Intraluminal Pressure Measurements Research Articles

About diverticular colon disease

Relevance. Despite many studies devoted to diverticular colon disease, the results of treatment of this pathology cannot be considered satisfactory. This is primarily due to the fact that the pathogenesis of this pathology has not been fully studied, there are conflicting data on the clinical significance of the level of intraluminal pressure in the intestine and the degree of violation of collagen synthesis in patients. To a certain extent, these criteria can be decisive in assessing the prognosis of the course of the disease in order to timely conduct proactive conservative therapy and adequate surgical aid. The purpose of the study. Improving the results of treatment of patients with complicated course of diverticular colon disease. Materials and methods. There were 194 patients with diverticular colon disease under observation. In 86% of cases, diverticula were localized in the left half of the colon, and isolated sigmoid colon diverticulosis was detected in 68.0% of patients, in the right half — in 4.7% of cases, total diverticulosis — in 9.3% of patients. In patients, the leukocyte intoxication index, the body resistance index, the neutrophil reactive response, the determination of connective tissue dysplasia, connective tissue metabolism indicators, and the measurement of intraluminal pressure in the sigmoid colon were calculated. Results. Conservative therapy was effective in 158 patients (81.4%). Surgical treatment was required for 36 patients (18.6%), with perforation of the diverticulum — in 13.4%, with stenosis — in 5.2% of cases. The nature of the operation was determined by the localization of diverticula and the variant of complication. Postoperative mortality was 2.8%. It was found that connective tissue dysplasia is observed in all patients with diverticular disease, mild — in 36.6% of patients, moderate — in 63.4%. When assessing the intraluminal pressure in 46 patients, its increase was found in all variants of the course of diverticular disease. The average intraluminal pressure was 13.5 ± 0.4 mm Hg. The maximum pressure level was detected in patients with uncomplicated course of the disease. With the development of complications, a decrease in intraluminal pressure was noted. A decrease in intraluminal pressure to 12 mm Hg or less was an unfavourable factor and a predisposition to the development of a complicated course of the disease. The following signs had a significant effect on the recurrence of the disease: age (61-68 years), complications, duration of the disease (more than 4 years), the size of the diverticulum mouth (less than 0.6 cm and more than 1.0 cm), leukocyte intoxication index (more than 2.4 conventional units), the maximum number of rows of the muscle plate of the mucosa and muscle membranes (more than 8.3 and 84 respectively). Conclusions. To predict the course of diverticular disease, a comprehensive analysis of the age of patients, the stage of the disease and its duration, the diameter of the diverticular mouth, the sum of alternative signs of trouble, leukocyte intoxication index, the reactive response of neutrophils, the number of rows of myocytes of the muscle plate of the mucosa and muscle membranes is necessary. Their evidentiary value exceeds 70%. The level of intraluminal pressure in the colon can act as a criterion for the complicated course of diverticular disease.

How I do it: direct pressure measurement in moyamoya bypass.

The direct quantitative measurement of donor and recipient pressures in patients with moyamoya vasculopathy (MMV) during superficial temporal artery-middle cerebral artery (STA-MCA) bypass surgery has yet to be reported in academic literature. Using a wireless pressure wire, we describe our approach to measuring seven pressure parameters in MMV patients step-by-step. Direct intraluminal pressure measurement of donor and recipient arteries provides a practical and accurate means to quantify cerebral hemodynamic parameters in MMV patients, enhancing understanding of individualized hemodynamic changes pre- and post-surgery.

