Maria Giovanna Trivella

BIOTEX—Biosensing Textiles for Personalised Healthcare Management

Textile-based sensors offer an unobtrusive method of continually monitoring physiological parameters during daily activities. Chemical analysis of body fluids, noninvasively, is a novel and exciting area of personalized wearable healthcare systems. BIOTEX was an EU-funded project that aimed to develop textile sensors to measure physiological parameters and the chemical composition of body fluids, with a particular interest in sweat. A wearable sensing system has been developed that integrates a textile-based fluid handling system for sample collection and transport with a number of sensors including sodium, conductivity, and pH sensors. Sensors for sweat rate, ECG, respiration, and blood oxygenation were also developed. For the first time, it has been possible to monitor a number of physiological parameters together with sweat composition in real time. This has been carried out via a network of wearable sensors distributed around the body of a subject user. This has huge implications for the field of sports and human performance and opens a whole new field of research in the clinical setting.

Some clinical considerations regarding the relation of coronary vasospasm to coronary atherosclerosis: A hypothetical pathogenesis

This study explores the relation between coronary arterial spasm and the development of coronary atherosclerosis. The clinical history and coronary angiographic and electrocardiographic data in 212 consecutive patients with ischemic heart disease were correlated. These patients were classified into four groups: Group 1, patients without angiographic evidence of atherosclerosis; Group 2, patients with single vessel disease; Group 3, patients with double vessel disease; and Group 4, patients with significant narrowing of major coronary arteries. Although spontaneous angina occurred in all four groups, it was more common (55 percent) in the patients in Group 1, who were predominantly female and young. Spontaneous angina was confirmed in Group 1 with several techniques, including thallium-201 scintigraphy, ergonovine administration and electrocardiography during attacks of pain. Prior myocardial infarction was present with similar frequency in all four groups. A patient is discussed whose spontaneously occurring coronary arterial spasm later progressed to fixed arteriosclerotic narrowing requiring coronary bypass surgery. These observations and a review of the literature lend support to the hypothesis that coronary arterial spasm can be a possible antecedent leading to the later development of fixed atherosclerotic coronary arterial obstruction.

A Wearable Sensor for Measuring Sweat Rate

Wearable sensors present a new frontier in the development of monitoring techniques. They are of great importance in sectors such as sport and healthcare as they enable physiological signals and biological fluids, such as human sweat, to be continuously monitored. Until recently this could only be carried out in specialized laboratories using cumbersome and often expensive devices. Sweat monitoring sensors integrated onto textile substrates are not only innovative but they also represent the first attempt to use such an idea in a system that will be worn directly on the body. This study outlines the development of a wearable sweat-rate sensor integrated onto a textile.

Measurement of Warfarin in the Oral Fluid of Patients Undergoing Anticoagulant Oral Therapy

Background Patients on warfarin therapy undergo invasive and expensive checks for the coagulability of their blood. No information on coagulation levels is currently available between two controls. Methodology A method was developed to determine warfarin in oral fluid by HPLC and fluorimetric detection. The chromatographic separation was performed at room temperature on a C-18 reversed-phase column, 65% PBS and 35% methanol mobile phase, flow rate 0.7 mL/min, injection volume 25 µL, excitation wavelength 310 nm, emission wavelength 400 nm. Findings The method was free from interference and matrix effect, linear in the range 0.2–100 ng/mL, with a detection limit of 0.2 ng/mL. Its coefficient of variation was <3% for intra-day measurements and <5% for inter-day measurements. The average concentration of warfarin in the oral fluid of 50 patients was 2.5±1.6 ng/mL (range 0.8–7.6 ng/mL). Dosage was not correlated to INR (r = −0.03, p = 0.85) but positively correlated to warfarin concentration in the oral fluid (r = 0.39, p = 0.006). The correlation between warfarin concentration and pH in the oral fluid (r = 0.37, p = 0.009) confirmed the importance of pH in regulating the drug transfer from blood. A correlation between warfarin concentration in the oral fluid and INR was only found in samples with pH values ≥7.2 (r = 0.84, p = 0.004). Conclusions Warfarin diffuses from blood to oral fluid. The method allows to measure its concentration in this matrix and to analyze correlations with INR and other parameters.

