制机械通气

Mechanical Ventilation,Wuhan Union HospitalSun Peng,Mechanical Ventilation is ventilation of the lungs by artificial means usually by a ventilator. A ventilator delivers gas to the lungs with either negative or positive pressure.,History of mechanical ventilation,The iron lung, also known as the Drinker and Shaw tank, was developed in 1929 and was one of the first negative-pressure machines used for long-term ventilation.,Negative-Pressure Ventilators,Early negative-pressure ventilators were known as “iron lungs.” The patients body was encased in an iron cylinder and negative pressure was generated .,1940 Boston Chilrden HospitalPatiens suffered from the poliomyelitis,Iron Lung,Negative pressure ventilation,铁肺退出历史舞台？,1952年，哥本哈根HCLassen和BIbsen首次气 管切开，施行“正压通气”，以提供有效的氧合和二氧化碳排出 24小时内，为75名病人进行持续通气，他们动员250名医学生用手捏气囊，260名护士参加床边护理，共消耗250筒氧气）他们提出呼吸道管理基本原则： 保持呼吸道通畅，湿化，防止氧分压过高等，病死率从80%降至25%,The design of the modern positive-pressure ventilators were based mainly on technical developments by the military during World War II to supply oxygen to fighter pilots in high altitude,Positive pressure ventilation,无创通气和负压通气再受重视,负压通气机如胸甲式及胸腹雨披式等呼吸机的研究取得了一定进展无创通气和负压通气更符合自然及生理状况，它代表了呼吸机的发展趋势和方向,无创（正压）机械通气的意义,1.实现了机械通气的“早期应用” 2.减少人工气道的并发症3.在单纯氧疗与有创通气之间，提供了“过渡性”的辅助通气选择4.作为一种短时或间歇的辅助通气方法扩展了机械通气的应用领域5. 形成了有创与无创通气相互配合的机械通气新时代，提高了呼吸衰竭救治的成功率,Overview of topics,IndicationsModesAdvantages and disadvantages between modesGuidelines in the initiation of mechanical ventilationCommon trouble shooting examples with mechanical ventilation,Purposes:,To maintain or improve ventilation, & tissue oxygenation.To decrease the work of breathing & improve patients comfort.,Initiation of Mechanical Ventilation,IndicationsIndications for Ventilatory SupportAcute Respiratory FailureProphylactic Ventilatory SupportHyperventilation Therapy,Initiation of Mechanical Ventilation,IndicationsAcute Respiratory Failure (ARF)Respiratory activity is inadequate or is insufficient to maintain adequate oxygen uptake and carbon dioxide clearance.Inability of a patient to maintain arterial PaO2, PaCO2, and pH acceptable levels PaO2 0.6 (PaO2/FiO2 50mm Hg and risingpH 7.25 and lower,Initiation of Mechanical Ventilation,IndicationsAcute Respiratory Failure (ARF)Hypoxic lung failure (Type