呼气触发灵敏度对压力支持通气时慢性阻塞性肺疾病患者人-机呼气同步性及呼吸功的影响

目的探讨呼气触发灵敏度(ETS)对压力支持通气(PSV)时慢性阻塞性肺疾病(COPD)患者呼气同步性及呼吸功的影响。方法对31例行机械通气治疗的COPD患者采用PSV模式,使用呼吸力学监护仪进行呼吸力学监测,同时进行膈肌肌电图检测。选择5个水平的ETS:1%、15%、25%、35%及50%吸气峰流速(PIF)进行研究。在每次改变ETS水平30min后,对所有数据进行3min的同步采集。通过测量膈肌肌电图与呼吸流速波形之间的呼气相位角(θ),计算总呼吸功(Wtot)、吸气肌做功(Wi,p)、呼气肌做功(Wex),分析ETS对人-机呼气同步性及呼吸功的影响。结果有10人被排除研究。ETS在25%PIF水平时人-机呼气同步性最佳,θ=(8±3)°,有16人-15°≤θ≤15°;Wtot、Wi,p、Wex也最小,分别为(1·86±0·53)J/L、(0·54±0·13)J/L、(0·16±0·08)J/L。随ETS水平降低,吸气结束延迟及Wex逐渐增多,1%PIF时θ=(86±22)°,有18人θ>15°,Wex为(0·48±0·10)J/L,此时Wi,p显著增高至(0·65±0·16)J/L;而随ETS水平升高,吸气结束提前的发生及Wi,p逐渐增加,50%PIF时θ=-(72±15)°,有19人θ<-15°,Wi,p为(1·33±0·14)J/L。结论PSV时适当调节ETS能够改善COPD患者的人-机呼气同步性,降低呼吸功。

Effects of expiratory triggering sensitivity on patient-ventilator expiratory synchrony and work of breathing in patients with chronic obstructive pulmonary disease during pressure support ventilation

OBJECTIVE: To study the effects of expiratory triggering sensitivity (ETS) on patient-ventilator expiratory synchrony and work of breathing in chronic obstructive pulmonary disease (COPD) patients during pressure support ventilation (PSV). METHODS: A total of 31 COPD patients were ventilated in PSV mode, and measured by a pulmonary monitor. Meanwhile, the electromyogram of the diaphragm (EMG(diaph)) was obtained with electromyography. Five levels of ETS, 1%, 15%, 25%, 35%, and 50% of peak inspiratory flow (PIF), were studied in random order. Each ETS level lasted 30 minutes and all the data were recorded simultaneously for 3 minutes at the end of each period. The effects of ETS on patient-ventilator expiratory synchrony were analyzed by measuring the phase angle of expiration between the EMG(diaph) and the flow wave curve, and the effects of ETS on work of breathing by calculating total work of breathing (Wtot), work of inspiration by patients (Wi, P) and expiratory work of breathing (Wex). RESULTS: Ten patients were excluded from the study. At the 25% PIF level of ETS, patient-ventilator expiratory synchrony was the best, theta = (8 +/- 3) degrees, 16 patients - 15 degrees < or = theta < or = 15 degrees, and the amount of Wtot, Wi, p, Wex was the smallest among all the 5 levels of ETS, which was (1.86 +/- 0.53) J/L, (0.54 +/- 0.13) J/L, and (0.16 +/- 0.08) J/L respectively. When the level of ETS decreased, the occurrence of delayed termination of inspiration and the amount of Wex increased. At the level of 1% PIF, 18 patients theta > 15 degrees, and Wex was (0.48 +/- 0.10) J/L; at this level of ETS, Wi, p also increased significantly to (0.65 +/- 0.16 ) J/L. But when the level of ETS increased, the occurrence of premature termination of inspiration and the amount of Wi, p increased: at 50% PIF level of ETS, theta < - 15 degrees and Wi, p was (1.33 +/- 0.14) J/L in 19 patients. CONCLUSION: The proper adjustment of ETS during PSV improves patient-ventilator synchrony and decreases work of breathing in COPD patients.