Ultrasound system to measure esophageal varix pressure: an in vitro validation study

Abstract

. Ultrasound system to measure esophageal varix pressure: an in vitro validation study. Am J Physiol Gastrointest Liver Physiol 288: G914-G919, 2005. First published December 30, 2004; doi:10.1152/ajpgi.00373.2004.-We report our experience with an ultrasound system to measure esophageal varix pressure in an in vitro model. The ultrasound system consists of a 12.5 MHz frequency intraluminal ultrasound probe, a water infusion catheter, and a manometry catheter, all contained within a nondistensible latex bag. Esophagi and external jugular veins were harvested from five pigs. The vein and ultrasound system were placed inside the esophagus. One end of the vein was connected to a water reservoir to modulate its pressure; the other end was connected in two different ways to simulate hydrodynamic and hydrostatic flow conditions. The bag was inflated with water until vein occlusion was discernible on the ultrasound images. The influences of vein pressure, vein cross-sectional area and esophageal elasticity on the ultrasound measurement of vein pressure were assessed. A total of 108 trials were performed at nine different vein pressures. Complete vein occlusion occurred when the bag pressure was slightly greater (1.4 Ϯ 0.7 mmHg) than the vein pressure. For a vein pressure of 25 mmHg, the average occlusion and opening pressures were 27 Ϯ 0.2 and 25.7 Ϯ 0.3 mmHg, respectively (P Ͻ .05) suggesting that the vein opening pressure on the ultrasound images is more accurate than the vein closing pressure. In conclusion, the ultrasound technique can accurately measure intravariceal pressure in vitro. The bag pressure at the point of vein reopening is the best determinant of the vein pressure. portal hypertension; variceal pressure; ultrasonography; noninvasive technique; variceal bleed BLEEDING FROM ESOPHAGEAL VARICES is a major complication of liver cirrhosis and portal hypertension. Approximately onethird of patients with varices will experience an episode of bleeding over a 2-yr period. Mortality from the first bleeding episode ranges from 30 to 50%. The major predictors of bleeding are the hepatic venous pressure gradient (HVPG), severity of underlying liver disease, varix size, and stigmata of variceal bleed (red color sign) (North Italian Endoscopic Club) (6). The least subjective of these parameters is the HVPG. Esophageal varices bleed only when the HVPG is Ն12 mmHg. However, when the HVPG is Ͼ12 mmHg, there is not a direct relationship between the HPVG and bleeding. Therefore, on the basis of the HVPG measurement, it has been difficult to predict which patient will bleed from the varices. Furthermore, the HPVG measurement technique is invasive.Varix wall stress is considered to be the primary determinant of its rupture. In accordance with Laplace's equation for the circumferential wall stress, ϭ (P⅐r)/t, the determinants of the variceal wall stress () are the varix radius (r), varix pressure (P) and varix wall thickness (t) (3-5, 9, 16). The measurement of variceal pressure has been attempted by a number of investigators...

A novel fiber‑optic pressure sensor device for measuring variceal pressure

“…In addition, the reliability of the Varipress in vivo remains controversial, as ideal placement of the gauge on the varix may be difficult and patient-dependent factors may influence variceal pressure measurements. It was estimated that ~25% of patients initially scheduled for variceal pressure measurements must be excluded due to poor contact between the gauge and the varices that result in unstable pressure values, particularly for varices of a small size (4,16,17).…”

Validation of an Endoscopic Fibre-Optic Pressure Sensor for Noninvasive Measurement of Variceal Pressure

“…This noninvasive method was first developed by Rigau et al and continuously improved by others. However, the reliability of the endoscopic gauge in vivo remained to be tested because ideal positioning of the gauge with diameter of 5.5 mm on the varix may be difficult and may result in variable readings, especially for the measurement in small varix [ 3 , 11 , 12 ]. In addition to the diameter of gauge, the measurement of variceal pressure by using the conventional pressure-sensitive gauge was likely to be affected by peristalsis in the esophagus, which would make pressure measurement more difficult [ 11 – 13 ].…”

A study on new method of noninvasive esophageal venous pressure measurement based on the airflow and laser detection technology

“…Therefore, for high-risk population of esophageal variceal bleeding in cirrhotic patients, how to effectively and timely make diagnoses and thus predict the probability of bleeding in advance would be particularly important. Since the 1950s, numerous studies have demonstrated that too high esophageal variceal pressure could directly cause esophageal variceal bleeding [3][4][5]. By means of endoscopy, there are two methods of measuring esophageal variceal pressure at present; specifically, one is to measure the intravenous pressure through variceal puncture and the other is performed non-invasively outside the vein [6].…”