title: Effects of continuous negative extra-abdominal pressure on cardiorespiratory function during abdominal hypertension: an experimental study.
abstract: OBJECTIVE
  To investigate whether negative extra-abdominal pressure (NEXAP) improves respiratory function and induces a blood shift from the intrathoracic compartment and to assess whether these effects are influenced by abdominal pressure.
  
  
  METHODS
  Prospective, randomized, controlled trial in the animal laboratory of a university hospital.
  
  
  METHODS
  Eight sedated and paralyzed pigs (19.6+/-3.4 kg).
  
  
  METHODS
  Application of NEXAP (-20 cmH(2)O).
  
  
  RESULTS
  Airway, esophageal, gastric and central venous pressures were recorded simultaneously. Intrathoracic blood volume was assessed by PiCCO. The effects of NEXAP were assessed with and without abdominal hypertension by intraperitoneal insufflation of helium. NEXAP caused a lasting drop of gastric (1.97+/-2.26 mmHg) and esophageal (1.21+/-0.67 mmHg) pressures, while end-expiratory airway pressure was similar, hence transpulmonary pressure increased. Intrathoracic blood volume dropped from 358+/-47 to 314+/-47 ml. The fall was associated with a decrease in central venous pressure (R(2)=0.820). When peritoneal pressure was raised (24.7+/-5.5 mmHg), the effects were less marked. However, the difference between negative pressure around the abdomen and the pressure inside the abdomen (effective NEXAP) was correlated with the proportional changes in intrathoracic blood volume (R(2)=0.648), being greater with more negative effective NEXAP. NEXAP improved chest wall elastance during abdominal hypertension (from 0.067+/-0.023 to 0.056+/-0.021 cmH(2)O/ml).
  
  
  CONCLUSIONS
  NEXAP increases lung volume and causes a shift of blood from the intrathoracic compartment. It needs to be tailored against abdominal pressure to be effective.
authors.affiliation: Istituto di Anestesia e Rianimazione, Ospedale Maggiore di Milano-Istituto di Ricovero e Cura a Carattere Scientifico, Università degli Studi di Milano, Via F. Sforza 35, 20122 Milan, Italy.
authors.forename: Franco
authors.initials: F
authors.lastname: Valenza
authors.forename: Manuela
authors.initials: M
authors.lastname: Irace
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Guglielmi
authors.forename: Stefano
authors.initials: S
authors.lastname: Gatti
authors.forename: Nicola
authors.initials: N
authors.lastname: Bottino
authors.forename: Cecilia
authors.initials: C
authors.lastname: Tedesco
authors.forename: Micol
authors.initials: M
authors.lastname: Maffioletti
authors.forename: Patrizia
authors.initials: P
authors.lastname: Maccagni
authors.forename: Tommaso
authors.initials: T
authors.lastname: Fossali
authors.forename: Gabriele
authors.initials: G
authors.lastname: Aletti
authors.forename: Luciano
authors.initials: L
authors.lastname: Gattinoni
mesh_terms: D000818:Animals; D006339:Heart Rate; D006973:Hypertension / Q000628:therapy*; D008150:Lower Body Negative Pressure / Q000379:methods*; D011175:Positive-Pressure Respiration; D011659:Pulmonary Gas Exchange; D012119:Respiration; D013552:Swine