Diurnal changes of lower leg volume in obese and non-obese subjects.

BACKGROUND/AIM: Obesity is a risk factor for chronic venous disease. However, the mechanisms behind this association are poorly understood. We tested the hypothesis that obese subjects have a higher diurnal leg volume increase compared with non-obese subjects. METHODS: In this prospective cohort study including obese (body mass index, BMI ≥30 kg m(-)(2)) and non-obese (BMI ≤25 kg m(-)(2)) subjects without venous insufficiency, lower leg volume was assessed by optoelectronic volumetry in the morning and in the evening. All subjects underwent duplex ultrasound and light reflection rheography (venous pump power and venous refill time, VRT) to investigate lower extremity venous function. A pedometer was carried between the morning and evening visit to assess the daily number of footsteps. A backward multivariable linear regression model was used to determine factors associated with diurnal lower leg volume increase. RESULTS: Forty-two limbs in 24 obese subjects and 29 limbs in 15 non-obese subjects were analyzed. Obese subjects had larger common femoral vein diameters (17.1±2.4 vs 15.5±2.4 mm, P<0.01) and slower peak, mean and minimal velocities (25.1±10.6 vs 44.3±14.3 cm s(-1); 6.8±2.4 vs 12.7±5.6 cm s(-1); -0.2±6.4 vs -6.3±11.9 cm s(-1); P<0.01 for all) than non-obese subjects. VRT was shorter in obese subjects (40.5±15.0 vs 51.0±12.1 s, P<0.01) and decreased significantly in the course of the day only in obese subjects (P<0.01). Obesity, male gender, CEAP (Clinical-Etiology-Anatomy-Pathophysiology) class, total time between the two visits and difference between morning and evening VRT were positively associated with higher lower leg volume increase; morning VRT and the total number of footsteps showed a negative association (P<0.04 for all). CONCLUSION: Obesity was found to be an independent predictor of higher diurnal leg volume increase. One potential mechanism is a progressive failure of venous valve function in the course of the day in obese subjects.

Quantitative stress echocardiography in coronary artery disease using contrast-based myocardial blood flow measurements: prospective comparison with coronary angiography.

AIM: To test whether quantitative stress echocardiography using contrast-based myocardial blood flow (MBF, ml x min(-1) x g(-1)) measurements can detect coronary artery disease in humans. METHODS: 48 patients eligible for pharmacological stress testing by myocardial contrast echocardiography (MCE) and willing to undergo subsequent coronary angiography were prospectively enrolled in the study. Baseline and adenosine-induced (140 microg x kg(-1) x min(-1)) hyperaemic MBF was analysed according to a three-coronary-artery-territory model. Vascular territories were categorised into three groups with increasing stenosis severity defined as percentage diameter reduction by quantitative coronary angiography. RESULTS: Myocardial blood flow reserve (MBFR)-that is, the ratio of hyperaemic to baseline MBF, was obtained in 128 (89%) territories. Mean (SD) baseline MBF was 1.073 (0.395) ml x min(-1) x g(-1) and did not differ between territories supplied by coronary arteries with mild (<50% stenosis), moderate (50%-74% stenosis) or severe (>or=75% stenosis) disease. Mean (SD) hyperaemic MBF and MBFR were 2.509 (1.078) ml x min(-1) x g(-1) and 2.54 (1.03), respectively, and decreased linearly (r2 = 0.21 and r2 = 0.39) with stenosis severity. ROC analysis revealed that a territorial MBFR <1.94 detected >or=50% stenosis with 89% sensitivity and 92% specificity. CONCLUSION: Quantitative stress testing based on MBF measurements derived from contrast echocardiography is a new method for the non-invasive and reliable assessment of coronary artery disease in humans.

Atmospheric CO2 concentrations over the last glacial termination.

A record of atmospheric carbon dioxide (CO2) concentration during the transition from the Last Glacial Maximum to the Holocene, obtained from the Dome Concordia, Antarctica, ice core, reveals that an increase of 76 parts per million by volume occurred over a period of 6000 years in four clearly distinguishable intervals. The close correlation between CO2 concentration and Antarctic temperature indicates that the Southern Ocean played an important role in causing the CO2 increase. However, the similarity of changes in CO2 concentration and variations of atmospheric methane concentration suggests that processes in the tropics and in the Northern Hemisphere, where the main sources for methane are located, also had substantial effects on atmospheric CO2 concentrations.

CO(2) concentration measurements on air samples by mass spectrometry

A new technique for measuring CO(2) concentration in air samples, based on mass spectrometry, is described as an alternative to the common gas chromatographic method. Using a dual inlet isotope ratio mass spectrometer (IRMS), the ratio of the abundances of the m/z peaks 44 and 28 is determined. The precision of measurements (standard deviation <3 ppmv) is generally as good as the analysis with gas chromatography for small air samples (<1 ml STP of air). A major advantage of this new method is the possibility of parallel elemental and isotopic measurements of many air components. The technique is further improved by new wide mass range mass spectrometers allowing simultaneous intensity measurements of several m/z values between 28 and 44, resulting in an uncertainty of <0.5 ppm. The precision is somewhat limited by the production of N(2)O and NO(2) from N(2) and O(2) in the ion source, which accounts for about half of the signal strength at m/z 44. Copyright 2000 John Wiley & Sons, Ltd.