环路分析在机械通气中的应用

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1、环路分析在机械通环路分析在机械通气中的应用气中的应用Critical in assessing the Mechanically Ventilated Patient机械通气目的机械通气目的提供足够的肺泡通气量（提供足够的肺泡通气量（V VA A）在安全的供氧浓度下达到适宜的动脉氧分压在安全的供氧浓度下达到适宜的动脉氧分压 胸腔压升高的情况下避免发生气压胸腔压升高的情况下避免发生气压病人舒适病人舒适 合适的呼吸肌负担合适的呼吸肌负担良好的人机同步良好的人机同步 进行波形分析的必要性进行波形分析的必要性lPatientventilator dyssynchrony imposes an addi

2、tional burden on the respiratory system and may increase the morbidity of critically ill patients.Thille A W,Rodriguez P,Cabello B,et al.Intensive Care Med,2006.32(10):p.1515-22.Ignorance of these issues may prevent the ventilator from achieving its goals and may cause patient harm.Georgopoulos D,Pr

3、inianakis G,and Kondili E.Intensive Care Med,2006.32(1):p.34-47.Inspection of pressure,flow and volume waveforms represents a valuable tool for the physician to recognize and take the appropriate action to improve patientventilator synchronyEumorfia Kondili,Nektaria Xirouchaki and Dimitris Georgopou

4、los.Curr Opin Crit Care 13:8489.Nilsestuen J O and Hargett K D.Respir Care,2005.50(2):p.202-34;discussion 232-4.Pressure versus TimePressure versus TimeInspirationExpirationPaw (cm H2O)Time(sec)TIPeak Inspiratory PressurePIPPEEPPEEPTEPressure-Volume LoopPressure-Volume LoopControlledAssistedSpontane

5、ousVol(ml)Paw(cm H2O)I:InspirationE:ExpirationIEEEIIFlow-Volume LoopFlow-Volume LoopVolume(ml)Volume(ml)PEFRFRCInspirationExpirationFlow(L/min)Flow(L/min)PIFRVTMechanical MonitoringAirway PressuresStatic or Plateau Pressure静态顺静态顺应性和平台压应性和平台压Separates resistance from elastic recoil吸气末测量吸气末测量Should be

6、 kept 10 L/min 常常提示撤机失败常常提示撤机失败VE,VA,and PaCO2 Flow versus TimeThe flow-time curve can be used to detect:Waveform shapeType of breathingPresence of Auto-PEEP(Intrinsic PEEP)Patients response to bronchodilatorsAdequacy of inspiratory time in pressure control ventilationPresence and rate of continuous

7、 air leaks判断流速波形判断流速波形Inspiratory flow patterns can vary based on the flow waveform setting or the set breath type as illustrated减速波减速波 呼气流速波形在下一个吸气相开始呼气流速波形在下一个吸气相开始呼气流速波形在下一个吸气相开始呼气流速波形在下一个吸气相开始之前呼气流速突然回到之前呼气流速突然回到之前呼气流速突然回到之前呼气流速突然回到0,0,这是由于这是由于这是由于这是由于小气道在呼气时过早地关闭小气道在呼气时过早地关闭小气道在呼气时过早地关闭小气道在呼气时过

8、早地关闭,使部使部使部使部分气体阻滞在肺泡内而引起分气体阻滞在肺泡内而引起分气体阻滞在肺泡内而引起分气体阻滞在肺泡内而引起Auto-PEEPAuto-PEEP(PEEPi)(PEEPi)存在存在存在存在不同类型呼吸下，五种类型的流速不同类型呼吸下，五种类型的流速-时间时间曲线曲线评估支气管扩张剂的反应评估支气管扩张剂的反应effect of inspiratory time in pressure control on flow delivery to the patient.may be desirable in some cases患者对支气管扩张剂的反应性患者对支气管扩张剂的反应性患者对

9、支气管扩张剂的反应性患者对支气管扩张剂的反应性BeforeTime(sec)Flow(L/min)PEFRAfterLong TEHigher PEFRShorter TE漏气对漏气对吸呼切换的影响吸呼切换的影响：漏气会导致：漏气会导致吸气流速下降缓慢吸气流速下降缓慢，达不到预设的切，达不到预设的切换标准（换标准（set termination threshold）吸气峰流量吸气峰流量Tinsp45%15%Threshold can not be reachedthe period of mechanical inflation must match the period of neural