243. INTRALUMINAL OXYGEN DELIVERY AT THE SITE OF THE ANASTOMOSIS AFTER A ROBOT ASSISTED MINIMAL INVASIVE ESOPHAGUS RESECTION; A FEASIBILITY STUDY

Abstract Anastomotic leakage (AL) is a severe complication after esophagus resection surgery. It is thought that local ischemia of the gastric conduit is one of the main reasons for the relative high incidence of AL (10–20%). Intraluminal oxygen delivery at the site of the anastomosis might improve the viability of the tissue and therefore reduce the incidence of AL. We present a feasibility study to the intraluminal oxygen delivery after an esophagus resection. Patients undergoing a robot assisted minimal invasive esophagus resection with an intrathoracic anastomosis were included in the study. Intraluminal oxygen was administered via an esophagus manometry catheter. In the control group, consisting of 3 patients without oxygen delivery, only intraluminal pressure measurements were conducted. In the next 10 patients, 1 mL/minute of oxygen was given in the first 5 days after surgery. Primary endpoint was the feasibility of successful placement of the catheter at the right position. In addition, patients were asked to evaluate the comfort of the setup with the use of a daily visual analogue scale. In 2 patients, intraoperative placement of the catheter did not succeed. These patients were replaced by 2 others according to the study protocol. Therefore, in total 15 patients were analyzed. In 4 patients, the catheter was accidently luxated or removed before the end of the study. No catheter related complications were observed. The measured intraluminal pressure stabilized on an average value of 7.6 mm Hg (± 2.1). As expected, the experiences comfort was decreasing over time. See the table 1 below for details on comfort evaluation of the catheter setup. This study shows that it is feasible to administer intraluminal oxygen in the first 5 days after a robot assisted minimal invasive esophagus resection. Future studies are required to prove the effectiveness of intraluminal oxygen delivery and its effect on AL. When the effectiveness study shows promising results, the optimal dosage and period of oxygen delivery will have to be determined.

Intraluminal Monitoring of Micro Vessels. A Surgical Feasibility Study.

Objective: Monitoring of vessel perfusion is of high clinical importance in vascular anastomosis of free flaps. Current sensor systems are based on different principles and show limitations in validity and accuracy. Fiber optic pressure sensors exhibit high accuracy and are small in size. The aim of the present study was to evaluate the surgical feasibility of intraluminal pressure (ILP) measurements with a fiber optic pressure sensor in an animal model.Methods: In a microsurgical setting we sedated 10 Wistar rats with weight adapted phenobarbital, xylazine, and fentanyl. We performed a surgical approach to A. carotis communis and V. jugularis and introduced a 600 μm fiber optic pressure sensor into the vessels followed by measuring the ILP. The sensor was stabilized by the surrounding tissue, and the vessels were closed.Results: In all cases, surgical placement was uneventful. Measurement of intra-venous and intra-arterial pressure was possible and stable over the whole measurement period of an hour.Conclusion: Fiber optic pressure measurement in microvessels is possible and surgically feasible. An application to monitor the perfusion of free flaps seems possible.

Horses are Obligate Nasal Breathers: But does this Obligation Still Apply when a Horses ‘Nasopharyngeal Air Supply’ and with this its ‘Defence through Flight’, is Compromised

It had been suggested that obligate nasal breathing had evolved to enhance a horses ability to detect predator scents whilst grazing. The singular opening of the vomeronasal organ into the nasal cavity had certainly developed in a manner that supported this form of breathing and thence theory. A horses ability to carry feed in its mouth, without this being drawn into the airway during flight, was another theory put forward to explain this obligation. The horse as a species is heavily reliant on flight as a means of defence and thence survival. Any reduction in nasopharyngeal patency would logically compromise a horses ability to maintain acceleration and thence its ability to evade a predator. The likelihood that a horse would elect to supplement a compromised nasal air supply with orally inspired air whilst fleeing a predator, seemed logical. Nasopharyngeal and upper tracheal intraluminal pressure measurements recorded during periods of intermittent dorsal displacement of the soft and experimentally induced palatal instability indicated that air was being acquired orally in these situations. Keywords: Palatal instability, mouth breathing, oropharyngeal seal, palatal instability, dorsal displacement of the soft palate. Read more →

Integrated pressure and temperature sensor with high immunity against external disturbance for flexible endoscope operation

