Intraluminal ultrasonic probe for volumetric monitoring of liquid gastroesophageal reflux

Methods for volumetric monitoring of liquid gastroesophageal reflux (GER) are still lacking. The aim of this study was to develop an automated intraluminal measurement technique which allows ambulatory volumetric quantification of liquid GER utilizing a minimum-cost intraluminal ultrasonic probe. This probe consists of two 2 MHz ultrasonic crystals longitudinally assembled along a multi-channel intraluminal impedance (MII) catheter. The proposed probe was initially tested with tubular phantoms of different diameters. Measurements of the cross-sectional areas of the phantoms showed high correlation with the actual areas (R(2)?= 0.99). Subsequently, two in-vivo human tests were performed. For each human test the catheter assembly was inserted transnasally and the ultrasonic probe was placed in the area of the lower esophageal sphincter. Multiple liquid swallows of different volumes were invoked using electrolyte drinks. Sectional luminal volume (SLV) in the esophagus between the two ultrasonic crystals was obtained. Results of the swallows demonstrated that measured SLVs correlated with the actual swallowed liquid volume. The ultrasonic probe was combined with a MII catheter to discriminate between antegrade and retrograde bolus transit. Increases of SLVs during liquid GER episodes could be utilized to evaluate GER volume in the vicinity of the ultrasonic probe.     

Movement of the Feline Esophagus Associated with Respiration and Peristalsis. AN EVALUATION USING TANTALUM MARKERS

The outer, lateral esophageal walls in the distal half of the esophagus in each of five cats were labeled with small tantalum wires. About 8 wk later, esophageal motion associated with respiration and peristalsis, induced by injecting barium boli (5 ml each) into the proximal esophagus, was recorded on cine and serial biplane roentgenograms while recording intraluminal esophageal pressures simultaneously by manometry. Esophageal motion was also evaluated without a manometric tube in place. The coordinates for each marker were digitized and a computer was used to plot marker position against time. During respiration, the markers passively made a shallow, 2-10 mm excursion on the longitudinal esophageal axis. This movement was synchronous with thoracic and diaphragmatic movement and changes in intraluminal esophageal pressure. Immediately after the onset of peristalsis, the markers made a pronounced oral movement of 10 mm or more above their mean respiratory position, as if to engulf the bolus. Markers in opposing esophageal walls approximated one another and commenced an aboral movement as the bolus tail, which was essentially co-incident with onset of the manometric pressure complex, passed the marker sites. The markers returned to their respective rest positions essentially coincident with passage of the pressure complex peak and then moved below their respective rest positions. The aboral excursion occurred predominantly after the bolus had emptied into the stomach. The magnitude and duration of oral excursion was significantly greater for the distal than for the more proximal markers; conversely, the magnitude and duration of aboral excursion was greater for the proximal than for the more distal markers. During the peristaltic sequence, the labeled portion of the esophagus shortened from 26 to 46% of its resting length. No evidence of esophageal torque was shown. These findings suggest that both the longitudinal and circular esophageal musculature play an active and important role during peristaltic transport of a bolus through the esophagus.     

Comparison of investigation modalities for evaluation of esophageal peristaltic function

We reviewed the recent literature concerning investigations of esophageal peristaltic function. The gold standard for the assessment of esophageal peristaltic function is manometry with pH monitoring. Even with this investigation modality, however, we are in fact doing no more than estimating esophageal peristaltic function from the manometry and pH results. With esophageal fluoroscopy and scintigraphy, where we observe esophageal motility, there are problems with radiation exposure and handling of radioactive agents that make widespread use difficult. In recent years, the development of multichannel intraluminal impedance (MII) manometry has allowed simultaneous measurement of intraesophageal pressure and assessment of esophageal peristalsis. Using MII it is also possible to distinguish whether gas or liquid is passing down the esophagus. When manometry is performed in conjunction with transnasal esophagogastroduodenoscopy, with this unique combination it is possible to measure the intraesophageal pressure while actually observing the swallowing motion at the same time. Assessment of esophageal peristaltic function is now moving from simple measurement of intraesophageal pressure to simultaneous impedance manometry and endoscopic observation of esophageal peristalsis itself.     

