Computer analysis of 24-h esophageal impedance signals.

OBJECTIVE: To assess the accuracy of newly developed software for detection of gastro-esophageal reflux episodes in ambulatory 24-h impedance tracings. MATERIAL AND METHODS. 24-h esophageal impedance recordings obtained from 60 consecutive patients with reflux symptoms were used in this study. The impedance tracings of the first 10 consecutive patients were analyzed manually by three investigators. Liquid-containing reflux episodes and their proximal extent were scored. A consensus between the three investigators was used as a gold standard. Computer analysis using dedicated software was performed, and the results were compared with the results of the consensus agreement. In addition, in order to assess the accuracy of symptom association analysis 24-h impedance tracings of all 60 patients were analyzed both manually by one investigator and using computer software. The number of reflux episodes and the results of symptom association analysis obtained by the human and computer analysis software were compared. RESULTS: The consensus meeting resulted in a total of 625 reflux episodes. The mean sensitivity and the percentage of true-positives of analysis by individual investigators was 89±1% and 94±1%, respectively. Automated analysis had a sensitivity of 73±4% and a proportion of true-positive reflux episodes of 62±8%. Symptom association analysis performed by the computer and a human observer showed concordant results in 83% of the patients. CONCLUSIONS: Although not as good as manual analysis by experts, computer analysis can be a helpful tool to identify reflux episodes and to assess the relationship between reflux episodes and symptoms.

Reliability of oesophageal pH recording for the detection of gastro-oesophageal reflux.

OBJECTIVE: Despite the new gold standard oesophageal impedance monitoring, pH monitoring is still used frequently for detection of gastro-oesophageal reflux (GOR). Besides drops in pH from above to below pH4, drops of > or =1 unit are also used as a marker for GOR. In this study the objective was to investigate the accuracy of drops in pH for detection of GOR, using impedance monitoring as the gold standard. MATERIAL AND METHODS: Nineteen GORD patients (9 M, 55+/-11 years) underwent combined 24-h pH-impedance recording off acid-suppressive therapy. All drops in pH > or =0.5 pH units, with a duration > or =4 s, reaching the nadir pH within 5 s after onset were included. Reflux events detected with impedance monitoring were taken as the reference. RESULTS: In total, 2221 drops in pH were found; 47% were acid (nadir pH <4), 47% weakly acidic (nadir pH between pH7 and 4) and 5% were superimposed (pH drop starting below pH4). The sensitivities of acid, weakly acidic and superimposed pH drops > or =1 were 91%, 28%, 24%, respectively, and the percentages of false-positive reflux episodes were 20, 56 and 54, respectively. Acid reflux with a cut-off > or =0.5 and < or =3.3 had a moderate-to-good sensitivity (94-70%) and low false-positive percentages (23-13%). In contrast, weakly acidic and superimposed reflux showed greater false-positive than true-positive percentages for all cut-off values. CONCLUSIONS: Compared to impedance monitoring, detection of reflux with pH monitoring is clearly inferior. When drops in pH > or =1 are used irrespective of nadir pH as an indicator of reflux episodes, the number of reflux episodes is overestimated. Decreases from above to below 4 with cut-offs between > or =0.5 and < or =3.3 are the most indicative of true reflux episodes.

Reproducibility of symptom association analysis in ambulatory reflux monitoring.

INTRODUCTION: The temporal relationship between reflux symptoms and reflux episodes during ambulatory reflux monitoring can be studied with symptom association analysis, and the strength of the relationship can be expressed using indices such as the SAP (symptom association probability), SI (symptom index), and SSI (symptom sensitivity index). The reproducibility of these indices has not been determined yet. METHOD: Twenty-one patients with typical reflux symptoms (9 men, 53 [38-57] yr) underwent two 24-h combined pH-impedance recordings off acid-secretory medication with an interval of 1-4 wk. The SAP, SI, and SSI were calculated for each measurement. Reproducibility of these indices was determined with Kendall's coefficients of concordance. RESULTS: The number of reflux events were highly reproducible (Kendall W = 0.92, P < 0.01). The number of symptoms related to reflux events was reproducible (Kendall W = 0.91, P < 0.01) while the number of reported reflux symptoms was not (Kendall W = 0.75, P= 0.07). The SAP and SSI were highly reproducible (Kendall W = 0.90, P= 0.01, and W = 0.86, P < 0.05, respectively) but the SI was not (W = 0.73, P= 0.09). The percentage of patients with similar outcomes on two separate test days for the SAP, SI, and SSI was 86%, 67%, and 86%, respectively. DISCUSSION: In 24-h pH-impedance recordings of patients with reflux symptoms, the number of reflux events and the number of symptoms related to reflux events were highly reproducible as were the SAP and SSI. This supports the use of these indices to express the relationship between symptoms and reflux episodes in clinical practice.

Effect of proton-pump inhibitor treatment on symptoms and quality of life in GERD patients depends on the symptom-reflux association.