In this study, an integrated pressure and temperature sensor device for a flexible endoscope with long-term stability in in vivo environments was developed and demonstrated. The sensor, which is embedded in the thin wall of the disposable endoscope hood, is intended for use in endoscopic surgery. The device surface is coated with a Cr layer to prevent photoelectronic generation induced by the strong light of the endoscope. The integrated temperature sensor allows compensation for the effect of the temperature drift on a pressure signal. The fabricated device pressure resolution is 0.4 mmHg; the corresponding pressure error is 3.2 mmHg. The packaged device was used in a surgical simulation in an animal experiment. Pressure and temperature monitoring was achieved even in a pH 1 acid solution. The device enables intraluminal pressure and temperature measurements of the stomach, which facilitate the maintenance of internal stomach conditions. The applicability of the sensor was successfully demonstrated in animal experiments.

Mo1884 Inter-Rater and Inter-Device Agreement for the Diagnosis of Primary Esophageal Motility Disorders Based on Chicago Classification Between Solid-State and Water-Perfused HRM System -A Prospective, Randomized, Double Blind, Crossover Study

Background:High ResolutionManometry (HRM) is a new technique for intraluminal esophageal pressure measurement that employs an increased number of pressure sensors spaced closely together. Two systems have now become widely available: the 36 solid-state (SS) pressure transducers system, used to create the new Chicago Classification (CC) for Primary Esophageal Motility Disorders, and the recently introduced 24-channel water perfused (WP) system. Comparative data in terms of inter-device pressure parameters variability and diagnostic accuracy are lacking. Aim: To assess and compare normal values for pressure measurements between the 36-SS and the 24-WP HRM systems. Moreover, diagnostic inter-rater and inter-device agreement in a group of patients with esophageal symptoms were assessed. Methods: In this prospective, randomized, double blind, crossover study, 20 healthy volunteers [HVs; 11M/9F; median age 29 (IQR 26-33)] and 20 patients [11M/9F; 48 (43-55)] with esophageal symptoms (i.e. reflux symptoms, chest-pain or dysphagia) underwent HRM with both 36-SS (Given Imaging, Los Angeles, CA) and 24-WP (EB Neuro, Firenze, Italy) systems, in random order. Normal values from HVs were obtained and compared using non-parametric statistical analysis. Two expert reviewers (RS, ES) performed a blindfolded analysis of the patients tracings. Diagnoses based on CC in patients with esophageal symptoms were formulated. Inter-rater and inter-device agreement for each reviewer were evaluated by means of Cohen's k value. Results: As shown in the Figure, there were significant differences between the 2 HRM systems, mainly regarding the measurements of Lower Esophageal Sphincter (LES) and Upper Esophageal Sphincter (UES) basal pressure (p<0.01 and p=0.02, respectively), wave amplitude at 3 cm above the LES (p<0.01) and wave duration at 3, 7 and 11 cm above the LES (p<0.01, p<0.01 and p=0.01, respectively). Almost, all CC parameters were significantly different between the two HRM systems: Integrated Relaxation Pressure (IRP) (p=0.01), Distal Contractile Integral (DCI) (p=0.02) and Distal Latency (DL) (p<0.01). Diagnostic inter-rater agreement was higher for SS system (k=1) than for WP system (k=0,68). Diagnostic inter-device agreement was moderate for both reviewers (k[RS]= 0.5; k[ES]=0.4).Conclusions:Compared to the SS system, theWP technique underestimated almost all pressure measurements, including the CC parameters. This is likely due to the increased compliance of the WP system at low water perfusion rates, leading to poor interrater diagnosis reproducibility and inter-device agreement. By contrast, the SS system appears high reproducible in terms of inter-rater agreement. Thus, caution about the interpretation and application of CC in all HRM systems is recommended.