Esophageal function testing: role of combined multichannel intraluminal impedance and manometry

Combined multichannel intraluminal impedance and manometry (MII-EM) is a relatively new technique that allows simultaneous measurement of intraesophageal pressures and bolus transit. Combined MII-EM has the ability to identify what percentage of manometric normal/peristaltic, ineffective, and simultaneous swallows have complete or incomplete bolus transit. Predictors of normal bolus transit in patients with ineffective esophageal motility are the distal esophageal amplitude, the number of sites with low amplitudes, and the overall number of manometric ineffective contractions. Outcome studies are necessary to evaluate whether combined MII-EM is superior to traditional manometry in evaluating patients with nonobstructive dysphagia and in identifying patients at risk for developing dysphagia after antireflux surgery.     

Analysis of intraluminal impedance measurements

Intraluminal impedance is an emerging technique to monitor the esophagus so that the occurrence of gastroesophageal reflux episodes can be observed. The impedance traces of the esophagus have wide variations which correspond to the occurrence of activities such as swallow or reflux that cause the impedance to change. This paper presents a technique to detect and classify reflux episodes from intraluminal impedance. Evaluation of the technique based on 660 h of combined data from 30 patients showed that the proposed methodology can detect episodes in the esophagus to a sensitivity of 89% with positive predictivity of 83%.     

The Esophageal Propulsive Force: Esophageal Response to Acute Obstruction

The response of the normal human esophagus to an obstructing intraluminal bolus was investigated and compared to the response evoked by transient intraluminal distention. A balloon, immobilized within the esophagus by external attachment to a force transducer, was inflated with from 3 to 25 ml of air for from 3 to 210 sec. Pressure phenomena occurring in the esophagus were simultaneously recorded from the body of the esophagus above and below the balloon.Transient distention (5 sec or less) with small volumes (5 ml or less) often evoked a secondary peristaltic wave in the esophagus distal to the balloon, but infrequently resulted in the registration of any force exerted upon the balloon to drive it downward. Conversely, distentions of longer duration and with greater volume elicited an esophageal propulsive force exerted upon the balloon oriented to propel it aborally, and much less often evoked a propagated wave of secondary peristalsis. The propulsive force, obviously resulting from esophageal muscular contraction, occurred promptly, and once initiated, was sustained until deflation of the balloon. It varied widely in magnitude, from 4 to 200 g, and was associated with no motor phenomena recorded from the body of the esophagus proximal or distal to the balloon which could account for its presence, onset, magnitude, or duration. The force was inhibited by deglutition, but arrival of the primary peristaltic wave at the bolus resulted in augmentation of the force. When the obstructing balloon was freed from its attachment, the persistent, stationary force was converted to a propagated one that propelled the balloon before it. It the balloon was arrested before entering the stomach, the moving contraction was also arrested and the persistent propulsive force acting upon the balloon was maintained. The velocity of the moving contraction wave was determined in great part by the resistance offered by the bolus. Unrestrained, the balloon was propelled aborally at 4-8 cm/sec by the esophageal propulsive force; when restrained by 50 g, the rate of passage was reduced to 0.2-0.8 cm/sec.The esophageal response to intraluminal distention is thus not limited to the uninterrupted wave of secondary peristalsis but is versatile and is determined by the nature of the distending bolus. Transient distention by a mobile or collapsible bolus elicits the propagated secondary peristaltic wave.     

Effect of esophagus status and catheter configuration on multiple intraluminal impedance measurements

Multiple intraluminal impedance measurement is used to investigate the esophagus condition. This procedure provides information about the esophagus status, reflux occurrence and clearance mechanism. This paper presents finite-element approximation of the forward problem of the catheter inside the esophagus, relating the real data obtained from multiple intraluminal impedance to the solution obtained from the finite-element approximation. Investigation of the effect of the esophagus status on the impedance, and the correlation between various factors that affect the impedance are presented. The results of this paper provide theoretical bases for relating the esophagus condition to the impedance waveforms.     

