Modelflow estimates of cardiac output compared with Doppler ultrasound during acute changes in vascular resistance in women

We compared Modelflow (MF) estimates of cardiac stroke volume (SV) from the finger pressure-pulse waveform (Finometer®) with pulsed Doppler ultrasound (DU) of the ascending aorta during acute changes in total peripheral resistance (TPR) in the supine and head-up-tilt (HUT) postures. Twenty-four women were tested during intravenous infusion of 0.005 or 0.01 μg kg -1 min-1 isoprenaline, 10 or 50 ng kg-1 min-1 noradrenaline and 0.3 mg sublingual nitroglycerine. Responses to static hand-grip exercise (SHG), graded lower body negative pressure (LBNP, from -20 to -45 mmHg) and 45 deg HUT were evaluated on separate days. Bland-Altman analysis indicated that SVMF yielded lower estimates than SVDU during infusion of 0.01 μg kg-1 min -1 isoprenaline (SVMF 92.7 ± 15.5 versus SV DU 104.3 ± 22.9 ml, P = 0.03) and SHG (SVMF 78.8 ± 12.0 versus SVDU 106.1 ± 28.5 ml, P \u3c 0.01), while larger estimates were recorded with SVMF during -45 mmHg LBNP (SVMF 52.6 ± 10.7 versus SVDU 46.2 ± 14.5 ml, P = 0.04) and HUT (SVMF 59.3 ± 13.6 versus SVDU 45.2 ± 11.3 ml, P \u3c 0.01). Linear regression analysis revealed a relationship (r2 = 0.41, P \u3c 0.01) between the change in TPR from baseline and the between-methods discrepancy in SV measurements. This relationship held up under all of the experimental protocols (regression for fixed effects, P = 0.46). These results revealed a discrepancy in MF estimates of SV, in comparison with those measured by DU, during acute changes in TPR. © 2010 The Physiological Society

Active Contours for Measuring Arterial Wall Diameter of Astronauts from Ultrasound Images

The non-invasive assessment of cardiovascular changes with spaceflightoften involves the measurement of blood vessel dimensionusing ultrasound imaging. However, many commonly used measurementtechniques are often manually intensive and dependenton the individual making the measurements. We propose a newautomated method for measuring the vessel dimensions which involvescreating a smoothed edge map of the image and using activecontours to converge to the upper and lower vessel boundaries.Preliminary results show that we are able to use this methodto detect vessels walls for vascular measurements from ultrasoundimages

Effect of short-term lycopene supplementation and postprandial dyslipidemia on plasma antioxidants and biomarkers of endothelial health in young, healthy individuals

The objective of this study was to test the hypothesis that the effect of a high-fat meal (HFm) on plasma lipid-soluble antioxidants and biomarkers of vascular oxidative stress and inflammation would be attenuated by short-term lycopene supplementation in young healthy subjects. Following restriction of lycopene-containing foods for 1-wk (LYr), blood was collected in a fasting state and 3 h after a HFm and a low-fat meal (LFm) in N = 18 men aged 23 ± 2 years, and after a HFm only in N = 9 women aged 23 ± 1 years. Blood was also sampled pre- and post-meals following 1-wk of 80 mg/day lycopene supplementation (LYs) under continued dietary LYr. In the fasting state, LYs compared with LYr not only evoked a >2-fold increase in plasma lycopene but also increased plasma β-carotene and α-tocopherol (p < 0.01), though LYs did not affect plasma nitrate/nitrite (biomarker of nitric oxide), malondialdehyde (biomarker of lipid oxidative stress), vascular- and intercellular-adhesion molecules or C-reactive protein (biomarkers of inflammation). Contrary to the hypothesis, the HFm-induced dyslipidemic state did not affect plasma malondialdehyde, C-reactive protein, or adhesion molecules in either LYr or LYs. Both the HFm and LFm were associated with decreases in the nitric oxide metabolites nitrate/nitrite and lipid-soluble antioxidants (p < 0.05). The data revealed that 1-wk of LYs increased plasma lycopene, β-carotene, and α-tocopherol yet despite these marked changes to the plasma lipid-soluble antioxidant pool, biomarkers of vascular oxidative stress and inflammation were unaffected in the fasted state as well as during dyslipidemia induced by a HFm in young healthy subjects

WISE-2005: prolongation of left ventricular pre-ejection period with 56 days head-down bed rest in women

