[Effects of permissive hypercapnia on pulmonary mechanics and hemodynamics in sheep with acute lung injury].
OBJECTIVE
To study the effects of permissive hypercapnia (PHC) on pulmonary mechanics and hemodynamics in sheep with acute lung injury (ALI).


METHODS
In 18 sheep with LPS induced ALI, gas exchange, pulmonary mechanics and hemodynamics were observed at different tidal volumes (VT).


RESULTS
When VT was decreased from 16 ml/kg to 4-7 ml/kg, PHC was induced. Arterial pressure of carbon dioxide increased markedly, arterial oxygen pressure, oxygen saturation and mixed venous oxygen saturation decreased (P < 0.05). Airway pressure decreased significantly (P < 0.05), but the airway resistance increased. Systemic and pulmonary vascular resistance index, right and left ventricular stroke work index increased in PHC, but heart rate decreased (P < 0.05). Compared with VT 16 ml/kg, cardiac index decreased markedly in PHC. In static pressure-volume curve, the pressure of upper inflection point was (21.8 +/- 3.2) cm H2O, volume was (10.7 +/- 1.3) ml/kg.


CONCLUSIONS
Alveolar overdistention may be prevented only when airway plateau pressure is less than 20-25 cm H2O, but cardiac index is decreased.
Department of Critical Care Medicine, Zhongda Hospital, Southeast University, Nanjing 210009, China.
Y
Y
Tan
H
H
Qiu
F
F
Guo
D000818:Animals; D006439:Hemodynamics; D006935:Hypercapnia / Q000503:physiopathology*; D008168:Lung / Q000503:physiopathology*; D011659:Pulmonary Gas Exchange; D012128:Respiratory Distress Syndrome / Q000503:physiopathology* / Q000628:therapy; D015656:Respiratory Mechanics; D012756:Sheep