BACKGROUND: Gastroesophageal reflux disease patients demonstrate various pathophysiologic backgrounds. Therefore, a heterogeneous response to proton-pump inhibitor (PPI) treatment can be expected. We investigated the effect of short-term PPI treatment on symptoms and quality of life (QOL) in primary care patients with and without pathologic esophageal acid exposure and in presence or absence of a positive association between symptoms and reflux episodes. STUDY: Seventy-four heartburn patients were categorized into 4 groups according to positive or negative symptom-reflux association, as expressed in symptom index, symptom sensitivity index, and symptom association probability (SAP) and presence or absence of pathologic reflux, defined as esophageal pH<4%>6% of the time (pH+/pH-). Overall and specific reflux symptoms were assessed 1 week before and the last week during a 2-week course of 40-mg esomeprazole daily. The QOL was scored by the Quality of Life in Reflux and Dyspepsia questionnaire 2 weeks before treatment and directly after. RESULTS: Using the SAP to assess symptom-reflux associations, the 4 groups [SAP+pH+(n=40); SAP+pH-(n=12); SAP-pH+(n=10); SAP-pH-(n=10)] had similar demographic characteristics. The SAP-pH- subgroup had the least overall symptom reduction (P<0.01) and in the SAP+pH+ subgroup the greatest heartburn symptom reduction was found (P<0.02). The residual symptom scores on treatment were lowest in SAP+pH+ and highest in SAP-pH- subgroups and relatively high in the SAP+pH-. QOL was severely reduced and SAP-pH- patients had the lowest QOL overall. Similar findings were made using symptom index and symptom sensitivity index. CONCLUSIONS: Symptomatic reflux patients without evidence of reflux disease on a 24-hour pH recording responded less favorably to PPI treatment than patients with a positive symptom-reflux association or with pathologic reflux.

Effect of dietary sodium chloride on gastro-oesophageal reflux: a randomized controlled trial.

OBJECTIVE: It has been suggested that a high consumption of sodium chloride (NaCl) is associated with reflux symptoms. The objective of this study was to investigate the effect of increased dietary NaCl intake on gastro-oesophageal reflux and reflux mechanisms. MATERIAL AND METHODS: In this double-blind, placebo-controlled, crossover study 10 healthy male subjects received 5 g NaCl or placebo in capsules per day for one week, after which concurrent manometric, pH and impedance monitoring was carried out for 4.5 h. RESULTS: Oesophageal acid exposure time (pH < 4) was similar for placebo (median 11% (25th 3-75th 36)) and NaCl (9% (1-36)). No differences in the numbers of reflux episodes were found for NaCl (16 (13.5-22)) and placebo (23 (14.8-27)). Furthermore, similar numbers of liquid acid reflux episodes (placebo 12 (6.5-17.3); NaCl 10 (2.3-14.3)), liquid weakly acidic reflux episodes (placebo 5.5 (4-12.3); NaCl 6.5 (3-10.8)) and gaseous reflux episodes (placebo 1 (0-1.8); NaCl 2 (0-3)) were seen. In both conditions transient lower oesophageal sphincter relaxations (TLOSRs) were the most common reflux mechanism, followed by swallow-induced reflux. High salt intake lowered LOS pressure overall and in the first postprandial hour (p<0.01). CONCLUSIONS: High dietary sodium intake does not increase gastro-oesophageal reflux in healthy volunteers, despite a decrease in LOS pressure.

A detailed analysis of sodium removal by peritoneal dialysis: comparison with predictions from the three-pore model of membrane function.

BACKGROUND: The development of fluid and salt retention is a potential problem for all peritoneal dialysis (PD) patients. Sodium removal by the peritoneum is predominantly determined by convective fluid loss but influenced by diffusion and sieving due to free water transport as predicted by the three-pore model (TPM). The aim of the study was to establish the effect of transport status, dwell length and glucose concentration on observed ultrafiltration (UF), dialysate sodium concentration ([Na(+)](D)) and removal, and compare this with that predicted by a computer program based on the principles of the TPM. METHODS: This was a cross-sectional study of UF and [Na(+)](D) collected prospectively from dwells classified by length, glucose concentration and membrane transport characteristics. Solute transport, converted to area parameter and UF capacity, was measured on each occasion by the peritoneal equilibration test. These parameters, along with plasma [Na(+)], were entered into the computer model. Fixed values for other parameters, e.g. hydraulic conductance and lymphatic absorption and sump volume, were used. RESULTS: A total of 1853 dwells from 182 patients [10% were on automated PD (APD)] were analysed. There was a high degree of correlation (r = 0.83-95, P<0.001) between the observed and predicted values for UF, [Na(+)](D) and sodium removal across the full range of dwell categories. The model overpredicted UF as the net volume increased with increasing glucose concentration, independently of solute transport. This bias was not fully explained by the preferential use of hypertonic dialysate by patients with reduced UF capacity. The prediction of [Na(+)](D) described sodium sieving, which was overestimated in a small number of patients with UF failure. There were no discrepancies between continous ambulatory PD (CAPD) and APD patients. CONCLUSION: This analysis endorses the TPM as a description of membrane function, particularly in relation to sodium sieving and removal. The relationship between dialysate glucose concentration and achieved UF appears to be more complex; even accounting for extended time on treatment and reduction in the osmotic conductance in patients preferentially using hypertonic exchanges, further adjustments may be needed to account for the tendency to overestimate UF.