Baseline Impedance Values Research Articles

Oesophageal baseline impedance values are decreased in patients with eosinophilic oesophagitis.

Gastro-oesophageal reflux has been suggested to play a role in eosinophilic oesophagitis (EoO). Oesophageal acid exposure decreases baseline intraluminal impedance, a marker of mucosal integrity, in patients with gastro-oesophageal reflux disease (GORD). The aim of this study was to assess oesophageal baseline impedance levels in EoO patients and to investigate their relationship with oesophageal acid exposure. Ambulatory 24-h pH-impedance monitoring was performed in 11 EoO patients and in 11 healthy controls with matched oesophageal acid exposure. We assessed baseline impedance levels in the distal, mid-, and proximal oesophageal impedance channels. BASELINE IMPEDANCE LEVELS IN EOO PATIENTS WERE MARKEDLY LOWER COMPARED TO CONTROLS IN THE DISTAL OESOPHAGUS (MEDIAN (INTERQUARTILE RANGE): 988 (757-1978) vs. 2259 (1767-2896) Ω, p = 0.015), mid-oesophagus (1420 (836-2164) vs. 2614 (2374-3879) Ω, p = 0.003), and proximal oesophagus (1856 (1006-2625) vs. 2868 (2397-3439) Ω, p = 0.005). Whereas baseline impedance decreased from proximal to distal in healthy subjects (p = 0.037), no such gradient was seen in EoO patients (p = 0.123). Throughout the oesophagus, baseline impedance values are decreased in EoO patients, indicating impaired mucosal integrity. Our findings suggest that factors other than acid reflux are the cause of low baseline impedance in EoO.

Mo2107 Vagal Activation and Changes in Peptidergic Neurotransmission With Vasoactive Intestinal Polypeptide and Substance P During Postoperative Ileus in Rat

Introduction: Simultaneous manometry and intraluminal ultrasound imaging studies show that similar to contraction wave, distension wave traversing ahead of contraction wave is also peristaltic. Cross sectional area (CSA) of the esophagus is one of the several variables that determine intraluminal esophageal impedance value. Aim: We recorded simultaneous intraluminal US images, impedance and high resolutionmanometry to determine the relationship between esophageal CSA and intraluminal esophageal impedance values. Studies were conducted in 15 normal healthy subjects. Impedance and manometry were measured along the whole length of the esophagus (Sierra Scientific) and US images were recorded at 2 and 12 cm above the LES. Swallow induced primary peristalsis was recorded using 5 ml bolus of 0.5 N saline. Impedance data were exported to Excel and analyzed for the baseline and lowest impedance value at each level. Cross sectional area of the esophagus at 4 and 14 cm of the esophagus were measured from the US images. Results: Impedance recordings show that following a swallow, the onset of drop in impedance as well as nadir impedance traverses the esophagus in a sequential fashion in front of the contraction wave (figure, left panel). There is strong linear relationship between the location and nadir impedance value such that the lowest impedance values are located just above the LES, with a difference of approximately 100 ohms every 1 cm along the length of the esophagus (right panel). Atropine injected intravenously (10 μgm/kg) abolished esophageal contractions, reduced baseline esophageal impedance and abolished sequential progression of nadir impedance along the esophagus). US image analysis shows that peak distension corresponds with nadir impedance value. Similar to nadir impedance, peak distension recorded by US imaging traverses the esophagus in a peristaltic fashion. US images show greater esophageal distension at 4 cm compared to 14 cm above the LES, cross sectional area of 1400 versus 600 mm2 respectively. Conclusion: These data prove: 1) intraluminal distension and contraction wave during peristalsis are tightly linked and 2) intraluminal impedance recording is a relatively simple technique to record luminal distension of the esophagus.

