心脏手术后患者撤机时比例辅助通气的效果

目的评价心脏手术后患者撤机时比例辅助通气（PAV）的效果。方法46例心脏手术后患者，年龄18—72岁，体重40—65kg，ASAⅠ或Ⅱ级。测得呼吸系统弹性阻力（Ers）及气道阻力（Rrs），先按80％辅助比例行PAV（PAV80），以PAV80时潮气量（VT）确定压力支持通气（PSV）的目标VT，再随机先后予PAV80、PSV及持续气道正压（CPAP）各通气30min，观察每种模式下呼吸方式指标[VT、呼吸频率（RR）、分钟通气量（VE）、浅快呼吸指数（RSBI）、吸气时间占呼吸周期比（Ti／Ttot）、气道峰压（PIP）、平均气道压（Paw）、呼气末正压（PEEP）、内源性呼气末正压（PEEPi）]；呼吸作功指标[（压力-时间积分（PTP）、患者呼吸功（WOBp）、呼吸机呼吸功（WOBv）]；血液动力学指标[心率（HR）、平均动脉压（MAP）、中心静脉压（CVP）]及动脉血气指标的变化。结果与CPAP时比较，PAV80、PSV时WOBv、PIP、Paw、VT、PaO2、SaO2升高，PTP、WOBp、WOBp／WOBt、RR、RSBI、Ti／Ttot、pH、PaCO2降低（P〈0．05或0．01）；与PSV时比较，PAV80时肿、WOBp和WOBp／WOBt升高（P〈0．01），PIP、Paw降低（P〈0．05）。PAV80与PSV间PaO2、SaO2、MAP、HR和CVP差异无统计学意义。结论PAV是适宜于心脏手术后患者撤机的一种通气模式。     

在Bench模型中模拟未插管呼吸暂停患者梗阻气道的通气策略

背景Smart Bag MO是一种设计用于成人的流量限制型球囊面罩装置,它可减少在无气道保护的情况下发生胃反流的风险。其在严重气道梗阻时的应用特性尚不明确。方法建立Bench模型以模拟无气道保护情况下发生呼吸暂停的患者,分别使用流量限制型球囊装置和标准球囊装置通气。测定并对比两者在气道阻力为4、10、20cmH2O·L-1·S-1时的呼吸力学和潮气量。结果使用流量限制型球囊装置较标准球囊装置能延长吸气时间。流量限制型球囊装置和标准球囊装置在模拟无气道梗阻组中肺潮气量分别为750±70ml和780±30ml（无统计学差异）;模拟中度气道梗阻组中肺潮气量分别为800±70ml和850±20ml（无统计学差异）;模拟严重气道梗阻组中肺潮气量分别为210±20ml和170±10ml（P〈0．01）。流量限制球囊装置和标准球囊装置在模拟无气道梗阻组中气道峰压分别为15±2cmH2O和22±4cmH2O（P〈0．01）;模拟中度气道梗阻组中气道峰压分别为22±1cmH2O和39±7cmH,O（P〈0．01）;模拟严重气道梗阻组中气道峰压分别为26±1cmH,O和61±3cmH,O（P〈0．01）。流量限制球囊装置和标准球囊装置在模拟无气道梗阻组中的胃胀气速率为0ml／min;模拟中度气道梗阻组中速率分别为0ml／min和200±20ml／min（P〈0．01）;模拟严重气道梗阻组中速率分别为0ml／min和1240±50ml／min（P〈0．01）。结论在模拟严重气道梗阻组中,与标准球囊装置相比,流量限制型球囊装置能延长吸气时间、增大潮气量、降低气道压并能避免胃胀气的发生。     

