Non-invasive and non-occlusive blood pressure estimation via a chest sensor.

The clinical demand for a device to monitor Blood Pressure (BP) in ambulatory scenarios with minimal use of inflation cuffs is increasing. Based on the so-called Pulse Wave Velocity (PWV) principle, this paper introduces and evaluates a novel concept of BP monitor that can be fully integrated within a chest sensor. After a preliminary calibration, the sensor provides non-occlusive beat-by-beat estimations of Mean Arterial Pressure (MAP) by measuring the Pulse Transit Time (PTT) of arterial pressure pulses travelling from the ascending aorta towards the subcutaneous vasculature of the chest. In a cohort of 15 healthy male subjects, a total of 462 simultaneous readings consisting of reference MAP and chest PTT were acquired. Each subject was recorded at three different days: D, D+3 and D+14. Overall, the implemented protocol induced MAP values to range from 80 ± 6 mmHg in baseline, to 107 ± 9 mmHg during isometric handgrip maneuvers. Agreement between reference and chest-sensor MAP values was tested by using intraclass correlation coefficient (ICC = 0.78) and Bland-Altman analysis (mean error = 0.7 mmHg, standard deviation = 5.1 mmHg). The cumulative percentage of MAP values provided by the chest sensor falling within a range of ±5 mmHg compared to reference MAP readings was of 70%, within ±10 mmHg was of 91%, and within ±15mmHg was of 98%. These results point at the fact that the chest sensor complies with the British Hypertension Society (BHS) requirements of Grade A BP monitors, when applied to MAP readings. Grade A performance was maintained even two weeks after having performed the initial subject-dependent calibration. In conclusion, this paper introduces a sensor and a calibration strategy to perform MAP measurements at the chest. The encouraging performance of the presented technique paves the way towards an ambulatory-compliant, continuous and non-occlusive BP monitoring system.

Influence of chronic hyperglycemia on cerebral microvascular remodeling: an in vivo study using perfusion computed tomography in acute ischemic stroke patients.

BACKGROUND AND PURPOSE: To investigate the effect of chronic hyperglycemia on cerebral microvascular remodeling using perfusion computed tomography. METHODS: We retrospectively identified 26 patients from our registry of 2453 patients who underwent a perfusion computed tomographic study and had their hemoglobin A1c (HbA1c) measured. These 26 patients were divided into 2 groups: those with HbA1c>6.5% (n=15) and those with HbA1c≤6.5% (n=11). Perfusion computed tomographic studies were processed using a delay-corrected, deconvolution-based software. Perfusion computed tomographic values were compared between the 2 patient groups, including mean transit time, which relates to the cerebral capillary architecture and length. RESULTS: Mean transit time values in the nonischemic cerebral hemisphere were significantly longer in the patients with HbA1c>6.5% (P=0.033), especially in the white matter (P=0.005). Significant correlation (R=0.469; P=0.016) between mean transit time and HbA1c level was observed. CONCLUSIONS: Our results from a small sample suggest that chronic hyperglycemia may be associated with cerebral microvascular remodeling in humans. Additional prospective studies with larger sample size are required to confirm this observation.

Effect of a whey-predominant starter formula containing LCPUFAs and oligosaccharides (FOS/GOS) on gastrointestinal comfort in infants.

Development of new infant formulas aims to replicate the benefits of breast milk. One benefit of breast milk over infant formulas is greater gastrointestinal comfort. We compared indicators of gastrointestinal comfort in infants fed a whey-predominant formula containing long-chain polyunsaturated fatty acids, galacto-oligo-saccharides and fructo-oligosaccharides, and infants fed a control casein-predominant formula without additional ingredients. The single-centre, prospective, double-blind, controlled trial randomly assigned healthy, full-term infants (n=144) to receive exclusively either experimental or control formula from 30 days to 4 months of age. A group of exclusively breast-fed infants served as reference (n=80). At 1, 2, 3, and 4 months, infants' growth parameters were measured and their health assessed. Parents recorded frequency and physical characteristics of infants' stool, frequency of regurgitation, vomiting, crying and colic. At 2-months, gastric emptying (ultrasound) and intestinal transit time (H2 breath test) were measured, and stool samples collected for bacterial analysis. Compared to the control (n=69), fewer of the experimental group (n=67) had hard stools (0.7 vs 7.5%, p<0.001) and more had soft stools (90.8 vs 82.3%, p<0.05). Also compared to the control, the experimental group's stool microbiota composition (mean % bifidobacteria: 78.1 (experimental, n=17), 63.7 (control, n=16), 74.3 (breast-fed, n=20), gastric transit times (59.6 (experimental, n=53), 61.4 (control, n=62), 55.9 (breast-fed, n=67) minutes) and intestinal transit times (data not shown) were closer to that of the breast-fed group. Growth parameter values were similar for all groups. The data suggest that, in infants, the prebiotic-containing whey-based formula provides superior gastrointestinal comfort than a control formula.

