title: The correlation between esophageal and abdominal pressures in mechanically ventilated patients undergoing laparoscopic surgery.
abstract: BACKGROUND
  Intrathoracic pressure in patients undergoing laparoscopic surgery may be affected by intra-abdominal pressure during surgery. We investigated the relationship between intra-abdominal pressure (Pabd) and esophageal pressure (Pes) in mechanically ventilated patients undergoing laparoscopic surgery.
  
  
  METHODS
  We prospectively studied 43 consenting patients over 18 y of age who were scheduled for elective laparoscopic surgery with plans for intra-operative intubation and paralysis. After establishing a good level of inter-observer agreement on Pes measurements, Pes was measured by one observer for each patient using an esophageal catheter. Pabd and Pes were recorded before and after abdominal insufflation. We used regression analysis to model the relationship between Pabd and Pes.
  
  
  RESULTS
  Patients' ages varied from 22 to 78 y, with a mean of 53.2 ± 14.6 y. Body mass index (BMI) varied from 13.7 to 60.5 kg/m2, with a mean of 33.7 ± 10.5. PEEP was 5-7 cm H2O for 19 patients and 0 cm H2O for the remainder. Most patients underwent gastric bypass surgery (n = 11); others underwent hernia repair (n = 9), colon resection (n = 7), cholecystectomy (n = 6), and various other surgeries (n = 10). Using univariate analyses, baseline Pabd was significantly correlated with baseline Pes (estimate of model coefficient [95% CI]: 0.79 [0.36-1.21], R2 = 0.24, P = .001), as was BMI (0.29 [0.19-0.40], R(2) = 0.41, P < .001). However, a multivariable analysis showed no significant correlation with baseline Pabd (0.10 [-0.46 to 0.65], P = .73), whereas BMI remained highly significant (0.27 [0.11-00.43], P = .001) with R2 = 0.40. Due to unexpected uniformity of abdominal inflation pressures (generally 20.4 cm H2O) during surgery, data were not amenable to assessment of correlation between changes in abdominal and esophageal pressures after inflation.
  
  
  CONCLUSIONS
  There was a limited correlation between baseline Pes and Pabd in patients undergoing elective laparoscopic surgery, suggesting a limited value of Pabd measurements in the management of mechanically ventilated patients.
authors.affiliation: Department of Anesthesia and Critical Care, King Abdulaziz University, Jeddah, Saudi Arabia.
authors.forename: Anees
authors.initials: A
authors.lastname: Sindi
authors.forename: Tom
authors.initials: T
authors.lastname: Piraino
authors.forename: Waleed
authors.initials: W
authors.lastname: Alhazzani
authors.forename: Marcel
authors.initials: M
authors.lastname: Tunks
authors.forename: Mazen
authors.initials: M
authors.lastname: Faden
authors.forename: Jinhui
authors.initials: J
authors.lastname: Ma
authors.forename: Lehana
authors.initials: L
authors.lastname: Thabane
authors.forename: Maureen
authors.initials: M
authors.lastname: Meade
mesh_terms: D000005:Abdomen / Q000502:physiology*; D000328:Adult; D000368:Aged; D015992:Body Mass Index; D004947:Esophagus / Q000502:physiology*; D006801:Humans; D007327:Insufflation; D007432:Intraoperative Period; D010535:Laparoscopy; D016014:Linear Models; D008365:Manometry; D008875:Middle Aged; D011175:Positive-Pressure Respiration; D011312:Pressure; D011446:Prospective Studies; D055815:Young Adult
keywords: abdominal insufflation; abdominal pressure; esophageal pressure; prospective study; transpulmonary pressure