右美托咪定与吗啡用于慢性阻塞性肺病患者机械通气时对呼吸力学影响的比较

目的研究右美托咪定（dexmedetomidine,DEx）和盐酸吗啡对慢性阻塞性肺病急性发作期（acute exacerbation of chronic obstructive pulmonary disease, AECOPD）行机械通气患者呼吸力学的影响。方法入选AECOPD伴呼吸衰竭行机械通气患者40例;在同样的分钟通气量和呼气末正压的设置下,采用随机对照的方法分为两组（对照组、试验组）,每组20例,对照组使用吗啡进行镇静治疗,实验组使用盐酸DEX。记录两组患者急性生理功能和慢性健康状况评分系统Ⅱ（acute physiology and chronic health evaluation, APACHE Ⅱ）评分、脑电双频指数（bispectral index,BIS）评分、Ramsay镇静评分等指标。比较两组患者镇静前后生命体征、血气的变化和镇静后呼吸力学参数的变化。结果与对照组比较,实验组中平均动脉压（mean arterial pressure,MAP）和脉搏[（80±3）mmHg比（75±4）mmHg（1mmHg=0．133kPa）和（90±3）次/min比（79±3）次/min]降低（P〈0．01）,平均气道压mean airway pressure,Paw）、平台压（plateau pressure,eplat）[（7．5±0．7）cm H2O比（6．2±0．6）cm H2O（1cmH2O=0．098kPa）、（19．8±1．7）cmH20比（18．0±1．1）cmH2O]明显降低（P〈0．01）,峰食道压力（peak esophageal pressure,PPEAKES）、PPEAKEE与基准食道压力差（the peak esophageal manometry reference esophagus pressure difference, dPEs）[（-3．4±0．7）cmH2O比（-5．4±1．0）cmH2O、（-6．9±1．0）cmH2O比（-9．8±1．3）cmH2O]变大（P〈0．01）,吸气末屏气期间的跨肺压（ folding Screen the end of the suction gas during transpulmonary pressure, Ptp Plat）、肺静态顺应性（pulmonary static compliance,cst）[（25．5±2．3）cmH2O比（26．0±2．6）cmH2O、（20．5±1．9）cmH2O比（20．1±1-2）cmH2O]变化无统计学意义（P〉0．05）,气道阻力（airway resistance,Raw）[（20．3±3．9）cmH2O·L-1·s-1比（15．6±1．4）cmH2O·L-1·s-1]变小（P〈0．01）,患者呼吸功（patient work of breathing,WOBp）[（0．11±0．02）j/L比（0．16±0．04）j／L]明显增加[1（P〈0．01）,机械呼吸功（mechanical work of breathing,WOBv）[（0．49±0．10）g/L比（0．43±0．06）j／L]明显降低（P〈0．05）。机械通气时间、重症监护室（ICU）入住时间[（76±5）h比（64±3）h、（6．0±1．5）d比（4．6±0．9）d]减少（P〈0．05）。结论与吗啡比较,DEX能提高机械通气患者的镇静效果、降低Raw、提高肺顺应性,有利于实施保护性通气策略,同时降低呼吸负荷和呼吸做功,因而能降低呼吸氧耗。     

无创正压机械的通气对慢性阻塞性肺疾病患者膈肌功能影响

目的：探索与评估膈肌功能测定对重度慢性阻塞性肺疾病（COPD）急性加重期患者无创正压机械通气（NPPV）疗效的意义。方法：选择住院的急性加重期COPD患者28例,施行常规治疗＋NPPV。分别记录无创通气前,通气后48小时、终止无创通气前的跨膈压（Pdi）,肺功能、动脉血气,同时综合评估通气前、后的支气管-肺部感染情况。结果：1、无创通气治疗成功组：通气后Pdi,第一秒用力呼气容积（FEV1）．动脉血二氧化碳分压（PaCO2）、动脉血氧分压（PaO2）、pH值分别为（14．04±2．40）cmH2O、（0．70±0.24）L、（48．2±4．2）mmHg．（70．0±6．3）mmHg、（7．37±0．05）,与通气前（（10．98±0．45）cmH20、（0．59±0．11）L、（68．2±10．2）mmHg、（52．5±6．1）mmHg、（7．34±0．06））比较差异均有统计学意义（P均〈0．05）。2、开创通气治疗失败者：2例。1例其Pdi在通气前为8．74cmH2O,通气48小时为9．24cmH2O;另1势9Pdi,通气前为7,56cmH2O,结论：在NPPV治疗过程中,Pdi和EIIFEV1．PaCO2、PaO2、pH值的变化有高度一致性,Pdi的动态变化．可以客观地反映膈肌的功能状态;NPPV有助手改善AECOPD患者的膈肌功能。     

