What is the name of the technique designed to study the filling of an organ with blood? This is plethysmography. In its framework, the volume of an organ is measured at different stages of the functional cycle. These indicators help to determine both the volume of blood intake and outflow from it (the moment of inhalation and exhalation), as well as changes in permeability, electrical resistance. All this together allows you to diagnose a wide range of diseases. Let's analyze the indications for plethysmography, the characteristics of its varieties, preparation for the examination, the significance of its results.
Indications for the procedure
Why is plethysmography assigned? This examination helps to identify the following pathologies and diseases:
- Phlebeurysm.
- Vascular thrombosis.
- Raynaud's disease.
- Thrombophlebitis.
- Vasculitis.
- Atherosclerotic arterial pathology.
- Circulatory disturbance in the brain.
- Neuropathies and angiopathies observed in diabetes.
- Lung diseases (valuable information on organ capacity is valuable) - emphysema, obstructive bronchitis, bronchial asthma, pneumosilicosis and other occupational injuries of pulmonary matter.
- Low erection in men. Assessing the conditioned reflex activity, the technique allows you to determine the causes of dysfunction.
By the way, plethysmography is used to diagnose a number of deviations of a psycho-sexual nature - pedophilia, homosexuality, a tendency to sexual violence. The subject is shown images, and the plethysmograph captures signs of sexual arousal at this moment.
What is plethysmograph?
Plethysmography is the examination using special devices (plethysmographs). The devices consist of the following elements:
- Volume calibrator equipped with a sensing system.
- The translating element.
- Wave Recorder. In turn, it consists of several elements - a mechanism that ensures the movement of the tape, and a latch for the duration of stimuli.
The first and modern devices
The first devices were completely mechanical. The principle of their work is quite simple: the research chamber was equipped with rigid walls, between which the study area was located. The water chamber was filled with water, and the air was sealed.
As soon as the organ expanded, it began to displace part of the air or liquid mass from the chamber. Under the influence of this, the movable part of the device began to move, which was recorded on a tape or photographed.
Modern plethysmography is a combined model. That is, electrical mechano- and cardiographs equipped with photographic recorders. They are distinguished by a wider range of applications. The devices help analyze the blood flow of such vast areas as the head, abdominal, thoracic zones and so on.
Electrophotopleismographs - combined photoelectric systems are also considered a very useful discovery. They allow you to examine flat areas of the body - for example, the ear, skin folds, hands. But such a method is not yet perfect - it does not give specific quantitative indicators. The results obtained provide only general data on blood circulation - it is normal or there is some kind of violation.
Varieties of research
Today, there are several methods of plethysmography. Each is aimed at a specific examination of the heart, kidneys, and other organs. A particular variety is prescribed by the attending specialist based on the objectives of the procedure, the need for a stress test.
Methods of studying vascular reactions (rheography, plethysmography) are divided into the following types:
- Impedance form.
- Venous impedance form.
- Integral form.
- Occlusal form.
Each of these examinations has its own set of contraindications. A leading specialist should inform you about them - a vascular surgeon, a therapist, a neurologist, a phlebologist.
Next, we will analyze each of the categories presented in detail.
Impedance method
Another name is rheography. The principle of operation is based on a change in the impedance (resistance) of the electric current. What does it mean? With a rush of blood mass, electrical conductivity increases. This is due to the fact that blood has the highest ability to conduct a pulsed electric wave (among all other biological fluids).
The rheogram is recorded of the electrodes that are superimposed on the body of the subject. An electric cardiograph with a special attachment can also be used for this task.
The resulting graph is a sinusoidal function. The rise on it is the flow of blood from the arteries, the decline - respectively, the venous outflow. To judge by the graph about the patient’s condition, the specialist should study a considerable amount of such fluctuations, evaluate their similarities and differences, the dynamics of growth, as well as the fact of the presence of additional waves during a decline.
The main purpose of rheography is to study the filling of the heart chambers with blood. It is most often carried out in parallel with the removal of the electrocardiogram.
Rheography Results
All rheograms obtained during the examination can be divided into main categories:
- Normal It is characterized by smooth descent and ascent, as well as the presence of a small depression on a round peak.
- Hypovolemia. Talks about low blood flow. The waves are small, steps are visible on their ascending part, while the descending half will be completely flat.
- Hypervolemia. The volume of blood supply to the body is above normal. On the graph this is indicated by a curve with sharp tops, sharp descents and a large amplitude.
