{'fraction_non_alphanumeric': 0.03620146904512067, 'fraction_numerical': 0.0236096537250787, 'mean_word_length': 4.675595238095238, 'pattern_counts': {'":': 0, '<': 2, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Acid exposure of proximal esophagus in healthy subjects.

BACKGROUND
An association between gastroesophageal reflux (GER) and pulmonary or laryngeal diseases has been recognized, and dual pH monitoring of both distal and proximal esophagus has been proposed to investigate chronic respiratory symptoms of unexplained etiology. However, the degree of acid reflux in the upper esophagus is still uncertain, making it difficult to discriminate between physiological and abnormal GER.


AIM
To define normal values for proximal esophageal acid exposure.


METHODS
Two-level esophageal pH monitoring was performed in 22 healthy subjects and 26 reflux patients. A dual pH sensor with electrodes spaced 15 cm that were positioned 5 and 20 cm above cardias was used. Two different thresholds of pH 4 and 5 were used to evaluate GER at proximal level.


RESULTS
In healthy subjects, at proximal level, the acid exposure time (% time pH < 4) was 0.4%, 0.7% and 0.1% for 24-hrs, upright and recumbent periods, respectively. Using pH 5 as threshold, acid exposure time (% time pH < 5) was 1.5%, 2.3% and 0.3% for 24-hrs, upright and recumbent periods, respectively. Twenty cm above cardias, acid exposure was greater in reflux patients in comparison to controls; however, all reflux values were significantly different between the two groups only when pH 5 was used as threshold. The percentage of distal reflux reaching the proximal site (16.0%, 27.9% and 7.1% in controls for 24-hrs, upright and recumbent periods, respectively) was similar in the two groups.


CONCLUSIONS
Acid reflux, to a limited extent, is physiologic in proximal esophagus. The technique of pH recording 20 cm above cardias might be useful in documenting the cephalic extend of GER, allowing to investigate patients with atypical presentations of GER disease. It may be best to use both thresholds 4 and 5 for evaluating proximal acid exposure.