无创双水平气道正压通气—同步间歇指令通气—压力支持通气治疗呼吸衰竭

目的 观察无创双水平气道正压通气－同步间歇指令通气－压力支持通气（NBIPAP－SIMV－PSV）组合模式对慢性阻塞性肺病（COPD）合并呼吸衰竭的疗效。方法 选择36例COPD合并呼吸衰竭患者,在常规治疗基础上加用NBIPAP－SIMV－PSV,监测并比较通气治疗前,治疗后2h,4h,HR,RR,Bp,PaO2,PaCO2和SaO2变化。结果 通气治疗前后各参数变化比较：通气治疗后HR、PR明显减慢;PaO2与SaO2显著提高;PaCO2显著下降;Bp无明显变化。全部病例经2－4d通气治疗后病情稳定,脱离呼吸机。结论 NBIPAP－SIMV－PSV可明显改善呼吸衰竭的症状和体征,迅速提高PaO2与SaO2值,有效降低PaCO2值。能明显改善人机同步性能,更节省呼吸功,患者更舒适。并明显缩短住院时间（P＜0．01）,显著减少医疗费用,可作为治疗COPD合并早、中期呼吸衰竭的一种简便、迅速、安全、有效的治疗方法。     

双水平正压通气对急性肺损伤患者血气及血流动力学指标的影响

目的探讨应用脉搏指数连续心排血量（PiCCO）容量监测仪技术研究双水平正压通气模式对急性肺损伤（ALI）患者血气及血流动力学的影响,探讨这种新型呼吸模式应用于ALI患者的临床疗效,对循环系统的影响程度,以提高ALI的治愈率。方法42例ALI患者,男27例,女15例;年龄15～75岁。按患者的入院先后顺序将40例患者（2例未完成研究）分为两组,每组20例。双水平正压通气组：入院的第1～20例患者,给予双水平正压通气呼吸支持,采用支持/时间（S/T）模式,吸气末压初始设为8～10cmH2O,逐渐增加至14～20cmH2O,以患者舒适为宜;呼气末压初设为3～5cmH2O,逐渐增加至8～12cmH2O,吸入氧浓度（FiO2）保持不变。对照组：入院的第21～40例患者,采用辅助/控制（A/C）通气模式,并依次按5cmH2O,10cmH2O,15cmH2O,20cmH2O增加呼气末正压（PEEP）,每种压力持续30min,通气支持过程中FiO2保持不变。观察两组患者的心排血量（CO）、体循环血管阻力（SVR）等血流动力学和血气指标改变。结果两组死亡13例,其中双水平正压通气组死亡5例,对照组死亡8例。死于多器官功能衰竭7例,感染性休克3例,循环衰竭3例。双水平正压通气组气管内插管时间（2.9±0.8dvs.4.2±0.9d,t=7.737,P=0.006）和住院时间（17.2±4.5dvs.18.5±3.6d,t=2.558,P=0.039）明显短于对照组。对照组：当PEEP在5～15cmH2O范围内,患者动脉血氧分压（PaO2）、氧合指数（PaO2/FiO2）随着PEEP的增高而逐渐增加（P〈0.05）;当PEEP增加至20cmH2O时CO降低,SVR、肺循环阻力（PVR）和气道峰值压（PIP）较5～15cmH2O范围时增加（P〈0.05）。双水平正压通气组：PaO2、PaO2/FiO2随着EPAP的增高而逐渐增加,当EPAP增加至10cmH2O时PaO2、PaO2/FiO2达最大值（P〈0.05）;与对照组比较PIP明显降低（t=7.831,P=0.000）。结论对ALI/急性呼吸窘迫综合征（ARDS）患者给予双水平正压通气治疗可减少对呼吸和血     

