the systolic-diastolic amplitudes in lower leg veins are very marked; in contrast to that, they are only modest in the popliteal vein. The mentioned authors documented marked decrease in pressure in the posterior tibial vein as well as in the great saphenous vein arising during calf pump activity in healthy people. Contrary to that, the pressure in the popliteal vein did not decrease; it kept principally the value of the resting hydrostatic pressure. This difference of pressure between the thigh veins and the lower leg veins has been called ambulatory pressure gradient; its value in the examined patient cohort was 37.4±6.4 mm Hg. Ambulatory pressure gradient constitutes the suction force that triggers reflux in incompetent superficial and deep veins; this refluxing flow causes ambulatory venous hypertension. Simultaneous pressure recordings in the posterior tibial vein and great saphenous vein in healthy volunteers documented that the systolic and diastolic pressure amplitudes were similar in both veins. The systolic pressure in the posterior tibial vein increased on average by 75 mm Hg; this generates a strong impulse propelling the venous blood mainly into the popliteal vein, and partially into the great saphenous vein. Thus, there is a double-barreled outflow of venous blood from the lower extremity toward the heart. The steep increase in systolic pressure in the great saphenous vein gave evidence of the incompetence of the calf perforators system in healthy people. At present, plethysmography is able to yield similar information on the hemodynamic status of the lower limbs like phlebodynamometry.

Aerobic exercise training reduces cerebrovascular impedance in older adults: a 1-year randomized controlled trial.

Older adults have higher cerebrovascular impedance than young individuals which may contribute to chronic brain hypoperfusion. Besides, middle-aged athletes exhibit lower cerebrovascular impedance than their sedentary peers. We examined whether aerobic exercise training (AET) reduces cerebrovascular impedance in sedentary older adults. We conducted a proof-of-concept trial that randomized 73 older adults to 1 yr of AET (n = 36) or stretching and toning (SAT, n = 37) interventions. Cerebrovascular impedance was estimated from simultaneous recordings of carotid artery pressure (CAP) via applanation tonometry and cerebral blood flow velocity (CBFV) in the middle cerebral artery via transcranial Doppler using transfer function analysis. Fifty-six participants completed 1-yr interventions, and 41 of those completed cerebrovascular impedance measurements. AET group showed a significant increase in V̇o2peak after the intervention [estimated marginal mean (95% confidence interval); from 22.8 (21.6 to 24.1) to 24.9 (23.6 to 26.2) mL·kg-1·cm-1, P < 0.001], but not SAT [from 21.7 (20.5 to 22.9) to 22.3 (21.1 to 23.7) mL·kg-1·cm-1, P = 0.114]. Coherence between changes in CBFV and CAP was >0.90 in the frequency range of 0.78-3.12 Hz. The averaged cerebrovascular impedance modulus (Z) in this frequency range decreased after 1-yr AET [from 1.05 (0.96 to 1.14) to 0.95 (0.92 to 1.06) mmHg·s·cm-1, P = 0.023], but not SAT [from 0.96 (0.87 to 1.04) to 1.01 (0.92 to 1.10) mmHg·s·cm-1, P = 0.138]. Reductions in Z were correlated positively with reductions in carotid pulse pressure (r = 0.628, P = 0.004) and inversely with mean CBFV (r = -0.563, P = 0.012) in the AET group. One-year AET reduces cerebrovascular impedance in older adults, which may benefit brain perfusion.NEW & NOTEWORTHY Estimation of cerebrovascular impedance is essential for understanding dynamic cerebral blood flow regulation. This randomized controlled trial demonstrated that aerobic exercise training reduced cerebrovascular impedance in older adults, which may benefit brain perfusion.

Si–C/G based anode swelling and porosity evolution in 18650 casing and in pouch cell

Silicon lithiation induces a high material expansion which leads to significant swelling and mechanical pressure at the anode and cell level. In this study, the effect of the various mechanical constrains on the swelling behaviour of pouch cell and cylindrical cell (18650) with high performance silicon carbon graphite (Si–C/G) anode material was evaluated. In case of 18650 cells, strain gauges were used to evaluate the strains and pressure generated from anode swelling during cycling process; in addition, individual cell components thickness change was captured at 8 different states of charge (SOC) during a cycle by in situ 3D imaging with X-Ray micro computed-tomography (voxel size 1.6 μm) combined with a specific image treatment. For bi-layer pouch cells, operando swelling was measured using an in-house high precision (<0.1 μm) compression set-up with simultaneous pressure and thickness recording as well as dynamic pressure regulation system. Combining these unique experimental techniques and the modelling of Si–C/G active material swelling in function of the SOC we were able to provide insights in porosity changes of anodes for the two cell formats.

