Search results
Results from the WOW.Com Content Network
Blood flow pulse wave in the central retinal artery (red) and vein (blue), measured by laser Doppler holography in the eye fundus of a healthy volunteer. The eye offers a unique opportunity for the non-invasive exploration of cardiovascular diseases. LDI by digital holography can measure blood flow in the retina and choroid. [7]
By calculating the frequency shift of a particular sample volume, for example, flow in an artery or a jet of blood flow over a heart valve, its speed and direction can be determined and visualized. Duplex ultrasonography sometimes refers to Doppler ultrasonography or spectral Doppler ultrasonography. [ 3 ]
Because blood flow to the skin can be modulated by multiple other physiological systems, the PPG can also be used to monitor breathing, hypovolemia, and other circulatory conditions. [5] Additionally, the shape of the PPG waveform differs from subject to subject, and varies with the location and manner in which the pulse oximeter is attached.
For this reason, the blood flow velocity is the fastest in the middle of the vessel and slowest at the vessel wall. In most cases, the mean velocity is used. [18] There are many ways to measure blood flow velocity, like videocapillary microscoping with frame-to-frame analysis, or laser Doppler anemometry. [19]
A man undergoing whole body plethysmography. A modern body plethysmograph using ultrasound. A plethysmograph is an instrument for measuring changes in volume within an organ or whole body (usually resulting from fluctuations in the amount of blood or air it contains).
More blood flows in to transport more glucose, also bringing in more oxygen in the form of oxygenated hemoglobin molecules in red blood cells. This is from both a higher rate of blood flow and an expansion of blood vessels. The blood-flow change is localized to within 2 or 3 mm of where the neural activity is.
Get AOL Mail for FREE! Manage your email like never before with travel, photo & document views. Personalize your inbox with themes & tabs. You've Got Mail!
Velocity Time Integral is a clinical Doppler ultrasound measurement of blood flow, equivalent to the area under the velocity time curve. The product of VTI (cm/stroke) and the cross sectional area of a valve (cm2) yields a stroke volume (cm3/stroke), which can be used to calculate cardiac output.