Clinical and biophysical data on the coordination of uterine contractions in childbirth

Recognition of the initial symptoms of violations of motor function of the uterus in childbirth, a comparative evaluation of the effectiveness of treatment of anomalies of labor activity based on clinical observations alone is very difficult, so now the methods of monitoring monitoring in pregnancy, even at home, internal hysterography, cardiotocography.

In recent years, methods of registering uterine contractile activity with external multichannel hysterography, as well as internal hysterography (tocopheraphy) by the radiotelemetric apparatus of the Capsule system, a transcervical method for recording intrauterine pressure using the open polyethylene catheter technique, the method of transabdominal examination of intrauterine pressure . Steer et al. Have developed a more advanced catheter for recording intrauterine pressure by the type of transducer that lacks the disadvantages of an open catheter. In 1986, Svenningsen, Jensen developed a fiber optic catheter for measuring intrauterine pressure. At present, Utah Medical Systems has developed an Intran 2 catheter.

Much attention to this problem, its solution is due to the serious importance of studying the contractile activity of the uterus for the diagnosis and prognosis of childbirth in the event of their complicated course.

The first who tried to measure the force of uterine contractions in childbirth was the native scientist NF Tolochinov (1870) who suggested a spring manometer mounted in a cylindrical vaginal mirror. The manometer was fed to the fetal bladder and measured the force of its pressure. In the years 1913-1914. The French obstetrician Fabre for the first time conducted a parallel recording of the contractile activity of the uterus with the help of external and internal hysterography and concluded that the curves obtained when recording the fights by both methods correspond to each other. In 1872, Schatz applied internal hysterography, which is now widely used.

It should be noted that the data obtained with the simultaneous registration of amniotic pressure by a catheter inserted through the abdominal wall and transcervical, showed complete identity of the obtained curves. According to Mosler, the basal tone is 15 mm Hg. The value of intrauterine pressure in the first stage of labor is 60 mm Hg. In the second period - 105 mm Hg. Art. To the given Alvarez, Caldeyro-Barcia, these figures were accordingly 8 mm, 35-100 mm Hg. Art. And 100-180 mm Hg. Art. According to Williams, Stallwoithy, the parameters of the contractile activity of the uterus were respectively 8 mm Hg, 40-90 mm Hg. Article, 120-180 mm Hg. Art. Williams and Stallworty point out that internal hysterography has the advantage, because it reflects the pressure in the hydrostatic cavity, so indicators based on hydrodynamic calculations reflect the true activity of the uterine contractile function.

Some authors use closed polyethylene tubes with one sensor and a pressure sensor to measure intrauterine pressure, which is located between the uterus wall and the fetal head along the largest circumference of the fetal head. However, there are many examples in obstetric practice showing that there is often a lack of correspondence between the clinical course of labor and the hysterographic indices.

Over the past 50 years, a large number of factors (hormones) and various pharmacological substances on the uterus have been studied. Mechanical factors also have a fairly long history. As early as 1872 Schatz showed that a sudden increase in the volume of the uterus leads to the appearance of uterine contractions. Reynolds in 1936 proposed the theory of uterine stress ("a uterine distention theory"), in 1963 Csapo - the theory of "progesterone block", considered by the author as a mechanical factor in pregnancy.

In this case, the physical laws of hydrodynamics can undoubtedly and can be applied to the study of the contractile activity of the uterus. For the first time in 1913 Sellheim in the monograph "Childbirth in Man" made a series of calculations on a hydrodynamic basis, these studies are reflected in many textbooks of domestic and foreign obstetricians. Reynolds (1965), devoted to the physiology of the uterus, gives detailed calculations showing the role of physical factors in uterine activity with hydrodynamic justification according to the laws of Laplace and Hooke. Referring to the Haughton studies conducted as far back as 1873, the proportion of the bending radius in the uterus bottom and the lower segment of the uterus is equal to 7: 4, that is, the difference in uterine tension in the upper and lower sections of the uterus is related as 2: 1 and therefore in the process of normal delivery there is a clear difference in muscle fiber tension in the region of the bottom and the lower segment of the uterus, and this also applies to the thickness of the myometrium in these sections, which corresponds to 2: 1. Therefore, the force is proportional to the thickness of the uterine tissue by Haughton. Based on the calculations and representations of Haughton and his own data based on the method of three-channel external hysterography, developed by Reynolds in 1948, the author believes that the opening of the cervix is observed only when rhythmic activity in the uterus bottom is predominant over the rest of its parts. In this case, in the middle zone of the uterus (body), with respect to the bottom of the uterus, contractions are less intense and they are usually shorter in duration and their frequency decreases with the progression of labor. The lower segment of the uterus remains inactive throughout the entire first stage of labor. Thus, the opening of the cervix in labor is the result of a decrease in the gradient of physiological activity from the bottom to the lower segment of the uterus. The functional components of this activity are the intensity and duration of uterine contractions. In this case, the uterine contractions in the bottom area last longer by 30 s than in the uterine body, that is, the so-called "triple descending gradient" is observed. These judgments of the author were confirmed by the works of Alvarez, Caldeyro-Barcia (19S0), which measured and evaluated intrauterine and intramuscular pressure in the uterus at various stages of pregnancy and labor with the use of complex micro-balloon technique. With the help of this method, it was possible to confirm the notion of a "triple descending gradient" characteristic of the normal course of labor. In addition, it was shown that the contraction wave began at one of the tube corners of the uterus, and a theory was confirmed about the dominant role of the uterine fundus and the presence of a triple descending gradient.

