Functional tests of lower limbs

Measurement of arthritic pressure in the ankle at rest in order to detect arterial insufficiency of the lower extremities in many clinical observations proves to be a sufficient test. A major problem is patients with complaints of intermittent claudication with normal or borderline indicators at rest. In such cases, it is necessary to study peripheral hemodynamics in conditions of stress, or so-called stress test, which is based on the effect of vasodilation in response to physical stress, post-cln hypoxia or the use of pharmacological agents, in particular nitroglycerin.

The value of stress tests is determined by the ability to detect hemodynamically significant lesions of arteries that are not detected at rest, and to assess the functional state of the circulation of the limbs.

The effect of the stress test is best demonstrated in the analysis of measurements in a patient with one healthy limb and another limb affected by the occlusive process. Arterial blood flow in the healthy leg is determined by the resistance of the outflow vessels (terminal arteries, arterioles, capillaries and venous bed); on the affected extremity, the blood flow is determined along with the resistance of the outflow channel by resistance in the proximal parts at the stenosis level. At rest both limbs have the same basal blood flow to maintain metabolism in muscles, skin and bones. On the affected side, the effect of proximal resistance is compensated for by moderate vasodilation, so that the blood flow becomes comparable to the normal side. However, stenosis causes turbulence with loss of kinetic energy and leads to a decrease in distal pressure.

At a load, increasing metabolic requirements lead to a pronounced dilatation of muscle arterioles and an increase in arterial blood flow. On the healthy side, it can increase 5 times in comparison with the baseline. In the affected limb, the increase in blood flow is limited by the proximal resistance at the stenosis level. When the metabolic needs of the working muscles are not satisfied with the limited arterial blood flow, the symptoms of claudication develop. In addition, there is a further drop in blood pressure at the level of arterial stenosis, as the resistance on it increases with increasing blood flow velocity. This pressure drop is measured as the systolic pressure drop on the ankle. The degree of its reduction and the duration of recovery are closely related to the severity of arterial insufficiency.

The simplest form of a stress test is walking up and down stairs until symptoms of claudication appear and the palpable heart rate disappears; the phenomenon of "disappearance of the pulse" indicates the presence of arterial occlusive disease.

In clinical practice, as a stress test, 2 variants of the load were widely used: dosed walking along the treadmill (treadmill test) and the flexion and extension test of the lower limb.

Treadmill test. A running track is installed next to the couch, on which the patient can lie down after the end of the test. Use the slope of the track 12 °, the speed of about 3 km / h. The duration of the test is until signs of claudication appear or 5 minutes. In their absence. At the end of the load, ankle segmental systolic pressure is measured every 30 seconds. During the first 4 minutes. And then every minute until the original data is restored. The test is evaluated by three indicators:

1. duration of the load;
2. maximum fall in the ankle pressure index;
3. time required to return to the original level.

Usually recovery occurs before the end of 10 minutes. However, with severe degrees of ischemia, it can last 20-30 minutes.

The test with flexion and extension of the limb. The examinee in the supine position performs full flexion and extension of the lower extremity in the knee joint (30 times per minute) or maximum back flexion and extension of the foot (60 times per minute) separately for each limb with an interval of 10-15 minutes. Exercises continue until the patient is forced to stop them due to pain in the limb. If the clinical symptoms of ischemia do not occur within 3 minutes, the sample is considered normal and discontinued. Evaluate the test for the same indicators as in the treadmill test.

At the same time, when carrying out stress tests, monitor ECG monitoring, special equipment and trained personnel are needed to assist in cases of acute cardiac dysfunction. In addition, the use of the sample limits a number of general and local factors: neurological disorders, the absence of one limb, severe limb ischemia, etc. Load tests are also not subjective in assessing the maximum walking time, which greatly complicates their standardization.

Postocclusional reactive hyperemia (PORG) - a common and alternative to stressful "stress" test-causes changes similar to post-loading. Being an equivalent physical load, the PORG has an undoubted advantage over it, since it is an objective, easily reproducible test that does not have the above limitations. In addition, PORG allows you to assess the state of the circulation in each limb separately, does not require a lot of time and can be performed in the early postoperative period.

Like the stress tests, the PORG allows to establish the presence of hemodynamically significant lesions that are not manifested in resting research, helps in the diagnosis in the early stages of the disease, which makes this test mandatory in patients with suspected occlusive disease.

The PORG can be used in two versions.

I option. Pneumatic cuffs are placed on the shoulder, on the upper third of the thigh and the lower third of the shin at the ankle. Measure the pressure at these levels according to the previously described procedure. Then into the femoral cuff for 4 min. Give a pressure exceeding 40-50 mm Hg. Art. The initial pressure for this level. After decompression of the femoral cuff, pressure is measured at the ankle and the pressure index is calculated after 30, 60 s and then for 9 min. Every minute. The reaction of the vessels of a healthy limb is manifested in a slight drop in the ankle pressure in relation to the initial and rapid (within 1 min) of its recovery.

Changes in monofocal stenosis are more pronounced. Proximal monofocal occlusion leads to more pronounced changes in comparison with the distal one. The most pronounced changes occur in patients with lesions in all three segments of the vascular system of the lower extremities and reach extreme degrees when involved in the GBA process.

II option. Reactive hyperemia is obtained in the same way as I variant. Prior to the procedure, record the average blood flow velocity in the BRA at rest. After decompression, a constant recording of the average blood flow velocity in the OBA is carried out until the amplitude values of the velocity return to the occlusal level. The dopplerogram obtained during the test is evaluated according to two parameters:

• by the relative growth (6V) of the average velocity in the process of hyperemia with respect to rest (in percent);
• time interval during which the mean flow rate returns to 50% of its peak value (index T _{1/ 2} ).

Nitroglycerin test is used as one of the main tests of pharmacological vasodilation in order to improve the detection of blood flow in the distal parts of the arteries of the shin. The permeability of the distal vessels of the lower extremities is one of the factors determining the success of the reconstructive operation. On radiopaque angiograms, especially with the most commonly used translumbral method, the shin and foot arteries are poorly visualized, and the role of ultrasound in the assessment of the distal channel increases. The main issue is the differential diagnosis of anatomical damage and functional hemodynamic insufficiency of peripheral vessels. The latter is related to the fact that the damage to the proximal parts of the vascular system (especially the multi-segment, with poorly developed collateral blood flow) and the emergence of vasospastic reactions, in particular, the Cold, lead to a failure of perfusion of unaffected distal vessels. The location of the vessels at UZDG becomes impossible, as the blood flow parameters decrease to values beyond the resolution of the method (LCS <1 cm / s, SSD (10-15 mm Hg)). Vasodilation (limb warming, pharmacological agents), when an increase in peripheral blood flow is achieved by reducing peripheral resistance.

Pharmacological vasodilation with nitroglycerin (1 tablet sublingually) is often used in patients with varying degrees of ischemia with the location of blood flow (before taking nitroglycerin and 1-3 min after its administration) in the ZBBA and ATS.

The frequency of arterial location progressively decreases, depending on the degree of limb ischemia. The intake of nitroglycerin increases the frequency of location of arteries, regardless of the degree of ischemia.

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