10、inspiratory time(the duration of inspiratory effort),and the period of mechanical inactivity must match the neural expiratory time While the ventilator was still pumping gas into the patient,his expiratory muscles were recruited,causing a bump in the airway-pressure curve.That the flow never returne

11、d to zero throughout expiration reflected the presence of autopositive end-expiratory pressure.Auto PEEP吸呼切换延迟吸呼切换延迟Delayed termination present患者患者呼气肌开始活动呼气肌开始活动时，呼吸机的吸气过程时，呼吸机的吸气过程还未完成，因此发生亚临床的人机对抗还未完成，因此发生亚临床的人机对抗。Note there is also a small airway pressure spike near the end of mechanical inflatio

12、n,which coincides with the patients neural expiratory activity.切换延迟切换延迟Cycle Criteria?吸气预置流速不足吸气预置流速不足吸气预置流速不足吸气预置流速不足Flow(L/min)Time(sec)NormalAbnormalActive Inspiration or AsynchronyActive Inspiration or AsynchronyPatients effort吸气预置流速不足或者患者主动吸气吸气预置流速不足或者患者主动吸气(SIMV)/volume-limited/pressure suppor

13、t approach“double breathing”assist volume control 恒定流速恒定流速患者持续吸气，气道压力下患者持续吸气，气道压力下降降，在呼气阀打开时，发生，在呼气阀打开时，发生double breathingAir TrappingAir TrappingInspirationExpirationNormalNormalPatientPatientTime(sec)Flow(L/min)Air TrappingAuto-PEEPPRESSURE-TIME CURVESBreath type delivered to the patientWork requi

14、red to trigger the breathBreath timing(inspiration vs exhalation)Pressure waveform shapeAdequacy of inspirationAdequacy of inspiratory plateauAdequacy of inspiratory flowResults and adequacy of a static mechanics maneuverAdequacy of the Rise Time settingBreath type delivered to the patientBreath typ

15、e delivered to the patientCMV,with auto-flow onMeasuring Static Mechanicsillustrates a stable static pressure plateau measurement that differentiates the pressure caused by flow through the breathing circuit and the pressures required to inflate the lungs.The pressure-time curve can be used to verif

16、y the stability of the plateau when calculating static compliance and resistance.C 代表不稳定的气道平台压代表不稳定的气道平台压力，常见原因为漏气或者患力，常见原因为漏气或者患者出现自主吸气者出现自主吸气Assessing Rise Time 吸气斜率吸气斜率Chiumello D,Pelosi P,Croci M,et al.,Eur.Respir.J.,2001.18(1):p.107-114.A the rise to pressure may be too slow.B ideal waveform 恰当

17、的斜恰当的斜率设置率设置C A rise time that is too fast流速不足流速不足 Adequate FlowInadequate FlowPaw (cm H2O)Time(sec)Inadequate Flow 预置流速不足预置流速不足The dished-out appearance of the airway pressure waveform illustrates the changes from the passive breath when flow does not meet patient demand.Progressive increases in pa

18、tient effort during breaths 2 and 3 were created by manually lifting the test lungTriggering difficulty and unnecessary patient work 触发困难触发困难第三次为患者触发的通气，第三次为患者触发的通气，虽然患者触发了呼吸机，但虽然患者触发了呼吸机，但是是P-TP-T曲线呈下凹型，显示曲线呈下凹型，显示了预制流速不足了预制流速不足 第一次呼吸患者未达到触发阈值，但第一次呼吸患者未达到触发阈值，但是启动了按需阀，为时间触发；是启动了按需阀，为时间触发；The sensit

19、ivity setting is 4 cm H2O.第二次患者仍打开了按需阀，启动了第二次患者仍打开了按需阀，启动了自主呼吸，自主呼吸末，时间触发了自主呼吸，自主呼吸末，时间触发了一次同步间歇指令通气一次同步间歇指令通气 吸气时的作功大小吸气时的作功大小 吸气做功主要由吸气负压大吸气做功主要由吸气负压大小和持续时间长短决定，吸小和持续时间长短决定，吸气负压越大和持续时间越长，气负压越大和持续时间越长，吸气功越大，反之亦然吸气功越大，反之亦然 人机不同步人机不同步 He was being mechanically ventilated and arterial blood gases were

