title: Normal values of 24-hour combined esophageal multichannel intraluminal impedance and pH monitoring in the Chinese population.
abstract: BACKGROUND
  There is a lack of data on combined esophageal multichannel intraluminal impedance and pH (MII-pH) monitoring in the Chinese population.
  
  
  OBJECTIVE
  To define the normal range and compare the parameters to those of the Western population.
  
  
  METHODS
  Healthy volunteers were recruited and underwent 24-hour ambulatory combined MII-pH monitoring. Gastroesophageal reflux episodes were detected and characterized by pH (acidic, weakly acidic and weakly alkaline reflux) and composition (liquid, mixed and gas reflux).
  
  
  RESULTS
  Seventy healthy volunteers (male:female 33:37) were recruited. The median and 95th percentile number of the total reflux episodes over 24 h in the Chinese population was 40 and 75, respectively, whereas the corresponding numbers of acidic, weakly acidic and weakly alkaline reflux episodes were 22 and 54, 16 and 40, and 0 and 4, respectively. Among all reflux episodes 53.3% were acidic, 44.7% were weakly acidic, and 2% weakly alkaline. More than half (52.4%) of the reflux episodes were mixed, 37.2% were liquid, and 10.4% were gas. A total of 26.6% of reflux episodes reached 15 cm above the lower esophageal sphincter. Male gender was associated with an increased number of acid, liquid, mixed and proximal reflux episodes (p < 0.05).
  
  
  CONCLUSIONS
  This study provides normal values for the Chinese population. Differences between genders in impedance parameters required caution during data interpretation. The number of reflux episodes in the Chinese population was similar to that in the Western population.
authors.affiliation: Department of Gastroenterology, First Affiliated Hospital, Sun Yat-sen University, Guangzhou 510080, China.
authors.forename: Ying L
authors.initials: YL
authors.lastname: Xiao
authors.forename: Jin K
authors.initials: JK
authors.lastname: Lin
authors.forename: Ting K
authors.initials: TK
authors.lastname: Cheung
authors.forename: Nina Y H
authors.initials: NY
authors.lastname: Wong
authors.forename: Li
authors.initials: L
authors.lastname: Yang
authors.forename: Ivan F N
authors.initials: IF
authors.lastname: Hung
authors.forename: Benjamin C Y
authors.initials: BC
authors.lastname: Wong
authors.forename: Min H
authors.initials: MH
authors.lastname: Chen
mesh_terms: D000328:Adult; D000368:Aged; D044466:Asian People; D002681:China; D017097:Electric Impedance; D050782:Esophageal pH Monitoring; D005260:Female; D005764:Gastroesophageal Reflux / Q000175:diagnosis; D006801:Humans; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D055815:Young Adult