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PEEP一般用于治疗低氧血症以改善PaO_2,但PEEP对PaCO_2不良影响尚未被充分认识。PEEP可使肺血流灌注减少,使肺通气/血流灌注比值(V_A/Q)增大,PaCO_2增高,生理无效腔/潮量比值(V_D/VT)增大。造成V_D/VT增大的原因,可能是由于心排血量(CO)减少,使整个肺灌注减少,也可能是由于肺泡压增高压迫肺泡间隔中毛细血管,致肺局部细血管血流减少。作者观察用PEEP后和用右旋糖酐使CO恢复后肺毛细血管灌注。V_D/VT和PaCO_2的变化。
PEEP is generally used to treat hypoxemia to improve PaO_2, but the adverse effect of PEEP on PaCO_2 has not yet been fully understood. PEEP can reduce pulmonary blood flow perfusion, pulmonary ventilation / perfusion ratio (V_A / Q) increased, PaCO_2 increased, physiologic invalid cavity / tidal volume ratio (V_D / VT) increased. V_D / VT increase may be due to decreased cardiac output (CO), so that the whole lung perfusion decreased, may also be due to increased alveolar pressure in the alveolar septum capillaries, local blood vessels leading to reduced blood flow to the lungs. The authors observed pulmonary capillary perfusion after recovery of CO with dextran and PEEP. V_D / VT and PaCO_2 changes.