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Title: [Effects of noninvasive proportional assist vs pressure support ventilation on respiratory work in chronic obstructive pulmonary disease patients with hypercapnia].
Author: Zhang JH, Luo Q, Zhang HJ, Chen RC.
Journal: Zhonghua Jie He He Hu Xi Za Zhi; 2017 Jun 12; 40(6):450-456. PubMed ID: 28592029.
Abstract:
Objective: To investigate the effect of noninvasive proportional assist ventilation (PAV) on respiratory work in chronic obstructive pulmonary disease(COPD) patients, in comparison to noninvasive pressure support ventilation(PSV). Methods: Ten severe COPD patients with hypercapnia during acute exacerbation were examined. The baseline inspiratory pressure of PSV (PS) and the assistance level of PAV(PA) were titrated by patients' tolerance. In addition to the baseline PS and PA, an additional decrease by 25% (PS-=75% PS, PA-=75% PA) or increase by 25% (PS+ =125% PS, PA+ =125% PA) of the assist level were applied to the patients. After the assessment of unassisted spontaneous breathing (SB), the patient was placed on the 6 levels of noninvasive-PSV and noninvasive-PAV in random sequence. Each level lasted at least 20 minutes. Respiratory rate (RR), tidal volume (Vt), and respiratory work(Wex, Wip and Wv) were measured. Asynchrony index (AI) was calculated. Results: During ventilation, Vt was significantly higher with each assist level than with SB. The Vt was significant increased with PS+ than with PA+ . An increase in expiratory work(Wex) and decrease in inspiratory work(Wip) were observed respectively, with the increasing assist level. The inspiratory muscles assessed by Wip were more unloaded at PS compared with PA [PS: (1.59±1.27) J/min vs PA: (4.99±3.48) J/min P<0.01]. However, the Wex was significantly higher with PS+ than with PA+ [PS+ : (1.17±0.54) J/min vs PA+ : (0.49±0.56)J/min, P<0.01]. The AI was increased with the increasing assist level of PSV [PS-: (0.46±0.57)%, PS: (1.36±1.24)% PS+ : (5.26±4.77)]. No asynchrony events were observed at PA- and PA. "Runaway" (expiratory asynchrony) was observed during PA+ [AI: (2.62±2.72)%]. Conclusions: Noninvasive-PAV can increase the Vt and decrease the Wip of the COPD patients with hypercapnia and avoid the over-assistance. The "Runaway" will occur at assist level higher than that set by tolerance. Physiological data can monitor the patient's responses and the ventilator-patient interaction, which may provide objective criteria for ventilator setting. 目的： 观察无创比例辅助通气(PAV)和压力支持通气(PSV)不同辅助水平对慢性阻塞性肺疾病(慢阻肺)患者的呼吸做功变化。 方法： 前瞻性纳入广州医科大学附属第一医院2011年8月至2013年12月10例极重度慢阻肺急性加重期患者，均为男性，年龄50～80岁，平均(65±13)岁，患者病情均较稳定，试验前行无创正压通气，测量患者可耐受的PAV和PSV压力辅助水平，分别增加或减少25%的压力，获得6个压力辅助水平：PS－、PS、PS＋、PA－、PA和PA＋。采集患者平静自主呼吸时的基础数据，然后按随机顺序先后应用2种通气模式的6个压力辅助水平，每个压力辅助水平通气20 min以上，直到呼吸平稳。用食道囊管法和胃囊管法测量胸膜腔内压和腹内压，同步检测气道内压。用层流型流量计检测呼吸流量和容量改变。计算呼吸频率、潮气量、分钟通气量(VE)并记录肺压力容积曲线和采用正常预计的胸壁压力容积曲线绘制Campbell图，计算患者呼气肌做功﹑吸气肌做功和呼吸机做功，并且通过食管压、气流及气道压监测人机同步性，计算不同步指数(AI)。 结果： PAV时患者耐受辅助比例为(77±13)%；PSV时耐受吸气相压力(IPAP)为(16.2±2.2)cmH(2)O(1 cmH(2)O＝0.098 kPa)。随着辅助水平提高，患者潮气量增加，吸气做功减少，分别为PS－：(6.15±2.37)J/min、PS：(1.59±1.27)J/min、PS＋：(0.90±0.70)J/min、PA－：(5.72±2.91)J/min、PA：(4.99±3.48)J/min、PA＋：(2.74±2.38)J/min，平静呼吸时吸气做功为(9.98±4.61)J/min；呼气做功增加，分别为PS－：(0.12±0.24)J/min、PS：(0.17±0.26)J/min、PS＋：(1.17±0.54)J/min、PA－：(0.20±0.38)J/min、PA：(0.16±0.37)J/min、PA＋：(0.49±0.56)J/min，平静呼吸时呼气做功为(0.18±0.30)J/min。随着辅助水平提高，PAV时患者吸气做功[PA：(4.99±3.48)J/min]高于PSV[(1.59±1.27)J/min，P<0.01)]，但呼气做功[PA＋：(0.49±0.56)J/min]低于PSV[PS＋：(1.17±0.54)J/min，P<0.01]。PAV时潮气量[PA＋：(573±112)ml]随辅助水平增加的程度不如PSV明显[PS＋：(670±123)ml, P<0.05]。PAV时，随着辅助水平提高，人机同步性下降，AI分别为PS－：(0.46±0.57)%、PS：(1.36±1.24)%、PS＋：(5.26±4.77)%。PAV时未发现误促发和双触发等现象，但在PA＋时观察呼气不同步，AI为(2.62±2.72)%。 结论： PAV可减轻慢阻肺患者吸气做功，增加潮气量，不容易出现过度充气，但是减轻呼吸肌肉负担功能不如PSV。在PAV过程中，未发现误促发、双触发等人机不同步现象，但在高辅助比例时出现"逃逸现象"。根据慢阻肺患者耐受性设置吸气压临床上可行，但仍需要摸索用客观指标去优化参数设置。.

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