20、 acceptable on ventilator settings of SIMV 12/min,VT 850 ml,PEEP 5 cmH2O and FiO2 0.40.He then became combative,requiring sedation and restraints.The end tidal CO2 had increased from 42 mmHg to 48 mmHg and arterial oxygen saturation had decreased from 98%to 94%.His heart rate increased from 80 to 11

21、0 and his blood pressure increased from 140/80 to 180/100.The physician increased the inspiratory flow rate and ventilator sensitivity.The patient immediately became calmer and all vital signs returned to baseline values.无效触发无效触发Further,if the peak flow rate of the ventilator is inadequate,then the

22、inspiratory flow will be scooped inwards,and the patient appears to be fighting the ventilator.If the number of triggering episodes is greater than the number of breaths,the patient is asynchronous with the ventilator.Loops a good thing all roundP-V loopF-V loop肺通气功能测定肺通气功能测定 一、肺容积(lung volume)（一）基本

23、肺容积(basal lung volume)1.潮气量(Tidal Volume,VT)2.补吸气量(Inspiratory Reserve Volume,IRV)3.补呼气量(Expiratory Reserve Volume,ERV)4.残气量(Residual Volume RV)（二）基本肺容量(basal lung capacity)1.深吸气量(Inspiratory Capacity IC)2.功能残气量(Function Residual CapacityFRC)3.肺活量(Vital Capacity VC)4.肺总量(Total Lung Capacity TLC)静态静态

24、 P-V 环环横轴为压力有正压横轴为压力有正压(机械通气机械通气)、负压负压(自主呼吸自主呼吸)之分之分,纵轴是容纵轴是容积积(潮气量潮气量Vt),此环说明压力与此环说明压力与容积的关系容积的关系.一般分为静态一般分为静态P-V、动态动态P-V曲线，上图为静态曲线，上图为静态P-V环，环，因为因为P-V主要反映呼吸系统顺应主要反映呼吸系统顺应性情况，因此需要去除阻力的影性情况，因此需要去除阻力的影响，而静态静态响，而静态静态P-V曲线是在流曲线是在流速为速为0的时候测量的，可以满足的时候测量的，可以满足此要求。此要求。但是在临床中，这是无法达到的，但是在临床中，这是无法达到的，因此可以尽量模仿

25、理想状态的静因此可以尽量模仿理想状态的静态环，一般认为流速态环，一般认为流速9L/min，可以消除呼吸系统由于阻力成分可以消除呼吸系统由于阻力成分造成的压力变化，称之为造成的压力变化，称之为”quasi-static”10.Harris R S.Respir Care,2005.50(1):p.78-98;discussion 98-9 动态动态PV 环环For this reason the PV loop does not give an accurate picture of the course of compliance.The greater the inspiratory bre

26、athing gas flow the greater the additional pressure gradient and thus the degree of inaccuracy.Dynamic PV loops的局限性的局限性随着流速的增加，随着流速的增加，PV PV looploop显著右移，显著右移，而且流速而且流速越大，由阻力带来的压力越大，由阻力带来的压力变化越大，变化越大，因此越不可信，因此越不可信，因此临床上常规描记的动因此临床上常规描记的动态态P-VP-V环可信性较差、临环可信性较差、临床指导意义不大床指导意义不大通气区间通气区间通气区间通气区间Volume(ml)P

27、ressure(cm HPressure(cm H2 2O)O)With little or no change in VWith little or no change in VTTPaw risesNormalAbnormal临床应用中，潮气量通常根据理想体重来设置，以保证临床应用中，潮气量通常根据理想体重来设置，以保证通气量及使通气量及使VTVTD。利用机控呼吸下的压力。利用机控呼吸下的压力-容量环可容量环可以有助于选择一个合适的肌控呼吸潮气量。事实机上，以有助于选择一个合适的肌控呼吸潮气量。事实机上，因为早期流速、环路顺应性、漏气等原因还需要一些额因为早期流速、环路顺应性、漏气等原因还