Urethral compliance in hypospadias operated by tubularized incised urethral plate (TIP) with and without a dorsal inlay graft: an experimental controlled study

Abnormal uroflowmetries are common after tubularized incised plate urethroplasties (TIP), perhaps due to low compliance. We hypothesized that (1) abnormal uroflowmetries after TIP might be caused by segmental lower compliance; (2) by adding a graft to the raw area in the incised plate (TIPG), compliance might be improved by preventing secondary intention healing of the dorsal incision. A standardized penectomy was performed in 27 adult male rabbits: 9 normal non-operated controls (G1), 6 weeks after TIP (G2: n = 9) or TIPG (G3: n = 9). A standardized isolated segment (including the whole urethroplasty in G1 and G2) was progressively distended with air (1, 2 and 3 ml) in the 3 groups. The respective intraluminal pressures were measured with a tensiometer. Pressure measurements were feasible and reproducible for this model. Mean pressures tended to be higher in the experimental groups (G1: 59.7 mmHg vs. G2: 79.6 mmHg vs. G3: 100.1 mmHg for 1 ml injections; G1: 233.1 mmHg vs. G2: 241 mmHg vs. G3: 308.4 mmHg for 2 ml injections and G1: 457.3 mmHg vs. G2: 429 mmHg vs. G3: 520 mmHg for 3 ml injections) without reaching the statistical significance. In this model, the elasticity of the TIP or TIPG neourethras tended to be reduced when compared to controls. The placement of an inlay graft on the dorsal incised area did not increase the compliance. This model allows the measurement of segmental intraluminal urethral pressures generated by controlled air distension and may be a useful tool to evaluate the experimental urethroplasty models.

An exploration of the control of micturition using a novel in situ arterially perfused rat preparation.

Our goal was to develop and refine a decerebrate arterially perfused rat (DAPR) preparation that allows the complete bladder filling and voiding cycle to be investigated without some of the restrictions inherent with in vivo experimentation [e.g., ease and speed of set up (30 min), control over the extracellular milieu and free of anesthetic agents]. Both spontaneous (naturalistic bladder filling from ureters) and evoked (in response to intravesical infusion) voids were routinely and reproducibly observed which had similar pressure characteristics. The DAPR allows the simultaneous measurement of bladder intra-luminal pressure, external urinary sphincter–electromyogram (EUS–EMG), pelvic afferent nerve activity, pudendal motor activity, and permits excellent visualization of the entire lower urinary tract, during typical rat filling and voiding responses. The voiding responses were modulated or eliminated by interventions at a number of levels including at the afferent terminal fields (intravesical capsaicin sensitization–desensitization), autonomic (ganglion blockade with hexamethonium), and somatic motor (vecuronium block of the EUS) outflow and required intact brainstem/hindbrain-spinal coordination (as demonstrated by sequential hindbrain transections). Both innocuous (e.g., perineal stimulation) and nociceptive (tail/paw pinch) somatic stimuli elicited an increase in EUS–EMG indicating intact sensory feedback loops. Spontaneous non-micturition contractions were observed between fluid infusions at a frequency and amplitude of 1.4 ± 0.9 per minute and 1.4 ± 0.3 mmHg, respectively and their amplitude increased when autonomic control was compromised. In conclusion, the DAPR is a tractable and useful model for the study of neural bladder control showing intact afferent signaling, spinal and hindbrain co-ordination and efferent control over the lower urinary tract end organs and can be extended to study bladder pathologies and trial novel treatments.

Two Independent Networks of Interstitial Cells of Cajal Work Cooperatively with the Enteric Nervous System to Create Colonic Motor Patterns