I)Ventilation/perfusion mismatchDiffusion defectRight-to-left shuntAlveolar hypoventilationDecreased inspired oxygenAcute life-threatening or vital organ-threatening tissue hypoxia,Initiation of Mechanical Ventilation,IndicationsAcute Respiratory Failure (ARF)Clinical Presentation of Severe HypoxemiaTachypneaDyspneaCentral cyanosisTachycardiaHypertensionIrritability, confusionLoss of consciousnessComa,Initiation of Mechanical Ventilation,IndicationsAcute Respiratory Failure (ARF)Acute Hypercapnic Respiratory Failure (Type II)CNS DisordersReduced Drive To Breathe: depressant drugs, brain or brainstem lesions (stroke, trauma, tumors), hypothyroidismIncreased Drive to Breathe: increased metabolic rate (CO2 production), metabolic acidosis, anxiety associated with dyspnea,Initiation of Mechanical Ventilation,IndicationsAcute Respiratory Failure (ARF)Acute Hypercapnic Respiratory Failure (Type II)Neuromuscular DisordersParalytic Disorders: Myasthenia Gravis, Guillain-Barre, ALS, poliomyelitis, etc.Paralytic Drugs: Curare, nerve gas, succinylcholine, insecticidesDrugs that affect neuromuscular transmission; calcium channel blockers, long-term adenocorticosteroids, etc. Impaired Muscle Function: electrolyte imbalance, malnutrition, chronic pulmonary disease, etc.,Initiation of Mechanical Ventilation,IndicationsAcute Respiratory Failure (ARF)Acute Hypercapnic Respiratory FailureIncreased Work of BreathingPleural Occupying Lesions: pleural effusions, hemothorax, empyema, pneumothoraxChest Wall Deformities: flail chest, kyphoscoliosis, obesityIncreased Airway Resistance: secretions, mucosal edema, bronchoconstriction, foreign bodyLung Tissue Involvement: interstitial pulmonary fibrotic diseases,Initiation of Mechanical Ventilation,IndicationsAcute Respiratory Failure (ARF)Acute Hypercapnic Respiratory FailureIncreased Work of Breathing (cont.)Lung Tissue Involvement: interstitial pulmonary fibrotic diseases, aspiration, ARDS, cardiogenic PE, drug induced PEPulmonary Vascular Problems: pulmonary thromboembolism, pulmonary vascular damageDynamic Hyperinflation (air trapping)Postoperative Pulmonary Complications,Initiation of Mechanical Ventilation,IndicationsAcute Respiratory Failure (ARF)Clinical Presentation of