Comparison between volume-controlled ventilation and pressure-controlled volume-guaranteed ventilation in postoperative lung atelectasis using lung ultrasound following upper abdominal laparotomies: a prospective randomized study

BACKGROUND: Atelectasis is a common side effect of general anesthesia. Prevention of lung atelectasis, carbon dioxide retention, and chest infection would improve the quality of medical care and decrease hospital stay and costs. The aim of this study was to compare the effects of volume-controlled ventilation (VCV) and pressure-controlled volume-guaranteed ventilation (PCVG) on postoperative lung atelectasis using lung ultrasound (LUS) following upper abdominal laparotomies. RESULTS: Sixty patients (male and female) scheduled for upper abdominal laparotomies. They were randomly allocated into two equal groups: Group A (n = 30): received intraoperative volume-controlled ventilation (VCV) mode and group (n = 30): received intraoperative pressure-controlled ventilation volume-guaranteed (PCV-VG) mode. Arterial blood samples were obtained immediately after extubation, and 30, 120, 240, and 360 min postextubation. Lung ultrasound was done intraoperatively at 30 min from induction, immediate, and 120 and after 360 min postoperatively. There was difference between two groups favoring PCV-VG group but that difference failed to be statically significant regarding arterial partial pressure of oxygen (PaO(2)) and arterial carbon dioxide tension (PaCo(2)) between the two groups in preoperative, immediate postoperative, and 120, 240, and 360 min postoperative. Arterial oxygen saturation (SaO(2)) was significantly lower among patients in the VCV group immediate postextubation compared with patients in group PCV-VG (p value = 0.009*). Although signs of atelectasis were low in group B, 36.7% of the patients showed normal lung ultrasound, 63.3% showed various abnormalities, 46.7% showed the presence of lung pulse (vertical rhythmic movement synchronous with cardiac pulsation through motionless lung), and 46.7% showed B lines (vertical lines indicate abnormal lung aeration), while 30% of the patients showed the absence of A-lines (indicates the absence of lung sliding and abnormal lung aeration). Also, some patients demonstrated more than one sign. However, there was no a significant difference between the two groups both showed atelectasis immediate, 2 h and 6 h postoperatively. CONCLUSION: PCV-VG offered no significant advantage over VCV regarding the occurrence of the postoperative atelectasis. However, we prefer to use PCV-VG as postoperative hypoxia and atelectasis was much less in that mode. Further, large-scale studies are required to confirm these findings and to establish a definite conclusion.