Shot noise anomalies in elastic nondegenerate diffusive conductors

We present a theoretical investigation of shot-noise properties in nondegenerate elastic diffusive conductors. Both Monte Carlo simulations and analytical approaches are used. Two interesting phenomena are found: (i) the display of enhanced shot noise for given energy dependences of the scattering time, and (ii) the recovery of full shot noise for asymptotic high applied bias. The first phenomenon is associated with the onset of negative differential conductivity in energy space that drives the system towards a dynamical electrical instability in excellent agreement with analytical predictions. The enhancement is found to be strongly amplified when the dimensionality in momentum space is lowered from three to two dimensions. The second phenomenon is due to the suppression of the effects of long-range Coulomb correlations that takes place when the transit time becomes the shortest time scale in the system, and is common to both elastic and inelastic nondegenerate diffusive conductors. These phenomena shed different light in the understanding of the anomalous behavior of shot noise in mesoscopic conductors, which is a signature of correlations among different current pulses.

Shot noise in linear macroscopic resistors

We report on direct experimental evidence of shot noise in a linear macroscopic resistor. The origin of the shot noise comes from the fluctuation of the total number of charge carriers inside the resistor associated with their diffusive motion under the condition that the dielectric relaxation time becomes longer than the dynamic transit time. The present results show that neither potential barriers nor the absence of inelastic scattering are necessary to observe shot noise in electronic devices.

Cerebral perfusion CT in the evaluation of children with severe head trauma : 12.06

Purpose: To assess the value of cerebral perfusion CT (PCT) in children with traumatic brain injury in prediciting their consecutive clinical outcome. Materials and methods: Twelve paediatric patients with acute traumatic brain injury underwent cerebral CT coupled with PCT during their admission at the emergency room (ER). PCT maps were reviewed for mean transit time (MTT), regional cerebral blood flow (rCBF) and regional cerebral blood volume (rCBV) abnormalities. PCT results were compared to short- and mid-term clinical outcome. Results: 3 patients with low Glasgow Coma Scale (GCS) (98) and bad clinical outcome showed an increased MTT and decreased rCBV and rCBF. 5 patients with low GCS and good clinical outcome showed an increased MTT without abnormalities of rCBV and rCBF. In patients with GCS 08 and good outcome, PCT maps were normal in 2 cases; transient PCT abnormalities were identified in one case with an embedded fracture of the skull and in one case with an epileptic seizure. Conclusion: Cerebral PCT can identify diffuse abnormalities of cerebral perfusion in children with traumatic brain injury showing a low initial GCS and a bad outcome. PCT can be a valuable tool to predict the severity of the prognosis of these patients as soon as they are evaluated by CT-scan during their admission at the ER.

Management of faecal incontinence and constipation in adults with central neurological diseases.