Normal motility of the colon is critical for quality of life and efforts to normalize abnormal colon function have had limited success. A better understanding of control systems of colonic motility is therefore essential. We report here a hypothesis with supporting experimental data to explain the origin of rhythmic propulsive colonic motor activity induced by general distention. The theory holds that both networks of interstitial cells of Cajal (ICC), those associated with the submuscular plexus (ICC–SMP) and those associated with the myenteric plexus (ICC–MP), orchestrate propagating contractions as pacemaker cells in concert with the enteric nervous system (ENS). ICC–SMP generate an omnipresent slow wave activity that causes propagating but non-propulsive contractions (“rhythmic propagating ripples”) enhancing absorption. The ICC–MP generate stimulus-dependent cyclic depolarizations propagating anally and directing propulsive activity (“rhythmic propulsive motor complexes”). The ENS is not essential for both rhythmic motor patterns since distention and pharmacological means can produce the motor patterns after blocking neural activity, but it supplies the primary stimulus in vivo. Supporting data come from studies on segments of the rat colon, simultaneously measuring motility through spatiotemporal mapping of video recordings, intraluminal pressure, and outflow measurements.

Computerized endoscopic balloon manometry to detect esophageal variceal pressure

Measuring the variceal pressure is important in predicting esophageal variceal bleeding. However, current noninvasive methods of measuring variceal pressure have not gained wide popularity. We have developed a computerized endoscopic balloon manometry (CEBM) system to detect variceal pressure. The aims of the study were to test the in-vitro accuracy of CEBM and to evaluate the clinical reliability and feasibility of this method. The CEBM system, comprising an esophageal variceal manometer and a computer, records variceal pressure and manometry images simultaneously. In the in-vitro study, variceal models were fixed inside an artificial esophagus, into which an endoscope with transparent balloon was inserted for intraluminal pressure measurement. The artificial varix was filled with water and connected to a water column to modulate the intraluminal pressure. This CEBM system was tested blindly in variceal models with different intraluminal pressures. CEBM was also used to measure variceal pressure in 23 patients with liver cirrhosis and esophageal varices, and the results were compared with the hepatic venous pressure gradient (HVPG). In the in-vitro study, the measured intraluminal pressure correlated significantly with the actual intraluminal pressure for different diameters (R > or = 0.993, P < 0.001). Variceal pressure measurements with CEBM were technically successful in 23 patients. Regression analysis showed a good correlation between variceal pressure measured with CEBM and the HVPG (R = 0.858, P < 0.001). Our preliminary results indicate that CEBM is feasible and accurate. CEBM may become a more reliable method for detecting variceal pressure.

American Neurogastroenterology and Motility Society consensus statement on intraluminal measurement of gastrointestinal and colonic motility in clinical practice

Tests of gastric, small intestinal and colonic motor function provide relevant physiological information and are useful for diagnosing and guiding the management of dysmotilities. Intraluminal pressure measurements may include concurrent measurements of transit or intraluminal pH. A consensus statement was developed and based on reports in the literature, experience of the authors, and discussions conducted under the auspices of the American Neurogastroenterology and Motility Society in 2008. The article reviews the indications, methods, performance characteristics, and clinical utility of intraluminal measurements of pressure activity and tone in the stomach, small bowel and colon in humans. Gastric and small bowel motor function can be measured by intraluminal manometry, which may identify patterns suggestive of myopathy, neuropathy, or obstruction. Manometry may be most helpful when it is normal. Combined wireless pressure and pH capsules provide information on the amplitude of contractions as they traverse the stomach and small intestine. In the colon, manometry assesses colonic phasic pressure activity while a barostat assesses tone, compliance, and phasic pressure activity. The utility of colonic pressure measurements by a single sensor in wireless pressure/pH capsules is not established. In children with intractable constipation, colonic phasic pressure measurements can identify patterns suggestive of neuropathy and predict success of antegrade enemas via cecostomy. In adults, these assessments may be used to document severe motor dysfunction (colonic inertia) prior to colectomy. Thus, intraluminal pressure measurements may contribute to the management of patients with disorders of gastrointestinal and colonic motility.

