机械通气的呼吸力学基础课件

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,.,*,机械通气的呼吸力学基础,主要内容,临床重要的呼吸力学指标,呼吸力学指标测定的方法和意义,呼吸力学曲线的分析,呼吸力学应用进展,呼吸力学监护已成为呼吸监护的重要内容,压力、阻力、顺应性、,auto-PEEP,呼吸力学曲线监测应用日趋广泛,提倡呼吸力学指导下的个体化通气治疗,肺保护通气策略的实施需要呼吸力学指导,Volume Change,Gas Flow,Pressure Difference,自 主 呼 吸,Volume Change,Time,Gas Flow,Pressure Difference,机 械 通 气,重要的呼吸力学指标,压力 阻力 容量,峰压力 吸气阻力 吸气潮气量,平台压力 呼气阻力 呼气潮气量,平均气道压力 弹性阻力 可压缩气量,胸膜腔内压力 呼气末肺容积,autoPEEP,重要的呼吸力学指标,顺应性,静态顺应性,动态顺应性,呼吸系统顺应性,肺顺应性（,C=V/ P,，正常肺,0.2-0.3L/cmH2O,）,胸壁顺应性（,C= V/ Ppl,，正常,0.2 L/cmH2O,）,流速,呼吸功,P-V,曲线,P0.1,呼吸力学三要素,压力（,P,）、阻力（,R,）、流速（,V,）,P=,R,V,压力和流速为可控因素,流速对时间积分得到容量,控制压力时阻力改变可导致容量降低,控制流速时阻力增大可导致压力增高,time,Pressure,PEEP,PIP,Pplat,Alveolar Distending (recoil),Pressure difference,(Pdis),Flow-Resistive,Pressure difference,(Pres),压力组成,dP = R x Flow + dV / C st,压力监测部位,流速监测部位,床旁监测气道压力的意义,峰压力增高而平台压无改变,气道阻力增高（分泌物堵塞、气管痉挛）,峰压力与平台压同时增高,提示肺或胸壁扩张受限,明显腹胀,肺不张,气胸,肺水肿、,ARDS,、肺炎,autoPEEP,人,-,机对抗,气道峰压降低,（管路漏气、气囊漏气）,肺（气道）阻力与顺应性的改变都可导致气道压力的改变,通过气道压力的,改变可以推测病,变的性质和部位,Paw (cm H,2,O),Normal,Normal P,Plat,(Normal Compliance),Increased PIP,Increased,P,TA,(increased Airway Resistance,),Normal,PIP,P,Plat,High R,aw,PIP,P,Plat,Increased Airway Resistance,DECREASED COMPLIANCE,Time (sec),Paw (cm H,2,O),Low Compliance,PIP,P,Plat,Normal,PIP,P,Plat,Normal P,Plat,(Normal Compliance),Increased,P,Plat,(Decreased Compliance,),Normal,PIP,小结,压力升高或降低都应进一步查找原因,压力增高,肺或胸腔顺应性下降（变硬）,气流阻力增高,顺应性降低和阻力增高处理原则不同,阻 力,气道阻力的计算公式和意义,R,I,=,（,PIPPpla,）,/,吸气末流速,R,E,=,（,PplaPEEP,）,/,最大呼气流速,气管插管阻力在总的呼吸阻力中占很大比例,与管腔内径关系最大,流速和气管插管长度,氦,-,氧混合气也可减低吸气阻力，减少呼吸功,气道阻力,大气道以湍流为主，占总阻力的,80%,小气道以层流为主，占总阻力的,20%,正常人气道阻力为,1cmH2O/L/S,哮喘和,COPD,患者气道阻力为,5-10cmH2O/L/S,8,号气管插管阻力为,5 cmH2O/L/S,7,号气管插管阻力为,8 cmH2O/L/S,气管插管时气道阻力相当于中度哮喘发作,气道阻力的计算方法,Resistance =,PIP - Plateau,Peak Flow,Resistance =,20 - 15,1 L / sec,= 5,cmH,2,0 / L / sec,Plateau Pressure 15 cm,PIP 20 cm,V,TE,500 cc,Peak Flow = 60 L/min,Volume Change,=,Pressure Difference x Compliance of the Balloon,Volume,Pressure,D,V,D,P,C,=,D,V,D,P,顺应性,静态顺应性与动态顺应性,顺应性,肺的“硬度”或弹性变性能力,Static,No flow,dynamic,flow and resistance,肺顺应性监测的意义,静态顺应性（,Cs,）反映肺和胸壁的弹性（弹性阻力）特征,排除了气道阻力成分,动态顺应性（,C,d,）反映气道的阻力（非弹性阻力）和呼吸系统弹性（弹性阻力）特征，气道阻力可明显影响,C,d,的水平,顺应性的动态变化趋势更有意义,顺应性测定要求,The gold standard for measuring compliance and resistance utilizes a volume breath delivered with a square wave flow and adequate