This study tested the hypothesis that prolonged physical deconditioning affects the coupling of left ventricular depolarization to its ejection (the pre-ejection period, PEPi) and that this effect is minimized by exercise countermeasures. Following assignment to non-exercise (Control) and exercise groups (Exercise), 14 females performed 56 days of continuous head-down tilt bed rest. Measurements of the electrocardiogram (ECG) and stroke volume (Doppler ultrasound) during supine rest were obtained at baseline prior to (Pre) and after (Post) the head-down tilt bed rest (HDBR) period. Compared with Pre, the PEPi was increased following head-down tilt bed rest (main effect, P \u3c 0.005). This effect was most dominant in the Control group [Pre = 0.038 ± 0.06 s (s.d.) versus Post = 0.054 ± 0.011 s; P \u3c 0.001]. In the Exercise group, PEPi was 0.032 ± 0.005 s Pre and 0.038 ± 0.018 s Post; P= 0.08. Neither the QRS interval nor cardiac afterload was modified by head-down tilt bed rest in Control or Exercise groups. Low-dose isoprenaline infusion reversed the head-down tilt bed rest-induced delay in the PEPi. These results suggest that head-down tilt bed rest leads to a delayed onset of systolic ejection following left ventricular depolarization in a manner that is affected little by the exercise countermeasure but is related to Β-adrenergic pathways. The delayed onset of systole following head-down tilt bed rest appears to be related to mechanism(s) affecting contraction of the left ventricle rather than its depolarization. © 2010 The Authors. Journal compilation © 2010 The Physiological Society

Ultrasound assessments of organs and blood vessels before and after 40 days isolation in a cavern (deep time experiment 2021)

Introduction: Spaceflight simulation studies like confinement in small volume habitat with limited physical activity have reported even after 60 days an abnormal arterial wall adaptation with increase thickness or stiffness. The purpose of the current study was to determine the effects on blood vessel and organ structure of 40 days of isolation in a huge habitat with intensive physical activity.Method: Data were collected from 14 individuals (7 male) who isolated in a cavern for 40-days while performing normal daily activities without time references. Ultrasound assessments were performed pre- and post-isolation using a teleoperated system with eight different acoustic windows to obtain 19 measurements on 12 different organ/vascular structures which included the common carotid artery, femoral artery, tibial artery, jugular vein, portal vein, bile duct, kidney, pancreas, abdominal aorta, cervical and lumbar vertebral distance, and Achilles tendon.Results: Common carotid artery measures, including the intima media thickness, stiffness index, and the index of reflectivity measured from the radiofrequency signal, were not changed with isolation. Similarly, no differences were found for femoral artery measurements or measurements of any of the other organs/vessels assessed. There were no sex differences for any of the assessments.Discussion: Results from this study indicate a lack of physiological effects of 40-days of isolation in a cavern, contrary to what observed in previous 60 days confinement. This suggests a potential protective effect of sustained physical activity, or reduced environmental stress inside the huge volume of the confined facility

Actigraph Accelerometer-Defined Boundaries for Sedentary Behaviour and Physical Activity Intensities in 7 Year Old Children

Background: Accurate objective assessment of sedentary and physical activity behaviours during childhood is integral to the understanding of their relation to later health outcomes, as well as to documenting the frequency and distribution of physical activity within a population.Purpose: To calibrate the Actigraph GT1M accelerometer, using energy expenditure (EE) as the criterion measure, to define thresholds for sedentary behaviour and physical activity categories suitable for use in a large scale epidemiological study in young children.Methods: Accelerometer-based assessments of physical activity (counts per minute) were calibrated against EE measures (kcal.kg(-1).hr(-1)) obtained over a range of exercise intensities using a COSMED K4b(2) portable metabolic unit in 53 seven-year-old children. Children performed seven activities: lying down viewing television, sitting upright playing a computer game, slow walking, brisk walking, jogging, hopscotch and basketball. Threshold count values were established to identify sedentary behaviour and light, moderate and vigorous physical activity using linear discriminant analysis (LDA) and evaluated using receiver operating characteristic (ROC) curve analysis.Results: EE was significantly associated with counts for all non-sedentary activities with the exception of jogging. Threshold values for accelerometer counts (counts. minute(-1)) were = 3841 for light, moderate and vigorous physical activity respectively. The area under the ROC curves for discrimination of sedentary behaviour and vigorous activity were 0.98. Boundaries for light and moderate physical activity were less well defined (0.61 and 0.60 respectively). Sensitivity and specificity were higher for sedentary (99% and 97%) and vigorous (95% and 91%) than for light (60% and 83%) and moderate (61% and 76%) thresholds.Conclusion: The accelerometer cut points established in this study can be used to classify sedentary behaviour and to distinguish between light, moderate and vigorous physical activity in children of this age