1、环路分析在机械通气中的应用,武警医学院附属医院呼吸科 刘阳,Critical in assessing the Mechanically Ventilated Patient,机械通气目的,提供足够的肺泡通气量（VA） 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 病人舒适 合适的呼吸肌负担 良好的人机同步,进行波形分析的必要性,Patientventilator dyssynchrony imposes an additional burden on the respiratory system and may increase the morbidity of c
2、ritically 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, Prinianakis G, and Kondili E. Intensive Care Med, 2006. 32(1): p.
3、 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 Georgopoulos. Curr Opin Crit Care 13:8489.,Nilsestuen J O and H
4、argett K D. Respir Care, 2005. 50(2): p. 202-34; discussion 232-4.,Pressure versus Time,Inspiration,Expiration,Paw (cm H2O),Time (sec),TI,TE,Pressure-Volume Loop,Controlled,Assisted,Spontaneous,Vol (ml),Paw(cm H2O),I: Inspiration E: Expiration,I,E,E,E,I,I,Flow-Volume Loop,Volume (ml),PEFR,FRC,Inspir
5、ation,Expiration,Flow (L/min),PIFR,VT,Mechanical Monitoring,Airway Pressures,Static or Plateau Pressure静态顺应性和平台压 Separates resistance from elastic recoil 吸气末测量 Should be kept 35 cm H2O to avoid volutrauma Allows computation of static compliance, which decreases as the lungs become stiff,Static compl
6、iance=,静态顺应性,Static compliance=,定容模式下压力、流速、容量-时间曲线简图,Normal Crs is approximately 100 mL/cm H2O in the range of usual operational lung volume.,通气模式为定容,the pressure in the ventilator circuit (“inspiratory plateau pressure“) equals the amount of pressure needed to distend the lungs and chest wall by th
7、e amount of tidal volume just delivered,因此静态顺应性可以表示为Crs = 潮气量/(气道平台压-PEEPi).,Static compliance=,Static compliance Crs, st =,肺纤维化的P-V曲线,阻力,R = P / flow,阻力,Opposition to airflow by nonelastic forces Normally 2-5 cmH2O/L/sec 气道分泌物增多或者气道痉挛时会显著增加 对于评价支气管扩张剂的效果十分有用,Raw=,Paw (cm H2O),Normal PPlat (Normal C
8、ompliance),Increased PIP,Increased PTA (increased Airway Resistance),Increased Airway Resistance,Measured Volumes,Tidal Volume 潮气量 5-7 mL/kg IBW VT = VA + VD VD = 1 mL/lb IBW Mechanical tidal volume varies with disease process 定容量模式下设定VT与呼出VT的差值为漏气量 leak: ETT cuff leak Pneumothorax Tubing disconnect
9、ion 随着气道顺应性的下降，在PCV模式下，VT将出现显著下降,Measured Volumes,Minute Ventilation (VE) 分钟通气量 VT x f 4-8 L/minute VE of 6 L/min associated with a PaCO2 of 40 mm Hg High PaCO2 with a high VE indicates increased dead space or increased metabolism 自主呼吸时（T-管实验）VE 10 L/min 常常提示撤机失败,VE,VA, and PaCO2,Flow versus Time,Th
10、e flow-time curve can be used to detect: Waveform shape Type of breathing Presence of Auto-PEEP (Intrinsic PEEP) Patients response to bronchodilators Adequacy of inspiratory time in pressure control ventilation Presence and rate of continuous air leaks,判断流速波形,Inspiratory flow patterns can vary based
11、 on the flow waveform setting or the set breath type as illustrated,减速波,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0, 这是由于小气道在呼气时过早地关闭, 使部分气体阻滞在肺泡内而引起Auto-PEEP( PEEPi)存在,不同类型呼吸下，五种类型的流速-时间曲线,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
12、气管扩张剂的反应性,Before,Time (sec),Flow (L/min),PEFR,After,Long TE,Higher PEFR,Shorter TE,漏气对吸呼切换的影响：漏气会导致吸气流速下降缓慢，达不到预设的切换标准（set termination threshold）,吸气峰流量,45%,15%,Threshold can not be reached,the period of mechanical inflation must match the period of neural inspiratory time (the duration of inspirator
13、y 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 returned to zero throughout expiration reflect
14、ed the presence of autopositive end-expiratory pressure.,Auto PEEP,吸呼切换延迟Delayed termination present,患者呼气肌开始活动时，呼吸机的吸气过程还未完成，因此发生亚临床的人机对抗。Note there is also a small airway pressure spike near the end of mechanical inflation, which coincides with the patients neural expiratory activity.,切换延迟,吸气预置流速不足
15、,Flow (L/min),Time (sec),Normal Abnormal,Active Inspiration or Asynchrony,吸气预置流速不足或者患者主动吸气,(SIMV)/volume-limited/pressure support approach,“double breathing”,assist volume control 恒定流速,患者持续吸气，气道压力下降，在呼气阀打开时，发生double breathing,Air Trapping,Inspiration,Expiration,Time (sec),Flow (L/min),PRESSURE-TIME
16、CURVES,Breath type delivered to the patient Work required to trigger the breath Breath timing (inspiration vs exhalation) Pressure waveform shape Adequacy of inspiration Adequacy of inspiratory plateau Adequacy of inspiratory flow Results and adequacy of a static mechanics maneuver Adequacy of the R