BACKGROUND: People with neurological disease have a much higher risk of both faecal incontinence and constipation than the general population. There is often a fine line between the two conditions, with any management intended to ameliorate one risking precipitating the other. Bowel problems are observed to be the cause of much anxiety and may reduce quality of life in these people. Current bowel management is largely empirical with a limited research base. OBJECTIVES: To determine the effects of management strategies for faecal incontinence and constipation in people with neurological diseases affecting the central nervous system. SEARCH STRATEGY: We searched the Cochrane Incontinence Group Specialised Trials Register (searched 26 January 2005), the Cochrane Central Register of Controlled Trials (Issue 2, 2005), MEDLINE (January 1966 to May 2005), EMBASE (January 1998 to May 2005) and all reference lists of relevant articles. SELECTION CRITERIA: All randomised or quasi-randomised trials evaluating any types of conservative or surgical measure for the management of faecal incontinence and constipation in people with neurological diseases were selected. Specific therapies for the treatment of neurological diseases that indirectly affect bowel dysfunction were also considered. DATA COLLECTION AND ANALYSIS: Two reviewers assessed the methodological quality of eligible trials and two reviewers independently extracted data from included trials using a range of pre-specified outcome measures. MAIN RESULTS: Ten trials were identified by the search strategy, most were small and of poor quality. Oral medications for constipation were the subject of four trials. Cisapride does not seem to have clinically useful effects in people with spinal cord injuries (three trials). Psyllium was associated with increased stool frequency in people with Parkinson's disease but did not alter colonic transit time (one trial). Prucalopride, an enterokinetic did not demonstrate obvious benefits in this patient group (one study). Some rectal preparations to initiate defaecation produced faster results than others (one trial). Different time schedules for administration of rectal medication may produce different bowel responses (one trial). Mechanical evacuation may be more effective than oral or rectal medication (one trial). There appears to be a benefit to patients in one-off educational interventions from nurses. The clinical significance of any of these results is difficult to interpret. AUTHORS' CONCLUSIONS: There is still remarkably little research on this common and, to patients, very significant condition. It is not possible to draw any recommendation for bowel care in people with neurological diseases from the trials included in this review. Bowel management for these people must remain empirical until well-designed controlled trials with adequate numbers and clinically relevant outcome measures become available.

Management of faecal incontinence and constipation in adults with central neurological diseases.

BACKGROUND: People with neurological disease have a much higher risk of both faecal incontinence and constipation than the general population. There is often a fine dividing line between the two conditions, with any management intended to ameliorate, one risking precipitating the other. Bowel problems are observed to be the cause of much anxiety and may reduce quality of life in these people. Current bowel management is largely empirical with a limited research base. OBJECTIVES: To determine the effects of management strategies for faecal incontinence and constipation in people with neurological diseases affecting the central nervous system. SEARCH STRATEGY: We searched the Cochrane Incontinence Group Trials Register, the Cochrane Controlled Trials Register, MEDLINE, EMBASE and all reference lists of relevant articles. Date of the most recent searches: May 2000. SELECTION CRITERIA: All randomised or quasi-randomised trials evaluating any types of conservative, or surgical measure for the management of faecal incontinence and constipation in people with neurological diseases were selected. Specific therapies for the treatment of neurological diseases that indirectly affect bowel dysfunction have also been considered. DATA COLLECTION AND ANALYSIS: All three reviewers assessed the methodological quality of eligible trials and two reviewers independently extracted data from included trials using a range of pre-specified outcome measures. MAIN RESULTS: Only seven trials were identified by the search strategy and all were small and of poor quality. Oral medications for constipation were the subject of four trials. Cisapride does not seem to have clinically useful effects in people with spinal cord injuries (two trials). Psyllium was associated with increased stool frequency in people with Parkinson's disease but not altered colonic transit time (one trial). Some rectal preparations to initiate defecation produced faster results than others (one trial). Different time schedules for administration of rectal medication may produce different bowel responses (one trial). Mechanical evacuation may be more effective than oral or rectal medication (one trial). The clinical significance of any of these results is difficult to interpret. REVIEWER'S CONCLUSIONS: It is not possible to draw any recommendation for bowel care in people with neurological diseases from the trials included in this review. Bowel management for these people must remain empirical until well-designed controlled trials with adequate numbers and clinically relevant outcome measures become available.

Diagnostic and Prognostic Impact of pc-ASPECTS Applied to Perfusion CT in the Basilar Artery International Cooperation Study.

BACKGROUND AND PURPOSE: The posterior circulation Acute Stroke Prognosis Early CT Score (pc-APECTS) applied to CT angiography source images (CTA-SI) predicts the functional outcome of patients in the Basilar Artery International Cooperation Study (BASICS). We assessed the diagnostic and prognostic impact of pc-ASPECTS applied to perfusion CT (CTP) in the BASICS registry population. METHODS: We applied pc-ASPECTS to CTA-SI and cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) parameter maps of BASICS patients with CTA and CTP studies performed. Hypoattenuation on CTA-SI, relative reduction in CBV or CBF, or relative increase in MTT were rated as abnormal. RESULTS: CTA and CTP were available in 27/592 BASICS patients (4.6%). The proportion of patients with any perfusion abnormality was highest for MTT (93%; 95% confidence interval [CI], 76%-99%), compared with 78% (58%-91%) for CTA-SI and CBF, and 46% (27%-67%) for CBV (P < .001). All 3 patients with a CBV pc-ASPECTS < 8 compared to 6/23 patients with a CBV pc-ASPECTS ≥ 8 had died at 1 month (RR 3.8; 95% CI, 1.9-7.6). CONCLUSION: CTP was performed in a minority of the BASICS registry population. Perfusion disturbances in the posterior circulation were most pronounced on MTT parameter maps. CBV pc-ASPECTS < 8 may indicate patients with high case fatality.