Abstract 10432: Simultaneous Recording of Skin Sympathetic Nerve Activity and Blood Pressure in Ambulatory Outpatients with Postural Orthostatic Tachycardia Syndrome

Introduction: neuECG is a method to simultaneously record ECG and skin sympathetic nerve activity (SKNA). Postural orthostatic tachycardia syndrome (POTS) is known to be associated with increased cardiac sympathetic norepinephrine release. Hypothesis: Average SKNA correlates positively with heart rate (HR) and blood pressure (BP) in POTS patients. Methods: We used Bittium Faros 180 Holter Monitor (sampling rate 1,000 Hz) to record neuECG and SpaceLab OnTrak arterial BP monitor (ABPM) to record BP simultaneously over 24-hr in 20 POTS patients (19 women, 38±12 years old). The Faros signals were high pass filtered at 300 Hz to display the SKNA. The same original signals were bandpass filtered 0.05-150 Hz to display ECG. BP was measured every 30-min when awake (7AM to 9 PM) and hourly at night (9 PM to 7 AM). Results: Fig 1 shows an example of typical recording from a 38-year-old woman. Panel A shows average SKNA (aSKNA) 1-min prior to HR and BP measurement. The overall successful ABPM measurement was 90% with average BP of 126/75 mmHg. B shows bursts of SKNA in daytime (red dot in A), but no bursts at night (blue dot in A). C shows a positive correlation between HR, systolic BP (SBP) diastolic BP (DBP) and mean BP (MBP) with aSKNA. For all patients studied, 16 of 20 showed positive correlation between MBP and aSKNA (r=0.559±0.152, p&lt;0.05 for all) and 15 of 20 showed positive correlation between HR and aSKNA (r=0.511±0.175, p&lt;0.05 for all). The nocturnal aSKNA averaged 0.919±0.059 μV (N=17) and 1.060±0.215 (N=3) (p&lt;0.001) in patients with and without nocturnal dip, respectively. However, the overall 24-hr aSKNA (1.036±0.120 vs 1.044±0.095, μV) was not different between these two groups. Conclusions: aSKNA positively correlated with BP and HR in ambulatory outpatients with POTS. High aSKNA at night was associated with nocturnal non-dipping of BP.

Clinical implications of antegrade diastolic pulmonary artery flow in adults

BackgroundEnd-diastolic opening of the pulmonary valve and subsequent antegrade diastolic pulmonary artery flow (ADPAF) reflect restrictive right ventricular (RV) physiology in children. However, this has attracted little attention in adults. PurposeTo clarify the clinical implications of ADPAF in adults. Methods and ResultsThe study population consisted of 23,049 consecutive adult patients who underwent echocardiography in our hospital between 2008 and 2015. ADPAF was found in 17 patients (0.07%). The simultaneous recording of RV and pulmonary artery pressures revealed marked elevation of RV diastolic pressure, which exceeded pulmonary artery pressure at the time of atrial contraction. These results suggested that ADPAF implies RV restriction. Based on the level of tricuspid annular plane systolic excursion (TAPSE), we classified these patients into two groups: reduced RV function (R-RVF) group (12 patients with TAPSE <17 mm) and preserved RV function (P-RVF) group (5 patients with TAPSE ≥17 mm). In the R-RVF group, four patients died, one patient underwent left ventricular assist device implantation, and two patients underwent unplanned hospitalization for heart failure during follow-up. The R-RVF group had poorer prognosis and higher mortality rate compared with the P-RVF group. ConclusionsADPAF reflects RV restriction in adults. ADPAF suggests a less favorable prognosis in patients with R-RVF.

