SUMMARY Diameter, blood flow velocity and volumic flow of the brachial artery were measured in 36 patients with sustained essential hypertension and compared with 25 normal subjects. Both hypertensives and control subjects were classified according to age into those younger than and those older than 40 years. For the determinations, a pulsed Doppler velocimeter with an adjustable range-gated time system and a double transducer probe was used. With the apparatus, the error in the determination of the angle between the ultrasound beam and the flowing stream of blood was less than 2%. In addition, the overestimation of the arterial diameter due to the sample volume size did not exceed 0.035 ± 0.015 cm. In hypertensives, the diameter of the brachial artery was significantly increased. The value was 0.482 ± 0.013 cm in subjects younger than 40 years and 0.517 ± 0,013 cm in those older than 40 years; in the corresponding controls, the values were 0.422 ± 0.011 cm and 0.436 + 0.013 cm (p < 0.01; p < 0.001). Blood flow velocity was reduced (p < 0.05; p < 0.01) and volumic flow remained within normal ranges. Both in the younger and the older groups, a significant positive correlation was observed between mean arterial pressure and the arterial diameter (r = 0.75; r = 0.60). In hypertensives, i.v. dihydralazine decreased mean arterial pressure from 120 ± 7 to 102 ± 7 mm Hg (p < 0.001). Arterial diameter also significantly decreased (p < 0.01) and returned toward normal. The study demonstrated that the diameter of the brachial artery was significantly increased in sustained essential hypertension and suggested that, with the chronic elevation of blood pressure, the large arteries dilate excessively, contributing to the maintainence of arterial blood flow within normal ranges.LARGE ARTERIES of hypertensives have been shown to be thicker and stiffer than normal vessels in both experimental animals' 4 and in human subjects.5 ,' However, in humans, these observations resulted either from invasive studies of the pressurevolume relationship of the brachial artery in vivo,5 or from the measurements of the thickness of the aorta at autopsy.6 Little information is available for intact large arteries, probably because of lack of appropriate techniques.We have developed a pulsed Doppler velocimeter7 12 particularly suitable for determining blood flow in peripheral arteries. In addition to its pulsed emission, the apparatus has an adjustable range-gated time system and a double transducer probe.'2 l With the double transducer probe, the angle of the ultrasound beam relative to the flowing stream of blood can be simply evaluated so that the diameter of the artery can be calculated.12 14 This method has been applied to the determination of the diameter, the blood flow velocity and the volumic flow of the brachial artery in 36 patients with essential hypertension. The measureFrom the

A pulsed Doppler velocimeter suitable for the determination of blood flow velocity and volumic flow in peripheral arteries is described. The apparatus has two main characteristics: an adjustable range-gated time system and a double transducer probe. The error in the determination of the angle between the ultrasound beam and flow of blood with this apparatus was less than 2%, and overestimation of the arterial diameter due to the sample volume size did not exceed 0.035 +/- 0.015 cm. The apparatus was used to determine diameter, blood flow velocity and volumic flow of the brachial artery of 22 healthy men. The values were respectively 0.440 +/- 0.010 cm, 9.15 +/- 1.01 cm.s-1 and 85 +/- 10 cm3.min-1. Administration of intravenous nitroglycerin significantly increased the arterial diameter (p less than 0.001) without any significant change in volumic flow. The described pulsed Doppler velocimeter provides an accurate noninvasive method for determining volumic flow in peripheral arteries in clinical investigation and cardiovascular pharmacology.

Total effective compliance, hemodynamic parameters, extracellular fluid volume, cardiopulmonary (CPBV) and total blood (TBV) volumes were determined in 32 men, including 14 normotensive controls and 18 sustained essential hypertensive patients. The effective compliance was calculated from the changes in central venous pressure recorded simultaneously with the changes in blood volume obtained after a rapid Dextran infusion. In normotensive controls, compliance was 2.08 +/- 0.09 ml/mm Hg/kg and was positively correlated with plasma (r = 0.79) and extracellular fluid (r = 0.84) volumes. In hypertensives, compliance was significantly reduced (1.49 +/- 0.06 ml/mm Hg/kg; P is less than 0.001) and was correlated negatively with the CPBV/TBV ratio (r = -0.75) and positively with the plasma volume/interstitial fluid volume ratio (r = 0.84). These results suggest that in normotensives, there is a regulatory mechanism between volume and compliance and that this contributes to maintaining filling pressure and cardiac output within normal ranges. In hypertensives, the reduced compliance could participate in the maintenance of normal values of cardiac output and extracellular fluid volume by influencing the partition of intravascular and extracellular fluid volumes.

Since systolic pressure is governed by the rate of ventricular ejection and the rigidity of the aortic wall, antihypertensive agents may have different effects on systolic and diastolic pressure. Despite an adequate decrease in diastolic pressure, systolic pressure may remain elevated due to structural alterations of large arteries. In the present study, a procedure is described to distinguish the dilation of small and large arteries. The former is evaluated from the calculation of forearm resistance and the latter from the determination of the arterial diameter of the brachial artery, using a bidimensional pulsed Doppler system. Nitroglycerin dilates the brachial artery, with no change in forearm resistance. Dihydralazine reduces the diameter of the brachial artery but decreases forearm resistance. Only calcium and converting-enzyme inhibitors dilate both small and large arteries and cause an increase in brachial blood flow.

Hemodynamic parameters and systemic arterial compliance were measured in patients with arteriosclerosis obliterans of the lower limbs before and after acute administration of propranolol. Arterial compliance was evaluated from a simple viscoelastic model, enabling the calculation of diastoiic drainage and diastoiic blood flow as indices of the reservoir role of the large arteries in overall circulation, in comparing basal conditions with normal subjects of the same age, patients with arteriosclerosis obliterans exhibited a significant decrease in arterial compliance (p < 0.01) and heart rate (p < 0.02) with a significant increase in systolic pressure (p < 0.001). Diastoiic drainage was increased (p < 0.01) and was positively correlated with diastoiic time (r = 0.73, p < 0.001). Diastoiic blood flow remained within normal ranges (52 ± 2 vs 49 ± 3 ml/m 2 /sec). After acute propranolol intravenous administration, heart rate and stroke volume decreased (p < 0.001), while total peripheral resistance increased (p < 0.001). Systemic arterial compliance and diastoiic blood flow significantly decreased (p < 0.01). The study provided evidence that in patients with arteriosclerosis obliterans, the diastoiic blood flow was maintained in basal conditions despite the observed reduction in arterial compliance, and that intravenous propranolol administration decreased systemic arterial compliance and diastoiic blood flow. (Arteriosclerosis 2:266-271, May/June 1982)