Comparison of volume-controlled versus pressure-controlled ventilation improved by PEEP during one-lung ventilation in patients undergoing thoracotomy

Objective To compare volume-controlled ventilation (VCV) versus pressure-controlled ventilation (PCV) improved by PEEP during one-lung ventilation (OLV).Methods Fifty ASA physical status Ⅰ-Ⅲ patients,aged 25-64 yr,weighing 40-80 kg,undergoing elective thoracotomy,were randomly divided into 2 groups (n =25 each) using a random number table:VCV + PEEP group (group Ⅴ) and PCV + PEEP group (group P).Those in group Ⅴ underwent OLV initially with VCV for 20 min followed by 4cm H2O PEEP for 20 min and then PEEP was removed.Those in group P underwent OLV initially with PCV for 20 min followed by 4cm H2O PEEP for 20 min and then PEEP was removed.At the beginning of two-lung ventilation before chest opening (T1),at 20 min of OLV before PEEP (T2),and at 20 min of ventilation with PEEP (T3),arterial blood samples were collected for blood gas analysis and the peak airway pressure (Ppeak) and development of SpO2 ＜ 95 ％ from beginning of OLV to T3 were recorded.Results Compared with group P,Ppeak at T2,3 and PaO2 at T3 were significantly increased in group Ⅴ (P ＜ 0.05).Compared with the baseline value at T1,PaO2 was significantly decreased and Ppeak was increased at T2.3 in Ⅴ and P groups (P ＜ 0.05).The incidence of SpO2 ＜ 95％ was significantly decreased and PaO2 was increased at T3 than at T2 in Ⅴ and P groups (P ＜ 0.05).Conclusion 4 cm H2O PEEP can improve VCV and PCV during OLV and the improved efficacy is better for VCV in patients undergoing thoracotomy. Key words: Positive pressure respiration;  Pulmonary gas exchange;  Respiration, artificial