Anatomy and physiology of feeding and swallowing: normal and abnormal

Eating and swallowing are complex behaviors involving volitional and reflexive activities of more than 30 nerves and muscles. They have two crucial biologic features: food passage from the oral cavity to stomach and airway protection. The swallowing process is commonly divided into oral, pharyngeal, and esophageal stages, according to the location of the bolus. The movement of the food in the oral cavity and to the oropharynx differs depending on the type of food (eating solid food versus drinking liquid). Dysphagia can result from a wide variety of functional or structural deficits of the oral cavity, pharynx, larynx, or esophagus. The goal of dysphagia rehabilitation is to identify and treat abnormalities of feeding and swallowing while maintaining safe and efficient alimentation and hydration.     

Evaluation of the esophagus with a marshmallow bolus: Clarifying the cause of dysphagia

We reviewed the radiographic examinations of the esophagus and medical records in 117 patients (55 women and 62 men; mean age, 52 years) in which a marshmallow bolus was also given. A one-third to one-half piece of a standard marshmallow was used with a mean size of 23 mm (±4.5 mm SD) measured in vivo. In 62 patients with no intrinsic structural narrowing of the esophagus, impaction occurred in only seven (11%). Four of these patients had an esophageal motility disorder, and three had a previous Nissen fundoplication. The remaining 55 patients had lower esophageal mucosal rings (47) or peptic strictures (8). Marshmallow impaction was seen in 27 of 47 rings (57%) and was inversely related to ring size, and in six of eight strictures (75%). Also, impaction was related to the ratio of bolus size to ring caliber, and invariably occurred when this ratio was greater than 1.5. Dysphagia was the presenting complaint in 76 (65%) patients, but was found equally in those without intrinsic narrowing and in those with ring or stricture. However, dysphagia was reproduced by the marshmallow bolus only in patients with esophageal narrowing or abnormal motility.     

Catheter-based pH monitoring: use in evaluation of gastroesophageal reflux disease symptoms (on and off therapy)

Tube-based ambulatory pH testing has rapidly evolved in the past 3 decades to become the standard by which other diagnostic approaches to gastroesophageal reflux disease are judged. Acid exposure 5 cm above the manometrically determined lower esophageal sphincter is the standard for documentation of pathologic acid exposure of the distal esophagus. Proximal esophageal or hypopharyngeal monitoring is an evolving technique that may shed light on patients with supraesophageal symptoms. The ability to simultaneously monitor esophageal and gastric acidity (usually in patients with persistent symptoms despite therapy) is another advantage of this technique. Whether the new system that allows simultaneous pH and impedance monitoring and the system that uses an implantable tubeless monitoring capsule will supplant this older but well-established technology remains to be determined.     

Endoscopic and histologic diagnosis of Barrett esophagus

Endoscopy plays an important role in the identification, diagnosis, and treatment of Barrett esophagus. Short-segment (<2-3 cm) and traditional long-segment (>2-3 cm) Barrett esophagus are distinguished solely on the length of metaplastic tissue above the esophagogastric junction. The histologic hallmark of intestinal metaplasia is required to confirm diagnosis. Biopsy specimens obtained from tissue of presumed Barrett esophagus or an irregular Z line confirm metaplastic glandular mucosa and permit evaluation of dysplastic or neoplastic changes. In the appropriate clinical setting, the use of adjunctive diagnostic techniques may facilitate the diagnosis of Barrett esophagus and sequelae such as dysplasia. Chromoendoscopy with high-resolution or magnified endoscopy is simple, safe, and desirable for surveillance but requires additional procedural time. The use of light-induced fluorescence endoscopy and light-scattering spectroscopy (i.e., optical biopsy) is appealing for the diagnosis and characterization of suspicious lesions. Adjunctive endoscopic techniques and adherence to a protocol for performing biopsies facilitate the early detection and subsequent surveillance of Barrett esophagus.     

Imaging of conductivity changes and electrode movement in EIT

Electrical impedance tomography (EIT) attempts to reconstruct the internal impedance distribution in a medium from electrical measurements at electrodes on the medium surface. One key difficulty with EIT measurements is due to the position uncertainty of the electrodes, especially for medical applications, in which the body surface moves during breathing and posture change. In this paper, we develop a new approach which directly reconstructs both electrode movements and internal conductivity changes for difference EIT. The reconstruction problem is formulated in terms of a regularized inverse, using an augmented Jacobian, sensitive to impedance change and electrode movement. A reconstruction prior term is computed to impose a smoothness constraint on both the spatial distribution of impedance change and electrode movement. A one-step regularized imaging algorithm is then implemented based on the augmented Jacobian and smoothness constraint. Images were reconstructed using the algorithm of this paper with data from simulated 2D and 3D conductivity changes and electrode movements, and from saline phantom measurements. Results showed good reconstruction of the actual electrode movements, as well as a dramatic reduction in image artefacts compared to images from the standard algorithm, which did not account for electrode movement.     