HypercapniaTachypneaDyspneaTachycardiaHypertensionHeadache (hallucinations when severe)Confusion (loss of consciousness, even coma when severe)Sweating,Initiation of Mechanical Ventilation,Hyperventilation TherapyVentilatory support is instituted to control and manipulate PaCO2 to lower than normal levelsAcute head injury,Initiation of Mechanical Ventilation,ContraindicationsUntreated pneumothoraxRelative ContraindicationsPatients informed consentMedical futilityReduction or termination of patient pain and suffering,Initiation of Mechanical Ventilation,Prophylactic Ventilatory SupportClinical conditions in which there is a high risk of future respiratory failureExamples: Brain injury, heart muscle injury, major surgery, prolonged shock, smoke injuryVentilatory support is instituted to:Decrease the WOBMinimize O2 consumption and hypoxemiaReduce cardiopulmonary stressControl airway with sedation,Types of Mechanical ventilators,Negative-pressure ventilators Positive-pressure ventilators,什么是呼吸机？呼吸机电子打气筒！呼吸机的作用改善肺的基本功能（摄入氧O2及排出CO2）取代或部分取代自主呼吸，缓解呼吸肌疲劳,Positive-pressure ventilators,Positive-pressure ventilators deliver gas to the patient under positive-pressure, during the inspiratory phase.,自主呼吸 vs. 正压通气,Pressure压力,Volume容量,如果没有波形分析反馈信息的帮助 管理病人是一件困难的事情 目的：是根据各种不同呼吸波形曲线特征, 来指导调节呼吸机的通气参数, 如通气 模式是否合适、人机对抗、气道阻塞、呼吸回路有无漏气、评估机械通气 时效果、用支气管扩张剂的疗效和呼吸机等.,基本波形,流速-时间波形压力-时间波形容量-时间波形压力-容量环流速-容量环,Volume = Flow X Time,“管道特征”,R =,D P,D F,气道阻力,压力差 = 流速 x 管道阻力,Types of Positive-Pressure Ventilators,1-Volume Ventilators.2- Pressure Ventilators,1- Volume Ventilators,The basic principle of this ventilator is that a designated volume of air is delivered with each breath.The amount of pressure required to deliver the set volume depends on : - Patients lung compliance - Patientventilator resistance factors.,2- Pressure Ventilators,A typical pressure mode delivers a selected gas pressure to the patient early in inspiration, and sustains the pressure throughout the inspiratory phase. By meeting the patients inspiratory flow demand throughout inspiration, patient effort is reduced and comfort increased.,11/30/2017,53,容量控制通气(VCV):Volume Controlled Ventilation,吸气流速波形：,潮气量固定,设定：潮气量、吸气流速、 呼吸频率和波形,压力控制(PCV): Pressure Controlled Ventilation,监测潮气量是否满足病人需求:,流速波形：递减波,潮气量：随气道阻力、病人顺应性变化,流量时间曲线,ACCELERATING,DECELERATING,SINE,SQUARE,Volume Control优缺点,最大的优点：无自主呼吸时,不管肺顺应性和气道阻力如何变化，能够保证通气量。 