title: The gastro-oesophageal pressure inversion point revisited.
abstract: BACKGROUND
  The pressure inversion point (PIP) is defined as the point at which, during stationary pull-through manometry of the oesophago-gastric junction, the polarity of the respiratory-associated pressure variations changes. Traditionally, the PIP is ascribed to transition of the pressure sensor from the abdominal to the thoracic cavity. We used high-resolution manometry to investigate the validity of this concept in six healthy volunteers and six patients with a sliding hiatus hernia.
  
  
  METHODS
  In the analysis, the position of the PIP was identified. When there was a second, more distal, PIP, its position was also noted. The amplitude of the respiratory-associated pressure variations, defined as the difference between end-expiratory and end-inspiratory pressure, was measured.
  
  
  RESULTS
  Double PIPs were found both in healthy controls (23 +/- 8% of time) and in patients (38 +/- 9% of time). Amplitudes of the respiratory-associated pressure variations were significantly higher at the proximal and distal border of the PIP (3.36 +/- 0.2 kPa and 2.29 +/- 0.2 kPa) than in the oesophageal body (0.54 +/- 0.03 kPa, P < 0.001) and in the stomach (0.54 +/- 0.03 kPa, P < 0.001). We also observed a relationship between the localization of the highest end-expiratory pressure and the position of the PIP. During TLOSRs respiratory variation amplitudes at the proximal and distal border of the PIP decreased to 0.61 +/- 0.02 kPa and 0.29 +/- 0.01 kPa, approximating respiratory pressure variation in oesophagus and stomach.
  
  
  CONCLUSIONS
  Our findings suggest that the PIP is caused by sliding of the high-pressure zone along pressure sensors rather than by the transition from the thoracic to the abdominal compartment.
authors.affiliation: Gastrointestinal Research Unit, Dept. of Gastroenterology, University Medical Center, Utrecht, The Netherlands.
authors.forename: A J
authors.initials: AJ
authors.lastname: Bredenoord
authors.forename: B L A M
authors.initials: BL
authors.lastname: Weusten
authors.forename: J M M
authors.initials: JM
authors.lastname: Roelofs
authors.forename: A J P M
authors.initials: AJ
authors.lastname: Smout
mesh_terms: D000328:Adult; D000403:Airway Resistance / Q000502:physiology*; D003964:Diaphragm / Q000503:physiopathology; D004943:Esophagogastric Junction / Q000503:physiopathology*; D005260:Female; D006551:Hernia, Hiatal / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008365:Manometry; D008875:Middle Aged; D011312:Pressure; D012016:Reference Values; D015203:Reproducibility of Results; D012129:Respiratory Function Tests