Self-limited nanosecond laser-induced bubble growth in sealed containers

We demonstrate that nanosecond laser-induced bubbles, generated in sealed containers, can experience self-limiting effects. We experimentally study such effects using simultaneous pressure and bubble dynamics recordings. We show that self-limiting effects can be drastic for mm-sized bubbles generated in sub-cm3 sized containers, resulting in 0.5-fold decrease in their size and fourfold decrease in their lifetime compared to those generated in non-sealed control containers. We use the Keller–Miksis equation to model self-limiting effects and discuss their technological implications in applications that exploit bubble growth in confined geometries.

Determination of Aortic Characteristic Impedance and Total Arterial Compliance From Regional Pulse Wave Velocities Using Machine Learning: An in-silico Study.

In-vivo assessment of aortic characteristic impedance (Zao) and total arterial compliance (CT) has been hampered by the need for either invasive or inconvenient and expensive methods to access simultaneous recordings of aortic pressure and flow, wall thickness, and cross-sectional area. In contrast, regional pulse wave velocity (PWV) measurements are non-invasive and clinically available. In this study, we present a non-invasive method for estimating Zao and CT using cuff pressure, carotid-femoral PWV (cfPWV), and carotid-radial PWV (crPWV). Regression analysis is employed for both Zao and CT. The regressors are trained and tested using a pool of virtual subjects (n = 3,818) generated from a previously validated in-silico model. Predictions achieved an accuracy of 7.40%, r = 0.90, and 6.26%, r = 0.95, for Zao, and CT, respectively. The proposed approach constitutes a step forward to non-invasive screening of elastic vascular properties in humans by exploiting easily obtained measurements. This study could introduce a valuable tool for assessing arterial stiffness reducing the cost and the complexity of the required measuring techniques. Further clinical studies are required to validate the method in-vivo.

Bay 60-7550, a PDE2 inhibitor, exerts positive inotropic effect of rat heart by increasing PKA-mediated phosphorylation of phospholamban

This study investigated the hemodynamic effect of Bay 60-7550, a phosphodiesterase type 2 (PDE2) inhibitor, in healthy rat hearts both in vivo and ex vivo and its underlying mechanisms. In vivo rat left ventricular pressure-volume loop, Langendorff isolated rat heart, Ca2+ transient of left ventricular myocyte and Western blot experiments were used in this study. The results demonstrated that Bay 60-7550 (1.5 mg/kg, i. p.) increased the in vivo rat heart contractility by enhancing stroke work, cardiac output, stroke volume, end-diastolic volume, heart rate, and ejection fraction. The simultaneous aortic pressure recording indicated that the systolic blood pressure was increased and diastolic blood pressure was decreased by Bay 60-7550. Also, the arterial elastance which is proportional to the peripheral vessel resistance was significantly decreased. Bay 60-7550 (0.001, 0.01, 0.1, 1 μmol/l) also enhanced the left ventricular development pressure in non-paced and paced modes with a decrease of heart rate in non-paced model. Bay 60-7550 (1 μmol/l) increased SERCA2a activity and SR Ca2+ content and reduced SR Ca2+ leak rate. Furthermore, Bay 60-7550 (0.1 μmol/l) increased the phosphorylation of phospholamban at 16-serine without significantly changing the phosphorylation levels of phospholamban at 17-threonine and RyR2. Bay 60-7550 increased the rat heart contractility and reduced peripheral arterial resistance may be mediated by increasing the phosphorylation of phospholamban and dilating peripheral vessels. PDE2 inhibitors which result in a positive inotropic effect and a decrease in peripheral resistance might serve as a target for developing agents for the treatment of heart failure in clinical settings.

Right ventricular pressure-volume loop produced with simultaneous application of three-dimensional echocardiography and high-fidelity micromanometry in a patient with pulmonary arterial hypertension.

Accurate assessment of right ventricular (RV) function has received a growing attention. Pressure-volume (PV) loop analysis is the gold standard method for evaluating RV function; however, it is not widely employed because of its invasive nature and complexity. The present report is the first to have drawn a RV PV loop in a patient with pulmonary hypertension, with a simultaneous recording of RV pressure and volume using high-fidelity micromanometry and three-dimensional echocardiography. This allows for less invasive and simple assessment of RV function, potentially promoting better understanding and management of pulmonary hypertension and other cardiovascular diseases.