- Hypertension of the pulmonary vessels. Pathology is determined by a sharp rise, a slow descent and a rounded peak.
Impedance venous method
This is a method of plethysmography of the veins of the lower extremities. The study is necessary to make the following diagnoses:
- Thrombophlebitis.
- Risk of pulmonary embolism.
- Deep vein thrombosis.
- Varicose veins.
Impedance Method Results
The results of impedance plethysmography are deciphered as follows:
- The insufficiency of the outflow through the veins is determined by the descending side of the graph, the presence of additional fluctuations on it. Attention is paid to the distance from the top to the lowest point of the curve.
- In case of violation of nutrition of the studied tissues with oxygen, the rheographic index will be reduced. For a specialist, this is a sure indicator that the blood both weakly enters these tissues and insufficiently flows from them through the venous vessels.
Occlusal method
In what cases is occlusive plethysmography used? To assess the stage of expansion and blockage of venous vessels, their response to a specific load. The method is associated with the creation of an artificial obstacle to the outflow of blood. To do this, a cuff is applied a little further from the test site to the vein.
After air is pumped into it (cuff), the specialist re-measures the resistance to electric current on the device. The data obtained are compared with those that were obtained before exposure to the obstacle. As a result of such a comparison, the doctor can judge the risk of developing venous insufficiency or its presence.
Integral method
It is also called body test, plethysmography of the whole body. The purpose of this study is to study the patient's pulmonary respiration.
How is plethysmography of the whole body? The patient is inside a special sealed chamber of the device, and his airways are connected to a pneumotachometer - a device that records the movement of air. A special catheter with a balloon is placed in the esophagus of a person, the pressure in which will be close to pleural.
This study (plethysmography of the whole body) helps to obtain a set of valuable indicators:
- The volume of inspiration and expiration.
- Lung reserves.
- The extensibility of pulmonary matter.
- The degree of resistance to bronchial air flow.
Preparation for the procedure
Thus, in modern medicine, the study of venous outflow is, to a large extent, carried out using plethysmography. The method is distinguished by high information content coupled with the complete safety of the patient. If compared with common angiography, then this method does not require the introduction of a contrast agent through a catheter, to which a number of contraindications are prescribed. Unlike radiography, radiation that is harmful to humans is not used here.
Another significant plus - plethysmography does not need to be specially prepared in any way. There are no restrictions on diet, lifestyle, activity, taking medications on the eve of the procedure.
The only wish: the patient during the examination should be in a relaxed and calm state. If this does not allow pain, muscle tension in a particular disease, then it makes sense to administer sedatives.
Procedure
Let's take an example of the most common procedure - plethysmography of the lower extremities. The algorithm here will be as follows:
- The examinee is asked to lie on his back, and put his feet on a special hill.
- Further, electrodes are fixed on his legs. The distance between them is about 7 cm.
- A special cuff is placed above the lower leg. Air will be pumped into it for the examination.
- The electrodes are connected to the plethysmograph apparatus.
- Then, air is pumped into the cuff through the device. But so as not to impede the flow of blood through the arteries.
- To keep the arterial flow under control, the specialist periodically monitors the pulse on the patient's ankle.
- Cuff compression can be reduced to 1.5-2 minutes for patients with suspected endarteritis and atherosclerosis.
Similar measurements are taken on both legs. The recording will feature 5-7 hemodynamic cycles. Based on the information received, the specialist confirms or refutes the previously made diagnosis. If the information received is assessed by him as uninformative, then the patient is sent for repeated plethysmography. Physiology can play a role here, which is why in the second procedure the location of the cuffs and electrodes is changed.
Normal indicators are as follows:
- Pinching the veins with the cuff leads to an early filling with venous blood.
- After cessation of compression by an obstacle, a sharp outflow of blood mass is observed.
The signs of thrombosis are as follows:
- After inflation of a cuff pressure does not increase.
- Slowed outflow of blood.
- Reduced blood flow through arterial vessels (with blockage of deep veins).
- The initial and final pressure in the veins is above normal.
In conclusion, we note that plethysmography does not always show completely correct results. Several factors influence the accuracy of the study at once:
- muscle or vascular spasms (due to cold, pain),
- motor activity of the patient, tension of his muscles,
- hematoma, tight bandage or swelling, compressing venous vessels,
- low arterial blood flow (as a result of shock, spasm, collapse or clogged arteries).