title: Lung recruitment and positive end-expiratory pressure have different effects on CO2 elimination in healthy and sick lungs.
abstract: BACKGROUND
  We studied the effects that the lung recruitment maneuver (RM) and positive end-expiratory pressure (PEEP) have on the elimination of CO(2) per breath (Vtco(2,br)).
  
  
  METHODS
  In 7 healthy and 7 lung-lavaged pigs at constant ventilation, PEEP was increased from 0 to 18 cm H(2)O and then decreased to 0 in steps of 6 cm H(2)O every 10 minutes. Cycling RMs with plateau pressure/PEEP of 40/20 (healthy) and 50/25 (lavaged) cm H(2)O were applied for 2 minutes between 18-PEEP steps. Volumetric capnography, respiratory mechanics, blood gas, and hemodynamic data were recorded.
  
  
  RESULTS
  In healthy lungs before the RM, Vtco(2,br) was inversely proportional to PEEP decreasing from 4.0 (3.6-4.4) mL (median and interquartile range) at 0-PEEP to 3.1 (2.8-3.4) mL at 18-PEEP (P < 0.05). After the RM, Vtco(2,br) increased from 3.3 (3-3.6) mL at 18-PEEP to 4.0 (3.5-4.5) mL at 0-PEEP (P < 0.05). In lavaged lungs before the RM, Vtco(2,br) increased initially from 2.0 (1.7-2.3) mL at 0-PEEP to 2.6 (2.2-3) mL at 12-PEEP (P < 0.05) but then decreased to 2.4 (2-2.8) mL when PEEP was increased further to 18 cm H(2)O (P < 0.05). After the RM, the highest Vtco(2,br) of 2.9 (2.1-3.7) mL was observed at 12-PEEP and then decreased to 2.5 (1.9-3.1) mL at 0-PEEP (P < 0.05). Vtco(2,br) was directly related to changes in lung perfusion, the area of gas exchange, and alveolar ventilation but inversely related to changes in dead space.
  
  
  CONCLUSIONS
  CO(2) elimination by the lungs was dependent on PEEP and recruitment and showed major differences between healthy and lavaged lungs.
authors: Department of Anesthesiology, Hospital Privado de Comunidad, Mar del Plata, Argentina. gtusman@hotmail.com
authors: Gerardo
authors: G
authors: Tusman
authors: Stephan H
authors: SH
authors: Bohm
authors: Fernando
authors: F
authors: Suarez-Sipmann
authors: Adriana
authors: A
authors: Scandurra
authors: Göran
authors: G
authors: Hedenstierna
mesh_terms: D000818:Animals; D001784:Blood Gas Analysis / Q000379:methods; D018893:Bronchoalveolar Lavage / Q000379:methods; D002245:Carbon Dioxide / Q000032:analysis*; D045853:Exhalation / Q000502:physiology*; D008168:Lung / Q000502:physiology*; D008171:Lung Diseases / Q000503:physiopathology*; D008176:Lung Volume Measurements / Q000379:methods; D011175:Positive-Pressure Respiration / Q000379:methods*; D011659:Pulmonary Gas Exchange / Q000502:physiology; D011897:Random Allocation; D015656:Respiratory Mechanics / Q000502:physiology*; D013552:Swine
chemical_list: D002245:Carbon Dioxide