plateau,40,P,CIRC,cmH,2,O,INSP,L,min,EXP,PLOT SETUP,30,20,10,0,10,-20,80,60,40,20,0,20,-80,40,60,V,.,0,4,8,12s,2,6,10,UNFREEZE,Compliance Calculations,500,15-5,= 50 ml/cmH,2,0,Compliance =,Vte,Plateau - PEEP,Plateau Pressure 15 cm,PEEP 5 cm,V,TE,500 cc,Peak Flow = 60 L/min,V,TE,500 cc,10 cmH,2,0,区分肺顺应性和胸壁顺应性的意义,C,RS,=,（,C,L,C,W,）,/,（,C,L,+,C,W,）,胸壁顺应性相对稳定时，,C,RS,的动态变化可代表肺的顺应性改变,评价,PEEP,对血流动力 学的影响,Crs = Vt / dP,dist,(aw),Ccw = Vt / dP,dist,(pl),CL = Vt / P,dist,(aw - pl),胸壁顺应性降低对跨肺压的影响,机械通气时气体分布,机械通气时气体在肺内分布特点,自主呼吸时气体主要进入肺的下垂区域和肺周边胸膜下部位,机械通气时气体主要分布在肺非下垂区和大气道内,ARDS,机械通气时气体主要进入非下垂区域,COPD,和哮喘患者除存在肺内气体分布不匀外，还存在较严重的小气道塌陷,气流波形（方波和正弦）对气体的分布无明显影响,机械通气时肺内气体分布,提倡应用自主通气模式,压力,-,容积曲线,P-V,曲线的测定方法,大注射器法,吸气阻断法,持续气流法,准静态顺应性,测定注意事项,镇静、肌松,近口端压力和流速监测,注意干扰因素（如明显腹胀）,PEEP,对血流动力学的影响,Ppl=,PEEPCL/,（,CL+CW,）,正常人,CL,CW,，故,Ppl,1/2,（,PEEP,）,相当于大约一半的胸腔内压（,PEEP,或,PEEPi,）传递到胸膜腔，引起胸内压增高。,当肺实变、肺顺应性减小时，传递比例减少。而胸壁顺应性减小时，气道内压力向胸膜腔内传递增加。,ARDSPEEP,水平在,15cmH2O,以下，可不必考虑对,PCWP,读数的影响。,肺顺应性增大（肺气肿）或胸壁顺应性减小时较低水平的,PEEP,就可能干扰肺毛细血管楔压的判断，测定值高于实际水平。,PEEP,对血流动力 学的影响,Compensation of the PCWP for PEEP:,Compliant lungs corrected PCWP = PCWP - PEEP (mm Hg),Noncompliant lungs corrected PCWP = PCWP - 1/4 PEEP (mm Hg),PEEP (cm H,2,O) /1.36 = PEEP (mm Hg),Low VT vs High VT,Low PEEP vs High PEEP,HFOV,Prone,Protective,Auto-PEEP,检查方法,呼气末阻断气流法,当存在严重气道狭窄及气体陷闭时不能反映真实的肺泡压力，用平台压更准确,吸气末肺容积（,VEI,）,食道内压测定,Auto-PEEP Maneuver,Press Exp Pause key to schedule automatic expiratory pause maneuver,During the next exhalation, the inspiratory and expiratory valves will close and pressure will equilibrate between the circuit and the patient,P,T,End Exp Hold,痰液栓对呼吸力学评估的影响,auto PEEP,临床迹象,不能解释的心动过速、低血压，特别是机械通气治疗刚开始时（,由人工通气过度为机械通气时）,患者触发每次呼吸非常费力,患者的吸气努力并非每次都能触发呼吸,下一次吸气开始时呼气（喘鸣音）仍在进行,压力流速图形显示异常,动态过度充气对循环功能影响,Air Trapping,Inspiration,Expiration,Normal,Patient,Time (sec),Flow (L/min),Air Trapping,Auto-PEEP,auto PEEP监测,auto PEEP,的处理,改变呼吸机参数,增加呼气时间，,减少通气频率，,减少潮气量,降低病人的通气需要,减少碳水化合物的摄取，减少死腔通气，治疗焦虑、寒战、疼痛、发热,减低呼吸道阻力,（用大口径的气管插管，经常吸痰避免分泌物潴留，应用支气管扩张剂）,加用适当的外源性,PEEP,，一般为,PEEPi,的,75%,左右,外源性,PEEP,改善触发的机理,重症哮喘患者外源性,PEEP,的影响,死腔通气问题,解剖死腔,正常人,100-150ml,机械通气时可明显增大（延长管、湿化器）,肺泡死腔,肺栓塞时,V,D,/V,T,可显著增大（,0.6,）,COPD,、,Asthma,时,V/Q,比例失衡，,V,D,/V,T,增大,V,D,/V,T,增大将导致分钟通气量显著增大,呼吸力学测定的质量控制,No significant leaks,Compliance should subtract out circuit compliance, especially in pediatrics,Manual calculations