Introductory message from the President of the American Motility Society: intraluminal pressure measurement in the GI tract – when to use it and what to expect

Introductory message from the President of the American Motility Society: intraluminal pressure measurement in the GI tract – when to use it and what to expect

Control of Circumferential Wall Stress and Luminal Shear Stress Within Intact Vascular Segments Perfused Ex Vivo

Proportional, integral, and derivative (PID) controllers have proven to be robust in controlling many applications, and remain the most widely used control system architecture. The purpose of this work was to use this architecture for designing and tuning two PID controllers. The first was used to control the physiologic arterial circumferential wall stress (CWS) and the second to control the physiologic arterial shear stress (SS) imposed on intact vascular segments that were implanted into an ex vivo vascular perfusion system (EVPS). In order to most accurately control the stresses imposed onto vascular segments perfused ex vivo, analytical models were derived to calculate the CWS and SS. The mid-vein-wall CWS was calculated using the classical Lame solution for thick-walled cylinders in combination with the intraluminal pressure and outer diameter measurements. Similarly, the SS was calculated using the Hagen-Poiseuille equation in combination with the flow rate and outer diameter measurements. Performance of each controller was assessed by calculating the root mean square of the error (RMSE) between the desired and measured process variables. The performance experiments were repeated ten times (N=10) and an average RMSE was reported for each controller. RMSE standard deviations were calculated to demonstrate the reproducibility of the results. Sterile methods were utilized for making blood gas and temperature measurements in order to maintain physiologic levels within the EVPS. Physiologic blood gases (pH, pO(2), and pCO(2)) and temperature within the EVPS were very stable and controlled manually. Blood gas and temperature levels were recorded hourly for several (N=9) 24 h perfusion experiments. RMSE values for CWS control (0.427+/-0.027 KPa) indicated that the system was able to generate a physiologic CWS wave form within 0.5% error of the peak desired CWS over each cardiac cycle. RMSE values for SS control (0.005+/-0.0007 dynescm(2)) indicated that the system was able to generate a physiologic SS wave form within 0.3% error of the peak desired SS over each cardiac cycle. Physiologic pH, pO(2), pCO(2), and temperature levels were precisely maintained within the EVPS. The built-in capabilities and overall performance of the EVPS described in this study provide us with a novel tool for measuring molecular responses of intact vascular segments exposed to precisely simulated arterial biomechanical conditions.

Methodology for the formation of functional, cell-based cardiac pressure generation constructs in vitro

We have previously described a model to engineer three-dimensional (3-D) heart muscle in vitro. In the current study, we extend our model of 3-D heart muscle to engineer a functional cell-based cardiac pressure generating construct (CPGC). Tubular constructs were fabricated utilizing a phase separation method with chitosan as the scaffolding material. Primary cardiac cells isolated from rat hearts were plated on the surface of fibrin gels cast in 35 mm tissue culture dishes. CPGCs (N = 8) were formed by anchoring the tubular constructs to the center of the plate with primary cardiac cells seeded in fibrin gels wrapped around the tubular constructs. Intraluminal pressure measurements were evaluated with and without external electrical stimulation and histological evaluation performed. The fibrin gel spontaneously compacted due to the traction force of the cardiac cells. By 14 d after original cell plating, the cardiac cells had completely formed a monolayer around the tubular construct resulting in the formation of a cell-based CPGC. The spontaneous contractility of the CPGC was macroscopically visible and resulted in intraluminal pressure spikes of 0.08 mmHg. Upon electrical stimulation, the CPGCs generated twitch pressures of up to 0.05 mmHg. In addition, the CPGC constructs were electrically paced at frequencies of up to 3 Hz. Histological evaluation showed the presence of a continuous cell monolayer around the surface of the tubular construct. In this study, we describe a novel in vitro method to engineer functional cell-based CPGCs and demonstrate several physiological metrics of functional performance.

