比例辅助通气对撤机阶段慢性阻塞性肺疾病合并呼吸衰竭患者通气参数的影响

目的 观察比例辅助通气(PAV)与压力支持通气(PSV)对撤机阶段慢性阻塞性肺疾病(COPD)合并呼吸衰竭患者通气参数的影响.方法 COPD合并呼吸衰竭患者15例,所有患者均为气管插管并接受机械通气支持1周以上者,在治疗过程中病情稳定准备撤机.随机选用PAV和不同水平的PSVPSV水平为10 cm H2O(PS10)和PSV水平为15 cm H2O(PS15),1 cm H2O=0.098 kPa]辅助通气60 min,应用PAV前采用最小平方拟合法(LSF)测定患者的呼吸系统弹性阻力(Ers)和气道阻力(Rrs),设置容量辅助(VA)和流量辅助(FA),辅助比例为80%.观察患者在不同通气条件下通气参数及动脉血气分析的变化.结果 与低水平PSV(PS10)时相比,高水平PSV(PS15)与PAV时的潮气量显著增加(443±12)ml与(532±34)ml、(464±23)ml,P<0.05];PAV时的呼吸频率与气道峰压稍高于PS10时,但差异无统计学意义.PAV支持后,患者的气道闭合压由PS10时的(5.70±0.25)cm H2O降至(4.53±0.25)cm H2O(P<0.05),气道压力及吸气触发压力时间乘积也显著降低由(0.42±0.04)cm H2O降至(0.32±0.03)cm H2O,P<0.05];而氧合指数与动脉血二氧化碳分压均得到明显改善,与PS15时相近.PAV时的浅快呼吸指数较PS10时无明显改变.结论 PAV通过采用正反馈调节机制,成比例地提供同步辅助,显著减少COPD呼吸衰竭患者的自主吸气做功,改善人机同步性.

Effects of respiratory mechanics in weaning patients with chronic obstructive pulmonary disease during proportional assist ventilation

Objective To evaluate the effects of proportional assist ventilation (PAV) and pressure support ventilation (PSV) on ventilate parameters of patients with chronic obstructive pulmonary disease (COPD) combined with respiratory failure.Methods Fifteen intubated stable patients recovering from acute exacerbation of COPD combined with respiratory failure were randomized to receive PAV or PSV support 60 min and then crossed over to alternative mode.Respiratory mechanics including respiratory systemelastic resistance and airway resistance were monitored by least square fitting (LSF) methed.During PAV support.the ratio of volume assist (VA) and flow assist (FA) level wag 80%.The ventilate parameters and arterialblood gas at different ventilate condition was observed.Results Compared with low level PSV (PS 10 cm H2O,1 cm H2O=0.098 kPa,PS10),tidal volume in high level PSV (PS 15 cm H2O,PS15) and PAV was significantly increased (443±12)ml vs(532±34)ml,(464±23)ml,P<0.05].There was no difference in respiratory rate and peak inspiratory pressure between PAV and PS10.Airway occlusion pressure and time product of triggering was d()reased from (5.70±0.25)cm H2O to (4.53±0.25)cm H2O and (0.42±0.04) cm H2O to (0.32±0.03)cm H2O(P<0.05),PaO2/FiO2 ratio and PaCO2 was also significantly improved after PAV supported compared with PS10,and similar with PS15.The rapid shallow breath index at PAV was similar with PS10.Condusion As a positive feedback system,PAV seems more efficacious than low level of PSV in decreasing the work of breathing during the inspiratory phase,resulting in fewer patient-ventilator asynchronism,and it may be beneficial for weaning.