Kw. Saupe et al., DIASTOLIC TIME - AN IMPORTANT DETERMINANT OF REGIONAL ARTERIAL BLOOD-FLOW, American journal of physiology. Heart and circulatory physiology, 38(3), 1995, pp. 973-979
In unanesthetized dogs we measured heart rate, blood pressure, and ext
ernal iliac, celiac, and renal artery flows on a beat-by-beat basis. A
ll three flows fluctuated in synchrony with breathing. Although the fl
uctuations in renal flow could to a large degree be explained by fluct
uations in blood pressure, this was not the case in the external iliac
artery where flow increased when pressure decreased and decreased whe
n pressure increased. These paradoxical fluctuations in flow appear to
be caused by respiratory fluctuations in heart rate, since we observe
d a strong (r = 0.89) correlation between external iliac flow and the
length of the preceding diastole. Single long diastolic periods, induc
ed by atropine, were always followed by a beat of increased flow even
though arterial pressure was constant. We conclude that diastolic time
has a profound impact on blood flow during the next beat. Our data su
pport a model of the arterial system in which backpressure to flow thr
ough a bed is dependent on the amount of time for diastolic runoff int
o the capillaries.