神经调节辅助通气研究进展

近年,引人了通过横膈电活动控制的神经调节辅助通气(neurally adjusted ventilatory assist,NAVA)这一机械通气模式,它能同时在时间和通气水平上与患者自身作功相协调一致.NAVA使呼吸机的通气支持能够与呼吸中枢所要求的通气量相匹配,从而提高了人机之间的协调性.在吸气过程中,NAVA能安全有效地使呼吸肌得以放松,且不会出现辅助通气的脱节和产生过度肺膨胀.此外,NAVA也不受漏气的影响,能够松弛呼吸肌并能与患者通气需求相协调.总之,NAVA开创了机械通气的新时代.     

神经电活动辅助通气对急性呼吸窘迫综合征患者人机同步性的影响

目的 观察神经电活动辅助通气(NAVA)对急性呼吸窘迫综合征(ARDS)患者人机同步性的影响.方法 以2008年1月至6月入住东南大学附属中大医院ICU 18例ARDS机械通气患者为研究对象,按随机数字表法选择NAVA或压力支持通气(PSV)模式进行通气,通气支持水平分4步递增.PSV压力支持水平从5 cm H2O(1 cm H2O=0.098 kPa)开始,每5 min增加5 cm H2O,分别为5、10、15、20 cm H2O.NAVA支持水平每5 min增加0.2～1.0 cm H2O/μY,使NAVA中通气支持水平分别与PSV 4个压力支持水平相当,观察不同支持条件下(PSV1～PsV4及NAVA1～NAVA4)人机同步性、呼吸肌负荷、血流动力学以及呼吸力学等指标.结果 (1)吸气触发:①触发延迟时间:随着支持水平增加,PSV中触发延迟时间明显延长(P<0.05),而应用NAVA通气时触发延迟时间无明显延长.与相同支持水平的PSV比较,应用NAVA的触发延迟时间均明显缩短(P<0.05).②无效触发:随着PSV支持水平增加,无效触发明显增加,PSV1时无效触发2.3%,PSV4时无效触发为22%(P<0.05).应用NAVA时,不同支持水平下,均未见无效触发.(2)吸/呼气转换:随着支持水平增加,PSV中吸/呼气转换延迟时间明显延长(P<0.05),而应用NAVA通气时吸/呼气转换延迟时间无明显延长.与相同支持水平的PSV比较.应用NAVA时吸/呼气转换延迟时间均明显缩短(P<0.05).(3)通气支持幅度(潮气量):PSV1和NAVA1的潮气量分别为(361±121)ml和(361±69)ml,差异无统计学意义.但NAVA3和NAVA4时的潮气量分别为(417±71)ml和(427±80)ml,明显低于PSV3和PSV4时的潮气量[分别为(604 ±141)ml和(675±108)ml,均P<0.05].(4)呼吸肌负荷:随着支持水平增加,应用NAVA和PSV通气的膈肌电活动幅度、食管压力时间乘积均逐渐降低(P<0.05).在相同支持水平时,两绢比较差异无统计学意义.结论 与PSV相比,NAVA通气支持时间、通气支持水平与自身呼吸形式更加匹;配,应用NAVA更能改善ARDS患者人机同步性.     

全新的通气模式:神经调节通气辅助模式

神经调节通气辅助模式(neurally adjusted ventilatory assist,NAVA)是一种全新的通气模式,其工作原理是通过监测神经呼吸信号感知患者的实际通气需求,进而提供生理化的呼吸支持.NAVA与当前的通气模式不同,无需设置容量、压力等参数,利用神经呼吸信号控制呼吸机送气,不仅能够实时监测患者的通气需求,而且实现了患者完全控制呼吸机送气,开创了机械通气的又一全新领域.     