often contribute to errors,Respiratory Mechanics Requirements For Accuracy,The patient must be at rest during peak and plateau pressure measurements,Adding plateau should not restrict exhalation and create auto-PEEP,Plateau time must not be too short or too long,Patient Effort During Inspiratory Plateau,P,T,Diaphragm Efforts,Plateau Pressure = ?,Plateau Time Too Short,500,20-5,= 33 ml / cmH,2,0,500,15 - 5,= 50 ml / cmH,2,0,Results in falsely low compliance values !,Displayed Plateau Pressure 20 cm,PEEP 5 cm,Actual Plateau Pressure 15 cm,V,TE,500 cc,P,T,Static Compliance Leaks and/or Too Long a Plateau,500,15-5,= 50 ml / cmH,2,0,500,10 - 5,= 100 ml / cmH,2,0,Results in falsely high compliance values !,Displayed Plateau Pressure 10 cm,PEEP 5 cm,Actual Plateau Pressure 15 cm,V,TE,500 cc,P,T,Air Leak,Volume (ml),Time (sec),Air Leak,Air Leak,Volume (ml),Pressure (cm H,2,O),Air Leak,Air Leak,Inspiration,Expiration,Volume,(ml),Flow,(L/min),Air Leak in mL,Normal,Abnormal,Response to Bronchodilator,Before,Time (sec),Flow (L/min),PEFR,After,Long T,E,Higher PEFR,Shorter T,E,Inadequate Inspiratory Flow,Adequate Flow,Time (sec),Inadequate Flow,P,aw,(cm H,2,O),Inadequate Inspiratory Flow,Flow,(L/min),Time (,sec,),Normal,Abnormal,Active Inspiration or Asynchrony,Patients effort,Flow versus Time,ACCELERATING,DECELERATING,SINE,SQUARE,Lung Compliance Changes and the P-V Loop,Volume (mL),Preset PIP,V,T,levels,P,aw,(cm H,2,O),COMPLIANCE,Increased,Normal,Decreased,Pressure Targeted Ventilation,V,P,PEEP: 3 cmH,2,O,V,P,PEEP: 8 cmH,2,O,Optimising PEEP,呼气阻力增加,Prolonged expiratory flow indicates an obstruction to exhalation and may be caused by obstruction of a large airway, bronchospasm, or expiratory valve failure of the ventilator,T,ime,Flow,Insufficient Expiratory Time,Expiratory flow is unable to return to baseline prior to the initiation of the next mechanical breath,Incomplete exhalation causes gas trapping, dynamic hyper-expansion and the development of intrinsic PEEP,T,ime,Flow,End-Expiratory Flow,F,V,V,F,After Suction,Before Suction,Airway Obstruction,Pressure-Volume Loop,Controlled,Assisted,Spontaneous,Vol (ml),P,aw,(cm H,2,O),I: Inspiration,E: Expiration,I,E,E,E,I,I,总结,呼吸力学是机械通气理论的重要内容,压力、阻力、顺应性是呼吸力学最基本内容,呼吸力学指标的测定需要标准化,呼吸力学曲线形态的异常对临床有指导意义,临床案例分析,呼吸力学病例,女，,83,岁,右股骨颈骨折,2,周,术后突然发生呼吸心跳骤停,呼吸机辅助呼吸,谢谢 ！,