RU2351281C1 - Method of cerebrovascular reactance estimation - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: invention concerns medicine and can be used in neurology, cardiology, neurosurgery and resuscitation. Measure linear blood flow speed (LBS) in medial cerebral artery (MCA) in rest and against hypercapnic loading test. Thus in quality of the hypercapnic test use inhalation of 4% admixture of carbon dioxide and air with injection supply of CO₂ within 2 minutes. Register changes of linear rate of blood flow and diameter of medial cerebral artery. The factor of change of rate of a blood flow (BSI_CO2) is calculated under the formula: BSI_CO2=V₂/V₀, where V₀ - initial LBS in cm/s, V₂ - LBS in 2 minutes of inhalation in cm/s; an index of change of rate of blood flow (BSC_CO2) under the formula: BSC_CO2=(V₂-V₀)/T, where V₀ - initial LBS in cm/s, V₂ - LBS in 2 minutes of inhalation in cm/s, inhalation T-time in s; factor of change of diameter DCC (DCC _CO2) under the formula: DCC _CO2=D₂/D₀, where D₀ - initial diameter MCA in mm, D₂ - diameter in 2 minutes of inhalation in mm; an index of change of diameter MCA (DCI_CO2) under the formula: DCI_CO2=(D₂-D₀)/T, where D₀-initial diameter MCA in mm, D₂ - diameter in 2 minutes of inhalation in mm, inhalation T - time in minutes; index posthypercapnic restoration BLS (RI_CO2) under the formula: RI_CO2=V₀/V₅, where V₀ - initial LBS in MCA in cm/s, V₅-LBS in 5 minutes from the research beginning in cm/s; autoregulatory response normalised to AP (HAO_CO2) under the formula: HAO_CO2=(V₂-V₀)/(V₀*(AP₂-AP₀), where V₀ - initial LBS in MCA in cm/s, V₂ - LBS in 2 minutes of inhalation in cm/s, AP₀-initial systolic BP in mm hg, AP₂-systolic BP in 2 minutes of inhalation in mm hg. At the indicators: BSI_CO2=1.51±0.23; BSC_CO2=0.28±0.13; DCC_CO2=1.27±0.12; DCI_CO2=0.48±0.26 mm/minutes; RI_CO2=0.95±0.12; HAO_CO2=5.26±1.44 a normal condition cerebrovascular reactance is estimated.

EFFECT: method raises accuracy of estimation of cerebrovascular reactance.

1 tbl, 3 dwg, 2 ex

Description

The invention relates to medicine, specifically to instrumental methods for assessing cerebrovascular reactivity, and can be used in neurology, cardiology, neurosurgery and resuscitation for the diagnosis of latent cerebrovascular insufficiency.

Known methods for assessing cerebrovascular reactivity consist in determining by the methods of angiography (contrast, magnetic resonance, spiral computed tomography) and transcranial dopplerography (TCD) the ability and ability of the cerebral vessels to change their diameter and blood flow in response to functional exercise stimuli physical (breath holding, vessel compression, orthostatic test) and chemical nature (acetazolamide, nitroglycerin, nimodipine, ketanserin, chimes) or on the effects of psycho iologicheskih incentives (read the text, talk, mental arithmetic, memorization of verbal and visual images, light and sound stimulation, motor load).

The main disadvantages of angiographic studies include the need for technically sophisticated equipment, the invasiveness of the procedure, radiation exposure during the study, the inability to assess the functional state of the vascular bed, including the hemodynamic features of blood flow at various levels, the inability to identify early preclinical signs of the disease [1].

The method of transcranial dopplerography provides fast and non-invasive registration of linear blood flow velocity (LSC) in the basal arteries of the brain [2]. To obtain information on the state of cerebrovascular reactivity, TCD methods are used with a variety of stress tests

[3]. However, these methods for assessing cerebrovascular reactivity are not accurate and objective enough, since they use effects that are unusual for the system of regulation of cerebral circulation as functional stress tests. Therefore, to obtain reliable information on cerebrovascular reactivity, it is advisable to use a physiological stimulus, namely carbon dioxide, which is a natural information carrier in the vascular system, as a stimulus of a chemical nature that affects the metabolic mechanism of autoregulation [4].