压力支持通气和双相气道正压通气通过肺血流重新分布从而提高氧合

背景机械通气时保留自主呼吸（spontaneousbreathing,SB）可改善气体交换,主要是因为这种通气方式可使萎陷的肺复张。在保留SB的机械通气中,常选择压力支持通气（pressuresupportventilation,PSV）和双相气道正压通气（biphasicpositiveairwaypressure,BIPAP）。但医师对这些辅助性机械通气方式改善肺功能的机制却不甚了解。我们评价了采用PSV和BIPAP改善氧合的机制。方法5头猪（25-29．3kg）于仰卧位行机械通气,并通过清除肺表面活性物质诱发其发生急性肺损伤（acutelung砸jury,Au）。状态稳定后,给予BIPAP通气,初期较低持续气道正压设置为5cmH2O,随后逐渐增加持续气道正压至维持潮气量在6-8ml／kg。减浅麻醉深度,当SB≥每分通气量的20％时,随机进行1小时的PSV或BIPAP＋SB通气。于呼气末行全胸螺旋式计算机体层扫描,并记录肺功能参数。静脉给予荧光微球体来记录肺血流（pulmonarybloodflow,PBF）,并利用空间聚类分析来评估每种通气方式对PBF重新分布的影响。结果Au损伤肺功能并加大了下肺萎陷或不张组织的面积（P〈0．05）。和对照组比较,PSV和BIPAP＋SB的通气模式提高了氧合并减少了静脉血掺杂（P〈0．05）。尽管如此,我们观察到自主呼吸时下肺的不张肺组织或通气不良组织明显增加,而可正常通气的肺组织减少。观察到6例中有5例行PSV或sB＋BIPAP通气时PBF由下至上重新分布,肺通气也较好。结论在ALI模型中采用PSV或BIPAP＋SB行机械通气可改善氧合,减少静脉血掺杂的原因为PBF由下至上的重新分布,而不是因为下肺复张。     

胃减容术3种机械通气对患者氧合情况的比较

目的：探讨病态肥胖患者行腹腔镜胃减容术时，3种机械通气参数对患者氧合情况的影响。方法：选择行腹腔镜胃减容术的病态肥胖24例，按手术时间顺序分为3组，每组8例。A组：潮气量12ml／kg，呼吸频率10次／min；B组：潮气量20ml／kg，呼吸频率10次／min；C组：潮气量12ml／kg，呼吸频率20次／min。分别于气腹前（T1）、气腹后（T2）抽取动脉血测量pH、PO2、PCO2、Plat（平台压）、Peak（峰压）、AaDO2（肺泡-动脉氧分压差）。结果：气腹后B组Plat（33．2±1．8）cmH2O、Peak（36．3±1．6）cmH2O显著高于A组Plat（29．5±3．9）cmH2O（q=3．053，P〈0．05）、Peak（33．0±2．9）cmH2O（q：2．823，P〈0．05）和C组Plat（28．0±4，1）cmH2O（q：4．290，P〈0．05）、Peak（31．8±2．8）cmH2O（q：4．704，P〈0．05）。其他观察指标无统计学差异。结论：病态肥胖患者在腹腔镜下施行胃减容术时，加大潮气量20ml／kg或加快呼吸频率20次／min不能改善患者的氧合情况。     

支气管封堵器单肺通气在新生儿电视胸腔镜手术中的应用

目的探讨支气管封堵器（bronchial blocker,BB）行单肺通气（one lung ventilation,OLV）在新生儿电视胸腔镜手术（video-assisted thoracoscopicsugery,VATS）中应用的有效性和安全性。方法择期行VATS的患儿60例,按OLV方法完全随机平均分为支气管插管组（A组）和BB组（B组）,每组30例。比较两组患儿术前双肺通气时（T0）、OLV 10min（T1）、肺萎陷即刻（T2）、肺萎陷后30min（T3）、肺萎陷后60min（T4）、恢复双肺通气后10min（T5）和术毕6h（T6）、术毕12h（T7）的SpO2、动脉血氧分压（arterial blood partial pressure of oxygen, PaO2）、PET CO2、动脉血二氧化碳分压（arterial blood partial pressure of carbondioxide, PaCO2）、乳酸水平及气道压变化情况,比较两组患儿OLV情况和围术期情况。结果两组息儿气道压从T1开始升高,T4达到最高,T4时A组（34．8±4．9）cmH2O（1cmH2O=0．098kPa）较B组（30．0±4．3）cmH2O更为显著（P〈0．05）;T4时两组患儿SpO2和PaO2下降至最低,两组间比较差异无统计学意义（p〉0．05）;T4时两组患儿PETCO2和PaCO2升至最高,A组较B组更为显著（P〈0．05）;两组患儿乳酸水平呈升高趋势,但各时点差异无统计学意义（P〉0．05）。B组肺萎陷效果、术中出血量、手术时间、拔管时间、监护室时间和气管黏膜损伤情况均显著优于A组（P〈0．05）。结论BB行OLV可为新生儿VATS提供充分的通气和良好的肺萎陷。     

