Objective    To evaluate the effects of continuous positive airway pressure (CPAP) for non-ventilated lung on the intrapulmonary shunt fraction and oxygenation during one-lung ventilation (OLV) in patients who received thoracoscopy and laparoscopy-assisted radical treatment of esophageal carcinoma.     Methods    Eighty ASA class Ⅰ-Ⅱ esophageal carcinoma patients scheduled for esophagectomy under thoracoscopy and laparoscopy were enrolled and randomly divided into 4 groups (n=20): a control group

a CPAP 2 cmH

2

O group

a CPAP 5 cmH

2

O group

and a CPAP 8 cmH

2

O group. The patients in control group had non-ventilated lungs connected with the air during OLV

while those in CPAP groups had 2

5

and 8 cmH

2

O CPAP for the non-ventilated lungs respectively. Blood gases of all patients were analyzed separately before OLV (T1) and 30 min (T2)

60 min (T3)

90 min (T4)

and 120 min (T5) after OLV to calculate intrapulmonary shunt (Qs/Qt).     Results    PaO

2

decreased and Qs/Qt increased significantly at T2-T5 time points in the control group and CPAP 2 cmH

2

O group

compared with those at T1 time point (P0.05). There was no significant difference in PaO2 and Qs/Qt between T1 and T2-T5 time points in the CPAP 5 cmH

2

O group and CPAP 8 cmH

2

O group (P0.05). PaO

2

was higher and Qs/Qt was lower at T2-T5 time points in the CPAP 5 cmH

2

O group and CPAP 8 cmH

2

O group than those in the control group and CPAP 2 cmH

2

O group (P0.05). There was no significant difference in PaO

2

and Qs/Qt at T2-T5 time points between the CPAP 5 cmH

2

O group and CPAP 8 cmH

2

O group (P0.05). The CPAP 8 cmH

2

O group had less satisfactory lung collapse than other groups. There was no significant difference among the 4 groups in average operative

time (P0.05).     Conclusion    CPAP at 5 or 8 cmH

2

O for non-ventilated lungs during OLV in patients who receive thoracoscopy and laparoscopy-assisted radical treatment of esophageal carcinoma can reduce intrapulmonary shunt

increase PaO

2

and prevent hypoxemia. Compared with 8 cmH

2

O CPAP

5 cmH

2

O CPAP can provide a better surgical field for operation.