Similar judgments on the application of the laws of hydrodynamics in the study of uterine dynamics are also given in the monograph by Mosier (1968). According to the concept of the author, two opposite forces control and complete the generic process: the strength of tension and elasticity. However, the author emphasizes that the results of the study of uterine contractions on animals and on the uterus of a person can not be transferred without reservations, as cited by Csapo et al. (1964), since animals have a bicornic uterus, while in humans it is simplex. Therefore, both research on the human uterus and the consideration of certain discrepancies in the laws of hydrodynamics with clinical observations are needed. Thus, at a maximum stress of the uterine walls, a decrease in the resistance of the cervical wall is simultaneously observed. At the same time, the contractile activity of the uterus in labor does not arise due to an increase in intrauterine pressure, but an increased stress of the uterine walls, which appears as a reaction to an increase in the total volume (diameter) of the uterine cavity. Here it can not be overlooked that the increase in uterine volume occurring during pregnancy occurs without a marked increase in pressure in the uterus, where the pressure varies from 0 to 20 mm Hg. Art. And increased pressure is only indicated at the end of pregnancy. Bengtson (1962) recorded the average values of intrauterine pressure at rest, during pregnancy, equal to 6-10 mm Hg. Art. The nature of this "resting pressure" - the residual or basal pressure of the Mosler is not entirely clear in detail, but is obviously causally related in part to the intrauterine pressure itself and intra-abdominal pressure, as pointed out as far back as 1913 by Sellheim.

Mosler emphasizes that the measurement of intrauterine pressure is an indirect determination of the stress of the uterine wall caused by contractions of the uterine musculature and depending also on the radius of the uterine cavity. The stress of the uterine wall can be described by the Laplace equation. At the same time, one can not but pay attention to the circumstance that when using a micro balloon technique (from 1 to 15 mm in volume) a rubber cylinder with a long registration gives on the basis of changes in elasticity the relatively inaccurate pressure data.

An important point for obtaining identical data is, from our point of view, an accurate definition of the depth of catheter insertion into the uterine cavity, which, unfortunately, is not taken into account when performing internal hysterography, as the authors proceed from the incorrect idea of the same pressure in the uterine cavity process of birth, if we proceed from the law of Pascal. Only in the work of Hartmann in the study of intrauterine pressure outside of pregnancy, it is indicated that all catheters have an inserted ring at a distance of 5 cm, showing the depth at which the catheter is located in the uterine cavity. However, as will be shown later, when determining the indices of intrauterine pressure, it is necessary to take into account the height of the hydrodynamic column - the height of the uterus and the angle of inclination of the uterus with respect to the horizontal line and, depending on the angle of incidence of the uterus in the lower parts of the uterus, the pressure will be higher than in the overlying regions of the uterus (bottom).

The study of contractile activity of the uterus with the help of a five-channel external hysterography during normal delivery, even accompanied by painful contractions, revealed the absence of discoordination of labor. Those slight differences in the duration and intensity of contractions of both halves of the uterus at the same level (in one segment) do not matter, since its contractions remain coordinated and the amplitude of contractions reaches its highest point simultaneously in all the recorded segments of the uterus, which allowed us to move further to a three-channel external hysterography, placing the sensors respectively in the area of the bottom, the body and the lower segment of the uterus.

The analysis of the obtained data was carried out by quantitative processing of hysterograms for every 10 min. The main parameters of the contractile activity of the uterus (the duration and intensity of the contraction, the frequency and duration of pauses between them, the coordination of various sections of the uterus among themselves, etc.) were studied. At present, electronic integrators are used for this purpose, when the active pressure area under the intrauterine pressure curve is measured, especially when using internal hysterography.

In order to rationalize the calculations and save time, we proposed a special line for the analysis of hysterograms.

[1], [2], [3], [4], [5]