Delay-sensitive and delay-insensitive deconvolution perfusion-CT: similar ischemic core and penumbra volumes if appropriate threshold selected for each.

INTRODUCTION: Perfusion-CT (PCT) processing involves deconvolution, a mathematical operation that computes the perfusion parameters from the PCT time density curves and an arterial curve. Delay-sensitive deconvolution does not correct for arrival delay of contrast, whereas delay-insensitive deconvolution does. The goal of this study was to compare delay-sensitive and delay-insensitive deconvolution PCT in terms of delineation of the ischemic core and penumbra. METHODS: We retrospectively identified 100 patients with acute ischemic stroke who underwent admission PCT and CT angiography (CTA), a follow-up vascular study to determine recanalization status, and a follow-up noncontrast head CT (NCT) or MRI to calculate final infarct volume. PCT datasets were processed twice, once using delay-sensitive deconvolution and once using delay-insensitive deconvolution. Regions of interest (ROIs) were drawn, and cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) in these ROIs were recorded and compared. Volume and geographic distribution of ischemic core and penumbra using both deconvolution methods were also recorded and compared. RESULTS: MTT and CBF values are affected by the deconvolution method used (p < 0.05), while CBV values remain unchanged. Optimal thresholds to delineate ischemic core and penumbra are different for delay-sensitive (145 % MTT, CBV 2 ml × 100 g(-1) × min(-1)) and delay-insensitive deconvolution (135 % MTT, CBV 2 ml × 100 g(-1) × min(-1) for delay-insensitive deconvolution). When applying these different thresholds, however, the predicted ischemic core (p = 0.366) and penumbra (p = 0.405) were similar with both methods. CONCLUSION: Both delay-sensitive and delay-insensitive deconvolution methods are appropriate for PCT processing in acute ischemic stroke patients. The predicted ischemic core and penumbra are similar with both methods when using different sets of thresholds, specific for each deconvolution method.

Impact of body tilt on the central aortic pressure pulse.

The present work was undertaken to investigate, in young healthy volunteers, the relationships between the forward propagation times of arterial pressure waves and the timing of reflected waves observable on the aortic pulse, in the course of rapid changes in body position. 20 young healthy subjects, 10 men, and 10 women, were examined on a tilt table at two different tilt angles, -10° (Head-down) and + 45° (Head-up). In each position, carotid-femoral (Tcf) and carotid-tibial forward propagation times (Tct) were measured with the Complior device. In each position also, the central aortic pressure pulse was recorded with radial tonometry, using the SphygmoCor device and a generalized transfer function, so as to evaluate the timing of reflected waves reaching the aorta in systole (onset of systolic reflected wave, sT1r) and diastole (mean transit time of diastolic reflected wave, dMTT). The position shift from Head-up to Head-down caused a massive increase in both Tct (women from 130 ± 10 to 185 ± 18 msec P < 0.001, men from 136 ± 9 to 204 ± 18 msec P < 0.001) and dMTT (women from 364 ± 35 to 499 ± 33 msec P < 0.001, men from 406 ± 22 to 553 ± 21 msec P < 0.001). Mixed model regression showed that the changes in Tct and dMTT observed between Head-up and Head-down were tightly coupled (regression coefficient 2.1, 95% confidence interval 1.9-2.3, P < 0.001). These results strongly suggest that the diastolic waves observed on central aortic pulses reconstructed from radial tonometric correspond at least in part to reflections generated in the lower limbs.