17、ise Time setting,Breath type delivered to the patient,Breath type delivered to the patient,CMV, with auto-flow on,Measuring Static Mechanics,illustrates a stable static pressure plateau measurement that differentiates the pressure caused by flow through the breathing circuit and the pressures requir
18、ed to inflate the lungs. The pressure-time curve can be used to verify the stability of the plateau when calculating static compliance and resistance.,C 代表不稳定的气道平台压力，常见原因为漏气或者患者出现自主吸气,Assessing Rise Time 吸气斜率,Chiumello D, Pelosi P, Croci M, et al.,Eur. Respir. J., 2001. 18(1): p. 107-114.,A the rise
19、 to pressure may be too slow. B ideal waveform 恰当的斜率设置 C A rise time that is too fast,流速不足,Adequate Flow,Inadequate Flow,Paw (cm H2O),Inadequate Flow 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 deman
20、d.,Progressive increases in patient effort during breaths 2 and 3 were created by manually lifting the test lung,Triggering difficulty and unnecessary patient work 触发困难,第三次为患者触发的通气，虽然患者触发了呼吸机，但是P-T曲线呈下凹型，显示了预制流速不足,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；,The sensitivity setting is 4 cm H2O.,第二次患者仍打开了按需阀，启动了自主
21、呼吸，自主呼吸末，时间触发了一次同步间歇指令通气,吸气时的作功大小,人机不同步,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,Loops a good thing all round,P-V loop,F-V loop,肺通气功能测定,一、肺容积(lung volume) （一）基本肺容积(basal l
22、ung 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 P-
23、V 环,横轴为压力有正压(机械通气)、负压(自主呼吸)之分, 纵轴是容积(潮气量Vt), 此环说明压力与容积的关系. 一般分为静态P-V、动态P-V曲线，上图为静态P-V环， 因为P-V主要反映呼吸系统顺应性情况，因此需要去除阻力的影响，而静态静态P-V曲线是在流速为0的时候测量的，可以满足此要求。 但是在临床中，这是无法达到的，因此可以尽量模仿理想状态的静态环，一般认为流速9L/min，可以消除呼吸系统由于阻力成分造成的压力变化，称之为”quasi-static”10.,Harris R S. Respir Care, 2005. 50(1): p. 78-98; discussion 98
24、-9,动态PV 环,For this reason the PV loop does not give an accurate picture of the course of compliance. The greater the inspiratory breathing gas flow the greater the additional pressure gradient and thus the degree of inaccuracy.,Dynamic PV loops的局限性,随着流速的增加，PV loop显著右移，而且流速越大，由阻力带来的压力变化越大，因此越不可信，因此临床
25、上常规描记的动态P-V环可信性较差、临床指导意义不大,通气区间,Volume (ml),Pressure (cm H2O),With little or no change in VT,Paw rises,Normal Abnormal,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VTVTD。利用机控呼吸下的压力-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，因为早期流速、环路顺应性、漏气等原因还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。,Pressure-Volume Loops,High Resistance 阻 力升高 容量控制通气时，容量 恒定，
26、压力依据阻力和顺 应性而变化 当阻力增加时， PIP 上 升（A-B）， PV loops 变宽。该种PV loop，称 为滞后,steepness of loop remains unchanged,Pressure-Volume Loops,3、High and Low Compliance 顺应性 容量控制通气时，顺应性 增加，输出lower PIP ；顺应 性降低，输出higher PIP,Yellow for High Compliance,Decreased compliance,PEEP and PV loop,Hypothetical respiratory system pr
27、essure-volume curves for a patient with ARDS showing a flatter than normal relationship (decreased respiratory system compliance, Crs = VT/P1).,Air Trapping,Inspiration,Expiration,Volume (ml),Flow (L/min),流速未回到基线,Normal Abnormal,Increased Raw,Pressure (cm H2O),Higher PTA,Normal Slope,Vol (mL),Lower
28、Slope,气道阻力升高,Inspiration,Expiration,Volume (ml),Flow (L/min),Decreased PEFR,Normal Abnormal,“Scooped out”pattern,P-V loop,“Scooped out”pattern,呼吸功,A: Resistive WorkB: Elastic Work,Pressure (cm H2O),Volume (ml),B,A,触发灵敏度的设置不当,Volume (mL),Paw (cm H2O),Increased WOB,预置吸气流速不足,Paw (cm H2O),Volume (ml),No
29、rmal Abnormal,Active Inspiration,Inappropriate Flow,d 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 expiratory flow.,a represents the in
30、itial drop in Paw associated with simulated patient effort to trigger the ventilator into inspiration,b 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 delivery,DECREASED COMPLIA
31、NCE,Time (sec),Paw (cm H2O),Normal PPlat (Normal Compliance),Increased PPlat (Decreased Compliance),Normal,PIP,Lung Compliance Changes and the P-V Loop,Volume (mL),预置气道峰压,VT levels,Paw (cm H2O),COMPLIANCE Increased Normal Decreased,Pressure Targeted Ventilation,Air Leak,Volume (ml),Time (sec),Air Leak,Volume (ml),Pressure (cm H2O),Air Leak,Air Leak,Inspiration,Expiration,Volume (ml),Flow (L/min),Air Leak in mL,Normal Abnormal,
