I.V. Klyucharov E.I. Prokhorov S.L. Borisov R.F. Kadyrov R.N. Fakhrutdinov Journal "Practical Medicine" No. 4 (89) June 2015 / Volume 1 Preset and Actual Pressure in the Uterine Cavity. Accuracy of Our Hysteropumps Modern operating rooms allow combining various hysteropumps and hysteroscopes. The authors have established the difference between the set pressure and the actual pressure obtained in the uterine cavity. The digital limits of this difference are presented. The practical significance of this finding lies in the need to correct the set pressure taking into account the detected error, which will ultimately increase the safety and efficiency of inpatient hysteroresection and comfort during outpatient hysteroscopy. Key words: hysteropump, hysteroscope, hysteroresectoscope, pressure, uterine cavity, office hysteroscopy, hysteroresection. Maintaining pressure at a minimum level that ensures adequate visualization of the uterine cavity is the primary characteristic of the hysteropump. Accurately matching actual parameters to the set ones ensures good tolerability during office hysteroscopy (minimum pressure level of 40-50 mmHg) and safety during resectoscopy (pressure greater than 80 mmHg). With repeated use of different hysteropump and hysteroscope sets during surgeries, a discrepancy between the expected clinical picture and the actual one is observed, depending on the degree of uterine distension. For example, sometimes a pressure of 50 mmHg provided sufficient distension, while other times it did not. Conversely, setting the uterine pressure to 80 mmHg resulted in significant intravasation, as determined by a number of clinical, instrumental, and laboratory parameters. A possible discrepancy between the set and actual pressure may be one of the causes of such manifestations and, consequently, the result of such a serious complication as acute excessive intravasation of the solution used for uterine distension into the bloodstream. This may result in a disruption of the fluid-electrolyte balance, edema of the parenchymal "hydrophilic" organs, the addition of neurological symptoms, cerebral edema, coma, and a fatal outcome. This issue has not been adequately addressed in modern foreign and domestic literature. The correspondence between the set and actual pressure was studied for two hysteropump models (A, B), two hysteroscope models (outer diameters of 3.5 and 6 mm), and one resectoscope (outer diameter of 9 mm) (Table 1). The studied pumps each had one roller pump for pumping fluid and their own systems for monitoring the fluid delivery parameters. The tests were conducted on a 95 ml cavity equipped with a pressure sensor and connected to a computer for digital and graphical parameter recording. The flow rate was set at 500 ml/min. The pressure preset on 2/7 of the hysteroscopes under study corresponded to 50, 70, 100, and 140 mmHg. The device recorded the actual cavity pressure and plotted the pressure change curve. Hysteroscope pump A. At a set pressure of 50 mmHg, the actual cavity pressure for different hysteroscope models was: a(d3.5 mm) = 41 mmHg (-9), b(d6 mm) = 20 mmHg (-30), c(d9 mm) = 64 mmHg (+14). At a given pressure of 70 mmHg, the real pressure was a(3.5) = 47 mmHg (-23), b(6) = 25 mmHg (-45), c(9) = 93 mmHg (+23). At a given pressure of 100 mmHg, the real pressure was a(3.5) = 60 mmHg (-40), b(6) = 38 mmHg (-62), c(9) = 117 mmHg (+32). At a given pressure of 140 mmHg, the real pressure was a(3.5) = 62 mmHg (-58), b(6) = 50 mmHg (-90), c(9) = 120 mmHg (+20). Hysteropump B. At a set pressure of 50 mmHg, the real pressure was a(d3.5 mm) = 38 mmHg (-9), b(d6 mm) = 40 mmHg (-10), c(d9 mm) = 60 mmHg (+10). At a set pressure of 70 mmHg, the real pressure was a(3.5) = 50 mmHg (-20), b(6) = 55 mmHg (-15), c(9) = 85 mmHg (+15). At a set pressure of 100 mmHg, the real pressure was a(3.5) = 82 mmHg (-18), b(6) = 90 mmHg (-10), c(9) =120 mmHg. (+20). At a set pressure of 140 mmHg, the actual pressure was a(3.5) = 98 mmHg (-42), b(6) = 122 mmHg (-18), c(9) = 160 mmHg (+20). The hypothesis that in the studied combinations of hysteropumps and hysteroscopes the actual pressure will differ from the set one was confirmed, and the boundaries of these differences for the studied combinations of devices were determined within the range from -90 to + 32 mmHg. This fact is apparently associated with the settings of hysteropumps for certain models of hysteroscopes, the algorithm for maintaining the set pressure and the features of the internal design of hysteroscopes (Fig. 1). [ /upload/medialibrary/243/1_1.jpg ] The change in pressure inside the cavity was also studied under the following conditions: with the supply tap fully open and the outflow tap in