Laminar flame speed determination at high pressure and temperature conditions for kinetic schemes assessment

Given the experimental difficulties, most of the available flame speed database is for relatively reduced thermodynamic conditions and for non-simultaneous variations of pressure and temperature. This limitation may be overpassed by using spherically expanding flames with the constant volume method. This methodology, introduced in the 30 s by Lewis and von Elbe, requires the knowledge of the pressure evolution in the combustion chamber. It has been penalized for a long time because of the underlying assumptions and problems in flame instability detection. This method has been greatly renewed recently by Egolfopoulos following a coupled experimental/numerical approach integrating the effects of radiation and dissociation while maintaining moderate computing costs. In parallel with this study, we have worked on an alternative method providing a maximum of information for each test minimizing uncertainties. The current study uses a new experimental device allowing simultaneous recording of pressure and flame radius inside the chamber during the full combustion process. The direct use of these data over the whole flame propagation allows testing kinetic schemes over large pressure and temperature domains with good accuracy. These new experimental targets allowed the identification of key reactions needing improvements.

Echocardiographic assessment of simultaneously measured left ventricular filling pressures in patients with normal left ventricular ejection fraction

Assessment of left ventricular (LV) diastolic function is part of routine echocardiographic examinations. Accuracy of the 2016 ASE/EACVI algorithm to detect LV diastolic dysfunction in patients with a normal LV ejection fraction (LVEF) has been examined but simultaneous measurements of LV pressures and echocardiographic parameters of diastolic function are sparse. The accuracy of multiple echo parameters of diastolic dynamics and the 2016 guidelines were assessed by simultaneous transthoracic echocardiography and LV pressure recordings in 120 patients (derivation cohort) and 60 patients (validation cohort) with suspected coronary artery disease and normal LVEF. Receiver-operating characteristic (ROC) curves defined optimal cut points for each echocardiographic parameter. A new algorithm was proposed to estimate LV diastolic pressures using 5 parameters based on ROC data: tricuspid regurgitation velocity >280cm/s, average e' <9cm/s, average E/e' ratio >13, velocity of pulmonary vein A-wave reversal >32cm/s, and left atrial volume index >32mL/m2 . Performances of the 2016 guidelines and a proposed algorithm were examined for detecting a LV pre-A >12 and LV end-diastolic pressure (LVEDP) >15mmHg. In the derivation cohort, the 2016 algorithm identified an elevated LVEDP >15mmHg with an accuracy of 74.2% (63.8-82.9); the modified algorithm improved accuracy to 86.0% (77.6-92.1), P<.05. In the validation cohort, the proposed algorithm improved sensitivities with accuracies remaining like the 2016 algorithm. LV diastolic pressures in patients with normal LVEF were reliably assessed by the 2016 guidelines. The proposed algorithm improved sensitivities and may improve the accuracies for detecting abnormal LV filling pressures.

Design of Pressure Sensor Arrays to Assess Electrode Contact Pressure During In Vivo Recordings in the Gut.

The gastrointestinal (GI) tract is in part controlled by slow wave electrical activity. Recordings of slow waves with high-resolution (HR) electrode arrays are used to characterize normal and abnormal conduction pathways. Improving the quality of these electrical recordings is important for developing a better understanding of abnormal activity. Contact pressure is one factor that can affect the quality of electrical recordings. We compared the performance of two pressure sensing devices for measuring HR electrode array contact pressure. A Velostat-based sensor array was custom designed and built in a 4 × 2 conguration (area: 30 mm2 per sensor) to be integrated into electrical recordings. Commercially available FlexiForce A201 sensors were used to compare to the Velostat-based sensors. Benchtop testing of these sensors was performed; the error of the Velostat-based sensors (14-31%) was better than that of the FlexiForce sensors (20-49%) within a range of 2666-6666 Pa. The Velostat-based sensors were also more repeatable than the FlexiForce sensors over the same pressure range. Simultaneous pressure and slow wave recordings were performed in vivo on a rabbit small intestine. The Velostat-based sensors were able to resolve spatiotemporal changes in contact pressure in the range of 0-10 000 Pa.