蛇形喉周通气道和喉罩用于儿科患者的随机前瞻性研究

背景蛇形喉周通气道（CobraPLA）在成人正压通气时,密封压力优于单纯喉罩（LMAU）,本研究旨在比较两者在婴儿和儿童中的使用效果。方法200例小儿患者随机分为CobraPLA组和LMAU组,测量套囊充气压力为40和60cmH2O时气道的密封效果,插入的难易度和时间,手术后咽痛、发声困难、喉痉挛、支气管痉挛和胃内胀气的发生率,间断测量CobraPLA端和麻醉呼吸回路Y型接口处的呼气末二氧化碳浓度（ETCO2）。对主要转归指标,各组又分为小型号和大型号CobraPLA及LMAU亚组进行分析。结果以均数±标准差表示,P〈0．05表示有显著性差异。结果套囊充气压为60cmH2O时,大型号CobraPLA亚组的气道密封压力（22±7cmH2O）明显高于小型号CobraPLA亚组（18±5cmH2O）及大型号LMAU亚组（16±5cmH2O）（P〈0．001）;CobraPLA组比LMAU组更不易移位（手术前和手术后的解剖合适度评分相同）,气体入胃也少;CobraPLA头端ETCO,测量值比Y型接口处高6．4±6mmHg。结论从大多数参数分析来看,CobraPLA与LMAU在儿科患者麻醉中的作用相当,某些方面优于后者。     

Non-invasive proportional assist and pressure support ventilation in patients with cystic fibrosis and chronic respiratory failure

BACKGROUND: Patients with advanced cystic fibrosis can benefit from non-invasive positive pressure ventilation (NPPV) for the treatment of acute decompensation as well as for the management of chronic respiratory failure. This study was undertaken to compare the physiological effects of non-invasive proportional assist ventilation (PAV) and pressure support ventilation (PSV) on ventilatory pattern, transcutaneous blood gas tensions, and diaphragmatic effort in stable patients with cystic fibrosis and chronic CO2 retention. METHODS: In 12 patients two periods of spontaneous breathing were followed randomly by PSV (12 (3) cm H2O) and PAV (flow assist 4.9 (1.3) cm H2O/l.s, volume assist 18.9 (5.1) cm H2O/l) set for the patient's comfort and administered for 40 minutes with 2 cm H2O continuous positive airway pressure. Ventilatory pattern, transcutaneous blood gas tensions, and surface diaphragmatic electromyography were measured in the last 10 minutes of each application. RESULTS: On average, both PSV and PAV improved ventilation (+30%), tidal volume (+30%), and transcutaneous CO2 (-7%) while reducing diaphragmatic activity (-30% with PSV, -20% with PAV). Mean inspiratory airway pressure was lower during PAV than during PSV (9.7 (1.9) and 12.9 (2.7) cm H2O, respectively; p<0.05). The mean coefficient of variation of tidal volume was about 20% (range 11-39%) during spontaneous breathing and did not change with either PAV or PSV. CONCLUSIONS: These results show that short term administration of nasal PAV and PSV to patients with stable cystic fibrosis with chronic respiratory insufficiency is well tolerated, improves ventilation and blood gas tensions, and unloads the diaphragm.     

Proportional assist ventilation combined with automatic tube compensation. A promising concept of augmented spontaneous breathing?

The combination of proportional assist ventilation (PAV) and automatic tube compensation (ATC) is a promising concept for partial ventilatory support. In contrast to conventional pressure support ventilation (PSV), PAV+ATC provides dynamic pressure support depending on the patient's initial inspiratory effort. PAV+ATC should selectively unload the respiratory muscles from the additional workload imposed by increased respiratory system resistance and elastance as well as by endotracheal tube resistance. Patients have the ability to modify the tidal volume in response to changes in ventilatory demand, thereby improving patient-ventilator interaction and breathing comfort when compared with PSV. However, since routine measurements of respiratory mechanics during augmented spontaneous breathing are currently unavailable but would be necessary for setting the support level as a function of respiratory system mechanics during PAV, this mode cannot yet be generally recommended for routine clinical use.     