Regional and global biventricular function during dipyridamole stress testing

This study assesses the relation between regional ventricular performance (using 2-dimensional echocardiography) and global systolic and diastolic indexes of biventricular myocardial function (using hemodynamic monitoring) during dipyridamole stress testing. Simultaneous 2-dimensional echocardiographic and biventricular hemodynamic monitoring during dipyridamole infusion (0.56 mg/kg over 4 minutes) was performed in 19 patients. All patients had a normal resting function. Eleven of the 19 patients had a positive echocardiography test (new wall motion dyssynergy with dipyridamole) and they formed group 1. Eight patients had a negative echocardiography test (group 2). During baseline conditions, no significant differences were found in the 2 groups: rate pressure product (107 +/- 16 vs 108 +/- 13 mm Hg x beats/min x 1/100), positive left ventricular (LV) dP/dt (1,950 +/- 473 vs 2,262 +/- 430 mm Hg/s), negative LV dP/dt (-2,069 +/- 620 vs -2,205 +/- 245), LV end-diastolic pressure (8.2 +/- 4.4 vs 9.6 +/- 4.0 mm Hg), right ventricular positive dP/dt (368 +/- 133 vs 400 +/- 190 mm Hg/s) and negative dP/dt (-281 +/- 89 vs -383 +/- 147). At peak dipyridamole, the 2 groups were different for LV end-diastolic pressure (20 +/- 10 vs 8 +/- 5 mm Hg, p less than 0.01), LV positive dP/dt (2,100 +/- 688 vs 3,013 +/- 851 mm Hg/s, p less than 0.01) and negative dP/dt (-1,868 +/- 518 vs -2,564 +/- 272, p less than 0.01). At peak ischemia, LV positive dP/dt increased slightly, but not significantly, while negative dP/dt decreased significantly (p less than 0.01) in comparison with resting values.(ABSTRACT TRUNCATED AT 250 WORDS)

Detection of Perfusion Defects During Coronary Occlusion and Myocardial Reperfusion After Thrombolysis by Intravenous Administration of the Echo-Enhancing Agent BR1

The purpose of this study was to detect myocardial perfusion defects as a result of coronary occlusion and myocardial reperfusion after thrombolysis with intravenous (i.v.) administration of the echo contrast agent BR1 (Bracco Research, Switzerland), which consists of microbubbles (median diameter 2.5 microm) containing sulfur exafluoride in a phospholipidic shell. To generate a coronary thrombosis, a copper coil was advanced into the left circumflex coronary artery in eight anesthetized dogs with opened chest cavities. Coronary occlusion occurred 18 +/- 10 minutes after the insertion of the coil and was documented both by an electromagnetic flow meter (as zero blood flow) and by radiolabeled microspheres (as myocardial perfusion defect). After 2 hours of occlusion, streptokinase was infused i.v.; reperfusion was documented by both the flow-meter and microspheres. Left ventricular cavity enhancement was apparent after all contrast injections. Peak cavity intensity did not increase with dose and was not affected by signal processing (suggesting signal saturation), whereas the duration of contrast effect significantly increased with the dose (from 26 +/- 16 to 147 +/- 74 seconds). Myocardial contrast intensity also increased after contrast (from 15 +/- 12 to 21 +/- 18 gray level/pixel, p < 0.001). Contrast echo detected myocardial perfusion defects (corresponding to 17% +/- 11% of LV cross-sectional area) in all the injections performed during coronary occlusion and detected myocardial reperfusion with a sensitivity of 50% versus microspheres. The extent of perfusion defects by contrast echo showed a good correlation with microspheres (r = 0.73). Myocardial reperfusion was not detected by changes in heart rate, aortic pressure, pulmonary arterial pressure, cardiac output, left ventricular fractional area change, or wall-motion score index. Hemodynamic parameters were not affected by contrast injections. Thus, the i.v. administration of BR1 allows us to accurately detect myocardial perfusion defects during coronary occlusion and, to a lesser extent, myocardial reperfusion after thrombolysis.

A new technique for total hepatectomy in the pig for testing liver support devices

BACKGROUND A large animal model of total hepatectomy is suitable to test the efficacy of any system designed to support patients in hepatic coma. The models previously described in the pig entail a significant degree of surgical trauma, which might alter the evolution of the ensuring hepatic failure and compromise the reproducibility of the model. METHODS Twenty-eight pigs underwent a total hepatectomy according to a new technique. A model was considered satisfactory when it required no blood transfusions and when hematologic and hemodynamic parameters determined before, during, and until 4 hours after hepatectomy showed no significant variations. Moreover, to revive the pattern of hepatic coma produced in the anhepatic model, 7 pigs were monitored until brain death occurred. RESULTS Twenty-five pigs (89%) underwent a smooth total hepatectomy with minimal variations of the selected parameters. They constituted a highly homogeneous group. Survival of the 7 pigs, followed up until brain death occurred, ranged from 625 to 1595 minutes (mean 1013.57 minutes). The animals remained stable until a few hours before brain death, an event heralded by a final sharp increase of the serum ammonia level and by a well-evident decline of both arterial pressure and liver-dependent clotting factors. CONCLUSIONS This technique of total hepatectomy allows the construction of a reproducible model of anhepaty suitable to test the efficacy of any system conceived to temporarily replace hepatic functions.