three positions: 1. fully open, closed (partially closed) and fully closed (Fig. 2); [ /upload/medialibrary/296/2_1.jpg ] 2. fully closed, partially opened and fully open (Fig. 3). [ /upload/medialibrary/d28/3_1.jpg ] At a set pressure of 100 mm Hg and a fully open tap for supplying liquid into the cavity, as well as a fully open outflow tap, the level of the actual pressure will be lower than the set one (maximum error), with partial closure, the actual pressure rises, tending to the set one (but the error remains), and with complete closure, a peak overload occurs with an excess of the set pressure, after which the pressure gradually decreases to the set one (Fig. 2). When the inlet valve is fully open and the outflow valve is fully closed, the actual pressure corresponds to the set value. When the outflow valve is fully open, a wave-like pressure decrease (maximum error) occurs, followed by a smooth increase (correction), which, however, is insufficient, and as a result, the actual pressure is lower than the set value (Fig. 3). Thus, the studied hysteropumps, in combination with various hysteroscopes, do not provide a precisely set pressure in the uterine cavity due to the specific operating algorithms and design features of the hysteroscopes. The deviation can range from -90 to +32 mmHg. Furthermore, it is important to consider that the process of opening and closing the valves also affects the actual pressure in the cavity. Discussion of the obtained results: Understanding the functional features of the hysteropump is essential for the effectiveness and safety of intrauterine interventions. The primary functions of a hysteropump—uniform delivery of the distension medium into the uterine cavity and maintenance of specified pressure parameters—are necessary to ensure visualization of the uterine cavity during diagnostic and therapeutic procedures during hysteroscopy. Various hysteropump models exist, each with its own unique operating algorithms [1]. The recommended pressure for hysteroresectoscopy is 80–100 mmHg, while for office hysteroscopy, it is 50–70 mmHg [2]. Exceeding the recommended pressure for resectoscopy leads to complications associated with the distension medium [3]. Considering that the expanding medium can be either liquids similar in electrolyte composition to blood (electrolytes), such as 0.9% NaCl, Ringer's lactate, or non-electrolyte liquids, such as 5% glucose solution, 1.5% glycine solution, it is necessary to take into account that in the "electrolyte" group, complications associated with overload of the circulating blood volume due to intravasation and the development of hypoNa-emia arise, and in the non-electrolyte group (glucose, glycine, dextrose, etc.), metabolic complications are added to the above [4, 5]. Currently, criteria for critical overload with an expanding medium have been formulated based on the calculation of fluid deficit. Fluid deficit (ml) = volume used (ml) - volume collected (during hysteroscopy of fluid, ml) [2, 3]. For electrolyte solutions, the permissible fluid deficit is 2000.0 ml. For non-electrolytes - 500.0 ml. Upon reaching the specified threshold, it is necessary to stop the operation, assess the patient's condition and, if necessary, begin restorative measures. The surgeon must be notified of the deficit of every 500.0 ml of fluid [2, 3]. If these recommendations are ignored, there is a high probability of developing complications associated with circulatory system overload and progression of cardiorespiratory problems, in addition to hypoNaemia with subsequent cerebral edema, sopor, stupor and coma [5, 6]. It is necessary to take into account that a standard vessel with an expanding medium may contain slightly less or slightly more medium and, therefore, create an error in the calculation of the deficit [7]. Data from domestic and foreign literature mainly describe complications associated with the use of various media for cavity expansion, their prevention and treatment, without paying sufficient attention to the hardware inaccuracies typical for the operation of combinations of various instruments. This situation can lead to unexpected complications during hysteroscopic surgery and the need for resuscitation measures, which undoubtedly reduces the safety of the procedures. The obtained data indicate the presence of another cause of disorders associated with the use of liquid media for distension of the uterine cavity, as well as the need to develop universal algorithms for manual or automatic compensation of the internal resistance of hysteroscopes to accurately maintain a given pressure inside the cavity. REFERENCES 1. Kumar A., ??Kumar A. 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