Tracheal Traction Effects on Upper Airway Patency in Rabbits: The Role of Tissue Pressure

To investigate the mechanisms via which lung volume related caudal tracheal traction decreases upper airway collapsibility. Acute physiological study. 20 male, supine, anesthetised, tracheostomised, spontaneously breathing, NZ white rabbits fitted with a sealed face mask. N/A. Upper airway extraluminal tissue pressure (ETP) was measured in the lateral (ETPlat) and anterior (ETPant) pharyngeal walls (pressure transducer tipped catheters). Graded traction was applied to the isolated upper airway (n = 17, 0-140 g). Subsequently, inflation and deflation was performed (with and without traction, 48 g, n = 13) with measurement of intraluminal pressure. Upper airway transmural pressure (PTM) was calculated (at closure and reopening) for both ETP sites (PTMlat and PTMant, respectively). A traction force of 144 g decreased ETPlat from 2.6 +/- 0.7 cm H2O (mean +/- SEM) to 2.1 +/- 0.7 cm H2O and ETPant from 1.1 +/- 0.4 cm H2O to 0.8 +/- 0.4 cm H2O (both P < 0.001). Increasing traction decreased closing and reopening pressures by 1.4 +/- 0.2 cm H2O for 48 g of traction (n = 13, P < 0.0001). In addition, 48 g of traction decreased ETPlat (at closure and reopening) by 0.2 +/- 0.05 cm H2O (P < 0.0001), and decreased ETPant by 0.5 +/- 0.1 cm H2O at closing pressure and 0.8 +/- 0.1 cm H2O at reopening (both p < 0.0001). Thus, for 48 g of traction, PTMlat (at closure and reopening) fell by 1.1 +/- 0.2 cm H2O and PTMant (reopening only) fell by 0.9 +/- 0.3 cm H2O (all P < 0.0001). Since tracheal traction decreased PTMlat and PTMant by a greater amount than ETPlat and ETPant, we conclude that the decrease in upper airway collapsibility mediated by lung volume related caudal tracheal traction is partially explained by reductions in ETP.

Function of longitudinal бvs�� circular muscle fibers in esophageal peristalsis, deduced with mathematical modeling

We summarize from previous works the functions of circular vs. longitudinal muscle in esophageal peristaltic bolus transport using a mix of experimental data, the conservation laws of mechanics and mathematical modeling. Whereas circular muscle tone generates radial closure pressure to create a local peristaltic closure wave, longitudinal muscle tone has two functions, one physiological with mechanical implications, and one purely mechanical. Each of these functions independently reduces the tension of individual circular muscle fibers to maintain closure as a consequence of shortening of longitudinal muscle locally coordinated with increasing circular muscle tone. The physiological function is deduced by combining basic laws of mechanics with concurrent measurements of intraluminal pressure from manometry, and changes in cross sectional muscle area from endoluminal ultrasound from which local longitudinal shortening (LLS) can be accurately obtained. The purely mechanical function of LLS was discovered from mathematical modeling of peristaltic esophageal transport with the axial wall motion generated by LLS. Physiologically, LLS concentrates circular muscle fibers where closure pressure is highest. However, the mechanical function of LLS is to reduce the level of pressure required to maintain closure. The combined physiological and mechanical consequences of LLS are to reduce circular muscle fiber tension and power by as much as 1/10 what would be required for peristalsis without the longitudinal muscle layer, a tremendous benefit that may explain the existence of longitudinal muscle fiber in the gut. We also review what is understood of the role of longitudinal muscle in esophageal emptying, reflux and pathology.

A quantitative approach to recording peristaltic activity from segments of rat small intestine in vivo

We have developed methods that allow correlation of propulsive reflexes of the intestine with measurements of intraluminal pressure, fluid movement and spatio-temporal maps of intestinal wall movements for the first time in vivo. A segment of jejunum was cannulated and set up in a Trendelenburg recording system while remaining connected to the vascular and nerve supply of the anaesthetized rat. The resting intraluminal pressure in intact intestine was 2-4 mmHg. Hydrostatic pressures of 2, 4, 8 and 16 mmHg were imposed. At a baseline pressure of 4 mmHg, propulsive waves generated pressures of 9 +/- 1 mmHg, that progressed oral to anal at 2-5 mm s(-1). Individual propulsive waves propelled 0.8 +/- 0.4 mL of fluid. The frequency of propulsive waves increased with pressure, but peristaltic efficiency (mL per contraction) decreased with pressure increase between 4 and 16 mmHg. Atropine, as a bolus, transiently blocked peristalsis, but caused maintained block when infused. Hexamethonium blocked propulsive contractions. Inhibition of nitrergic transmission converted regular peristalsis to non-propulsive contractions. These studies demonstrate the utility of an adapted Trendelenburg method for quantitative investigation of motility and pharmacology of enteric reflexes in vivo.

