Stochasticity of flow through microcirculation as a regulator of oxygen delivery.

Objective: Observations of microcirculation reveal that the blood flow is subject to interruptions and resumptions. Accepting that blood randomly stops and resumes, one can show that the randomness could be a powerful means to match oxygen delivery with oxygen demand.

Method: The ability of the randomness to regulate oxygen delivery is based on two suppositions: (a) the probability for flow to stop does not depend on the time of uninterrupted flow, thus the number of interruptions of flow follows a Poisson distribution; (b) the probability to resume the flow does not depend on the time for flow being interrupted; meaning that time spent by erythrocytes at rest follows an exponential distribution.

Heart blood volume by dilution in patients on hemodialysis.

Cardiomegaly and accompanying complications contribute to morbidity and mortality in patients on hemodialysis. Our objective is to provide a measure of heart blood volume from data collected during routine measurement of cardiac output during hemodialysis. A heart model based upon the probability of transfer between chambers during a cardiac cycle generates both the distribution of transit times (dilution curve) and the blood volumes in the chambers of the heart.