Imaging pathologic pulmonary air and fluid accumulation by functional and absolute EIT

The increasing use of EIT in clinical research on severely ill lung patients requires a clarification of the influence of pathologic impedance distributions on the validity of the resulting tomograms. Significant accumulation of low-conducting air (e.g. pneumothorax or emphysema) or well-conducting liquid (e.g. haematothorax or atelectases) may conflict with treating the imaging problem as purely linear. First, we investigated the influence of stepwise inflation and deflation by up to 300 ml of air and 300 ml of Ringer solution into the pleural space of five pigs on the resulting tomograms during ventilation at constant tidal volume. Series of EIT images representing relative impedance changes were generated on the basis of a modified Sheffield back projection algorithm and ventilation distribution was displayed as functional (f-EIT) tomograms. In addition, a modified simultaneous iterative reconstruction technique (SIRT) was applied to quantify the resistivity distribution on an absolute level scaled in Omega m (a-EIT). Second, we applied these two EIT techniques on four intensive care patients with inhomogeneous air and fluid distribution and compared the EIT results to computed tomography (CT) and to a reference set of intrathoracic resistivity data of 20 healthy volunteers calculated by SIRT. The results of the animal model show that f-EIT based on back projection is not disturbed by the artificial pneumo- or haematothorax. Application of SIRT allows reliable discrimination and detection of the location and amplitude of pneumo- or haematothorax. These results were supported by the good agreement between the electrical impedance tomograms and CT scans on patients and by the significant differences of regional resistivity data between patients and healthy volunteers.     

Movement artefact rejection in impedance pneumography using six strategically placed electrodes

In this paper, we have proposed a technique for reducing movement artefacts in impedance pneumography by placing six electrodes at appropriate locations and suitably combining the measurements obtained. The strategy for electrode placement was based on the observation that the electrodes appeared to slide over the rib cage along with the skin, during movement. A volume conductor model of the thoracic cavity was developed and movement artefacts were simulated by shifting the electrodes to a different location on the surface. The impedance changes due to movement in one of the measurements of a 'symmetrical pair' were 180 degrees out of phase with respect to those observed in the other measurement of that pair. However, the impedance changes due to breathing were in phase in both these measurements. Thus, it was possible to reduce movement artefacts by taking a mean of these measurements without affecting the breathing related changes. The six electrodes could be configured into two such symmetrical pairs. The same observation was made in experimental data recorded from human subjects. This indicated that movement artefacts were caused by sliding of electrodes along with the skin and could be reduced by using the six-electrode configuration.     

Foreign bodies

The spectrum of gastrointestinal (GI) foreign bodies includes food bolus impaction in the esophagus, nonfood objects that are swallowed, and various objects that may be inserted into the rectum. The risk depends upon the type of object and its location. Fortunately, 80% to 90% of ingested foreign bodies will pass without intervention. Objects with sharp edges or pointed tips have the highest risk of complications, up to 35%. All objects impacted in the esophagus require urgent or emergent treatment. Rectal foreign bodies are usually removable transanally, although general anesthesia and operative intervention sometimes are required.     

Electrical impedance tomography in extremely prematurely born infants and during high frequency oscillatory ventilation analyzed in the frequency domain

Functional electrical impedance tomography (EIT) measures relative impedance change that occurs in the chest during a distinct observation period and an EIT image describing regional relative impedance change is generated. Analysis of such an EIT image may be erroneous because it is based on an impedance signal that has several components. Most of the change in relative impedance in the chest is caused by air movement but other physiological events such as cardiac activity change in end expiratory level or pressure swings originating from a ventilator circuit can influence the impedance signal. We obtained EIT images and signals in spontaneously breathing healthy adults, in extremely prematurely born infants on continuous positive airway pressure and in ventilated sheep on conventional mechanical or high frequency oscillatory ventilation (HFOV). Data were analyzed in the frequency domain and results presented after band pass filtering within the frequency range of the physiological event of interest. Band pass filtering of EIT data is necessary in premature infants and on HFOV to differentiate and eliminate relative impedance changes caused by physiological events other than the one of interest.     

