Fifteen healthy subjects were tilted at 70° from the horizontal during a period of 4 min while recording the Doppler signal from the middle cerebral artery. Digital signal analysis carried out off-line provided the following data: mean spatial velocity (v), signal power (p) as an index of cross-sectional area, (v•p) as an index of volume flow. Flow as averaged over the entire period of tilted position was found to be 101 ± 25% of the supine steady state. There was evidence for autoregulatory vasodilation including the trunk of the middle cerebral artery. In a patient suffering from orthostatic dysregulation flow fell to 49% of its value as measured in supine position. From the evidence of this observation the clinical application of the method seems to warrant further study.
SUMMARY Transcutaneous blood flow measurements were performed by means of a pulsed Doppler ultrasound flowmeter in the femoral artery of healthy subjects. The pulsatile flow pattern was changed characteristically from resting state by postocclusive reactive hyperaemia, by the application of amyl nitrite, xanthinol nicotinate, and angiotensin amide. During reactive hyperaemia systolic flow was increased, diastolic reverse flow was abolished, and the forward flow continued throughout diastole. Amy1 nitrite augmented the negative flow phase and reduced mean flow, while xanthinol nicotinate decreased the negative component and augmented mean flow. Angiotensin amide produced enhancement of the average flow by elevating systolic and diastolic flow equally over the base line. In each of these interventions the changes in flow were determined mainly by variations during the diastolic flow phase.
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