解读神经调节通气辅助模式

神经调节通气辅助模式(NAVA)是利用膈肌电活动(Ed i)控制呼吸机送气的全新通气模式。在NAVA模式下,呼吸中枢可以直接控制呼吸机的辅助水平,呼吸机变成了"呼吸肌"。目前研究表明,NA-VA可实现个体化的通气支持,极大地改善人机协调性,有效减轻呼吸中枢负荷,并能防止肺过度膨胀。     

COPD患者使用NAVA或ASV通气模式的对比研究

目的探讨COPD患者机械通气时选择不同通气模式下,人机同步性及舒适性的比较。为COPD病人探索更适宜的通气方案。方法选择80例行有创机械通气的COPD患者,分为神经调节辅助通气(NAVA)组17例、适应性支持通气组(ASV)33例、实施压力控制通气-压力支持的常规对照组30例。在保持分钟通气量基本相似的情况下,对比所有组患者的呼吸力学指标、血气指标和血流动力学指标,并采用量表分析患者上机时的呼吸机不合拍程度(人机对抗率)。结果各组患者的年龄、性别、APACHEⅡ评分结果无差异;NAVA组患者指令呼吸频率较低,NAVA组和ASV组患者的潮气量均比对照通气组大,P值均0.05。量表评估NAVA、ASV、对照组的人机对抗率分别为29.4%(5/17)、21.2%(7/33)、40%(12/30),差异显著(P0.01)。结论 NAVA和ASV通气均可保持较好的自主呼吸,降低人机对抗率,是符合COPD患者需要的通气模式。     

体外膈肌起搏对老年神经调节辅助通气患者预后的改善作用

目的探讨体外膈肌起搏（external diaphragm pacemaker, EDP）对老年神经调节辅助通气（neurally adjusted ventilatory assist, NAVA）患者预后的改善作用。 方法选择2017年1月至2019年6月浙江医院收治的60例老年机械通气患者，采用随机数字表法分为NAVA组（25例）和NAVA+EDP组（35例）。NAVA组患者给予常规治疗，NAVA+EDP组患者在常规治疗的基础上增加EDP，两组患者均符合脱机程序并应用NAVA模式进行脱机。观察比较两组患者入组时和撤机时的呼吸力学指标、膈肌活动度（diaphragm excursion, DE）、膈肌增厚分数（diaphragm thickening fraction, DTF），以及机械通气时间和14 d撤机成功率。组间计量资料的比较采用t检验，计数资料的比较采用χ²检验。 结果两组患者入组时的呼吸力学指标及DE、DTF的差异均无统计学意义（t=0.505、0.026、0.506、1.203、0.561、0.979，P>0.05）。撤机时，两组患者呼吸力学指标均较入组时显著降低（t=20.560、13.389、20.206、8.237，12.488、8.961、12.478、4.919；P<0.01）、DE和DTF均较入组时显著增高（t=23.839、16.982，10.336、8.688；P<0.01）；而且与NAVA患者组比较，NAVA+EDP患者组呼吸力学指标均明显降低（t=12.488、8.961、12.478、4.919，P<0.05）、DE和DTF均显著增高（t=9.943、5.919，P<0.01）。NAVA+EDP组患者机械通气时间显著短于NAVA组、14 d撤机成功率明显高于NAVA组，差异均有统计学意义（t=4.033，χ²=5.350；P<0.05或0.01）。 结论对于采用NAVA模式的老年机械通气患者，EDP能一定程度改善肺功能和膈肌功能，从而改善预后。     

