title: Correlation of CO2 pneumoperitoneal pressures between rodents and humans.
abstract: BACKGROUND
  Many studies have reported on the effects of pneumoperitoneum in a rat model, using a wide range of intra-abdominal pressures. The correlation between pneumoperitoneal pressures in rodents to pressures in humans has not been established. This study evaluates changes in various physiological parameters in different pneumoperitoneum pressures in the rat model with a comparison to known data in humans.
  
  
  METHODS
  Three groups of eight Wistar rats each were anesthetized, tracheostomized, and mechanically ventilated with fixed tidal volume and respiratory rate. After a stabilization phase, CO(2) pneumoperitoneum was established to 12, 8, and 5 mmHg in the different groups. Changes in blood pressure, heart rate, peak ventilatory pressure, and end-tidal CO(2) (ETCO(2)) were recorded throughout the experiment.
  
  
  RESULTS
  There were no significant changes in blood pressure and heart rate in all groups. No increase in ETCO(2) was demonstrated following induction of pneumoperitoneum in the 12 and 8 mmHg groups. A statistical significant increase in ETCO(2) occurred only in the 5 mmHg group (39.4 to 41.3 mmHg, p = 0.023). Ventilatory pressures increased after induction of pneumoperitoneum in all groups. The increase reached a maximal level in the 8 and 12 mmHg groups (from 3 to 12 mmHg) and was lower in the 5 mmHg group (from 3 to 7 mmHg)
  
  
  CONCLUSIONS
  The neglected increase in ETCO(2) in pressures > or =8 mmHg, in the rat correlates to high pressures in humans (above 14-20 mmHg) when CO(2) diffusion through the peritoneum declines due to pressure occlusion of peritoneal capillaries. The maximal ventilatory pressures generated in the rat in intra-abdominal pressures > or =8 mmHg correlate to pressures, which are higher than the standard working pressures in humans. Thus, pneumoperitoneal pressures >8 mmHg in the rat do not simulate routine working pressures employed in humans. A pressure of 5 mmHg is optimal in a rat model to simulate laparoscopy in humans.
authors.affiliation: Surgery, Tel-Aviv Sourasky Medical Center, Tel Aviv, Israel. shmuelavital@hotmail.com
authors.forename: Shmuel
authors.initials: S
authors.lastname: Avital
authors.forename: Refael
authors.initials: R
authors.lastname: Itah
authors.forename: Samuel
authors.initials: S
authors.lastname: Szomstein
authors.forename: Raul
authors.initials: R
authors.lastname: Rosenthal
authors.forename: Roye
authors.initials: R
authors.lastname: Inbar
authors.forename: Yehuda
authors.initials: Y
authors.lastname: Sckornik
authors.forename: Avi
authors.initials: A
authors.lastname: Weinbroum
mesh_terms: D000403:Airway Resistance / Q000502:physiology; D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D002245:Carbon Dioxide; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D023421:Models, Animal; D011028:Pneumoperitoneum, Artificial / Q000379:methods*; D011312:Pressure; D051381:Rats; D017208:Rats, Wistar; D015203:Reproducibility of Results; D013990:Tidal Volume / Q000502:physiology
chemical_list: D002245:Carbon Dioxide