Hirabayashi Go, Yokose Yuuki, Oshika Hiroyuki, Saito Minami, Maruyama Koichi, Andoh Tomio
Department of Anaesthesiology, Mizonokuchi Hospital Teikyo University School of Medicine, Kanagawa, Japan.
BJA Open. 2022 Jul 20;3:100020. doi: 10.1016/j.bjao.2022.100020. eCollection 2022 Sep.
The effect of inverse inspiration:expiration (I:E) ratio on functional residual capacity (FRC) during pneumoperitoneum is unclear. We hypothesised that volume-targeted pressure-controlled inverse ratio ventilation (vtPC-IRV) would increase FRC by increasing the level of auto-PEEP in low respiratory compliance situations.
During robot-assisted laparoscopic radical prostatectomy, 20 obese patients were sequentially ventilated with four different settings for 30 min in each setting: (1) control, I:E ratio of 1:2 and baseline airway pressure (BAP) of 5 cm HO; (2) IRV2, I:E ratio of 2:1 and BAP off; (3) IRV3, I:E ratio of 3:1 and BAP off; and (4) IRV4, I:E ratio of 4:1 and BAP off. The changes in FRC were identified and compared among these settings.
The FRC significantly increased as the I:E ratio increased. The FRC values expressed as median (inter-quartile range) during control, IRV2, IRV3, and IRV4 were 1149 (898-1386), 1485 (1018-1717), 1602 (1209-1775), and 1757 (1337-1955) ml, respectively. Auto-PEEP increased significantly as the I:E ratio increased and correlated with FRC (rho=0.303; =0.006). Shunt and physiological dead space were significantly lower in all IRV groups than in the control group; however, there were no significant differences among the IRV groups.
vtPC-IRV with shortened expiratory time and increased auto-PEEP effectively increases FRC during robot-assisted laparoscopic radical prostatectomy in obese patients. FRC increases progressively as the I:E ratio increases from 1:2 to 4:1; however, an I:E ratio higher than 2:1 does not further improve the dead space.
UMIN000038989.
气腹期间反向吸呼比（I:E）对功能残气量（FRC）的影响尚不清楚。我们假设在低呼吸顺应性情况下，容量目标压力控制反比通气（vtPC-IRV）通过提高内源性呼气末正压（auto-PEEP）水平来增加FRC。
在机器人辅助腹腔镜根治性前列腺切除术中，20例肥胖患者依次采用四种不同设置进行通气，每种设置持续30分钟：（1）对照组，I:E比为1:2，基线气道压力（BAP）为5 cmH₂O；（2）IRV2，I:E比为2:1，BAP关闭；（3）IRV3，I:E比为3:1，BAP关闭；（4）IRV4，I:E比为4:1，BAP关闭。确定并比较这些设置下FRC的变化。
随着I:E比增加，FRC显著增加。对照组、IRV2组、IRV3组和IRV4组期间以中位数（四分位间距）表示的FRC值分别为1149（898 - 1386）、1485（1018 - 1717）、1602（1209 - 1775）和1757（1337 - 1955）ml。随着I:E比增加，auto-PEEP显著增加，且与FRC相关（rho = 0.303；P = 0.006）。所有IRV组的分流和生理死腔均显著低于对照组；然而，IRV组之间无显著差异。
在肥胖患者的机器人辅助腹腔镜根治性前列腺切除术中，缩短呼气时间并增加auto-PEEP的vtPC-IRV可有效增加FRC。随着I:E比从1:2增加到4:1，FRC逐渐增加；然而，高于2:1的I:E比并不能进一步改善死腔。
UMIN000038989。
