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1、机械通气的呼吸力学Respiratory mechanics of mechanical ventilationWWW,Xiangyu Zhang, MD, FCCP张翔宇SICUShanghai Tenth Peoples HospitalShanghai Tongji UniversityShanghai, China,呼吸机波形与参数,压力pressure近端压力远端压力气管内压力食管压力，内源性PEEP容量volume，压力-容量环流量flow，流速-容量环呼吸做功，等,基本图形,Flow,Volume,Pressure,P-V loop,F-V loop,各压力参数,吸气峰压（PIP
2、） PIP = PRAW + Pplateau 平台压（ Pplateau） Pplateau = VT/CRS 呼气末压（EEP） 气道阻压（PRAW） PRAW = RAW （flow rate）,呼吸力学监测,顺应性（Compliance） 静态顺应性（Cst ）Cst = VT/（Pplateau PEEP） 动态顺应性(Cdyn)Cdyn = VT/（PIP PEEP） 气道阻力(RAW) RAW = PRAW/(flow rate) : 23 (cmH2OL/s) 包括呼吸道与气管导管的阻力,Airway Pressure (VCV),Airway Pressure (VCV),压
3、 力,Why Spontaneous Breath Should Be Needed,Better cardiac output Better ventilation/perfusion Better end expiratory lung volume (EELV) Better clinical outcome,Current Opinion in Critical Care 2005, 11:6368,Christian Putensen,August, 2006,Current Opinion in Critical Care 2002, 8:5157,Fabry Chest 1995
4、:107:1387,Asynchrony is still a problem,Patient-ventilator asynchrony during assisted mechanical ventilation ArnaudW. Thille Pablo Rodriguez Belen Cabello Franois Lellouche Laurent Brochard Intensive Care Med (2006) 32:15151522,Ti in PSV,Inspirationtermination Criteria(Esens),25% of peak flow in mos
5、t cases,压力上升时间与吸气终止,Overshoot,supraplateau,Intrathoracic pressures,TRACHEAL PRESSURE,PROX. AIRWAY PRESSURE,PLEURALPRESSURE,ALVEOLAR PRESSURE,Resp Lab MGH,Asia Vent Forum Shanghai TCI,亚洲通气论坛,Our study settings,Pressure Support,P circuitP esoP plural,Rise time 1%,P circuitP esoP plural,Rise time 1%,P
6、circuitP esoP plural,Rise time 100%,P circuitP esoP plural,Esens 1%,P circuitP esoP plural,Esophageal Balloon,Approximates pleural pressurePolyethylene10 cm long balloon100 cm long tubingPositioned in the lower 1/3 of the esophagusFilled with 0.5-1.0cc air,Proper placement of the balloon is imperati
7、ve for accurate measurements. An approximate level of placement can be made by measuring the distance from the tip of the nose to the bottom of the earlobe and then from the earlobe to the distal tip of the xiphoid process.,Baydur Method, to confirm balloon placement,Calculations based on differenti
8、al pressures,Tracheal Pressure Measurements,Intended typically for intermittent useMore accurately displays actual pressures transmitted to the airwaysProvides ability to measure imposed Work and Resistance,Tracheal Pressures,Measures pressure at distal end of endotracheal tube5 Fr polyethylene tube
9、PAW-PTR/Flow (L/s) = Resistance of ETTAdvance Tracheal Pressure catheter to 1 cm less than ET plus adaptersWithdraw 1-2cm if patient continues to cough,Evaluation of pressure/volume loops based on intratracheal pressure measurements during dynamic conditions;S.Karason et al, Acta Anesthesiol Scand 2
10、000;44:571-577,Evaluation of pressure/volume loops based on intratracheal pressure measurements during dynamic conditions;S.Karason et al, Acta Anesthesiol Scand 2000;44:571-577,Tidal volume remains constantAs I:E ratio is changed, autoPEEP is seen only with tracheal pressuresPIP increases and Compl
11、iance decreases,TC,气道阻力与流速的关系,7.5mm导管两端压力差,TC/ATC,ATC,Haberthur ICM 1999;25:514,Does the tube-compensation function of two modern mechanicalventilators provide effective work of breathing relief?,Critical Care October 2003 Vol 7 No 5 Maeda et al.,TC 100%, ETT 6.5mm,PcircuitPesoPplural,气管压力监测,设计为间断性监