Mo2106 Peristaltic Distension of the Esophagus: Detected by Multiple Intraluminal Impedance Measurements

Introduction: Simultaneous manometry and intraluminal ultrasound imaging studies show that similar to contraction wave, distension wave traversing ahead of contraction wave is also peristaltic. Cross sectional area (CSA) of the esophagus is one of the several variables that determine intraluminal esophageal impedance value. Aim: We recorded simultaneous intraluminal US images, impedance and high resolutionmanometry to determine the relationship between esophageal CSA and intraluminal esophageal impedance values. Studies were conducted in 15 normal healthy subjects. Impedance and manometry were measured along the whole length of the esophagus (Sierra Scientific) and US images were recorded at 2 and 12 cm above the LES. Swallow induced primary peristalsis was recorded using 5 ml bolus of 0.5 N saline. Impedance data were exported to Excel and analyzed for the baseline and lowest impedance value at each level. Cross sectional area of the esophagus at 4 and 14 cm of the esophagus were measured from the US images. Results: Impedance recordings show that following a swallow, the onset of drop in impedance as well as nadir impedance traverses the esophagus in a sequential fashion in front of the contraction wave (figure, left panel). There is strong linear relationship between the location and nadir impedance value such that the lowest impedance values are located just above the LES, with a difference of approximately 100 ohms every 1 cm along the length of the esophagus (right panel). Atropine injected intravenously (10 μgm/kg) abolished esophageal contractions, reduced baseline esophageal impedance and abolished sequential progression of nadir impedance along the esophagus). US image analysis shows that peak distension corresponds with nadir impedance value. Similar to nadir impedance, peak distension recorded by US imaging traverses the esophagus in a peristaltic fashion. US images show greater esophageal distension at 4 cm compared to 14 cm above the LES, cross sectional area of 1400 versus 600 mm2 respectively. Conclusion: These data prove: 1) intraluminal distension and contraction wave during peristalsis are tightly linked and 2) intraluminal impedance recording is a relatively simple technique to record luminal distension of the esophagus.

Tu1100 Endoscopic Surveillance for Barrett's Esophagus: A Population-Based Study of Surveillance Practice and Outcomes

Introduction: In patients with Barrett's esophagus (BE) low distal esophageal impedance baseline levels are found. It is unknown whether these low impedance baselines are caused by an intrinsically low impedance of the cylindrical epithelium or by excessive reflux. With radiofrequency ablation (RFA) it is possible to eradicate all Barrett's epithelium. After successful RFA the cylindrical epithelium is conversed into normal squamous epithelium. As a result, decreased esophageal impedance baseline levels in BE might normalize after RFA. In addition, little is known about esophageal motility after RFA treatment. The aim of the present study is to evaluate the effect of RFA on esophageal motility and esophageal baseline impedance in patients with BE. Methods: In 10 patients conventional esophageal manometry and 24-h pH-impedance measurements were performed before and after RFA. Number and type of reflux episodes were assessed and baseline impedance values were measured in all recording segments. In another 5 patients high-resolution manometry (HRM) was performed before and after RFA. Results: Complete regression of all Barrett's epithelium was achieved in all 15 BE patients (C2M6 (IQR C1-3, M5-7cm)) after 3±1 RFA sessions. Conventional manometry revealed a hypotensive lower esophageal sphincter in 5 of the 10 patients. RFA did not significantly alter the percentage of peristaltic contractions (60±11 vs 73±12%) or distal contraction amplitudes (53±12 vs 53±9mmHg). In patients measured with HRM low IRP1 (9.5±3.1 vs 12.3±3.7mmHg), IRP4 (11.9±3.5 vs 16.7±3.0mmHg), and DCI values (328±25 vs 491±188mmHg s-1 cm-1) were found, with no significant differences between both measurements pre and post RFA. Patients showed very high acid exposure times before and after RFA (28.9±5.7% and 17.8±3.7% resp., p=0.12). Impedance signals were not suitable for analysis of reflux parameters in 3 patients before and in 6 patients after RFA due to low impedance baseline and multiple artifacts. In the other patients, reflux parameters did not differ between both measurements. Baseline esophageal impedance values were low, with lower values in the distal recording segments. After RFA baseline impedance increased in all channels: before vs. after (proximal to distal recording segments): 2575±187Ω vs 3111±226Ω, 2325±174Ω vs 2903±276Ω, 1417±160Ω vs 2126±136Ω, 987±100Ω vs 1456±116Ω, 709±42Ω vs 1075±71Ω, 563±33Ω vs 834±64Ω, (p<0.01). No significant relationship was found between impedance baseline levels and esophageal acid exposure or length of the Barrett's segment. Conclusions: Repeated RFA did not significantly alter esophageal motility. In patients with BE low esophageal baseline impedance levels increased after successful RFA treatment. This suggests that low distal esophageal impedance levels are caused by the presence of cylindrical epithelium in patients with BE.

