title: Abdominal lymph flow in an endotoxin sepsis model: influence of spontaneous breathing and mechanical ventilation.
abstract: OBJECTIVE
  Lymph flow from the abdomen was investigated in a sepsis model. We also compared the effect on thoracic duct lymph flow of mechanical ventilation with different levels of positive end-expiratory pressure (PEEP) and spontaneous breathing with continuous positive airway pressure (CPAP).
  
  
  METHODS
  Experimental study.
  
  
  METHODS
  Research laboratory in a university hospital.
  
  
  METHODS
  Thirty-two pigs.
  
  
  METHODS
  Animals were anesthetized. In study 1 (n = 18), an ultrasonic flow probe was put around the intact thoracic duct just caudal to the diaphragm, and animals were randomized to receive mechanical ventilation with a PEEP of 5 cm H2O or 15 cm H2O or breathed spontaneously in CPAP with a PEEP of 5 cm H2O. In study 2 (n = 6), the thoracic duct was cannulated and the cannula externalized through the abdominal wall for lymph collection; animals were then ventilated as in study 1. In all animals, endotoxin was infused at 15 microg/kg/hr for 2.5 hrs and then continued at 5 microg/kg/hr. In study 3, healthy (n = 4) and endotoxin-exposed (n = 4) pigs had intra-abdominal pressure increased to 27 cm H2O for 2 hrs by pneumoperitoneum. Lymph flow was measured as in study 1.
  
  
  RESULTS
  Lymph flow (mean +/- SE) was 2.5 +/- 0.4 mL/min at baseline and increased to 3.9 +/- 0.8 mL/min after 90 mins and 6.3 +/- 1.6 mL/min after 150 mins (p < .005) of endotoxin exposure. PEEP 15 cm H2O decreased lymph flow in pigs with intact thoracic duct (flow probe recording) and in pigs with cannulated lymph duct when drained against the central venous pressure. However, when drained against atmospheric pressure, PEEP increased flow. Spontaneous breathing increased flow both in intact and in cannulated animals.
  
  
  CONCLUSIONS
  Endotoxin increases lymph flow from the abdomen. Mechanical ventilation with high PEEP impedes lymph drainage and could increase lymph production. Spontaneous breathing increases flow and improves drainage of abdominal edema.
authors.affiliation: Department of Medical Sciences, Clinical Physiology, University Hospital, Uppsala, Sweden.
authors.forename: Marco
authors.initials: M
authors.lastname: Lattuada
authors.forename: Göran
authors.initials: G
authors.lastname: Hedenstierna
mesh_terms: D000005:Abdomen; D000818:Animals; D045422:Continuous Positive Airway Pressure; D008070:Lipopolysaccharides; D008196:Lymph / Q000378:metabolism*; D011175:Positive-Pressure Respiration / Q000379:methods*; D018805:Sepsis / Q000503:physiopathology / Q000628:therapy*; D013552:Swine; D013897:Thoracic Duct / Q000378:metabolism
chemical_list: D008070:Lipopolysaccharides