Evaluation of lung protective property of expiratory flow initiated pressure-controlled inverse ratio ventilation in robot-assisted laparoscopic radical prostatectomy

Abstract

Background: We have shown that expiratory flow initiated pressure-controlled inverse ratio ventilation (EF initiated PC-IRV) reduces physiological dead space (VD_phys).

Objective: To evaluate lung protection with EF initiated PC-IRV.

Design: A randomised controlled trial.

Patients: 28 consecutive subjects undergoing robot-assisted laparoscopic radical prostatectomy.

Interventions: EF initiated PC-IRV strategy (n=14) includes pressure control ventilation volume guarantee (PCV-VG) mode, V_T setting of 6–10 ml/kg so that plateau pressure ≤ 30 cmH₂O. I/E ratio was adjusted to initiate inflation at the midpoint between the expiratory flow change point and the return point to the expected baseline. Volume control ventilation (VCV) strategy (n=14) includes VCV mode, pause ratio of 20%, I/E ratio of 1/2, VT setting of 6–10 ml/kg so that plateau pressure ≤ 30 cmH₂O. Hypercapnia (>50 mmHg) was permitted at the maximum RR of 18 bpm, plateau pressure of 30 cmH₂O. Serum IL-6 levels were measured at the end of surgery.

Results: There were no significant differences in serum IL-6 after surgery between PC-IRV 34 (10-122) pg/ml and VCV 31 (18-273) pg/ml [median (min - max)].

VD_phys/V_TE ratio in VCV correlated negatively with FVC % predicted. There were 2 permissive hypercapnia cases in VCV, in the cases with low FVC % predicted.

VD_phys/V_TE ratio were reduced in PC-IRV and did not correlated with FVC % predicted. There was no permissive hypercapnia in PC-IRV.

Conclusion: EF initiated PC-IRV was useful in low respiratory compliance cases, but its protective effect estimated by systemic IL-6 levels was not evident in this study.