Variations in results of simultaneous ambulatory esophageal pH monitoring

Diagnostic modalities for gastro-esophageal reflux in infantile wheezers

OBJECTIVE

To compare the diagnostic value of Gastro-intestinal (GI) scintiscan with 24-h pH study in detecting gastro-esophageal reflux (GER) among infantile wheezers.

SUBJECTS

Fifty-two children < 2 years of age.

METHODS

All patients, irrespective of symptom underwent study to evaluate for GER.

RESULTS

GER studies were positive in almost 45% of cases. The agreement between positivity of these two tests is best among children between 7 and 12 months of age (κ = 0.591, p = 0.002). Overall GI scintiscan was a better test with higher sensitivity and specificity as compared to 24-h pH study when compared with the history suggestive of reflux and clinical response with anti-reflux treatment as standard (p ≤ .001).

CONCLUSION

Both GER scan and 24-h pH study are complimentary to each other, however, if both the tests are available then GI scintiscan is better as a single test for GER in these early wheezers.

The classification of oesophageal 24 h pH measurements using a Kohonen self-organizing feature map

Analysis of 24 h oesophageal pH studies can be problematic with many patients asymptomatic during the investigation, despite observations of reflux. The aim of this study was to carry out a cluster analysis of ambulatory pH studies to determine any underlying patterns and classes within the data. The results of 900 24 h pH studies were investigated using the Kohonen self-organizing feature map (SOFM), a neural network that can be used to identify clusters within multidimensional data. The clinical features were presented to the network and the main classes identified. The SOFM-based analysis showed that patients clinically assessed as having symptomatic reflux during the study could be described by four major classifications. The results also showed that the probability of identifying a correlation between symptoms and reflux during an investigation varies from 0.49 to 0.78 for the classes identified. The developed network may be a useful tool in the classification of pH data. The cluster-based technique may offer an alternative to standard statistical techniques for high-dimensional gastrointestinal data and form the basis of an expert system for the automated analysis of pH data.

pH probe positioning for 24-hour pH-metry by manometry or pH step-up

OBJECTIVES

Before pH measurement, manometry is recommended for precise pH probe positioning. We investigated whether the pH probe could be positioned accurately by the pH difference between the oesophagus and the stomach (pH step-up).

METHODS

Dual-channel 24-h pH-metry with probes positioned 5 cm above either the manometrically determined upper lower oesophageal sphincter margin or the pH step-up was performed in healthy volunteers and reflux patients. To determine the pH step-up, the pH probe was pulled back from the stomach until a sudden rise to pH greater than four occurred. Probe position, reflux episodes and the fraction of the time pH was less than four were compared using the Wilcoxon test for difference and the Hodges-Lehman estimate inclusive confidence interval for equivalence. The pH step-up method was evaluated further during proton pump inhibitor therapy and after drug discontinuation.

RESULTS

The pH probe was positioned 2 cm and 1 cm closer to the stomach by the pH step-up method in the volunteers and reflux patients, respectively. A small increase in upright reflux episodes but not in supine reflux episodes was registered by the probe positioned by pH step-up. No significant differences in the fraction of the time pH was less than four were obtained between the two probes. The Hodges-Lehman calculation proved equivalence for both methods of probe positioning for 24-h pH-metry. During proton pump inhibitor therapy, no pH step-up was detectable in three volunteers and in one patient. On the first day after discontinuing therapy, the pH step-up method yielded clear-cut results again.

CONCLUSION

The pH probe for diagnostic 24-h pH-metry and, with some limitations, also for 24-h pH-metry for therapy control, can be positioned accurately by the pH step-up method.

A pH-mucosa area unit of measure to consider morphology of the oesophagus when evaluating oesophagitis

Gastro-oesophageal pH measurements are routinely carried out to quantify and determine if levels of acid reflux are responsible for symptoms. Although considered the 'gold standard', evidence suggests that pH measurements do not correlate well with the degree of oesophagitis seen during endoscopy. In this study the current measure of pH was critically examined taking into account both the effects of changes in luminal diameter and endoscopy observations. The oesophageal lumen diameter was investigated using a barium swallow for 25 patients presenting with oesophageal disorders. For each subject the widest luminal diameter was measured for a series of five controlled swallows. The results showed that the lumen diameter varied widely from 0.9 to 3.8 cm. An alternative approach to the current measurement of pH was explored. In this approach the exposure not only included the luminal pH and time exposed but also the area of mucosa exposed as a result of differing luminal diameters. Although it is currently not possible to assess the diameter or morphology of the oesophageal lumen during a pH study, the analysis highlighted that the current measure of pH exposure time does not include the area of mucosa exposed. These results may explain, to some extent, the poor correlation between pH measurements and degree of oesophagitis seen during endoscopy.

Intra-esophageal pH probe movement during eating and talking. A videoradiographic study

PURPOSE

To registrate the oscillations of the pH probe in the esophagus during phonation and swallowing in the erect and supine positions.

MATERIAL AND METHOD

Sixty-seven patients with suspicion of gastroesophageal reflux disease underwent manometry, 24-h pH monitoring, and videoradiography. In 43 patients the effect of dry, wet, and solid swallows in the erect and supine positions was determined, making a total of 258 swallows. In another 24 patients the effect of pH probe movement during phonation was studied.