Changes in occlusion pressure (P0.1) and breathing pattern during pressure support ventilation

BACKGROUND: The purpose of this study was to investigate changes in breathing pattern, neuromuscular drive (P0.1), and activity of the sternocleidomastoid muscles (SCM) during a gradual reduction in pressure support ventilation (PSV) in patients being weaned off controlled mechanical ventilation. METHODS: Eight non-COPD patients recovering from acute respiratory failure were included in this prospective interventional study. All patients were unable to tolerate discontinuation from mechanical ventilation. Each patient was evaluated during a period of spontaneous breathing and during PSV. Four successive levels of PSV were assessed in the following order: 20 cm H2O (PS20), 15 cm H2O (PS15), 10 cm H2O (PS10), and 5 cm H2O (PS5). RESULTS: When pressure support was reduced from PS20 to PS10 the respiratory rate (f) and the rapid shallow breathing index (f/VT) significantly increased and tidal volume (VT) significantly decreased. These parameters did not vary when pressure support was reduced from PS10 to PS5. Conversely, P0.1 varied negligibly between PS20 and PS15 but increased significantly at low PSV levels. P0.1 values were always greater than 2.9 cm H2O (4.1 (1.1) cm H2O) when SCM activity was present. When contraction of the SCM muscles reappeared the P0.1 was the only parameter that changed significantly. CONCLUSIONS: In postoperative septic patients the value of P0.1 seems to be more useful than breathing pattern parameters for setting the optimal level of pressure assistance during PSV.     

Tracheal pressure regulated volume assist ventilation in acute respiratory failure

PURPOSE: Proportional assist ventilation (PAV) uses volume assist (VAV) and flow assist ventilation (FAV) to reduce elastic and resistive effort, respectively. Proportional assist ventilation may be difficult to apply clinically, particularly due to FAV related considerations. It was hypothesized that regulating tracheal (Ptr) rather than airway opening pressure (Pao), to overcome endotracheal tube related resistive effort, during VAV would provide an effective alternative method of ventilation. We therefore compared the effects of Pao and Ptr regulated VAV on breathing pattern and inspiratory effort. METHODS: In seven intubated patients, flow, volume, Pao, Ptr, esophageal and transdiaphragmatic pressure were measured during VAV (0-80% respiratory system elastance) using Pao vs Ptr to regulate ventilator applied pressure. Breathing pattern and the pressure-time integral of the inspiratory muscles (integralP(mus) . dt) and diaphragm (integralP(di) . dt) were determined. RESULTS: Compared to spontaneous breathing, the respiratory rate to tidal volume ratio, or rapid shallow breathing index (RSBI), improved progressively with increasing VAV (130 +/- 64 vs 70 +/- 35, VAV 0 vs 80%; P < 0.05) while inspiratory effort fell (integralP(mus) . dt = 39.6 +/- 7.5 vs 28.5 +/- 7.2 cm H(2)O.sec.L(-1), integralP(di) . dt, = 35.4 +/- 7.8 vs 24.2 +/- 5.9 cm H(2)O.sec.L(-1), VAV 0 vs 80%; P < 0.05) due to a decrease in elastic related effort. At any given level of support, there was further reduction in RSBI, integralP(mus) . dt, and integralP(di) . dt (which averaged 23.6 +/- 2.7, 33.7 +/- 4.4, and 38.5 +/- 5.1%, respectively; P < 0.05) for Ptr compared to Pao regulated VAV due to a decrease in resistive effort. CONCLUSIONS: Tracheal pressure regulated VAV can be a simple and effective method of partial ventilatory support in acute respiratory failure. Further work will be needed to determine its efficacy and potential benefit relative to PAV and other modes of ventilation in routine clinical practice.     

气管导管阻力变化对呼吸收缩压变异试验的影响

目的研究气管导管阻力变化对呼吸收缩压变异试验（RSVT）的影响。方法对20例患者进行预测液体反应的RSVT,试验运用3个连续改变的压力[10、20、30cmH2O（1cmH20=0．098kPa）]控制呼吸,测定3个最低收缩压值并与相应的气道压力作图得到斜率（RSVT斜率）。比较正常气管导管阻力和导管阻力增加两种情况下的RSVT斜率,气管导管阻力增加用在气管导管内插入Cooperdech支气管封堵导管来模拟。结果在正常气管导管阻力时,导管阻力为（5．19±2．38）（cmH2O·s）／L,RSVT斜率为（0．39±0．21）mmHg／cmH20（1mmHg=0．133kPa）,3个不同控制压力水平（10、20、30cmH2O）对应的潮气量分别为（461．5±95．9）、（891．5±149．8）和（1207．5±159．1）ml;在高气管导管阻力时,导管阻力为（8．77±1．64）（cmH2O·s）／L,RSVT斜率为（0．27±0．17）mmHg/cmH2O,3个不同控制压力水平对应的潮气量显著降低,分别为（434．5±92．8）、（796．5±96．6）和（1097．5±68．4）ml,与正常气管导管阻力比较,差异均有统计学意义（P〈0．05或〈0．01）。结论气管导管阻力的增加会导致RSVT斜率的降低。     