12、测更准确地显示气管内压力能够监测做功与阻力,Ptr (tracheal pressure) 作为压力控制呼吸的向导,在压力控制通气时，由于气管内插管造成的气流阻力升高，导致肺内压力达不到理想水平AVEA可以测量气管内压力，并作为一条曲线显示。吸气压力可以根据气管内压进行调节,Paw = 28Ptr = 25,Ptr (tracheal pressure) 作为压力控制呼吸的向导,用气管压和食道压计算力学负担,为何测量呼吸功?,WOBpt 测定病人实际的呼吸功水平正常 .3-.6 Joules/Liter.75 病人可能出现疲劳长期机械通气病人脱机成功的关键是能否为他们提供一个正常的呼吸功Mac
13、Intyre; Crit Care Med 1999; 27:1040机器支持的力度应根据病人呼吸功来调节AVEA 可以提供此类数据,用气管压和食道压计算力学负担,用气管压和食道压计算力学负担,用气管压和食道压计算力学负担,Real-time assessment of WOB.,Effort is amplified by a factor of 4 with a proportionality ratio of 3:1,PAV+ Software Option Clinical Description,D. Georgopoulos, Intensive Care Med. 2008 Ju
14、l 8.,Auto PEEP (Air Trapping),Static PEEPi End-Expiratory Hold,Problems with auto PEEP expiratory hold measurements,Will not work if patient is breathing spontaneouslyWill not work if patient has small airway closure, (flow dependent airways)False negatives,1. Patient trigger work before PEEP applie
15、d,2. Note PEEP application,3. Patient trigger work after PEEP applied,监测由于气流受限而引起的内源性PEEP而增加的触发功,F-V loop,F-V loop and leaking,漏气,Leak,漏气,SIMV+PSV，通气管路存在漏气,Auto PEEP,MIP 测量-定义,MIP (Maximum Inspiratory Pressure，最大吸气压) / P100 ，测量病人在自主呼吸状态下，压力曲线上的负向最大值。,MIP 测量-意义,正常值: 成人 -70 to -100 cm H2O 儿童 -20 to -1
16、00 cm H2O 脱机标准 -20 cm H2O意义: 病人的呼吸力量参数.病人吸气肌力量的标志物.作为脱机以及评价神经肌肉疾病进展情况的标准.在脊柱后侧突，老年，COPD 以及神经肌肉疾病的病人会其绝对值会降低。,P100 测量-定义,呼吸驱动 (P100), 探测到病人吸气努力开始计算，第一个100 ms 内所形成的最大吸气负压。,P100测量-正常值及意义,正常值: 成人-1 to -4 cm H2O 儿童-0.5 to -4 cm H2O注意:在吸气已经启动，而吸气阀仍处于关闭状态的前100 ms所产生的压力。 正常情况下，病人感知气路阻塞所需要的时间为 300 ms ，因此，P10
17、0是一个很好的测量呼吸中枢驱动力信号的输出指标。 在最初的这300 ms 时间里，肺容量和气体流量没有改变，因此，肺脏力学的异常对本指标的测量没有影响。超过 -5 cm H2O 意味着呼吸驱动过高，可能会增加呼吸功并导致呼吸肌疲劳。,Intra-thoracic pressures while playing musical instruments,Trans-pulmonary Pressures,Esophageal balloon pressures reflect pleural pressuresPleural pressures can indicate external pres
18、sures working against the lungTrans-pulmonary pressures can help us determine safe ventilation and effective PEEP,Numerical Assessments Paw, Pes, Ptp Insp & Exp Holds,Trans-pulmonary Inspiratory Plateau:Obtain alveolar distending (Paw) and chest wall (Pes) pressuresPaw Pes produces the Trans-pulmona
19、ry Plateau PressureThese measurements are done by performing an inspiratory hold,Numerical Assessments Trans-pulmonary Insp Plateau,The pressures trying to expand the lung are met by the increased elastic forces of the chest wall resisting expansion,39,39,30,30,30,The inspiratory trans-pulmonary pla
20、teau pressure of 9 cmH2O is the pressure being exerted across the alveolar wall,Numerical Assessments Paw, Pes, Ptp Insp & Exp Holds,Trans-pulmonary Expiratory Plateau:Measuring the pressures of lung recruitment Airway PEEP and the pressures of de-recruitment Esophageal PEEPThese measurements are do
21、ne by performing an expiratory hold,Chest wall or Lung?,Similar airway pressure curvesCurve on left is limited by chest wallCurve on right is limited by lung disease,Recruitment Maneuver,Lung Protective Strategy,1.Set Pplat below the upper Pflex to avoid regional overdistensionApply small Vt to mini