Endosonographic Doppler-Guided Manometry of Esophageal Varices: Experimental Validation and Clinical Feasibility

The risk of variceal bleeding cannot be accurately predicted using endoscopy alone. Although variceal pressure has been demonstrated to be a major determinant for the rupture of esophageal varices, direct determination by needle puncture is unsuitable for routine clinical use. Due to their operator-dependency, current noninvasive endoscopic methods for determination of variceal pressure have not gained wide acceptance. We have developed a new method of measuring variceal pressure, using endoscopic power Doppler imaging to monitor the manometry of esophageal varices. The aims of this study were to test in vitro the accuracy of Doppler-guided manometry and to assess the clinical feasibility of this method. Experimental validation of this technique was performed using an in vitro model of artificial varices of different sizes. A linear-array endosonography (EUS) probe with power Doppler capability was used to assess flow in the varices and a balloon for manometry of esophageal varices was attached to the tip of the probe. Pressure readings were made at the time of disappearance of the Doppler signal during variceal compression by the balloon. Linear regression analysis was used to compare the results of Doppler-guided and direct intraluminal pressure measurement in the artificial varices. Variceal pressure was then measured with this technique in 28 patients with portal hypertension and esophageal varices without previous bleeding, and the results were compared with portal pressure assessed according to the hepatic vein pressure gradient (HVPG). In vitro studies demonstrated a good correlation between the pressure measured with Doppler monitoring and the actual intravariceal pressure (r > or = 0.922; P < 0.001). The determination of variceal pressure with this method was technically successful in 26/28 patients (93 %). The intraoperator variance was 9.3 +/- 8.6 %. Overall, the mean variceal pressure was significantly lower than the mean HVPG (21.2 +/- 5.3 mmHg vs. 24.3 +/- 7.8 mmHg; P < 0.01). Variceal pressure and portal pressure (as assessed by the HVPG) correlated significantly (r = 0.64; P < 0.001). Our preliminary results indicate that EUS Doppler-guided manometry of esophageal varices is feasible and accurate. This technique may become a more reliable method for noninvasive measurement of variceal pressure and warrants further investigation.

Pattern of upper airway obstruction during sleep before and after uvulopalatopharyngoplasty in patients with obstructive sleep apnea

Objective: To investigate the pre-and postoperative pattern of upper airway obstruction in obstructive sleep apnea (OSA) patients treated by uvulopalatopharyngoplasty (UPPP). Background: The response rate to UPPP in unselected OSA patients is generally about 50%. Methods: Intraluminal pressure measurements during sleep were employed to analyze the pattern of upper airway obstruction before and after surgery. Results: Ten patients with mild to moderate OSA (respiratory disturbance index 19.7 (16.9–27.5) events/hr underwent a full night polysomnography before and 114 (6 1–138) days after UPPP. UPPP resulted in a significant improvement in subjective snoring and daytime sleepiness, but did not significantly alter the severity of sleep-disordered breathing. Preoperatively, the major site of obstruction was located at the oropharynx in nine patients, seven of them had additional minor obstruction sites outside the oropharynx. Complete relief of upper airway obstruction was only observed in those two patients with collapse confined to the oropharynx. Conclusions: In unselected OSA patients, UPPP improved subjective snoring and daytime sleepiness but did not result in a significant improvement in RDI or sleep architecture. Our results emphasize the need for a pre-operative investigation of the upper airway during sleep to select patients with collapse confined to the oropharynx.