Esophageal Acid Exposure Decreases Intraluminal Baseline Impedance Levels

Intraluminal baseline impedance levels are determined by the conductivity of the esophageal wall and can be decreased in gastroesophageal reflux disease (GERD) patients. The aim of this study was to investigate the baseline impedance in GERD patients, on and off proton pump inhibitor (PPI), and in healthy controls. Ambulatory 24-h pH-impedance monitoring was performed in (i) 24 GERD patients with and 24 without pathological esophageal acid exposure as well as in 10 healthy controls and in (ii) 20 patients with refractory GERD symptoms despite PPI, once on PPI and once off PPI. Baseline impedance levels in the most distal and the most proximal impedance channels were assessed. Median (interquartile range) distal baseline impedance in patients with physiological (2,090 (1,537-2,547) Ω) and pathological (781 (612-1,137) Ω) acid exposure was lower than in controls (2,827 (2,127-3,270) Ω, P<0.05 and P<0.001). A negative correlation between 24-h acid exposure time and baseline impedance was observed (r=-0.7, P<0.001). In patients measured off and on PPI, median distal baseline impedance off PPI was significantly lower than on PPI (886 (716-1,354) vs. 1,372 (961-1,955) Ω, P<0.05) and distal baseline impedance in these groups was significantly lower than in healthy controls (P<0.05 and P<0.001). Proximal baseline impedance did not differ significantly between the patients off PPI and on PPI (1,793 (1,384-2,489) vs. 1,893 (1,610-2,561) Ω); however, baseline impedance values in both measurements were significantly lower than in healthy controls (3,648 (2,815-3,932) Ω, both P<0.001). These findings suggest that baseline impedance is related to esophageal acid exposure and could be a marker of reflux-induced changes to the esophageal mucosa.

Rapid differentiation of fermentative from nonfermentative gram-negative bacilli in positive blood cultures by an impedance method.

Rapid differentiation of fermentative gram-negative bacilli (fermenters) from nonfermentative gram-negative bacilli (nonfermenters) in positive blood cultures may help physicians to narrow the choice of appropriate antibiotics for empiric treatment. An impedance method for direct differentiation of fermenters from nonfermenters was investigated. The bacterial suspensions (or positive culture broths containing gram-negative bacteria) were inoculated into the module wells of a Bactometer (bioMérieux, Inc., Hazelwood, Mo.) containing 1 ml of Muller-Hinton broth. The inoculated modules were incubated at 35 degrees C, and the change in impedance in each well was continuously monitored. The amount of time required to cause a series of significant deviations from baseline impedance values was defined as the detection time (DT). The percent change of impedance was defined as the change of impedance at the time interval from DT to DT plus 1 h. After testing 857 strains of pure cultures (586 strains of fermenters and 271 strains of nonfermenters), a breakpoint (2.98%) of impedance change was obtained by discriminant analysis. Strains displaying impedance changes of greater than 2.98% were classified as fermenters; the others were classified as nonfermenters. By using this breakpoint, 98.6% (340 of 345) of positive blood cultures containing fermenters and 98% (98 of 100) of positive blood cultures containing nonfermenters were correctly classified. The impedance method was simple, and the results were normally available within 2 to 4 h after direct inoculation of positive blood culture broths.