Effects Of Different Methods Of Ventilation On Perioperative Respiratory Function In Elderly Patients With General Anesthesia In Prone Position

Objective To observe the effects of different methods of ventilation on perioperative respiratory function, respiratory mechanics and hemodynamics during general anesthesia in the elderly patients with prone position.Methods Sixty elderly patients undergoing spinal surgery with general anesthesia in prone position who aged 65~75 yr, weighting 50~75kg, BMI 20~25kg/m2 and ASA physical status I or II, were randomly assigned into three groups(n=20 in each group) : group C(Vt:10ml?kg-1), group LV(Vt:6ml?kg-1) and group LV+PEEP(Vt:6ml?kg-1,PEEP:5cm H2O). Respiratory function, respiratory mechanics and hemodynamics indexes were recorded at the time of before anesthesia induction(T0), 10 min after mechanical ventilation under supine position with tracheal intubation(T1), 10 min after mechanical ventilation under prone position(T2), 60 min after mechanical ventilation under prone position(T3), 30 min after tracheal extubation(T4), 24 h after tracheal extubation(T5), and 48 h after tracheal extubation(T6).Results There were no significant differences of the baseline characteristics in three groups of patients(P >0.05). At the time points of T2, T3, T4, T5, the Pa CO2 in group LV was higher than that of group C and group LV+PEEP(P<0.05). At the time points of T2, T3, T4, T5, T6, the Pa CO2 in group LV was higher than that of time point of T0(P<0.05). At the time points of T4, T5, T6, A-a DO2 and RI in group LV+PEEP was significantly lower than that in group C and group LV(P<0.05), and Pa O2/Fi O2 was significantly higher than that of group C and group LV(P<0.05). At the time point of T4, T5, T6, A-a DO2 and RI in group LV+PEEP was significantly lower than that of time point of T0(P<0.05). At the time points of T1,T2,T3, T4, T5, T6, Pa O2/Fi O2 in group LV+PEEP was significantly higher than that of time point of T0(P<0.05). The Ppeak and Pmean in group C was higher than that of group LV and group LV+PEEP(P<0.05), the Ppeak and Pmean in group LV+PEEP was higher than that of group LV(P>0.05), but the Ppeak and Pmean of three groups increased with the increasing aeration time(P<0.05). At the time points of T2, T3, the Cdyn of group LV+PEEP was significantly higher than that of group C(P<0.05), but the Cdyn of the three groups were decreased in the duration of ventilation(P<0.05). At the same time points, hemodynamic indexes of HR, MAP between three groups of patients were not statistically significant(P>0.05).Conclusion The mechanical ventilation mode that Low tidal volume combined with low level PEEP(6ml/kg+5cm H2 O PEEP) would accelerate the recovery of respiratory functions in elderly patients with general anesthesia in prone position undergoing spinal surgery.