神经调节辅助通气对慢性阻塞性肺疾病急性加重期患者呼吸力学指标、肺顺应性及机械通气触发延迟时间的影响

目的探讨神经调节辅助通气(NAVA)对慢性阻塞性肺疾病急性加重期(AECOPD)患者肺通气、肺顺应性及机械通气触发延迟时间的影响。方法选取2016年5月至2021年2月连云港市第一人民医院收治的72例AECOPD患者作为研究对象,采用随机数字表法将其分为对照组和观察组,各36例。所有患者经口气管插管,连接呼吸机,对照组患者予以传统压力支持通气(PSV)模式,观察组患者予以NAVA模式,待患者自主呼吸试验通过后尝试撤机,撤机后转为无创辅助通气,若失败则继续有创机械通气。比较两组患者通气前及通气24 h后呼吸力学指标(吸气压力、气道峰压、平台压)及通气过程中呼吸力学指标〔分钟通气量(VE)、吸入潮气量(VTi)、呼吸频率、膈肌电活动(EAdi)峰值〕,通气前及通气24 h后肺顺应性,机械通气时间及机械通气触发延迟时间(包括吸气触发延迟时间和吸呼气切换延迟时间),并发症发生率。结果通气24 h后,两组患者吸气压力、气道峰压、平台压分别低于本组通气前,且观察组低于对照组(P<0.05);观察组患者通气过程中VE、VTi及EAdi峰值均低于对照组(P<0.05)。通气24 h后,两组患者肺顺应性分别低于本组通气前,且观察组低于对照组(P<0.05)。观察组患者机械通气时间、吸气触发延迟时间及吸呼气切换延迟时间均短于对照组(P<0.05)。对照组患者并发症发生率为11.1%(4/36),与观察组患者的8.3%(3/36)比较,差异无统计学意义(χ^(2)=0.158,P=0.691)。结论相较于PSV模式,NAVA模式能更有效地改善AECOPD患者呼吸力学指标,提高肺顺应性,缩短机械通气触发延迟时间,且安全性良好,临床应用前景较好。     

无创机械通气对伴有意识障碍的重症呼吸衰竭患者治疗价值的探讨

目的 探讨无创机械通气抢救伴有意识障碍的重症慢性阻塞性肺疾病(COPD)呼吸衰竭患者的临床疗效.方法 COPD伴意识障碍的重症呼吸衰竭患者42例,使用硅胶面膜口鼻面罩接瑞士Hamilto n公司生产的GALILEO或RAPHAEL急救用呼吸机,采用压力-同步间歇指令通气P-(SIMV)+压力支持通气(PSV)+呼气未正压通气(PEEP)模式进行无创机械通气,同时采取常规抗感染等综合治疗.观察治疗前后生命体征、神志、呼吸肌疲劳程度及血气指标的变化等指标.其中神志评估采用Glasgow昏迷评分(GCS),以辅助呼吸肌评分评价呼吸肌疲劳程度. 结果 42例均成功接受治疗,与人院时(O h)相比,治疗后2 h、6 h及24 h的pH值、二氧化碳分压(PaCO2)、氧和指数即动脉氧分压/吸氧浓度(PaO2/FiO2)均显著改善.24 h后呼吸频率及心率均明显下降,提示患者病情趋于稳定并对治疗较为耐受.平均GCS由(5.69±0.93)分,提高为(10.45±1.23)分(t=31.68,P<0.001),意识状态明显改善.全部患者辅助呼吸肌评分由(3.70±0.45)分降至(2.06±0.52)分(t=31.21,P<0.001),呼吸肌疲劳缓解. 结论 无创机械通气在抢救重症感染及伴有意识障碍的重症COPD呼吸衰竭患者中临床疗效显著.     

双水平正压无创通气治疗呼吸肌麻痹的疗效观察

目的观察双水平正压无创通气治疗呼吸肌麻痹的临床效果。方法19例呼吸肌麻痹的患者，予双水平正压面罩辅助呼吸。结果19例呼吸肌麻痹患者抢救成功17例，抢救成功率89．5％；2例因自主呼吸微弱改有创通气。治疗2小时后多数患者由烦躁转安静，呼吸频率、心率减慢，氧分压明显提高，通气前后血气分析比较差异有统计学意义（P〈0．01）。结论双水平正压无创机械通气是抢救呼吸肌麻痹是简单、有效、易接受的治疗方法。     

胸外伤后急性肺损伤的无创机械通气治疗效果观察

目的探讨应用多功能呼吸机无创通气治疗胸部外伤所致急性肺损伤ALI。方法对我院45例胸部外伤导致ALI患者进行前瞻性对照研究。观察无创通气组动脉血氧分压、氧合指数、呼吸频率及辅助呼吸肌动用评分,并对两组病死率、呼吸机并发症发生率、机械通气治疗时间及住院时间进行统计学分析。结果无创通气组动脉血氧分压、氧合指数较通气前均有明显改善（P〈0.05）,呼吸频率及辅助呼吸肌动用评分在通气后12 h及撤机后较通气前下降（P〈0.05）;无创通气组机械通气并发症发生率、机械通气治疗时间及住院时间优于有创通气组（P〈0.05）。结论无创机械通气是治疗胸部外伤所致急性肺损伤特别是恶化至急性呼吸窘迫综合征的有效方法。     