Textile sensors to measure sweat pH and sweat-rate during exercise

Sweat analysis can provide a valuable insight into a persons well-being. Here we present wearable textile-based sensors that can provide real-time information regarding sweat activity. A pH sensitive dye incorporated into a fabric fluidic system is used to determine sweat pH. To detect the onset of sweat activity a sweat rate sensor is incorporated into a textile substrate. The sensors are integrated into a waistband and controlled by a central unit with wireless connectivity. The use of such sensors for sweat analysis may provide valuable physiological information for applications in sports performance and also in healthcare.

Intracoronary air-filled albumin microspheres for myocardial blood flow measurement

OBJECTIVES The aim of this study was to explore the possibility of quantifying coronary blood flow by myocardial contrast echocardiography with air-filled serum albumin microspheres (Albunex). BACKGROUND Air-filled albumin microspheres have been proposed as an intravascular tracer for the study of myocardial perfusion by contrast echocardiography. METHODS In six anesthetized open chest dogs, the left circumflex coronary artery was cannulated and perfused by a roller pump with blood from the femoral artery. Both air-filled albumin microspheres (0.4 ml, 2 x 10(8) spheres/ml) and technetium-99m-labeled albumin were injected as a bolus into the coronary cannula at baseline and after treatment with dipyridamole (0.56 mg/kg body weight intravenously for 4 min). Two-dimensional echographic images of the left ventricular short axis were digitized to generate myocardial time-intensity curves; myocardial radioactivity was measured by an external detector to generate radionuclide time-activity curves. RESULTS After dipyridamole, left circumflex coronary artery blood flow (as measured by both the pump and an electromagnetic flow meter) significantly increased (from 1.06 +/- 0.28 to 3.61 +/- 1.43 ml/min per g of myocardium). Peak intensity and rise time of contrast echo curves were able to differentiate baseline myocardial perfusion from coronary hyperemia but did not show any significant correlation with coronary blood flow. A weak inverse correlation with coronary blood flow was provided by myocardial mean transit time of air-filled albumin microspheres (r = 0.33). Conversely, a close inverse correlation with coronary blood flow was obtained by myocardial mean transit time of technetium-99m-labeled albumin (r = 0.95). Myocardial transit time of air-filled albumin microspheres (1.95 +/- 0.60 s) was also markedly shorter than that of labeled albumin (5.35 +/- 3.43 s, p < 0.001) and the measurements were less reproducible. CONCLUSIONS In this experimental study, coronary blood flow was not adequately quantified by myocardial contrast echocardiography with intracoronary injection of air-filled albumin microspheres.

Reproduction of Continuous Flow Left Ventricular Assist Device Experimental Data by Means of a Hybrid Cardiovascular Model With Baroreflex Control

Long-term mechanical circulatory assistance opened new problems in ventricular assist device-patient interaction, especially in relation to autonomic controls. Modeling studies, based on adequate models, could be a feasible approach of investigation. The aim of this work is the exploitation of a hybrid (hydronumerical) cardiovascular simulator to reproduce and analyze in vivo experimental data acquired during a continuous flow left ventricular assistance. The hybrid cardiovascular simulator embeds three submodels: a computational cardiovascular submodel, a computational baroreflex submodel, and a hydronumerical interface submodel. The last one comprises two impedance transformers playing the role of physical interfaces able to provide a hydraulic connection with specific cardiovascular sites (in this article, the left atrium and the ascending/descending aorta). The impedance transformers are used to connect a continuous flow pump for partial left ventricular support (Synergy Micropump, CircuLite, Inc., Saddlebrooke, NJ, USA) to the hybrid cardiovascular simulator. Data collected from five animals in physiological, pathological, and assisted conditions were reproduced using the hybrid cardiovascular simulator. All parameters useful to characterize and tune the hybrid cardiovascular simulator to a specific hemodynamic condition were extracted from experimental data. Results show that the simulator is able to reproduce animal-specific hemodynamic status both in physiological and pathological conditions, to reproduce cardiovascular left ventricular assist device (LVAD) interaction and the progressive unloading of the left ventricle for different pump speeds, and to investigate the effects of the LVAD on baroreflex activity. Results in chronic heart failure conditions show that an increment of LVAD speed from 20 000 to 22 000 rpm provokes a decrement of left ventricular flow of 35% (from 2 to 1.3 L/min). Thanks to its flexibility and modular structure, the simulator is a platform potentially useful to test different assist devices, thus providing clinicians additional information about LVAD therapy strategy.