The Development And Basic Applied Study Of An Automatic Non-pump Gravity Distension Device With Constant Pressure

BackgroundHysteroscopy is widely utilized for the diagnosis and treatment of intrauterine diseases due to its relatively safe and minimally invasive characteristics.The distension system plays an important role in providing a clear surgical field.However,its peristaltic working mode can lead to instability in the surgical field.It may affect the surgeon’s judgment during the procedure,leading to a mistaken belief that the instability of the surgical field is due to the patient’s rapid absorption of fluid.Furthermore,if the fluid is used up during the surgery without detection,the liquid delivery pump can result in excessive gas entering the patient’s body through exposed blood vessels in the endometrium or myometrium,thereby increasing the risk of venous gas embolism.On the other hand,gravity distention relies on the height difference between the distention fluid and the uterus to provide pressure.The linear flow of the fluid helps maintain the stability of the surgical field.Even if the fluid is exhausted without external intervention,there will be minimal air injected into the uterine cavity.However,during hysteroscopy,as the distention fluid is consumed,the height difference between the distention fluid and uterus gradually decreases,making it impossible to maintain a constant pressure.Therefore,the objective of this study is to develop an automatic non-pump gravity distension device with constant pressure.This device utilizes a program to control mechanical automatic lifting and lowering,ensuring a constant pressure.Furthermore,the device incorporates fluid monitoring functionality.This will provide a foundation for subsequent clinical applications.ObjectiveThis study aims to develop a device that utilizes gravity distention principles to automatically regulate the level of distention fluid,ensuring a constant pressure.Subsequently,the effectiveness and safety of the device will be verified through laboratory and clinical applications.Additionally,the device’s fluid monitoring function will be utilized to analyze the factors influencing liquid absorption during hysteroscopy.The findings will then enable surgeons to implement intervention measures,thereby enhancing the safety of the surgical procedure.Method（1）Device development:（1）Exploration of the descending law of the liquid in the distention liquid bag:Utilizing a non-contact liquid sensor,the initial position of the liquid level is measured and marked.Sequentially measuring and marking the position of the remaining liquid level after releasing every 100 m L of liquid until depletion.This process is repeated three times.Fit the measurement data to identify the most suitable curve and establish the corresponding equation.Incorporate the equation into the software system.（2）Device development:a.Positioning device:Utilize a laser pointer to determine the position of the patient’s uterus（zero point）as the reference for calculating the rise in liquid height.b.Liquid weighing device:Measure the input,residual,and output of the distention liquid to facilitate the calculation of the initial rise in distention liquid level and subsequent level changes based on the remaining liquid amount.c.Software system:Calculate the target height of the distention liquid and issue instructions considering the real-time liquid weight,the set uterine cavity pressure value,and the"zero"position.The system should also incorporate the descending law of the liquid level and calculate the amount and rate of liquid absorption.Additionally,it should trigger a voice alarm when the predefined warning values are reached.d.Lifting structure:Raise the distention liquid to the target height to provide pressure based on the instructions issued by the software.（3）Device validation:Simulate the consumption of distention fluid during hysteroscopy by artificially releasing fluid.Divide the remaining weight of uterine distention fluid into 6000 m L group,4000m L group,and 2000 m L group.Measure the fluid level height once in each group,treating all three groups as one cycle.Repeat this process for three cycles to obtain an average value.Evaluate whether there is a significant difference in distention pressure between the three groups within the range of 80 to 140 mm Hg to verify the device’s ability to maintain constant pressure.（2）Laboratory validation:The research group utilized an automatic non-pump gravity distension device with constant pressure,while the control group utilized a liquid delivery pump.The distention fluid was divided into a stationary state and a flowing state based on whether it was flowing.The differences in the distention pressure provided by the two groups were compared within the range of 80 to 140 mm Hg to validate the effectiveness of the gravity distention device.To simulate the fluid flow state,different models of hysteroscopes were employed,and the opening degree of the water outlet was controlled,resulting in five distinct levels.The fluid leakage progressively increased:Level 1:A disposable intravenous injection needle was installed.Levels 2 and 3:Hysteroscopes with a 4.9mm outer sheath were installed,with the inlet hole fully open and the outlet hole partially or fully open,respectively.Levels 4 and 5:Hysteroscopes with a 5.4mm outer sheath were installed,with the inlet hole fully open and the outlet hole partially or fully open,respectively.