Optimum electrode configuration for detection of leg movement using bio-impedance

Impedances and joint angles were simultaneously measured during ankle and knee movements. The correlation coefficients of the joint angle and the impedance change from human leg movement were obtained using an electro-goniometer and a four-channel impedance measurement system. Because the impedance changes resulting from ankle and knee movements depended heavily on the electrode placement, we determined the optimum electrode configurations for those movements by searching for high correlation coefficients, large impedance changes and minimum interferences in ten subjects (age: 20+/-4). Our optimum electrode configurations showed strong relationships between the ankle joint angle and lower leg impedance (correlation coefficient=-0.91+/-0.06) and between the knee joint angle and knee impedance (correlation coefficient=0.94+/-0.04). The reproducibilities of the impedance changes of five subjects due to the ankle and knee were 6.3+/-1.9% and 5.1+/-1.7% for the optimum electrode pairs, respectively. We propose that this optimum electrode configuration would be useful for future studies involving the convenient measurement of leg movements by the impedance method.     

5-Aminolevulinic acid-induced protoporphyrin IX for the detection of gastrointestinal dysplasia

The detection of gastrointestinal dysplasia is an unresolved problem. Fluorescence detection of these premalignancies after exogenous application of 5-aminolevulinic acid, which is converted to protoporphyrin IX and accumulates selectively in tumors, is an interesting approach. Illumination with light of appropriate wavelength allows the discrimination and detection of gastrointestinal neoplasia either by spectroscopy or fluorescence endoscopy because of a typical red fluorescence of protoporphyrin IX. Surveillance of patients with Barrett's esophagus and ulcerative colitis might benefit from this new technique.     

Dedicated multi-detector CT of the esophagus: spectrum of diseases

Multi-detector computed tomography (CT) offers new opportunities in the imaging of the gastrointestinal tract. Its ability to cover a large volume in a very short scan time, and in a single breath hold with thin collimation and isotropic voxels, allows the imaging of the entire esophagus with high-quality multiplanar reformation and 3D reconstruction. Proper distention of the esophagus and stomach (by oral administration of effervescent granules and water) and optimally timed administration of intravenous contrast material are required to detect and characterize disease. In contrast to endoscopy and double-contrast studies of the upper GI tract, CT provides information about both the esophageal wall and the extramural extent of disease. Preoperative staging of esophageal carcinoma appears to be the main indication for MDCT. In addition, MDCT allows detection of other esophageal malignancies, such as lymphoma and benign esophageal tumors, such as leiomyma. A diagnosis of rupture or fistula of the esophagus can be firmly established using MDCT. Furthermore, miscellaneous esophageal conditions, such as achalasia, esophagitis, diverticula, and varices, are incidental findings and can also be visualized with hydro-multi-detector CT. Multi-detector CT is a valuable tool for the evaluation of esophageal wall disease and serves as an adjunct to endoscopy.     

Bolus effective dose of ketamine for preventing withdrawal movement on injection of rocuronium in paediatric patients

The bolus effective dose of ketamine required to prevent withdrawal movement on injection of rocuronium was determined in 27 paediatric patients undergoing elective surgery. A predetermined dose of ketamine was given intravenously on arrival in the operating room and anaesthesia (2.5% thiopental, 5 mg/kg) was administered 1 min later. After loss of consciousness, 1% rocuronium at 0.6 mg/kg was injected over 5 s and the presence or absence of withdrawal movement recorded. The effective dose of ketamine was determined using a modified Dixon up-and-down method with a step size of 0.1 mg/kg, successful prevention of withdrawal movement being defined as no response or movement at the wrist only. The bolus effective dose of ketamine for preventing withdrawal movement after injection of rocuronium following thiopental anaesthesia in 50% of paediatric patients (ED(50)) was 0.21 mg/kg according to the modified Dixon up-and-down method. Probit analysis indicated an ED(50) of 0.18 mg/kg and an ED(95) of 0.33 mg/kg. The latter was the most satisfactory dose in the clinical setting.