Methods of recording contractile activity of the uterus

Diagnosis of abnormalities of labor can be carried out by analyzing clinical symptoms or by graphically depicting the opening of the uterine pharynx in childbirth in the form of partograms. Another way to improve the diagnosis of labor is to study the contractile activity of the uterus by objective methods: external and internal hysterography. Wide distribution at one time received external hysterographs with pneumatic sensors, however, hysterographs with the use of strain gauges are more advanced, since they are easier to use and are inertial.

The method of internal hysterography is based on the recording of intrauterine pressure (AMD). As far back as 1870 the native scientist NF Tolochinov proposed a manometer mounted in a cylindrical vaginal mirror. The manometer was fed to the fetal bladder and measured the value of intrauterine pressure.

Transcervical method of recording intrauterine pressure with a polyethylene catheter was suggested by Williams, Stallworthy (1982). It has become widespread both in our country and abroad.

One of the variants of internal hysterography is the method of radiotelemetry, the essence of which is that a miniature radio station is introduced into the uterine cavity, which registers intrauterine pressure, transforming it into radio waves recorded as curves on a special apparatus.

The device and the method of two-channel internal hysterography were developed. Registration of intrauterine pressure in two channels became possible due to the discovery of a previously unknown dependence of uterine self-regulation during labor. During fights, a zone of increased intrauterine pressure in the region of the lower segment of the uterus is formed due to the appearance of a functional hydrodynamic cavity, bounded by the lower segment of the uterus, the head and the hock of the fetus.

Studies of contractile activity of the uterus (SDM) with simultaneous registration of intrauterine pressure and external hysterography are of interest. The contractions of the uterus begin earlier than the intrauterine pressure increases. At the same time, in the first stage of labor, the increase in intrauterine pressure occurs later than the reduction of all parts of the uterus, on average by 9.4 ± 1.5 s.

A comparative analysis of the methods of external and internal hysterography has shown that the latter has a number of advantages, since it allows recording the basal tone of the uterus, which is especially important in diagnosing hypo- and hyperdynamic types of uterine contractile activity.

The main difficulty in diagnosing violations of contractile activity of the uterus is to determine the most informative indicators. It is a pleasure for researchers to analyze the contractile activity of the uterus by 15-20 parameters. However, the analysis of these indicators requires a great deal of time and computer application.

In order to quantify the contractile activity of the uterus according to external and internal hysterography, some researchers proposed various methods: the mathematical analysis of hysterograms, the evaluation of the effectiveness of labor activity by pulse pressure, i.e. The product of the mean pressure and time of its action, the units of Montevideo, the Alexandrian unit, active planimetric unit, and so on.

Multichannel external hysterography. For a more detailed study of the contractile activity of the uterus in labor, multichannel external hysterography is used. Five-channel hysterography was applied with the location of sensors in the bottom and body of the uterus on the right and left to the lower segment of the uterus along the middle line. Later, an electronic hysterograph with a mechanophoto-electronic converter was developed. In recent years, the dynamouterograph Du-3 three-channel with ink recording has been designed. The device uses modern strain gauges. The device is reliable in operation, portable.

Analysis of hysterograms:

• the external hysterogram is more indicative of the dynamics of the volume of the uterus and its shell at the site of the sensor than the magnitude of the stress of the uterine membrane;
• In the uterus during labor clutch can clearly distinguish 3 hydrodynamic systems:
  • cavity and shell of the body of the uterus;
  • cavity and shell of the lower segment;
  • cavity of vascular cords of the uterus, which influence the amplitude of external and internal hysterograms;
• the pathological birth contract differs from the physiological contraction not so much by the absolute magnitude of the myometrium tension during its contraction, but rather by a violation of the order of the changes in the volumes of various sections of the uterus, which leads to a violation of the mechanism of the transformation of the isometric strain of the myometrium into external work to change the cervical tissue;
• since external and internal hysterograms are of fundamentally different physical nature, the use of the same methods of their analysis and interpretation is incorrect in relation to the basic physical laws that operate in the contracting uterus during labor.

Despite the presence of contradictory data on the contractile activity of the uterus, further study of the qualitative and quantitative characteristics of the contractile activity of the uterus will help to identify such informative indicators of its disorders that can be used to diagnose it.

[1], [2], [3], [4], [5], [6], [7], [8]