22、mize stretching forcesSet PEEP at level to avoid alveolar collapse,Volume,Pressure,Respiratory Mechanics in ARF*,Reduced range of volume excursion: Low complianceFlattening at low and high volumes: Lower and upper inflection points*Bigatello: Br J Anaest 1996,Volume,Pressure,NORMAL,ARDS,P-V loop,Pfl
23、ex测量,测量完成后，屏幕会自动冻结。如欲重新测量，按压冻结键解冻，屏幕恢复到测量屏幕。,Inflection point,Recruitment Maneuver and PV curve hysteresis,Airway Pressure cmH2O,%,Opening and Closing Pressures,0,5,10,15,20,25,30,35,40,45,50,0,10,20,30,40,50,5 patients,ALI / ARDS,Am J Respir Crit Care Med Vol 164. pp 131140,2001,Marini & Gattinoni,
24、P-V curve Methodology,The supersyringe technique,Recruitment maneuver is needed,Methodology Sustained inflation Stepwise Recruitment Strategy Pressure control with prone position, with HFOV, et al Titrating PEEPdeflex after RM PV curve (looking for Pdeflex) Oxygenation (PaO2 drop 10%) Stress Index P
25、V slope,Titrating PEEP fellowing RM,Pdeflex + 2cmH2O, (PV curve) Super-syringe Low-flow Multiple occlusion Stress Index Low-flow for both limb (inflation & deflation) Oxygenation PaO2 drop 10% PV slope,吸入和呼出均保持流量恒定与超级注射器法的良好相关性消除了阻力造成的影响,低流量PV环测定- 准确的恒定低流量,PEEP的设置，传统的方法: Amato 1, Takeuchi 2, Matamis
26、 3, Moloney et al. 4,PEEP的设置，最近的方法: Mehta et al. 5 , Kallet 6, Hickling 7, Harris 8, Bugedo 9, Arnold 10, Pelosi 11, Rimensberger 12,过度膨胀或复张的结束? Hickling 13, Jonson 14, Maggiore 15, Moloney et al. 5,低流量PV环测定,选择吸气和/或呼气枝仅吸气枝 以预设低流量进行充气；当达到压力或容量限制时（以先到的为准），压力将以5cmH2O/秒的速度降低 (避免心脏过负荷) 吸气和呼气枝以预设低流量进行充气和放
27、气；当达到压力或容量限制时，充气转为放气。,低流量PV环测定- 灵活设置,PV curve for Pdeflex,Recognizable? And percentage of them? Is this Pdeflex constant over time? Or RM? Is Pdeflex after RM repeatable? Is PEEP on Pdeflex clinically practical? Not answered yet,Pflex,“maximum difference of 11 cm H2O for the same patient”AM J RESPIR
28、 CRIT CARE MED 2000;161:432439.R. SCOTT HARRIS, DEAN R. HESS, and JOS G. VENEGAS,Effect of the chest wall on pressurevolume curve analysis of acute respiratory distress syndrome lungs,For most patients, the chest wall had little inuence on the total respiratory system P-V curve. However, there were
29、patients in whom the chest wall did potentially have clinical signicance. （N=22, 23-77 yrs old）,Dean R. Hess Crit Care Med 2008 Vol. 36, No. 11,Dean Hess, et al,22 pts ALI/ARDS Chest wall compliance: 21462 ml/cmH2O,Dean R. Hess Crit Care Med 2008 Vol. 36, No. 11,Hickling K. AJRCCM 2001;163:69-78.,Hi
30、ckling K. AJRCCM 2001;163:69-78.,最佳顺应性 “ PEEP递降测试法,肺复张趋势图 in Draeger LPP,Alveolar recruitment can be predicted from airway pressure-lung volume loops: an experimental study in a porcine acute lung injury model,Critical Care 2008, 12:R7 (doi:10.1186/cc6771),Conclusion,A PV-loop-derived parameter, MH/
31、TLC of 0.3, predicted changes in lung mechanics better than changes in gas exchange in this lung injury model.,Critical Care 2008, 12:R7 (doi:10.1186/cc6771),Mechanical Ventilation Guided by Esophageal Pressure in Acute Lung Injury,As compared with the current standard of care, a ventilator strategy using esophageal pressures to estimate the transpulmonary pressure significantly improves oxygenation and compliance. Multicenter clinical trials are needed to determine whether this approach should be widely adopted.,NEJM，2008；359（20）：2095,Daniel Talmor NEJM，2008；359（20）：2095,