28、需要一些额外的容量，新型呼吸机对于这些因素有一定补偿功能。外的容量，新型呼吸机对于这些因素有一定补偿功能。Pressure-Volume LoopsHigh Resistance 阻阻力升高力升高 容量控制通气时，容量容量控制通气时，容量恒定，压力依据阻力和顺恒定，压力依据阻力和顺应性而变化应性而变化当阻力增加时，当阻力增加时，PIP 上上升（升（A-B），），PV loops 变宽。该种变宽。该种PV loop，称，称为滞后为滞后steepness of loop remains unchangedPressure-Volume Loops3、High and Low Compliance

29、顺应性顺应性容量控制通气时，顺应性容量控制通气时，顺应性增加，输出增加，输出lower PIP；顺应；顺应性降低，输出性降低，输出higher PIPYellow for Yellow for High High ComplianceComplianceDecreased compliance正常人和正常人和ARDS患者患者PV曲线曲线P-V loops in ARDSa region of low compliance at low lung volumea lower inflection pointa region with a steeper slope showing higher

30、compliancea region with a flatter slope(poorly compliant)PEEP and PV loopHypothetical respiratory system pressure-volume curves for a patient with ARDS showing a flatter than normal relationship(decreased respiratory system compliance,Crs=VT/P1).With addition of PEEP,a shift to a more compliant curv

31、e may occur such that Crs=VT/(P2-PEEP)increases.The change in compliance may represent recruitment of poorly ventilated or nonventilated lung units with application of PEEP and may be correlated with improved oxygenation and gas exchange.Air TrappingAir TrappingInspirationExpirationVolume(ml)Volume(

32、ml)Flow(L/min)流速未回到基线流速未回到基线流速未回到基线流速未回到基线NormalAbnormalIncreased RIncreased RawawPressure(cm HPressure(cm H2 2O)O)Higher PTANormal SlopeNormal SlopeVol(mL)Vol(mL)Lower SlopeLower Slope气道阻力升高气道阻力升高气道阻力升高气道阻力升高InspirationExpirationVolumeVolume(ml)(ml)Flow(L/min)Decreased PEFRNormalNormalAbnormal“Scoo

33、ped out”patternP-V loop“Scooped out”pattern呼吸功呼吸功呼吸功呼吸功 A:Resistive Work B:Elastic WorkPressure(cm H2O)Volume(ml)B BA A触发灵敏度的设置不当触发灵敏度的设置不当触发灵敏度的设置不当触发灵敏度的设置不当Volume Volume(mL)(mL)P Pawaw(cm H(cm H2 2O)O)Increased WOB预置吸气流速不足预置吸气流速不足预置吸气流速不足预置吸气流速不足P Paw aw(cm H(cm H2 2O)O)Volume Volume(ml)(ml)Norma

34、lAbnormalActive InspirationActive InspirationInappropriate FlowInappropriate Flowd represents the secondary rise in Paw with the cessation of simulated effort and the cycling of the ventilator into expiration.The pressure spike above PEEP reflects initial expiratory valve resistance at peak expirato

35、ry flow.a represents the initial drop in Paw associated with simulated patient effort to trigger the ventilator into inspirationb represents the rapid rise in Paw as ventilator I delivery exceeds simulated I demand;c represents a secondary drop in Paw as simulated patient effort continues after VT d

36、elivery DECREASED COMPLIANCE DECREASED COMPLIANCETime(sec)Paw (cm H2O)Low CompliancePIPPPlatNormalNormalPIPPPlatNormal PPlat(Normal Compliance)Increased PPlat(Decreased Compliance)NormalPIPLung Compliance Changes and the P-Lung Compliance Changes and the P-V LoopV LoopVolume(mL)Volume(mL)预置气道峰压预置气道峰

37、压VT levelsP Pawaw(cm H(cm H2 2O)O)COMPLIANCEIncreasedNormalDecreasedPressure Targeted VentilationAir LeakAir LeakVolume(ml)Volume(ml)Time(sec)Time(sec)Air LeakAir LeakAir LeakAir LeakVolume(ml)Pressure(cm HPressure(cm H2 2O)O)Air LeakAir LeakAir LeakInspirationExpirationVolume(ml)Flow Flow(L/min)(L/min)Air Leak in mLNormalAbnormal