Closest to the proposed method for assessing cerebrovascular reactivity is the method we selected as a prototype for assessing the state of cerebral perfusion reserve [5], which consists in registering LSC in the M ₃ segment _{of the} middle cerebral artery at rest and with inhalation for 3-5 minutes 5-6% a mixture of air with carbon dioxide injected into the bag, the calculation of the index of cerebral perfusion reserve and its evaluation.

However, this method has disadvantages, namely: the used carbon dioxide air supply system does not provide a constant concentration of CO ₂ in the inhaled mixture, which requires the use of additional equipment - a capnograph, makes it impossible to standardize the sample in time and increases the duration of the study; at a carbon dioxide concentration of 5-6%, patients experience unpleasant sensations of lack of air, a rush of blood to the head, nonspecific reactions of the respiratory and cardiovascular systems appear, which mask the results of the sample [4]; when calculating the index of cerebral perfusion reserve, the change in systemic blood pressure, which naturally increases with hypercapnia and changes cerebral blood flow, is not taken into account [6]; and also have not developed specific criteria for indicators of cerebrovascular reactivity for patients of different age groups, which narrows the scope of the known method.

A new technical task is to increase the information content, reproducibility and accuracy of cerebrovascular reactivity assessment, optimization of the technique, standardization and reduction of research time.

индекс изменения скорости кровотока

коэффициент изменения диаметра

индекс изменения диаметра

индекс постгиперкапнического восстановления

нормализованный к АД ауторегуляторный ответ

и при показателях

оценивают нормальное состояние цереброваскулярной реактивности.The problem is solved by using a new method for assessing cerebrovascular reactivity, which consists in studying blood flow and the diameter of the middle cerebral artery (SMA) at rest and against the background of a hypercapnic exercise test - inhalation of a mixture of air with carbon dioxide for 2 minutes at a partial content of carbon dioxide ( FiCO ₂ ) 4%, whereby changes in the average blood flow velocity (V) and the diameter of the MCA (D) are recorded, coefficients and indices are calculated, namely: the coefficient of change in blood flow velocity

blood flow velocity index

diameter change factor

diameter change index

posthypercapital recovery index

autoregulatory response normalized to blood pressure

and with indicators

assess the normal state of cerebrovascular reactivity.

New in the proposed method is to reduce the effective concentration of carbon dioxide to 4% and the study time to 2 minutes while maintaining a deterministic vascular reaction, which is achieved by using an original device for evaluating the cerebrovascular reserve [7], which provides a stable concentration of the supplied gas mixture by injection supply of carbon dioxide, low resistance of the respiratory system and a decrease in the volume of "dead" space and leads to better tolerance of the sample patz cients; allows you to optimize and standardize the technique of the study.

In addition, new in the proposed method is the study of changes in the diameter of the SMA against the background of hypercapnic stress test; calculation and assessment of the index of posthypercapnic restoration of the linear blood flow velocity and correction of the autoregulatory response coefficient depending on systemic blood pressure, which increases the information content and accuracy of cerebrovascular reactivity assessment.

The essential features characterizing the invention, showed in the claimed combination of new properties that are not explicitly derived from the prior art in this field and which are obvious to a specialist.

An identical set of features was not found in the study of patent and medical literature. This invention can be used in practical health care to improve the quality of diagnosis and the timely start of treatment of disorders of the cerebrovascular reserve in hypercapnia.

Based on the foregoing, the proposed invention should be considered relevant to the conditions of patentability "novelty", "inventive step", "industrial applicability".

The invention will be clear from the following description and the accompanying drawings.