Shot noise anomalies in elastic nondegenerate diffusive conductors

We present a theoretical investigation of shot-noise properties in nondegenerate elastic diffusive conductors. Both Monte Carlo simulations and analytical approaches are used. Two interesting phenomena are found: (i) the display of enhanced shot noise for given energy dependences of the scattering time, and (ii) the recovery of full shot noise for asymptotic high applied bias. The first phenomenon is associated with the onset of negative differential conductivity in energy space that drives the system towards a dynamical electrical instability in excellent agreement with analytical predictions. The enhancement is found to be strongly amplified when the dimensionality in momentum space is lowered from three to two dimensions. The second phenomenon is due to the suppression of the effects of long-range Coulomb correlations that takes place when the transit time becomes the shortest time scale in the system, and is common to both elastic and inelastic nondegenerate diffusive conductors. These phenomena shed different light in the understanding of the anomalous behavior of shot noise in mesoscopic conductors, which is a signature of correlations among different current pulses.

Psychophysiological responses to appraisal dimensions in a computer game

A computer game was used to study psychophysiological reactions to emotion-relevant events. Two dimensions proposed by Scherer (1984a, 1984b) in his appraisal theory, the intrinsic pleasantness and goal conduciveness of game events, were studied in a factorial design. The relative level at which a player performed at the moment of an event was also taken into account. A total of 33 participants played the game while cardiac activity, skin conductance, skin temperature, and muscle activity as well as emotion self-reports were assessed. The self-reports indicate that game events altered levels of pride, joy, anger, and surprise. Goal conduciveness had little effect on muscle activity but was associated with significant autonomic effects, including changes to interbeat interval, pulse transit time, skin conductance, and finger temperature. The manipulation of intrinsic pleasantness had little impact on physiological responses. The results show the utility of attempting to manipulate emotion-constituent appraisals and measure their peripheral physiological signatures.

Characteristic magnetic field and speed properties of interplanetary coronal mass ejections and their sheath regions

Prediction of the solar wind conditions in near-Earth space, arising from both quasi-steady and transient structures, is essential for space weather forecasting. To achieve forecast lead times of a day or more, such predictions must be made on the basis of remote solar observations. A number of empirical prediction schemes have been proposed to forecast the transit time and speed of coronal mass ejections (CMEs) at 1 AU. However, the current lack of magnetic field measurements in the corona severely limits our ability to forecast the 1 AU magnetic field strengths resulting from interplanetary CMEs (ICMEs). In this study we investigate the relation between the characteristic magnetic field strengths and speeds of both magnetic cloud and noncloud ICMEs at 1 AU. Correlation between field and speed is found to be significant only in the sheath region ahead of magnetic clouds, not within the clouds themselves. The lack of such a relation in the sheaths ahead of noncloud ICMEs is consistent with such ICMEs being skimming encounters of magnetic clouds, though other explanations are also put forward. Linear fits to the radial speed profiles of ejecta reveal that faster-traveling ICMEs are also expanding more at 1 AU. We combine these empirical relations to form a prediction scheme for the magnetic field strength in the sheaths ahead of magnetic clouds and also suggest a method for predicting the radial speed profile through an ICME on the basis of upstream measurements.

Effect of method of application of a fibrolytic enzyme product on digestive processes and milk production in Holstein-Friesian cows

Four multiparous cows with cannulas in the rumen and proximal duodenum were used in early lactation in a 4 x 4 Latin square experiment to investigate the effect of method of application of a fibrolytic enzyme product on digestive processes and milk production. The cows were given ad libitum a total mixed ration (TMR) composed of 57% (dry matter basis) forage (3:1 corn silage:grass silage) and 43% concentrates. The TMR contained (g/kg dry matter): 274 neutral detergent fiber, 295 starch, 180 crude protein. Treatments were TMR alone or TMR with the enzyme product added (2 kg/1000 kg TMR dry matter) either sprayed on the TMR 1 h before the morning feed (TMR-E), sprayed only on the concentrate the day before feeding (Concs-E), or infused into the rumen for 14 h/d (Rumen-E). There Was no significant effect on either feed intake or milk yield but both were highest on TMR-E. Rumen digestibility of dry matter, organic matter, and starch was unaffected by the enzyme. Digestibility of NDF was lowest on TMR-E in the rumen but highest postruminally. Total Tract digestibility was highest on TMR-E for dry matter, organic matter, and starch but treatment differences were nonsignificant for neutral detergent fiber: Corn silage stover retention time in the rumen was reduced by all enzyme treatments but postruminal transit time vas increased so the decline in total tract retention. time with enzymes was not significant. It is suggested that the tendency for enzymes to reduce particle retention time in the rumen may, by reducing the time available for fibrolysis to occur, at least partly explain the variability in the reported responses to enzyme treatment.