Efficiency of the newly introduced ventilatory mode “pressure controlled ventilation-volume guaranteed” in thoracic surgery with one lung ventilation

Background
Anesthesia for thoracic surgery routinely involves one lung ventilation (OLV). Volume controlled ventilation (VCV) was and still the most common method of performing OLV. We assumed that pressure controlled ventilation-volume guaranteed (PCV-VG) is a better ventilation strategy for OLV than VCV as regard the inspiratory pressures, oxygenation parameters and post-operative ventilatory outcome.
Methods
Forty patients undergoing elective thoracic surgery in the lateral position requiring at least 1 h of OLV were randomly assigned into two groups. Group VCV: VCV was performed throughout the operation. Group PCV-VG: PCV-VG was performed throughout the operation. Blood gas analysis, peak inspiratory pressure (), mean inspiratory pressure (), plateau inspiratory pressure () were measured: (1) During two lung ventilation (TLV1) 30 min after turning the patient to the lateral decubitus prior the beginning of OLV; (2) 30 min after initiation of OLV(OLV); (3) End of surgery: 30 min after reestablishing TLV (TLV2).
Results
The and the were significantly lower in PCV-VG compared with VCV in all stages of the study ( < 0.05). There was significant increase in all pressure values in OLV compared with TLV1 in the two groups ( < 0.05). There were significant decrease in the mean Pao2 values during OLV and TLV2 compared with TLV1 in the two groups ( < 0.05). Yet the Pao2 was significantly higher in the PCV-VG group at OLV and TLV2 compared to the OLV and TLV2 in VCV group. Also Pao2 was significantly lower in TLV2 compared with TLV1 in both groups ( < 0.05).
Conclusion
In patients undergoing thoracic surgery with OLV, pressure controlled volume guaranteed mode of ventilation decreases inspiratory pressure parameters and improve arterial oxygenation better than volume controlled ventilation.