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Orthostatic test - a method of functional diagnostics
Last reviewed: 07.06.2024
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Diagnostic procedure for the study of the functions of the autonomic nervous system - orthostatic test - is based on the increase of its sympathetic and decrease of parasympathetic tone when changing the body position from horizontal to vertical (orthostatic). [1]
Indications for the procedure
Disorders of the autonomic nervous system (ANS), which regulates blood pressure, respiratory rate and blood flow in blood vessels and provides synchronization between the heart and respiration, can affect any process in the body, and study of the autonomic nervous system by orthostatic tests can reveal changes in the cardiovascular system and systemic hemodynamics - blood pressure, vascular resistance, cardiac output, pulmonary artery pressure.
Abnormal ANS response to orthostatic load (change in body positioning) may be a sign of disease or pathologic condition and may result in dizziness, fatigue, cognitive dysfunction, chest and abdominal discomfort, and manifestations of pain.
Conducting orthostatic test is shown in symptoms of vegeto-vascular dystonia; if neurocirculatory dystonia is suspected - with cerebral disorders of ANS and insufficiency of its efferent nerve pathways (sympathetic and parasympathetic).
This diagnostic test reveals and confirms the presence of peripheral autonomic insufficiency in patients; makes it possible to objectively assess the ANS response in neuroreflex syncopal states - neurogenic syncope; helps to clarify the etiology of postural orthostatic tachycardia syndrome - orthostatic (postural) hypotension.
To assess the ANS (autonomic status) - in case of rapid fatigue and general weakness, dizziness and headaches, instability of attention and mood - an orthostatic test is performed in children. Complaints of adolescents about occipital headaches, poor sleep, unreasonable fatigue, palpitations and aching pains in the heart (associated with physical exertion) are also indications for the study of ANS using orthostatic tests. [2]
See also - Autonomic nervous system research methods
Preparation
Preparation for the orthostatic test consists of limiting daily water intake to 0.5-1L (one day before the examination) and salt (two days before).
Alcohol should be avoided 24 hours before your appointment, caffeinated drinks, chocolate and heavy foods four to five hours before, exercise and smoking should also be avoided.
In addition, before the study (at least three days) it is necessary to stop taking hypotensive and cardiotonic agents, CNS stimulants and antidepressants, systemic corticosteroids, drugs of beta-adrenoblockers and beta-adrenomimetics.
Technique Orthostatic test - a method of functional diagnostics
The technique of this examination, based on fixation of vital functions of the organism when changing the body position from horizontal (clinostatic) to vertical (orthostatic) - orthostatic and clinostatic tests - has been worked out and standardized.
What does the orthostatic test indicate? If in the absence of vegeto- and cardiovascular disorders, changing the body position has a minimal effect on blood pressure (BP) and heart rate (HR), then in the presence of these disorders, the recorded values will be significantly different.
It is obligatory to measure arterial pulse patients and repeated BP measurement during orthostatic test.
This takes into account the difference in heart rate during the orthostatic test: heart rate at rest (lying on the back) and HR shortly after changing the position of the body to upright. In normality, HR increases by 10-15 beats per minute; in ANS problems, diabetes, some autoimmune diseases and neurodegenerative disorders - by 20 beats per minute or more, and an increase in heart rate of 30 or more beats per minute indicates postural orthostatic tachycardia.
Significant difference in BP during orthostatic test - by 20-80 mmHg, as well as delayed recovery of its initial level may be in patients with cardiovascular insufficiency, decreased elasticity of vascular walls and impaired myocardial contractile function. A decrease in systolic BP by 20 mmHg with a decrease in diastolic BP by 10 mmHg or more gives reason to suspect orthostatic hypotension.
In addition, resting systolic BP values with HR give an indication of how well the patient's ANS is coping with cardiovascular regulation.
The orthostatic test lying on the back, i.e. In the clinostatic position (from Greek kline - bed), when the heart and brain are approximately at the same height, assesses BP (systolic and diastolic) and heart rate in a calm state.
In the same position electrocardiography - ECG with orthostatic test: first readings are taken in a lying patient, and then in a standing position.
Passive orthostatic test is also started in the clinostatic position, for which the patient is placed on a special table-verticalizer (with a foot rest) and after 10 minutes measure pulse, BP, take ECG readings. Then from the side of the head, the table is raised at an angle of about 60-70 ° and within five minutes again record readings. The same is done after the patient returns to the supine position.
When an active orthostatic test is performed, first the pulse and BP are measured in the supine position on the table, and then the patient stands up from it independently, and the readings are recorded in the upright position of the body.
The orthostatic squatting test begins by measuring BP and HR in a sitting patient, after which the patient squats (raising and straightening the arms forward) for 30 seconds, and when he or she sits up, BP and pulse are measured again.
The orthostatic test results are orthostatic pulse and blood pressure readings, and a positive orthostatic test is defined if the patient has either an increase in pulse rate (by 20-30 beats per minute), a decrease in systolic blood pressure (by 20-30 mmHg), or weakness and dizziness.
To determine the physical load optimal for the cardiovascular system of athletes, self-monitoring with the use of orthostatic test - self-measurement of heart rate before and after the performance of certain exercises (running, swimming, etc.) is practiced. [3], [4], [5], [6], [7]
Contraindications to the procedure
Orthostatic test can not be performed in the postinfarction and post-stroke state of the patient; immediately after prolonged bed rest; in the presence of acute infectious diseases and exacerbation of chronic inflammatory diseases; with severe cardiac arrhythmias and heart block; high-grade arterial hypertension; acute and subacute cerebral circulation disorders; severe mental disorders.
Complications after the procedure
The most common consequences of orthostatic testing are heart rhythm disturbances (tachycardia and tachyarrhythmia), loss of consciousness (due to decreased cerebral vascular tone and cerebral ischemia), and a sharp increase in BP.
Possible complications of this diagnostic procedure are vasospasm and vasomotor syncope (fainting), compressive chest pain, development of hypertensive crisis.
The development of bradycardia with cardiac ventricular asystole cannot be ruled out.
Testimonials
According to experts in the field of clinical physiology, for studying the state of ANS, cardiovascular system and hemodynamics, the data obtained during orthostatic tests have undeniable diagnostic value.