[Effect of different tidal volume ventilations on atelectasis in patients during general anesthesia by CT scan]

To investigate the effect of different tidal volume ventilations on the amount of atelectasis during general anesthesia.

Twenty adults, ASA physical status I and status II patients, who were scheduled for elective excision of intracranial lesion were randomly divided into 2 groups: Group TV (traditional tidal volume ventilation, 10 mL/kg) and Group LV (low tidal volume ventilation, 6 mL/kg). Atelectasis, as determined by CT and artery blood gas (ABG) analysis, was measured before the anesthesia, after the tracheal intubation, and at the end of the operation, respectively. Respiratory mechanical parameters were measured at 30, 120, and 240 min after the intubation.

After the tracheal intubation, CT scan showed obvious atelectasis in both groups. The atelectasis area was(4.35+/-2.15)cm2 (3.12%+/-1.94%) in the TV group and (4.80+/-2.45)cm2 (3.89%+/-2.11%) in the LV group, with a nonsignificant difference between the 2 groups. At the end of the operation, there was no significant increase in the amount of atelectasis between and within the 2 groups. Artery blood gas analysis showed no difference after the tracheal intubation and at the end of the operation in either group. Ppeak, Pplat, Pmean and lung compliance(Cst)were significantly higher in the TV group than those in the LV group.

Low tidal volume(6 mL/kg) ventilation is more feasible during general anesthesia in patients with healthy lungs, and it does not increase the atelectasis and impairment of gas exchange.