Figure 1 shows a device for assessing cerebrovascular reserve, consisting of two cast metal cylinders with a capacity of 2 liters, containing oxygen (1) and carbon dioxide (2), mounted on the device; two-chamber gearboxes (3, 4) (GOST 5313-59); a unit of rotametric dosimeters - two dosimeters for oxygen (5) with measurement limits from 0 to 2 l / min and from 2 to 10 l / min and a dosimeter for carbon dioxide (6) with measurement limits from 0 to 2 l / min; directional valves (7); breathing hoses - corrugated large diameter (22 mm) for oxygen / air (8) and small diameter (8 mm) for injection of carbon dioxide during hypercapnic tests (9); non-reversing valve (10); face mask (11) with an inflatable obturator and a recording device - an ultrasound diagnostic apparatus HDI 5000 SonoCT (Philips-ATL, Germany - USA) (12).

Figure 2 presents the dynamics of changes in the diameter of the middle cerebral artery during the functional hypercapnic load test in patients in age groups: 20-30 years, 30-40 and older than 40 years.

Figure 3 presents the dynamics of changes in the linear velocity of blood flow in the middle cerebral artery during the functional hypercapnic load test in patients in age groups: 20-30 years, 30-40 and older than 40 years.

The method is as follows.

Stage 1. A sterile face mask (11) is applied to the face of the patient lying on his back and, for 2 minutes, using a volume meter, the indicators of external respiration are measured - tidal volume (DO), minute lung ventilation (MVL) and respiratory rate (BH) . At the same time, using a recording device (12), transcranial Dopplerography of the middle cerebral artery is performed through the temporal window and qualitative indicators (the nature of the Doppler signal, the shape of the Dopplergram, frequency distribution of the Dopplergram, the direction of blood flow) and the initial quantitative characteristics of cerebral blood flow are evaluated, namely: maximum (peak) systolic blood flow velocity, final diastolic velocity and average blood flow velocity. The diameter of the middle cerebral artery is estimated by Doppler cast.

2 stage. To conduct a hypercapnic load test with carbon dioxide, the valve (4) of the CO ₂ cylinder (2) is opened. Using a rotametric dosimeter (6) set the gas flow (l / min) in accordance with the results of the measurement of MVL. The partial content of carbon dioxide (FiCO ₂ ) is 4%. The carbon dioxide is injected through a small diameter hose (9). The recording device (12) records the change in the parameters of cerebral blood flow and the diameter of the MCA for 2 minutes. Cut off the carbon dioxide supply by closing the valve (4) of the CO ₂ cylinder (2). Determine the time of return of cerebral blood flow to baseline values.

3 stage. The coefficients and indices are calculated, namely:

1) the coefficient of change in blood flow velocity

where V ₀ is the initial BFV in the MCA (cm / s), V ₂ is BFK after 2 minutes of inhalation of the hypercapnic mixture (cm / s);

2) index of changes in blood flow velocity

where V ₀ is the initial BFV in the MCA (cm / s), V ₂ is BFK after 2 minutes of inhalation of the hypercapnic mixture (cm / s), T is the time of inhalation of the hypercapnic mixture (s);

3) coefficient of change in diameter

where D ₀ is the initial diameter of the SMA (mm), D ₂ is the diameter after 2 minutes of inhalation of the hypercapnic mixture (mm);

4) index of change in diameter

where D ₀ is the initial diameter of the SMA (mm), D ₂ is the diameter after 2 minutes of inhalation of the hypercapnic mixture (mm), T is the inhalation time of the hypercapnic mixture (min);

5) post hypercapnic recovery index

where V ₀ is the initial BFV in the MCA (cm / s), V ₅ is BFK after 5 minutes from the start of the study (cm / s);

6) AD-normalized autoregulatory response

where V ₀ is the initial BFV in the MCA (cm / s), V ₂ is BFK after 2 minutes of inhalation of the hypercapnic mixture (cm / s), BP ₀ is the initial systolic blood pressure (mmHg), BP ₂ is the systolic blood pressure through 2 minutes of inhalation of a hypercapnic mixture (mmHg).

According to these indicators assess the state of cerebrovascular reactivity.

Throughout the study, a continuous recording of the electrocardiogram is carried out, blood pressure and respiratory rate are measured. The total study time is 10 minutes.

As clinical examples, confirming the advantages of the proposed method for assessing cerebrovascular reactivity, the examination protocols of patients are given.