缺点：肺顺应性差、气道阻力大时，吸气峰压高, 容易引起气压伤，对心血管功能影响大。,容量控制VC,缺点 :容易造成过度膨胀或局部肺泡的不张 不利于肺保护,容量控制（VC）气流特征,Pressure controlled ventilation, PCV,概念：预设压力控制水平（PS）、呼吸频率（RR）和吸气时间（Ti）。 吸气开始后，呼吸机提供的气流在气道压达到预设水平后送气速度减慢以维持预设压力到吸气时间结束，呼气开始。,Pressure Control 特点,1）流量减速波-使峰压较低，减少了肺部气压伤的危险性； 能改善气体分布和V/Q，有利于气体交换。 适用于肺顺应性较差和气道压力较高的患者，ARDS。,Pressure Control 特点,2）需随胸肺顺应性及气道阻力的变化不断调节压力控制水平，以保证适当水平的VT。 3）补偿漏气-少量漏气时可以防止通气不足。但如大量漏气,使得通气机达不到预先设定的压力水平，可能造成吸气相的持续或延长。,定容通气和定压通气的主要区别,定容通气 以“潮气量”为目标控制气流，完成通气定压通气 以“压力”为目标控制气流，完成通气,定容通气和定压通气只是呼吸机同一种工作方式下的不同表现形式。,通气模式,通气模式可以理解为呼吸机如何对呼吸进行控制和辅助，也就是呼吸机何时开始送气、如何进行送气、何时停止送气 通气模式正不断发展并应用于临床,机械通气的模式,选择机械通气各种模式的目的改善气体交换增加患者舒适性加速自主呼吸的恢复,MODES OF VENTILATION,Controlled Mechanical Ventilation (CMV)Assist Control (AC)Continuous Positive Airway Pressure (CPAP)Intermittent Mandatory Ventilation (IMV)Synchronized Intermittent Mandatory Ventilation (SIMV)Pressure Support (PSV)Pressure Regulated Volume Control (PRVC),“基本”模式最常用,控制呼吸(controlled mechanical ventilation CMV ),呼吸频率和潮气量均由机器决定用于病人没有自主呼吸 或自主呼吸频率不好时,辅助呼吸 (assist mechanical ventilation AMV),病人呼吸触发机器, 机器提供预定的潮气量, 即呼吸频率由病人决定, 潮气量 由机器决定 用于自主呼吸好 但潮气量不够的病人,同步控制通气（A/CMV）,概念：1）自主呼吸触发呼吸机送气，呼吸机按预设参数送气-AMV；2）患者无力触发或自主呼吸频率低于预设频率，呼吸机则完全以预设参数通气。,11/30/2017,75,CMV和A/C的区别,CMV没有触发功能。A/C时患者所作的呼吸功仅仅是吸气时产生一定的负压，去触发通气机产生一次呼吸，而通气机则完成其余的呼吸功-提高了人机协调性。,注意： A/C时，任何一次自主呼吸只要达到触发水平，均会引起一次机器送气-自主呼吸强而快时，MV可达到20L以上，过度通气导致呼吸性碱中毒。,概念：按预置频率给予CMV，两次CMV间隙期间允许自主呼吸存在。,间歇控制通气（Intermittent Mandatory Ventilation，IMV）,A/CMV与IMV的区别,IMV=CMV+自主呼吸，间歇期内患者可以进行完全的自主呼吸，但是没有触发 A/CMV时患者可以触发呼吸，但是不能进行完全的自主呼吸-任何一次自主呼吸只要达到触发水平，呼吸机就按预置参数送气。,IMV特点1：非同步性,1）人机对抗：IMV按照预设时间给予强制通气，人机同步性差，如强制通气发生在患者自主呼吸期间或终末患者感觉不舒服，可使患者产生呼吸肌疲劳，反而增加耗氧量。,IMV特点2：无辅助性,2）指令通气之外的自主呼吸也通过呼吸机管路进行，需克服按需阀开放和呼吸机回路阻力做功，可能加重呼吸肌疲劳，增加氧耗，甚至使循环功能恶化。为了克服呼吸机回路的阻力，可加用6-8cmH2O的吸气压力支持。,同步间断指令呼吸（synchronize intermittent mandatory ventilation SIMV ),机器按每分钟指令的次数和预定的潮气量给病人 呼吸, 不足的部分由病人自己的呼吸频率和潮气量补充 指令部 分潮气量和频率由机器决定, 非指令部分潮气量和频率由病人决定允许病人在两次指令呼吸间自由呼吸在逐渐脱呼吸机时用,CMV(IMV)与SIMV的差别,触发窗,CMV,AMV,CMV,持续气道内正压( continuous positive airway pressure CPAP),呼吸频率和潮气量均由病人决定, 机器仅在一定的吸入氧浓度和压 力下送气在脱机前使用,压力支持通气 ( pressure support ventilation PSV ),呼吸频 率由病人决定 在吸气时给予压力, 效果是增加潮气量 潮气量由病人和机器共同决定,双气道正压通气 ( biphasic positive airway pressure Bipap),带有PEEP的压力支持,BIPAP为一种双水平CPAP的通气模式，设置吸气压较高、呼气压较低，VT的大小取决于吸气压和呼气压的压差及呼吸器官的顺应性。