title: [Comparative prospective study of two positioning modes of 24-hour esophageal pH monitoring: by esophageal manometry and by the pH step-up technique].
abstract: BACKGROUND
  By internationally accepted standardization, the esophageal pH-meter distal sensor is positioned 5 cm above the superior border of the lower esophageal sphincter, identified by esophageal manometry. However, several authors suggest alternative positioning techniques that leave out the manometry; among such techniques, the pH step-up is the one to be pointed out. This subject is controversial; some publications state that the step-up technique is not reliable while some others consider it reliable.
  
  
  OBJECTIVE
  Considering the existent controversy and the small number of prospective works with suitable sample and methodology, we have idealized the present study, that aims the evaluation of the suitability of the pH-meter distal sensor positioning based on the step-up technique, by analyzing the presence, the type and the degree of the error of positioning that such technique provides and the influence of the position adopted by the patient during the procedure.
  
  
  METHODS
  One thousand and thirty one patients conducted to the esophageal pH-meter procedure were studied in a prospective way. During the clinical interview, the demographic data and the presented clinical complaints were registered. All the patients were submitted to both esophageal manometry in order to localize the lower esophageal sphincter and the pH step-up technique, that consists of the introduction of the pH-meter sensor in the gastric chamber and in the sensor's gradual traction until the pH steps up to levels over 4. The step-up point was identified by two distinct ways, characterizing two study groups: with the sitting patient (group I - 450 patients) and with the patient in supine position (group II - 581 patients). After the step-up point identification, the pH-meter distal sensor was placed in the standard position (based on the sphincter manometric placement). It was registered where the pH sensor would be positioned if the step-up technique were adopted. To evaluate the positioning suitability, the error was considered to be represented by the difference (in centimeters) between the suitable placement (manometry) and the one that would be adopted in case the step-up technique were adopted. The positioning error was considered rough if it were larger than 2 cm. The most frequent type of error was also analyzed (if above or below the standard position).
  
  
  RESULTS
  It was observed that if the step-up technique were adopted, there would be error in the sensor positioning in 945 patients (91.6%). In terms of error degree, there would be a rough error in 597 (63.2%) cases. Concerning the type of error, the sensor would be positioned below the standard place in 857 (90.7%) patients. As to the interference of the position adopted by the patient during the step-up technique, it was observed that there was no significant difference among the groups of study in any of the analyzed parameters.
  
  
  CONCLUSIONS
  1. The positioning of the pH-meter distal sensor by the step-up technique is not reliable; 2. the step-up technique provides expressive error margin; 3. the most common type of error that such technique mode provides is the placement of the sensor below the standard positioning, which may overestimate the reflux occurrence; 4. there is no influence in the position adopted by the patient during the pH step-up technique procedure, in terms of method efficiency.
authors.affiliation: Laboratório de Investigação Funcional do Esôfago do Serviço de Cirurgia do Esôfago do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo. ary.nasi@fleury.com.br
authors.forename: Ary
authors.initials: A
authors.lastname: Nasi
authors.forename: Rita de Cássia
authors.initials: Rde C
authors.lastname: Frare
authors.forename: Jeovana F
authors.initials: JF
authors.lastname: Brandão
authors.forename: Angela M
authors.initials: AM
authors.lastname: Falcão
authors.forename: Nelson H
authors.initials: NH
authors.lastname: Muchelsohn
authors.forename: Daniel
authors.initials: D
authors.lastname: Sifrim
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D003951:Diagnostic Errors / Q000706:statistics & numerical data*; D004567:Electrodes, Implanted; D050782:Esophageal pH Monitoring / Q000295:instrumentation / Q000592:standards*; D005260:Female; D005764:Gastroesophageal Reflux / Q000175:diagnosis*; D006801:Humans; D008297:Male; D008365:Manometry / Q000379:methods* / Q000592:standards; D008875:Middle Aged; D011187:Posture / Q000502:physiology*; D011446:Prospective Studies; D018709:Statistics, Nonparametric; D016683:Supine Position / Q000502:physiology; D055815:Young Adult