Example 1. Patient R., 44 years old, underwent a clinical examination in clinics of the State Scientific Research Institute of Cardiology, Scientific Center of the Siberian Branch of the Russian Academy of Medical Sciences. No neurological complaints. When studying cerebral blood flow according to the generally accepted method — transcranial dopplerography of the middle cerebral artery — the following results were obtained: the maximum (peak) systolic blood flow velocity of 107.1 cm / s, the final diastolic blood flow velocity of 54.0 cm / s, and the average blood flow velocity for the heart a cycle of 71.7 cm / s, which corresponded to the norm, but did not allow judging the state of compensatory-adaptive mechanisms (cerebrovascular reactivity), which adapt the resistance of cerebral vessels to changing mussing with perfusion pressure, blood chemistry and increased brain activity, providing functional stability of the cerebral circulation system.

In the study of cerebrovascular reactivity according to the proposed method, the following results were obtained: the coefficient of change in blood flow velocity 1.35, the index of change in blood flow velocity 0.32, the coefficient of change in diameter of the middle cerebral artery 1.25, the index of change in diameter of the middle cerebral artery 0.40, post-hypercapnic index restoration of linear blood flow velocity 0.87, normalized to blood pressure autoregulatory response 6.17. The data obtained allowed us to assess the normal state of cerebrovascular reactivity.

Example 2. Patient L., 49 years old, underwent a clinical examination in clinics of the State Research Institute of Cardiology, Scientific Center of the Siberian Branch of the Russian Academy of Medical Sciences. No neurological complaints. In transcranial dopplerography of the middle cerebral artery, the maximum (peak) systolic blood flow velocity was 104.0 cm / s, the final diastolic blood flow velocity was 32.3 cm / s, and the average blood flow velocity for the cardiac cycle was 56.2 cm / s, which was normal. Computed tomography of the brain did not reveal organic changes.

In order to assess cerebrovascular reactivity, a study was conducted according to the proposed method, namely: registration of changes in the linear velocity of blood flow and the diameter of the middle cerebral artery against the background of hypercapnic loading test. The following results were obtained: coefficient of change in blood flow velocity 0.96, index of change in blood flow velocity 0.03, coefficient of change in diameter of the middle cerebral artery 1.0, index of change in diameter of the middle cerebral artery 0.00, index of posthypercapnic restoration of the linear velocity of blood flow 0.76 , normalized to blood pressure autoregulatory response 1.24. The data obtained indicated a decrease in cerebrovascular reactivity, i.e. a decrease in the ability and ability of cerebral vessels to change their diameter and blood flow velocity in response to exposure to load stimuli.

The data obtained using the proposed method made it possible, at an early, preclinical stage, to identify the vulnerability of the circulatory and metabolic support of brain activity at increased load and provided the opportunity to give the patient practical recommendations to reduce the risk of developing acute cerebrovascular accident, namely: to exclude work in extreme conditions ( highlands, underwater works); avoid being in rooms with high gas contamination and high content of CO ₂ ; optimize the mode of work (alternation of work and rest, full sleep, exclude night work); prevent a decrease in systemic blood pressure; regularly examined by a neurologist.

The criteria proposed for assessing cerebrovascular reactivity were selected based on the interpretation of the results of applying the proposed method in 40 healthy volunteers of three age groups: 20-30 years old, 30-40 and older than 40 years old, who underwent clinical examination in clinics of the State Research Institute of Cardiology of the Siberian Branch of the Russian Academy of Medical Sciences.

According to the use of the criteria of the proposed method, threshold values of blood flow parameters and the diameter of the middle cerebral artery were determined, which ensure the normal state of cerebrovascular reactivity (Table 1).