Inspiratory muscle unloading by neurally adjusted ventilatory assist during maximal inspiratory efforts in healthy subjects

BACKGROUND: Neurally adjusted ventilatory assist (NAVA) is a mode of mechanical ventilation in which the ventilator is controlled by the electrical activity of the diaphragm (EAdi). During maximal inspirations, the pressure delivered can theoretically reach extreme levels that may cause harm to the lungs. The aims of this study were to evaluate whether NAVA could efficiently unload the respiratory muscles during maximal inspiratory efforts, and if a high level of NAVA would suppress EAdi without increasing lung-distending pressures. METHOD: In awake healthy subjects (n = 9), NAVA was applied at increasing levels in a stepwise fashion during quiet breathing and maximal inspirations. EAdi and airway pressure (Paw), esophageal pressure (Pes), and gastric pressure, flow, and volume were measured. RESULTS: During maximal inspirations with a high NAVA level, peak Paw was 37.1 +/- 11.0 cm H(2)O (mean +/- SD). This reduced Pes deflections from - 14.2 +/- 2.7 to 2.3 +/- 2.3 cm H(2)O (p < 0.001) and EAdi to 43 +/- 7% (p < 0.001), compared to maximal inspirations with no assist. At high NAVA levels, inspiratory capacity showed a modest increase of 11 +/- 11% (p = 0.024). CONCLUSION: In healthy subjects, NAVA can safely and efficiently unload the respiratory muscles during maximal inspiratory maneuvers, without failing to cycle-off ventilatory assist and without causing excessive lung distention. Despite maximal unloading of the diaphragm at high levels of NAVA, EAdi is still present and able to control the ventilator.     

神经电活动辅助通气:一种新的机械通气模式

机械通气是呼吸衰竭患者重要的支持手段,但传统的机械通气存在明显人机不同步,可能导致机械通气时间延长、呼吸机相关肺损伤等相关并发症.神经电活动辅助通气,通过监测膈肌电活动.根据自身吸气驱动,成比例地持续辅助通气.目前研究表明神经电活动辅助通气明显改善有创及无创机械通气人机同步性;减轻呼吸肌肉负载;能自动调节通气支持水平,具有一定的肺保护作用;利用膈肌电活动,发挥独特的监测功能.     

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??Abstract??Mechanical ventilation is still one of the main treatment measures of acute respiratory distress syndrome (ARDS).From the traditional high tidal volume ventilation (10 ~ 15 mL/kg) to the current use of lung protective ventilation strategies??low tidal volume ventilation (VT)??positive end-expiratory pressure (PEEP)??airway pressure release ventilation (APRV)??bilevel positive airway pressure(BIPAP)??considerable progress has been made.In addition to the well-known conventional mechanical ventilation modes and methods??there are many non-standard mechanical ventilation modes and methods??such as prone position ventilation??neurally adjusted ventilatory assist (NAVA)??extracorporeal membrane oxygenation (ECMO)??high-frequency ventilation and etc.All these measures produce unique effects on the treatment of ARDS.     

Ventilatory muscle loads and the frequency-tidal volume pattern during inspiratory pressure-assisted (pressure-supported) ventilation