可辅助或控制呼吸。能实现从PCV到CPAP的逐渐过渡。,VCV-SIMV,VCV-SIMV+PSV,不同呼吸模式特点,潮气量 频率C 机器 机器A 机器 病人SIMV 指令 机器 机器 非指令 病人 病人CPAP 病人 病人PSV 病人+机器 病人,How to use the ventilator?,常用人工气道的选择,口咽通气道 无法完全封闭气道,经口/鼻气管插管,气管切开,有创呼吸机连接方式,气管插管（经口，经鼻）气管切开,呼吸机参数的设定,呼吸机参数的设定,FiO2：50%时需警惕氧中毒。原则是在保证氧合的情况下，尽可能使用较低的FiO2。,VT:一般为615ml/kg，实际应用时需根据血气和呼吸力学等监测指标不断调整。对VT的调节以避免气道压过高为原则，即平台压不超过3050cmH2O；而对于肺有效通气容积减少的疾病（如ARDS），应采用小潮气量（68mm/kg）通气。PSV的水平一般不超过2530 cmH2O，若在此水平仍不能满足通气要求，应考虑改用其它通气方式,RR:应与VT相配合，以保证一定的MV；应根据原发病而定；一般为1220次/分；应根据自主呼吸能力而定；如采用SIMV时，可随着自主呼吸能力的不断加强而逐渐下调SIMV的辅助频率。,呼吸机参数的设定,I/E：一般为1/2。采用较小I/E，可延长呼气时间，有利于呼气。适当增大I/E，甚至采用反比通气（I/E1）,使吸气时间延长，平均气道压升高，甚至使PEEPi也增加，有利于改善气体分布和氧合。,呼吸机参数的设定,触发灵敏度（trigger）压力触发，流速触发设置：在避免假触发的情况下尽可能小。一般置于-1-3 cmH2O或12L/min。,呼吸机参数的设定,流速波形种类：方波、正弦波、加速波和减速波。特点：减速波与其他三种波形相比，气道峰压更低、气体分布更佳、氧合改善更明显。叹气（sigh）间断给予高于潮气量50%或100%的大气量；用于长期卧床、咳嗽反射减弱、分泌物引流不畅的患者,呼吸机参数的设定,呼气末正压（positive end expiratory pressure, PEEP）,借助于呼气管路中的阻力阀等装置使气道压高于大气压水平即获得PEEP,重力依赖区域的肺不张,PEEP生理学效应,（1）增加或恢复减少了的功能残气量, 气体分布在各肺区间趋于一致，降低QS/QT，改善V/Q。（2）使萎缩陷肺泡重新开放，避免肺泡反复的开放/闭合造成的剪切力。 （3）对抗内源性呼吸末正压（PEEPi）的作用，有利于触发，降低呼吸功。,PEEP生理学效应,使平均气道压升高，影响回心血量。PEEP过高，还使肺泡处于过度扩张的状态，顺应性下降，持久会引起肺泡上皮和毛细血管内皮损，通透性增加，形成所谓的“容积伤” （volutrauma）。,概念：呼吸肌用力和呼吸机送气方式不协调表现和监测患者躁动不安，呼吸节律和动度不规则，心率和血压波动，SpO2下降，呼吸机报警。呼吸力学波形：压力-时间曲线和流速-时间曲线形态不稳定。定量监测：WOB(呼吸功)、VO2(氧耗量)、EE（静息能量消耗）和PTP（压力-时间乘积）增加。,呼吸机与自主呼吸的对抗,气道阻力增加,Paw (cm H2O),Normal PPlat(Normal Compliance),Increased PIP,Increased PTA(increased Airway Resistance),导致气道阻力增加的因素,分泌物过多 分泌物潴留粘膜水肿(哮喘, 气管炎, 肺水肿)肺气肿(气道压迫)异物肿瘤所致狭窄,肺顺应性下降,Time (sec),Paw (cm H2O),Normal PPlat(Normal Compliance),Increased PPlat(Decreased Compliance),Normal,PIP,导致肺顺应性下降的原因,肺实质改变ARDS, (支气管)肺炎, 肺水肿, 纤维化表面活性物质功能障碍ARDS, 肺泡肺水肿, 肺不张, 误吸肺容量减少气胸, 膈肌抬高,呼吸机与自主呼吸的对抗,处理患者因素：除做好解释工作外，各种病情变化是常见原因，应通过查体和必要的辅助检查进行鉴别。呼吸机、呼吸管路因素：如为呼吸机故障，应以简易呼吸器代替呼吸机；呼吸管路原因：如管路脱开、插管移位和痰痂形成等。呼吸模式和参数设置不当：应针对吸气触发、流速波形、潮气量大小、吸呼切换各环节进行处理必要时可使用镇静或肌松剂。,对呼吸机报警的反应,气道高压报警,手法通气困难?,呼吸机故障,N,吸痰管伸入 25 cm,Y,气管插管阻塞,调整头部位置可否解除,患者是否咬住气管插管,插入牙垫或肌松,重新插管,N,N,Y,N,对呼吸机报警的反应,气道高压报警,手法通气困难?,呼吸机故障,N,吸痰管伸入 25 cm,Y,镇静肌松,顺利进行通气,寻找呼吸窘迫的原因低血容量，CO2潴留休克，CNS病变,气 胸肺不张实 变,Y,呼吸肌费力,体检及胸片,Y,N,对呼吸机报警的反应,手法通气,通气阻力,呼吸机或管路漏气,气管插管套囊漏气,正常,过低,低压报警,漏气时的表现,Volume (ml),Time (sec),Air Leak,对呼