If veins were rigid tubes, then a change in mean right auricular pressure would cause a corresponding change in the peripheral venous pressure, provided the velocity of blood flowing along the veins remained constant. However, veins are not rigid, but collapsible, and it has been shown by Lyon, Kennedy and Burwell (1938), and by Holt (1940), that peripheral venous pressure, referred to the leve...

If veins were rigid tubes, then a change in mean right auricular pressure would cause a corresponding change in the peripheral venous pressure, provided the velocity of blood flowing along the veins remained constant. However, veins are not rigid, but collapsible, and it has been shown by Lyon, Kennedy and Burwell (1938), and by Holt (1940), that peripheral venous pressure, referred to the leve...

Insects are known to exchange respiratory gases in their system of tracheal tubes by using either diffusion or changes in internal pressure that are produced through body motion or hemolymph circulation. However, the inability to see inside living insects has limited our understanding of their respiration mechanisms. We used a synchrotron beam to obtain x-ray videos of living, breathing insects...

In familial dysautonomia (FD), i.e., Riley-Day syndrome, parasympathetic dysfunction has not been sufficiently evaluated. The cold face test is a noninvasive method of activating trigeminal brain stem cardiovagal and sympathetic pathways and can be performed in patients with limited cooperation. We performed cold face tests in 11 FD patients and 15 controls. For 60 s, cold compresses (0-1 degre...

The cardiovascular and respiratory effects of intravenous adenosine were studied in conscious normal volunteers. Bolus injections of adenosine increased systolic and diastolic pressures initially (+15 and +13 mm Hg after 100 micrograms/kg) followed by a subsequent reduction in systolic and diastolic pressures (-12 and -16 mm Hg). Heart rate increased during trough blood pressure (R-R interval s...

Previous studies demonstrated the presence of Monochromatic Ultra-Slow Oscillations (MUSO) in human EEG. In the present study we explored the biological origin of MUSO by simultaneous recordings of EEG, Near-Infrared Spectroscopy (NIRS), arterial blood pressure, respiration and Laser Doppler flowmetry. We used a head-up tilt test in order to check whether MUSO might relate to Mayer waves in art...

BACKGROUND HeartLander is a miniature mobile robot designed to navigate over the epicardium of the beating heart for minimally invasive therapy. This paper presents a technique to decrease slippage and improve locomotion efficiency by synchronizing the locomotion with the intrapericardial pressure variations of the respiration and heartbeat cycles. METHODS Respiratory and heartbeat phases wer...