Plethysmography – what is it, application, when to perform?

Every year, new solutions are added to the Polish medical services market, allowing for specialist and precise diagnosis of disease states. Currently, a method called plethysmography or bodyplethysmography is gaining more and more interest.

Plethysmography has two purposes. First, it is a measurement of blood circulation and free flow of blood at a given location in the body, which also allows to determine whether and to what extent there is reverse blood flow, called venous reflux. Secondly, plethysmography measures the effect of the respiratory system on reducing or increasing the volume of a selected body site. This allows plethysmography to discover changes in pressure between different parts of the body. The determination of these physiological parameters is very important at every stage of the diagnostic procedure. Thus, plethysmographic examination enables a precise look at potentially affected places inside the body and precise determination of their symptoms and physiological changes.

Plethysmography – types of research and application

The advantage of plethysmography is that it is easy to use. This method belongs to the non-invasive and painless type of diagnostic procedures. In addition, it is very accurate, as it allows you to determine the exact amount of blood flowing through a specific blood vessel. There are several types of plethysmography, based on the specific site in the body being tested:

  1. lower limb plethysmography – performed using the so-called pneumatic cuffs, measuring pressure and recognizing the smallest changes in the volume of the examined limb,
  2. upper limb plethysmography – also performed with pneumatic cuffs,
  3. Chest plethysmography – assessing, among other things, the respiratory efficiency of our lungs.

The most important types of plethysmography are:

  1. Classic plethysmography – consists in measuring the regularity of blood flow in the examined limb by comparing it to the results obtained in the examination of a healthy limb. If the results are similar, then the tested limb is considered healthy. If we see different results in the results of individual limbs, they may indicate problems with the proper functioning of the circulatory system.
  2. Segmental plethysmography – is more detailed than classical plethysmography. It consists in taking measurements on specific sections of the examined limb. For example, you can perform segmental plethysmography on different sections of the hand, which allows you to compare the functioning of the arm, forearm and hand. This test compares the blood pressure of the individual test fragments and also checks their value in relation to the distance from the heart. If the test site, located far from the heart, shows a large difference in pressure compared to the proximal tissues of the heart, it tells us about problems with pressure.
  3. Photoplethysmography – is one of the types of plethysmography, also used to diagnose abnormalities in the venous circulation. Photoplethysmography is based on a different principle of operation. The test is performed using a specialized probe that emits delicate infrared waves. As they pass through soft tissues, the emitted waves are reflected and returned to the detector. However, getting into the blood vessels, they are absorbed by red blood cells. As a result, photoplethysmography, based on the returning light pulses, creates a detailed distribution of the functioning of the circulatory system at the selected site.
  4. Lung plethysmography – involves examining the breathing pattern in a tightly closed chamber equipped with numerous pressure sensors. In such conditions, the course of the respiration process is closely monitored by observing the changes in the volume and shape of the chest. This examination allows for a detailed diagnosis of the degree of lung ventilation, their potential impairment or failure.

When should a plethysmography be performed?

The most common reasons for using plethysmography as a diagnostic test include:

  1. venous blockages,
  2. inflammation of the veins,
  3. narrowing of the arteries
  4. atherosclerosis,
  5. obliterating arteritis,
  6. diabetic changes,
  7. complications after surgery or trauma to blood vessels,
  8. various forms of deep vein insufficiency,
  9. venous valve insufficiency.

Before plethysmography

Before starting the test, you should properly prepare your body. First of all, on the day of plethysmography, you should avoid consuming substances that disrupt the work of our circulatory system or alter blood pressure. Therefore, it is not advisable to consume strong coffee, tea or drink alcohol on the day of the plethysmography. Also, some medications may affect the result obtained in the study. Therefore, before arranging the examination, it is necessary to discuss the influence of the medications taken on the examination result. It is also recommended – both in the case of vascular and lung plethysmography – to refrain from smoking on the day of the examination.

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