分侧肺通气时不同呼气末正压和潮气量对单侧肺损伤犬循环的影响

目的 观察不同步分侧肺通气和同步分侧肺通气对单侧急性肺损伤(ALI)犬循环的影响.方法 取健康杂种犬12只,建立盐酸所致单侧肺损伤动物模型,行容积控制通气,将犬按随机数字表法分为不同步分侧肺通气组(NS组)和同步分侧肺通气组(S组).参数:患侧潮气量3.5 ml/kg保持不变,呼气末正压(PEEP)选择15、20、25 cm H2O(1 cm H2O=0.098 kPa);患侧PEEP 10 cm H2O不变,潮气量用随机数字表法选择5、7.5、10 ml/kg.健侧通气参数始终不变,检测不同通气条件下两组犬血流动力学和氧动力学指标.结果 (1)患侧潮气量3.5 ml/kg不变,PEEP为15、20 cm H2O时,两组血流动力学和氧动力学参数差异无统计学意义.当患侧PEEP为25 cm H2O时,NS组心率、体循环平均压(mABP)、心输出量、氧合指数和混合静脉血氧饱和度(SvO2)分别为(98±8)次/min、(84±6)mm Hg(1 mm Hg=0.133 kPa)、(1.10±0.13)L/min、(199±14)mm Hg和(55±6)%,明显低于S组[分别为(124±9)次/min、(103±7)mm Hg、(1.52±0.28)L/min、(221±15)mm Hg和(62±4)%,t值分别为-7.852、-16.561、-15.043、-13.314和-5.653,均P＜0.01].(2)患侧PEEP 10 cm H2O不变,潮气量分别为5、7.5 ml/kg时,两组的血流动力学和氧动力学参数比较差异无统计学意义.当患侧潮气量为10 ml/kg时,NS组HR、mABP、心输出量、氧合指数和SvO2均低于S组(均P＜0.01).结论 在本实验动物模型中,患侧与健侧所用PEEP水平相差≤20 cm H2O或患侧潮气量≤7.5 ml/kg时,同步和非同步分侧肺通气均能保持循环稳定.若需要更高水平PEEP时,建议选用同步分侧肺通气.

Hemodynamic effects of synchronous and asynchronous independent lung ventilation with different levels of positive end-expiratory pressure and tidal volumes on unilateral lung injury in dogs

Objective To investigate the effects of asynchronous independent lung ventilation and synchronous independent lung ventilation with different levels of positive end-expiratory pressure (PEEP)and tidal volumes on hemodynamics and gas exchange in dogs with a hydrochloric acid induced acute lung injury. Methods Twelve dogs with hydrochloric acid induced acute lung injury (left lung) were ventilated with volume controlled ventilation (VCV). The animals were randomly divided by random digit table into 2 groups. The first group ( group NS, n = 6) received asynchronous independent lung ventilation with the left lung PEEP 10 cm H2O ( 1 cm H2O =0. 098 kPa), VT 3.5 ml/kg and the right lung PEEP 0 cm H2O, VT 5 ml/kg. The second group ( group S, n = 6) received synchronous independent lung ventilation with the parameters as same as group NS. HR, mABP, mPAP, PAWP, CO and blood gas levels were measured during ventilation with different levels of PEEP (15, 20, 25 cm H2O) and VT (5, 7.5, 10 ml/kg) for 30 min. Results (1) After 30 min ventilation, no significant differences for hemodynamics and gas exchange were found between group NS and group S when Left lung PEEP was 15 or 20 cm H2O and VT was 5 or 7.5 ml/kg. (2) After 30 min ventilation, HR, mABP, CO, PaO2/FiO2, SvO2 in group NS [(98 ± 8)beats/min, (84 ± 6)mm Hg(1 mm Hg =0.133 kPa), (1.10 ±0.13) L/min, (199 ± 14)mm Hg and (55 ±6)%, respectively] were significantly lower than those in group S [(124 ±9)beats/min, ( 103 ±7)mm Hg, ( 1.52 ± 0.28 ) L/min, ( 221 ± 15 ) mm Hg and ( 62 ± 4 ) % , respectively] when PEEP was 25 cm H2O(all P ＜0.01 ). (3) After 30 min ventilation, HR, mABP, CO, PaO2/FiO2, SvO2 in group NS [(92±6)beats/min, (83 ±9)mm Hg, (1.23 ±0.08) L/min, (196 ±8)mm Hg and(57 ±2)%,respectively] were significantly lower than those in group S [(122 ± 10)beats/min, (104 ± 4 )mm Hg,(1.56 ±0.12)L/min,(216 ± 14)mm Hg and(63 ±4)% , respectively] when VT was 10 ml/kg (all P＜0.01 ). Conclusions In this animal model, the hemodynamics kept stable when the difference between the left lung PEEP and the right lung PEEP was less than 20 cm H2O. Synchronous independent lung ventilation caused less hemodynamic compromise when higher PEEP ( ＞25 cm H2O) was used because of the marked asymmetry in the mechanics of the 2 lungs.