ABSTRACT
Objective To monitor and compare the breathing mechanics on PC,VC and PRVC during pneumoperitoneum,and to discuss the significance of the clinic use of PRVC.Method Ninety laparoscopic cholecystectomy patients were equally divided into 3 groups (PC,VC,PRVC).Levels of PES,PAWM,PAP,PaCO2,ETCO2,TV MAP and HR were detected before pneumoperitoneum,and at 5,10,15 and 20 minutes postpneumoperitoneum.Results Pneumoperitoneum made three respiratory patterns with different levels of PAWM,PAP,and PES.PES post-pneumoperitoneum in the VC model was obviously higher than that in the PC and PRVC group.At 10 min post-pneumoperitoneum,levels of PaCO2 and ETCO2 increased obviously in the PC and VC group(P ＜ 0.05).Levels of PaCO2 and ETCO2 were increased in the PC group,but TV level post-pneumoperitoneum was significantly lower than that in the other two groups (P ＜ 0.05).Level of PaCO2 and ETCO2 were increased in the PC and VC group post-pneumoperitoneum,along with increases of MAP and HR (P ＜ 0.05).Levels of MAP and HR in the PRVC group post-pneumoperitoneum were significantly lower than those in the PC and VC group (P ＜ 0.05).Conclusion PRVC mode can effectively reduce the increases of pneumoperitoneum-induced PAWM,PAP,PES,without the unusual increase of PaCO2 and ETCO2 during surgeries,contributing to the stability of vital signs of perioperative patients.
ABSTRACT
BACKGROUND: Since the late 1960s, mechanical ventilation has been accomplished primarily using volume controlled ventilation(VCV). While VCV allows a set tidal volume to be guaranteed, VCV could bring about excessive airway pressures that may be lead to barotrauma in the patients with acute lung injury. With the increment of knowledge related to ventilator-induced lung injury, pressure controlled ventilation(PCV) has been frequenfly applied to these patients. But, PCV has a disadvantage of variable tidal volume delivery as pulinonary impedance changes. Since the concept of combining the positive attributes of VCV and PCV(dual control ventilation, DCV) was described firstly in 1992, a few DCV modes were introduced. Pressure-regulated volume control(PRVC) mode, a kind of DCV, is pressure-limited, time-cycled ventilation that uses tidal volume as a feedback control for continuously adjusting the pressure limit. However, no clinical studies were published on the efficacy of PRVC until now. This investigation studied the efficacy of PRVC in the patients with unstable respiratory mechanics. METHODS: The subjects were 8 mechanically ventilated patients(M: F= 6 : 2, 56+/-26 years) who showed unstable respiratory mechanics, which was defined by the coefficients of variation of peak inspiratory pressure for 15 minutes greater than 10% under VCV, or the coefficients of variation of tidal volume greater than 10% under PCV. The study was consisited of 3 modes application with VCV, PCV and PRVC for 15 minutes by random order. To obtain same tidal volume, inspiratory pressure setting was adjusted in PCV. Respiratory parameters were measured by pulmonary monitor(CP-100 pulmonary monitor, Bicore, Irvine, CA, USA). RESULTS: 1) Mean tidal volumes(VT) in each mode were not different(VCV, 431+/-102ml ; PCV, 417+/-99ml; PRVC, 414+/-97ml) 2) The coefficient of variation(CV) of VT were 5.2+/-3.9% in VCV, 15.2+/-7.5% in PCV and 19.3+/-10.0% in PRVC. The CV of VT in PCV and PRVC were significantly greater than that in VCV(p<0.01). 3) Mean peak inspiratory pressure(PIP) in VCV(31.0+/-6.9cm HD) was higher than PIP in PCV(26.0+/-6.5cm H20) or PRVC(27.0+/-6.4cm HD)(p<0.05). 4) The CV of PIP were 13.9+/-3.7% in VCV, 4.9+/-2.6% in PVC and 12.2+/-7.0% in PRVC. The CV of PIP in VCV and PRVC were greater than that in PCV(p<0.01). CONCLUSIONS: Because of wide fluctuations of VT and PIP, PRVC mode did not seem to have advantages compared to VCV or PCV in the patients with unstable respiratory mechanics.