Table 1
Threshold values of blood flow parameters and SMA diameter during functional hypercapnic loading test Indicators All patients Age 20-30 years 30-40 years old > 40 years old

The coefficient of change in blood flow velocity

1.51 ± 0.23 1.50 ± 0.21 1.67 ± 0.23 1.39 ± 0.17 Blood flow velocity index

0.28 ± 0.13 0.32 ± 0.11 0.30 ± 0.15 0.23 ± 0.10 Diameter Change Factor

1.27 ± 0.12 1.26 ± 0.10 1.24 ± 0.08 1.31 ± 0.12 Diameter Change Index

0.48 ± 0.26 0.48 ± 0.15 0.42 ± 0.17 0.52 ± 0.37 Posthypercapnic Recovery Index

0.95 ± 0.12 0.92 ± 0.17 0.98 ± 0.08 0.96 ± 0.09 Autoregulatory response normalized to BP

5.26 ± 1.44 4.19 ± 1.30 7.12 ± 1.63 4.85 ± 1.35

Note: data are presented as M ± SD

Cerebrovascular reactivity is an integrative indicator of the functional state of the cerebral circulatory system and is impaired in the pathology of any cerebral vascular pool [8]. The pathogenesis of pre-stroke stages of cerebrovascular diseases, which include the initial manifestations of cerebrovascular insufficiency and early forms of discirculatory encephalopathy, is based on the insufficient hemodynamic support of increased functional activity of the brain, due to the ineffectiveness of compensatory-adaptive reactions [9].

Thus, the proposed criteria characterizing the state of cerebrovascular reactivity can be used in neurology. cardiology, neurosurgery and resuscitation for the diagnosis of latent cerebrovascular insufficiency, can recognize cerebrovascular diseases at an early, preclinical stage and are threshold for determining the period of application of therapeutic measures.

The proposed method is distinguished by the determinism of the vascular reaction, the standardization of the study, ease of implementation, the speed of obtaining and a high degree of reproducibility of the results, the use of physiological stimulus (CO ₂ ) in a low concentration (4%), which ensures safety, non-invasiveness and good tolerance of the study and allows the use of this method for rapid diagnosis of cerebrovascular reactivity.

Bibliography

1. Lelyuk V.G. Cerebrovascular reserve for atherosclerotic lesions of the brachiocephalic arteries. Studies of modern ultrasound diagnostics / V.G. Lelyuk, S.E. Lelyuk. - K .: Ukrmed, 2001. - Issue 2. - P.31-41.

2. Gaidar B.V. Semiquantitative assessment of autoregulation of blood supply to the brain is normal / B.V. Gaidar, D.V. Svistov, K.N. Khrapov. // Journal of Neurology and Psychiatry. - 2000. - No. 6. - S. 38-41.

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4. Ultrasound Doppler diagnostics of vascular diseases / Ed. Nikitina Yu.M., Trukhanova A.I. - M .: Vidar, 1998 .-- S.241-248.

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Claims (1)

A method for assessing cerebrovascular reactivity, including measuring the linear blood flow velocity (LSC) in the middle cerebral artery (SMA) at rest and against the background of a hypercapnic exercise test, characterized in that inhalation using a 4% mixture of carbon dioxide and air with an injection is used as a hypercapnic test by supplying CO ₂ for 2 min, the changes in the linear blood flow velocity and the diameter of the middle cerebral artery are recorded, and the coefficient of change in the blood flow velocity is calculated

according to the formula

where V ₀ - the initial LKS, cm / s, V ₂ - LSC after 2 minutes of inhalation, cm / s; blood flow velocity index

according to the formula

where V ₀ is the initial BFV, cm / s, V ₂ is BFK after 2 minutes of inhalation, cm / s, T is the inhalation time in s; diameter change factor

according to the formula

where D ₀ is the initial diameter of the SMA, mm, D ₂ is the diameter after 2 minutes of inhalation, mm; diameter change index

according to the formula

where D ₀ is the initial diameter of the SMA, mm, D ₂ is the diameter after 2 minutes of inhalation, mm, T is the inhalation time in minutes; posthypercapital recovery index

according to the formula

where V ₀ is the initial BFV in the MCA, cm / s, V ₅ is BFK after 5 minutes from the start of the study, cm / s; autoregulatory response normalized to

according to the formula

where V ₀ is the initial BFV in the MCA, cm / s, V ₂ is BFK after 2 minutes of inhalation, cm / s, BP ₀ is the initial systolic blood pressure, mmHg, BP ₂ is systolic blood pressure after 2 minutes of inhalation, mm Hg. Art., and with indicators:

assess the normal state of cerebrovascular reactivity.

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