Experimental And Clinical Study Of Esophageal Variceal Pressure Measured By Medical Fiber-optic Pressure Sensor

BackgroundIncreasing variceal pressure has been identified as a key factor leading to esophageal variceal rupture of portal hypertension.Measuring esophageal varix pressure plays important roles in predicting variceal bleeding and evaluation the therapeutic effects of drug treatment.Noninvasive measurements of esophageal varix pressure are including pressure-sensitive capsule,balloon manometry and ultrasound-guided manometry.All techniques assume that varices behave as an elastic structure that the pressure needed to compress a varix equals the pressure inside the varix,which relied on the visual appearance of the varices and,therefore,was subjected to observer bias.These noninvasive methods have not been widely used because of the high devices requirment and complicated procedure.In recent years,according to the development of fiber-optic technique,the pressure of organs and tissues can be measured by fiber-optic pressure sensors which have more advantages than ordinary pressure-sensitive capsule such as high sensitivity,fast responsibility,light weight and high mechanical strength.We have recently developed a medical fiber-optic pressure manometry which can measure the pressure of esophageal variceal non-invasively when put fiber-optic capsule on the surface of varix.In this study,we report the preliminary results of in-vitro and in-vivo testing of medical fiber-optic pressure manometry.Aims1.Develop a new medical fiber-optic pressure manometry;2.Validate the technique of medical fiber-optic pressure manometry in vitro;3.Validate the technique of medical fiber-optic pressure manometry in animal models,compare with the actual pressure which measured by invasive blood pressure monitor;4.Test the clinical reliability and feasibility of this manometry by compared with portal venous pressure gradient(PPG).Material and methods1.The medical fiber-optic pressure manometry system,comprising a fiber-optic pressure capsule,a fiber-optic sensor receiving device,endoscopy imaging system and a computer,records curve of variceal pressure when put fiber-optic capsule on the surface of varix,and calculates variceal pressure by using software.2.In vitro study,put a fiber-optic capsule on the surface of variceal models through the biopsy channel of endoscopy when the artificial variceal pressure measurement.Variceal models have two kinds of diameter(4mm,8mm)which simulate small and middle-large esophageal varix respectively.The artificial varix was filled with water and connected to a glass column to modulate the intraluminal pressure.The medical fiber-optic pressure manometry system was tested blindly by two operators with different intraluminal pressures,ranging from 6 to 40 cm H2 O.3.In the animal study,the medical fiber-optic pressure manometry system was used to measure the pressure of superior mesenteric vein(the pressure equal to portal vein)and inferior vena cava in 10 dogs.The results were compared with the actual pressure which measured by invasive blood pressure monitor.The procedure were tested blindly by two operators to assess the operability of this method.4.The medical fiber-optic pressure manometry system was also used to measure variceal pressure in 81 patients with portal hypertension and esophageal varices.The results were compared with the portal venous pressure gradient(PPG)which evaluated during TIPS,to assess the accuracy of this method.We also campared esophageal variceal pressure with patients presence or absence of ascites,different diameter of varix,and Child-Pugh’s class.Results1.The medical fiber-optic pressure manometry system has been tested with high stability.Variceal pressure measurements were technically satisfactory in vitro,in vivo animal models and in clinical study.2.In vitro study,the measured intraluminal pressure correlated significantly with the actual intraluminal pressure for different diameters(r ≥0.998,P <0.001).The measured intraluminal pressure between two operators has also a significant correlation(r ≥0.998,P <0.001).The diameter of artificial varices and different operators did not affect the measurement of variceal pressure.3.In vivo animal study,the measured superior mesenteric vein pressure by medical fiber-optic pressure manometry system correlated significantly with the actual pressure measured by invasive blood pressure monitor(r = 0.731,P <0.001).The measured superior mesenteric vein pressure between two operators has a significant correlation(r = 0.757,P <0.001).The measured inferior vena cava pressure by medical fiber-optic pressure manometry system correlated significantly with the actual pressure measured by invasive blood pressure monitor(r = 0.862,P <0.001).The measured superior mesenteric vein pressure between two operators has a significant correlation(r = 0.778,P <0.001).The pressure measured by medical fiber-optic pressure manometry system is more accurately than that measured by invasive blood pressure monitor.4.Variceal pressure measurements with medical fiber-optic pressure manometry system were technically successful in 81 portal hypertension patients.No adverse effects related to the measuring procedure and sedation were observed.We noticed that in particular there was no retrosternal pain,variceal bleeding,or uncontrolled coughing during slow inflation of the balloon.The value for mean variceal pressure(22.9±4.0 mm Hg)was lower than that for mean PPG(38.0±6.4 mm Hg,P<0.001).Regression analysis showed a good correlation between variceal pressure measured with medical fiber-optic pressure manometry system and the PPG(r=0.932,P<0.001).We also found the mean variceal pressure of patients who presence of ascites(n=56)was higher than patients who absence of asictes(n=25)(24.56±4.36 mm Hg vs15.74±3.92 mm Hg,P<0.05).The variceal pressure of F3 varix(n=71)was higher than F2 varix(n=10)(23.6±4.8 mm Hg vs 19.5±3.7 mm Hg,P<0.05).Child–Pugh class parameter did not correlate with variceal pressure.The average of variceal pressure in Child–Pugh class A(n=15)was 23.5±3.4 mm Hg,the average of variceal pressure in Child–Pugh class B plus C(n=66)were 22.2±4.1 mm Hg(t=1.09,P=0.28).ConclusionsOur results indicate that the medical fiber-optic pressure manometry system for esophageal varices is feasible and accurate.The level of variceal pressure is a major predictor for esophageal variceal bleeding in portal hypertension patients.This technique is considered a more reliable method for noninvasive measurement of variceal pressure and has a potential application in future clinical settings.