Cardiovagal Baroreflex Sensitivity is Reduced in Middle‐Age and Older Men with Low Testosterone

BACKGROUNDMale aging is associated with a general decline in serum testosterone (T) concentrations. Endogenous low T is associated with increased cardiovascular disease risk. Following orchiectomy or androgen suppression, rats have reduced cardiovagal baroreflex sensitivity (BRS), a key antecedent to the development of hypertension and other cardiovascular diseases. BRS is determined by mechanical (i.e. arterial stiffness) and neural factors, and heart rate variability (HRV) may provide insight into the contribution of these mechanical and neural factors. However, the effects of low T on BRS in middle‐age and older men is unknown.PURPOSEDetermine whether BRS and HRV are reduced in middle‐age and older men with low T.METHODSEight healthy older men between the ages of 50–75 years (BMI: 28.7±6.3 kg/m2, systolic blood pressure: 130±9 mmHg, diastolic blood pressure: 78±7 mmHg; mean±SD) with either low (&lt;300 ng/dL; n=4) or normal (≥400 ng/dL; n=4) T underwent simultaneous recordings of blood pressure (finger photoplethysmography) and R‐R interval (electrocardiogram) during supine rest. Spontaneous cardiovagal BRS was assessed in sequences of ≥4 cardiac cycles in which R‐R interval and systolic blood pressure changed in the same direction. Time (standard deviation of R‐R intervals of normal sinus beats; SDNN, and root‐mean‐square of successive differences in R‐R interval differences; RMSSD) and frequency (low frequency and high frequency power) domain indices of HRV were determined during six minutes of paced breathing at 0.2 Hz. Serum T was measured in the morning under fasting conditions.RESULTST concentrations were significantly lower in the low T group compared to the normal T (269.3±40.5 vs. 561.0±109.8 ng/dL; p=0.002). Age (56±3 vs. 57±5 years; p=0.836) and mean arterial pressure (96±9 vs. 98±8 mmHg; p=0.794) were similar between groups. Cardiovagal BRS was significantly lower in the low T compared to normal T group ( 8.2±3.1 vs. 16.2±4.2 ms/mmHg; p=0.021). Cardiovagal BRS was strongly correlated with T concentrations when considered as a continuous variable (R=0.71, p=0.049), but cardiovagal BRS was not correlated to age (R=0.06, p=0.891). No indices of HRV were significantly different between groups (p≥0.20 for all).CONCLUSIONSThese preliminary data indicate that spontaneous cardiovagal BRS is reduced in men with low T. The absence of differences in HRV suggest that differences in BRS may be influenced by mechanical (i.e. arterial stiffness), rather than neural mechanisms.Support or Funding InformationSupported by NIH Grants R01AG049762 and T32AG000279‐16A1

Pathophysiological changes of the lower urinary tract behind voiding dysfunction in streptozotocin-induced long-term diabetic rats

We evaluated pathophysiological characteristics of the lower urinary tract dysfunction in a streptozotocin (STZ)-induced diabetic rat model. STZ (60 mg/kg) was injected intraperitoneally into male Wistar rats. In vitro bladder muscle strip experiments, in vivo cystometry, and simultaneous recordings of bladder pressure + urethral perfusion pressure (BP + UPP) with or without intravenous administration of L-arginine (300 mg/kg) or tadalafil (0.03 mg/kg) were performed at several time points. In vitro muscle strip experiments demonstrated that diabetic rats had significantly higher contractile responses to carbachol at 4–16 weeks, and a tendency for higher contractile responses to electrical field stimulation at 4–12 weeks, but this was reversed at 16 weeks. Diabetic rats had significant increases in voided volume, residual volume, bladder capacity, maximal voiding pressure, and amplitude and frequency of non-voiding contractions at 16 weeks. Tadalafil decreased the residual volume in diabetic rats. Diabetic rats had significantly higher UPP nadir and mean UPP during high-frequency oscillation at 16 weeks, which were reversed by tadalafil or L-arginine administration. The present results suggest that urethral relaxation failure, probably related to impairment of the NO/cGMP signalling pathway, rather than bladder contractile dysfunction may be a prominent cause for voiding dysfunction in STZ-induced chronic diabetic rats.