Pressure support ventilation (PSV) is a new form of mechanical ventilatory support that assists a patient's spontaneous ventilatory effort with a clinician-selected amount of inspiratory pressure. In order to assess the muscle unloading effect and the ventilatory pattern response to increasing levels of this inspiratory pressure assist, we first utilized a computer respiratory system model with variable alveolar ventilation demands and impedances. From this model, we calculated ventilatory muscle loads (expressed either as the work/min or as the pressure time index) during simulated, unassisted breathing and during simulated breathing with levels of inspiratory pressure assist up to that which resulted in a VT of 800 ml and no work being performed by the muscles (defined as PSVmax for the model conditions being studied). The optimal ventilatory pattern (i.e., frequency-tidal volume) under each ventilation and impedance condition was defined as that which resulted in minimal muscle load. Under these model conditions, we found that PSVmax ranged from 5 to 41 cm H2O and that as the level of inspiratory pressure assist was increased from zero to PSVmax, there was a biphasic response of both the ventilatory muscle loading and the ventilatory pattern. Specifically, at low levels of inspiratory pressure assist, the model predicted that the applied pressure would only partially unload the ventilatory muscles. Continued muscle energy expenditure would thus still be required, whereas the ventilatory pattern would change little. Conversely, at higher levels of inspiratory pressure assist, the model predicted that the applied pressure would be sufficient to completely unload the ventilatory muscles.(ABSTRACT TRUNCATED AT 250 WORDS)     

Proportional assist ventilation

Partial ventilatory support techniques are intended for patients who are unable to maintain a normal alveolar ventilation, despite normal central control for respiration. Proportional assist ventilation (PAV) is a novel mode of partial ventilatory support in which the ventilator generates an instantaneous inspiratory pressure in proportion to the instantaneous effort of the patient. In theory, PAV should normalize the neuro-ventilatory coupling by making the ventilator an extension of patient's respiratory muscles, while leaving to the patient the entire control of all aspects of breathing. PAV, however, shares a common problem with the conventional partial ventilatory support modes. In mechanically ventilated patients, the respiratory system impedance may change over time. These changes may impair the good matching between ventilator output and patient's ventilatory demand and lead to patient-ventilator asynchrony. To take full advantage of PAV, the authors believe that PAV should continuously and automatically adapt to the respiratory system passive mechanics, assessed by continuous noninvasive measurement of total elastance and resistance.     

Effects of chemical feedback on respiratory motor and ventilatory output during different modes of assisted mechanical ventilation.

The purpose of the study was to examine the effects of chemical feedback on respiratory motor and ventilatory output in conscious subjects ventilated on various modes of assisted mechanical ventilation. Seven subjects were connected to a ventilator and randomly ventilated on assist-volume control (AVC), pressure support (PS) or proportional assist ventilation (PAV). On each mode, the assist level was set to the highest comfortable level. Airway and oesophageal (Poes) pressures, tidal volume, respiratory frequency (fR) and end-tidal carbon dioxide tension (PET,CO2) were measured breath-by-breath. When the subjects were stable on each mode, the fraction of inspired carbon dioxide (FI,CO2) was increased stepwise, and changes in minute ventilation (V'E) and respiratory motor output, estimated by the pressure-time product of all the respiratory muscles per breath (PTPrm) and per minute (PTPminute), were observed. At zero FI,CO2, PTPminute/PET,CO2 did not differ between modes, while V'E/ PTPminute was significantly lower with PAV than that with PS and AVC. As a result V'E/PET,CO2 was significantly lower with PAV, preventing, unlike AVC and PS, a significant drop in PET,CO2. With PAV, independent of CO2, V'E/PTPminute remained constant, while it decreased significantly with increasing CO2 stimulus with PS and AVC. At high PET,CO2 respiratory effort was significantly lower with PAV than that with PS and AVC. In conclusion, the mode of mechanical ventilation modifies the effects of chemical feedback on respiratory motor and ventilatory output. At all carbon dioxide stimulus levels neuroventilatory coupling was better preserved with proportional assist ventilation than with pressure support and assist-volume control ventilation.     

Patient-ventilator interaction during the triggering phase

Partial patient-controlled mechanical support mode ventilators provide positive pressure assistance whenever a patient's inspiratory effort decreases pressure or flow in the ventilator circuit below the sensitivity set by clinicians; these modes minimize disuse atrophy of the respiratory muscles, can facilitate the weaning process, and usually require lower ventilator pressures. The capability of restoring gas exchange, unloading respiratory muscles, and relieving the patient's dyspnea with partial patient-controlled mechanical support modes depends on matching between the ventilator setting and the patient's ventilatory demand (ie, patient-ventilator interactions).