（3）Clinical validation:A prospective study was conducted involving200 patients with moderate to severe intrauterine adhesions（IUAs）who underwent treatment at The Third Xiangya Hospital of Central South University from October 2021 to May 2022.The patients were randomly assigned to either the research group or the control group.The effectiveness of the device was evaluated by comparing the stability of the surgical field of view and the clarity of the bilateral uterine horns.Safety assessments of the device included comparing the patient’s surgical duration,the amount and rate of liquid absorption,the degree of postoperative abdominal pain,and indicators such as hemoglobin（Hb）and serum electrolytes.（4）Factor analysis:Clinical data from patients with IUAs,who were included in the clinical trial,were collected for factor analysis.The collected data encompassed various parameters,including the patient’s age,gestation,production,abortion,body mass index（BMI）,course of disease,type of visit（first or return）,degree of adhesion,mean arterial pressure（MAP）,depth and width of uterine cavity,density of endometrial glandular openings,injury of myometrium,the shaking of the surgical field of view,intraoperative cervical leakage,postoperative vaginal bleeding,the duration of surgery and the amount of fluid used.To determine the influencing factors of fluid absorption in hysteroscopic adhesiolysis（HA）,the amount of fluid absorption was considered as the dependent variable.Single or multiple factor linear regression analyses were conducted to explore the impact of each variable on fluid absorption.Result（1）Device development:（1）The law governing the decrease in the liquid level in the distention fluid bag was investigated:Curve fitting was applied on the measurement data of the remaining amount of distention fluid and the height of the liquid level in the distention fluid bag.The cubic model exhibited the highest degree of fitting（R²=1）.The final fitting curve equation obtained is h₁=9×10^-11m³-10^-6m²+6.6×10^-3m+0.4514（h₁is the liquid level height of the distention fluid in its bag,in centimeters,and m is the mass of the distention fluid measured by the input measurement device,in grams）（2）The validation result of the device is that within the range of 80 to 140 mm Hg,there is no statistical difference（P>0.05）in the actual distention pressure of each group.（2）Laboratory validation:There was no statistically significant difference in the distention pressure provided by the two groups under static state（P>0.05）.There was no statistically significant difference in the distention pressure provided by the two distention methods under the five scenarios of flow state（P>0.05）.（3）Clinical validation:A prospective study involving 200 patients with IUAs.However,there were a few data storage format errors in the research group（3 cases）and one case of intraoperative leakage of uterine distention fluid,resulting in significant data errors.In the control group,there were 4 cases of data storage format errors.Consequently,the final statistical analysis was performed on 96 cases in each group.（1）Basic information:The average age of the research group was 32.73±4.78 years old,while the average age of the control group was 33.15±5.32 years old.There were 47 moderate IUAs and 49 severe IUAs patients in the research group,43 moderate IUAs and 53 severe IUAs patients in the control group,There was no statistically significant difference in basic information between the two groups（P>0.05）.（2）Effectiveness:In the research group,there were 6 cases of surgical field shaking,while in the control group,there were 22 cases of surgical field shaking.There was a statistical difference between the two groups（P<0.05）.The research group rated the clarity of the uterine horn as excellent in 94 cases,while the control group rated the surgical field as excellent in 91 cases.There was no statistically significant difference between the two groups（P>0.05）.（3）Safety:The average surgical duration of the research group was 772.82±302.10 seconds,with an average amount of fluid absorption of 244（122,477）m L.The average surgical duration of the control group was 768.50±273.31 seconds,with an average amount of fluid absorption of 252.5（120.25,430.5）m L.There was no statistically significant difference between the two groups（P>0.05）.There was no statistically significant difference in the degree of abdominal pain and changes in it between the research group and the control group at the 0th and 30th minutes after awakening from anesthesia（P>0.05）.There was no statistically significant difference in the values and changes of Hb and electrolytes before and after HA surgery between the two groups（P>0.05）.（4）Influencing factors:The results of single-factor linear regression analysis showed that the influencing factors of the amount of fluid absorption include age,BMI,type of visit,degree of adhesion,depth of uterine cavity,myometrium injury,postoperative vaginal bleeding,surgical duration and the amount of distention fluid used（P<0.05）.The results of multiple-factor linear stepwise regression analysis showed that the influencing factors of the amount of fluid absorption include the amount of distention fluid used,injury of myometrium,cervical leakage,depth of uterine cavity,BMI and postoperative vaginal bleeding.The standardized coefficients for these factors were 0.529,0.214,-0.237,0.166,-0.143 and 0.126,respectively（P<0.05）.ConclusionThis study successfully developed an automatic non-pump gravity distension device with constant pressure,and verified its effectiveness and safety.The amount of fluid absorption during HA is primarily affected by the patient’s BMI,the amount of distention fluid used,injury of myometrium,cervical leakage,depth of uterine cavity and postoperative vaginal bleeding.Specifically,lower BMI,greater amount of distention fluid used,myometrium injury,no cervical leakage of fluid,postoperative vaginal bleeding and deeper uterine cavity are associated with a higher amount of distention fluid absorption.