RESULTS

During every swallow the probe moved in the proximal direction from 0.5 to 2.0 cm, returned to baseline, and in 48 swallows an additional descendent movement of up to 2.0 cm was seen, the last mentioned more pronounced during solid swallows. In the erect position, no significant difference was observed for the different swallowing types, whereas in the supine position, movements were significantly more pronounced during solid food swallows. During phonation the pH probe only ascended and returned to the baseline, with no descending part.

CONCLUSION

The pH probe movements are dependent on body position, bolus size, bolus composition, and talking. The ascending movements can only partially compensate for the esophageal shortening during swallow because of the time difference, and could perhaps explain the variation in results and reproducibility of 24-h pH monitoring.

The role of gastro-oesophageal reflux in the aetiology of SIDS

Gastro-oesophageal reflux (GOR) has been identified as a possible cause of SIDS. Several features of GOR unique to infants presenting with apparent life-threatening events (ALTEs) have led to its 'pathogenic' definition. One is that the life-threatening apnoea itself is initiated by GOR, another is that the ALTE relates to prolonged reflux during sleep, in a vulnerable sleep-state, and finally that the ALTE relates to excessive quantities of GOR. The presumption of GOR 'pathology' as a cause of SIDS however, is questionable in these susceptible infants for three reasons: firstly, GOR is physiological and occurs in most infants; secondly, there is no general consensus on what constitutes normal physiological reflux, and thirdly, variation in the recording technique and methods of data analysis and interpretation may account for the differences between study groups. It seems likely therefore if GOR is implicated in SIDS, additional factors are involved. Under certain circumstances, physiological GOR may trigger life-threatening apnoea in apparently healthy infants, that leads to SIDS. One mechanism that could explain such a death is reflex apnoea by stimulation of laryngeal chemoreceptors (LCR) during sleep. The conditions under which this could be fatal are the occurrence of gastric contents refluxed to the level of the pharynx during sleep, in the young infant who has depressed swallowing and arousal. That is, the occurrence of GOR to the level of the pharynx during sleep, an infrequent event that is usually innocuous, could be converted to a fatal event if swallowing is impaired and arousal depressed, by a variety of mediating factors such as prone sleeping, prematurity, sedatives, seizures or upper respiratory tract infections. The identification of LCR responses, particularly in prone sleeping and premature infants provide further evidence that this mechanism may be implicated in the aetiology of SIDS in apparently healthy infants.

Effect of smoking on the results of esophageal pH measurement in clinical routine

Because data on the effects of smoking on gastroesophageal reflux are controversial, we evaluated the effect of smoking on the results of esophageal 24-hour pH-metry in clinical routine. Participants were 280 consecutive patients with symptoms suggestive of reflux disease, 78 smokers, and 202 nonsmokers. Of the smokers, 45 actually smoked during the pH measurement and 33 abstained from smoking. The frequency of reflux episodes, the fraction of time pH was < 4, and the percentage of abnormal 24-hour pH-metry results were compared among actual smokers, abstaining smokers, and nonsmokers. In actual smokers, the effect of smoking on gastroesophageal reflux was further analyzed by comparing the reflux frequency and the fraction of time that pH was < 4 for a 10-minute period before, during, and after smoking. We found no difference in reflux frequency and fraction of time that pH was < 4 among actual smokers, abstaining smokers, and nonsmokers, regardless of a normal or an abnormal pH-metry result. The percentage of patients with a pH-metry result indicating disease was similar in the three groups, at 53%, 52%, and 50%, respectively. Gastroesophageal reflux was not increased during smoking a cigarette or in the postsmoking period compared with the presmoking period. Neither being a smoker nor actually smoking a cigarette had a negative influence on gastroesophageal reflux. Thus smoking or abstaining from smoking does not modify the results of pH-metry in clinical routine.

New method for improving accuracy of 24-hour continuous intragastric pH-metry. Reflections on physiological and pharmacological studies

Continuous 24-hr intragastric pH-metry was prospectively performed in 801 subjects with different clinical conditions using two pH electrodes placed closely adjacent. The aim was to assess the in situ repeatability of the test and to verify whether the removal of artifacts, interference, and noise usually superimposed onto the fundamental signal recorded by the measuring apparatus improves the clinical usefulness of experimental data. The following debugging/filtering procedure was used: first, pH recordings of each channel were amended separately from artifacts, then they underwent 7 min windowed median interference debugging, and finally Wiener noise filtering was applied. Afterwards, the 24-hr mean pH profile was obtained in each subject by averaging the pH tracings of the two channels every minute (1440 data points/24 hr). The efficiency of this procedure was assessed at each step by evaluating the difference among groups using the O'Brien test, a distribution-free nonparametric method well-suited for evaluating differences among groups allocated onto a two-way layout. The differences among groups calculated from raw pH data of the single channels can be very misleading, in that it is possible to find that they are significant on one channel and not significant on the other channel. Conversely, the significance of the differences among groups increases progressively at each step of the above debugging/filtering procedure applied to raw pH profiles of each channel. Seven minutes was shown to be the most suitable time lag for windowed median removal of interference.(ABSTRACT TRUNCATED AT 250 WORDS)