Procedure for performing functional tests

The sensor is located in the projection of the supra-lateral artery and records a clear antegrade physiological arterial signal with the corresponding age of the patient with normal systolodiastolic flow parameters.

• Compression (5-10 s) homolateral to the located common carotid artery sensor. At the same time, the signal from the supra-lateral artery terminates or sharply decreases.
• Compression (5-10 s) branches of the homolateral external carotid artery - superficial temporal artery and mandibular. The clamping of the said vessels can be carried out either sequentially or simultaneously - while I and II fingers with the finger free from the hand sensor the operator performs synchronous pressing in the area of the mandibular fossa (at the point of the exit of the mandibular branch of the external carotid artery) and the tragus of the ear (in the source of the superficial temporal artery ). In this case, the specified compression of the branches of the homolateral external carotid artery either increases the intensity of the signal from the supra-lateral artery, or does not change it. The possibility of increasing circulation through the orbit artery at the time of compression of the branch of the homolateral external carotid artery reflects a natural redistribution of blood flow when an unexpected obstruction to passage of blood through the external carotid artery dramatically changes the pressure gradient between the systems of the inner and outer carotid arteries. In this case, the entire volume of blood delivered by the common carotid artery, rushes along the internal carotid artery, which is reflected in the increased sounding of its periorbital branches. A sharp weakening or disappearance of the blood flow signal from the orbit artery during the compression of the branches of the homolateral external carotid artery is characteristic of subtotal stenosis or occlusion of the internal carotid artery of the same side with collateral compensation along the branches of the ipsilateral external carotid artery. Even more typical (if not pathognomonic) for plugging of the internal carotid artery is the phenomenon of recording the change in the direction of circulation along the orbit artery on the side of the alleged blockage of the internal carotid artery, especially in combination with complete cessation of the periorbital circulation signal when the temporal branch of the homolateral external carotid artery is clamped.
• Conjugation (5-10 s) of the contralateral sensor of the common carotid artery. Normally, this either does not change the linear velocity of blood flow along the supra-lateral artery, or enhances its circulation, probably due to the flow of blood from the opposite carotid artery along the anterior connective artery (the consistency of the anterior part of the Willis circle). If, however, this compression causes a noticeable decrease in the amplitude of circulation along the scribed supra-lateral artery, the stenotic / occlusive carotid artery lesion on the side of the altered blood flow in the orbit artery should be excluded. In a similar pattern of periorbital ultrasound dopplerography, it is legitimate to assume the presence of a syndrome of intracerebral stealing with blood flow from the unimpaired hemisphere "to help" the ischemic hemisphere through the anterior connective artery.

The sensor is then positioned at the point of scoring of the vertebral artery and the following samples are performed.

• Compression (5 s) of the homolateral common carotid artery. Normally, this manipulation either does not affect the intensity of circulation along the vertebral artery, or increases the linear velocity of blood flow along it, which indirectly indicates the good functioning of the unilateral posterior connective artery (vascular potential of the posterior part of the Willis circle).
• A cuff test, or a test of reactive hyperemia, consists in a significant compression of the brachial artery of the homolaterally examined vertebral artery, where a continuous monitoring of the linear velocity of the blood flow and its direction before, at the time and after the compression is completed. Normally, in none of the stages of the cuff test the systolodiastolic parameters and the direction of blood flow along the vertebral artery do not change. Any change in these circulatory parameters along the vertebral artery at the height of compression or immediately after decompression is very characteristic of the subclavian steal syndrome due to the flow of blood from the brain to the upper limb with proximal occlusion of the homolateral subclavian artery.
• Functional test with intensive head turns (10-15 times).

The values of the initial linear velocity of blood flow and circulation along the vertebral arteries at the end of the movements are estimated. Normally, a uniform increase in the linear blood flow velocity by 5-10% is usually recorded in comparison with the baseline values. In cases of moderate initial asymmetry (about 20%), physiological or conditional extravascular effects, a sample with head turns most often leads to equalization of the velocity indicators at a somewhat higher level of flow. With stenosing / occlusive lesions, as well as congenital hypoplasia, the initial difference in the linear velocity of the blood flow is not only not leveled, but sometimes even increases. At the same time, these changes in the linear velocity of the blood flow through the vertebral artery can not be considered reliable signs of its stenosis or gross extravasal compression, in particular, they can reflect the change in the angle of location of the vertebral artery.

It should be noted that although the location of extracranial segments of carotid, vertebral and peripheral arteries and veins is absolutely safe in itself, but the clamping, even of very short duration, of the carotid arteries is not always asymptomatic. In particular, in patients with carotid sinus hypersensitivity, compression of the carotid artery causes pronounced vagal reactions - nausea, hypersalivation, pre-stupor and, most importantly, a sharp slowing of the heartbeats. In such situations, you should immediately stop research, it is advisable to let in a couple of ammonia sprinkles, and put the patient on the couch. Even more risky, and according to some experts it is absolutely unacceptable, compression of the carotid artery in patients with acute impairment of cerebral circulation, which can lead to iatrogenic cerebral embolism (this does not concern the compression of the branches of the external carotid artery, which are absolutely safe for any patient).

[1], [2], [3], [4]