Pressure support ventilation versus continuous positive airway pressure ventilation with the ProSeal laryngeal mask airway: a randomized crossover study of anesthetized pediatric patients

Continuous positive airway pressure (CPAP) and pressure support ventilation (PSV) improve gas exchange in adults, but there are little published data regarding children. We compared the efficacy of PSV with CPAP in anesthetized children managed with the ProSeal laryngeal mask airway. Patients were randomized into two equal-sized crossover groups and data were collected before surgery. In Group 1, patients underwent CPAP, PSV, and CPAP in sequence. In Group 2, patients underwent PSV, CPAP, and PSV in sequence. PSV comprised positive end-expiratory pressure set at 3 cm H(2)O and inspiratory pressure support set at 10 cm H(2)O above positive end-expiratory pressure. CPAP was set at 3 cm H(2)O. Each ventilatory mode was maintained for 5 min. The following data were recorded at each ventilatory mode: ETco(2), Spo(2), expired tidal volume, peak airway pressure, work of breathing patient (WOB), delta esophageal pressure, pressure time product, respiratory drive, inspiratory time fraction, respiratory rate, noninvasive mean arterial blood pressure, and heart rate. In Group 1, measurements for CPAP were similar before and after PSV. In Group 2, measurements for PSV were similar before and after CPAP. When compared with CPAP, PSV had lower ETco(2) (46 +/- 6 versus 52 +/- 7 mm Hg; P < 0.001), slower respiratory rate (24 +/- 6 versus 30 +/- 6 min(-1); P < 0.001), lower WOB (0.54 +/- 0.54 versus 0.95 +/- 0.72 JL(-1); P < 0.05), lower pressure time product (94 +/- 88 versus 150 +/- 90 cm H(2)O s(-1)min(-1); P < 0.001), lower delta esophageal pressure (10.6 +/- 7.4 versus 14.1 +/- 8.9 cm H(2)O; P < 0.05), lower inspiratory time fraction (29% +/- 3% versus 34% +/- 5%; P < 0.001), and higher expired tidal volume (179 +/- 50 versus 129 +/- 44 mL; P < 0.001). There were no differences in Spo(2), respiratory drive, mean arterial blood pressure, and heart rate. We conclude that PSV improves gas exchange and reduces WOB during ProSeal laryngeal mask airway anesthesia compared with CPAP in ASA physical status I children aged 1-7 yr.     

Pressure Support Ventilation versus Continuous Positive Airway Pressure with the Laryngeal Mask Airway: A Randomized Crossover Study of Anesthetized Adult Patients

Background: The authors tested the hypothesis that pressure support ventilation (PSV) provides more effective gas exchange than does unassisted ventilation with continuous positive airway pressure (CPAP) in anesthetized adult patients treated using the laryngeal mask airway.

Methods: Forty patients were randomized to two equal-sized crossover groups, and data were collected before surgery. In group 1, patients underwent CPAP, PSV, and CPAP in sequence. In group 2, patients underwent PSV, CPAP, and PSV in sequence. PSV comprised positive end expiratory pressure set at 5 cm H2O and inspiratory pressure support set at 5 cm H2O above positive end expiratory pressure. CPAP was set at 5 cm H2O. Each ventilatory mode was maintained for 10 min. The following data were recorded every minute for the last 5 min of each ventilatory mode and the average reading taken: end tidal carbon dioxide, oxygen saturation, expired tidal volume, leak fraction, respiratory rate, noninvasive mean arterial pressure, and heart rate.

Results: In both groups, PSV showed lower end tidal carbon dioxide (P < 0.001), higher oxygen saturation, (P < 0.001), and higher expired tidal volume (P < 0.001) compared with CPAP. In both groups, PSV had similar leak fraction, respiratory rate, mean arterial pressure, and heart rate compared with CPAP. In group 1, measurements for CPAP were similar before and after PSV. In group 2, measurements for PSV were similar before and after CPAP.