呼吸力學(xué)與呼吸機(jī)波形及其臨床意義

1、呼吸力學(xué)與呼吸機(jī)波形及其臨床意義,浙江大學(xué)醫(yī)學(xué)院附屬第一醫(yī)院方強(qiáng),,,,,,,吸 氣,,,自主呼吸,,呼 氣,,,,O2,CO2,,,CO2,O2,呼吸,氧氣和二氧化碳在組織間與外界環(huán)境的交換,,,,,,,,O2,CO2,呼吸,通氣機(jī)械運(yùn)動(dòng)壓力差彌散分子運(yùn)動(dòng)濃度梯度灌注,呼吸道,管道 + 氣囊的模型氣道 (管子)肺泡 (氣囊),,,三向彈簧,胸腔內(nèi)壓,,,,,,,,,,,,氣管壓,近氣

2、道壓,胸膜壓,肺泡壓,,,,,,,,,,,自主吸氣,,,,容量變化,氣流,壓力改變,機(jī)械通氣,,,,壓力變化,容量改變,氣流,,,,,,,吸氣,機(jī)械通氣,自主呼吸,Pressure,Time,,,肺泡內(nèi)壓力變化,術(shù)語: Flow and Volume,分鐘通氣量 = 潮氣量 x 送氣頻率,Pressure,,,,,,,,,,,Flow,,Time,潮氣量,,,,Volume = Flow X Time,切換 vs. 限制,,,,Pres

3、sure,Flow,,,Time,容量控制通氣（PCV）,流量恒定恒定的潮氣量不受肺阻力影響變化的壓力,增加吸氣壓力,順應(yīng)性 ?,,,,,,,,,,,,Volume,Pressure,,容量控制通氣（PCV）,Guaranteed tidal volume, not affected by the changes in pulmonary mechanics,What is measured?,壓力Pressure時(shí)間Time

4、 流速Flow (dV /dt )容量Volume(calculated),,,,,time,Volume,Flow,,,順應(yīng)性,靜態(tài)和動(dòng)態(tài)順應(yīng)性,,,動(dòng)力學(xué)特性,動(dòng)力特點(diǎn):Cdyn = dV / dP,,,,,Volume,Pressure,,,,dP,dV,Hysteresis,靜態(tài)和動(dòng)態(tài)壓力,,,,time,Pressure,,,,PEEP,PIP,Pplat,,,肺泡膨脹 (recoil) 壓力差 (Pdis),流速阻

5、抗 壓力差 (Pres),基本計(jì)算,Cst = dV / (Pplat-PEEP)R = (PIP-Pplat) / Flow,,,,time,Pressure,,,,PEEP,PIP,Pplat,,,dP = R x Flow + dV / C st,慢速?zèng)_氣法,慢吸氣流速S (5-10 lpm) 大 Vt 和 ZEEP 動(dòng)態(tài) P-V 環(huán) 接近靜態(tài)曲線由流速阻抗產(chǎn)生的壓力減小容易做, 省時(shí) 和相對(duì)舒服Ser

6、villo: AJRCCM 1997Lu: AJRCCM 1999,Pressure,,,,Volume,,,,LPIflex,UPIflex,,,,inspiration,,Static curve,,,順應(yīng)性,順應(yīng)性描述呼吸系統(tǒng)各個(gè)部分的彈性特征。順應(yīng)性為容量改變除以壓力變化。順應(yīng)性（C）=容量變化（ΔV）/壓力變化（ΔP）或 順應(yīng)性=ml/cmH2O呼吸系統(tǒng)的順應(yīng)性包括胸壁順應(yīng)性和肺順應(yīng)性。總靜態(tài)順應(yīng)性是在吸氣末和呼氣末

7、均無主動(dòng)的呼吸氣流時(shí)測(cè)出。,,總動(dòng)態(tài)順應(yīng)性是在主動(dòng)吸氣時(shí)測(cè)出。它們反映容量—壓力關(guān)系的兩項(xiàng)指標(biāo)，根據(jù)流速-時(shí)間曲線、壓力-時(shí)間曲線和壓力-容量環(huán)也可以評(píng)估病人的順應(yīng)性。,,“管道特征”,,,,,,,,R =,,D P,D F,氣道阻力,壓力差 = 流速 x 管道阻力,壓力差 = 流速 x 阻力,,,,,,,,,dP = Q x R,氣道阻力,順應(yīng)性和阻力,阻力和回縮力,動(dòng)態(tài)特性dP = dV / Cdyn,阻力DPre

8、sistive = R x Flow,靜態(tài)順應(yīng)性dPdistensive = dV / Cst,dP = dPresist. + dP dist. dP = R x Flow + dV / C st,3 個(gè)水平的呼吸力學(xué),動(dòng)態(tài)特性:dP = dV / Cdyn,阻力:dP = R x Flow,靜態(tài)順應(yīng)性:dP = dV / Cst,氣道阻力dP = Raw x Flow,增加阻力:dP = Rimp x

9、Flow,胸廓順應(yīng)性dP = dV / Ccw,肺順應(yīng)性 dP = dV / CL,容量 = 流速 X 時(shí)間,機(jī)械通氣時(shí)工作的目標(biāo),保證和維持適當(dāng)?shù)臍怏w交換盡可能減小肺損傷的危險(xiǎn)減小病人的呼吸功盡可能使得病人的痛苦減少,理想的呼吸狀態(tài),理想呼吸的界定:呼吸機(jī)與病人自主吸氣和呼氣同步盡可能在低氣道壓下維持適當(dāng)及恒定的潮氣量和分鐘通氣量對(duì)肺的力學(xué)變化和病人的需求迅速反應(yīng)保證最低的呼吸作功,輔助機(jī)械通氣時(shí)的WOB,在

10、高水平的機(jī)械通氣支持下，相當(dāng)?shù)牟∪说暮粑κ歉叩脑谳o助通氣下仍病人用力的吸氣病人的WOB 增加可以導(dǎo)致或加重呼吸肌疲勞和呼吸困難Marini, et al.: Am Rev Resp Dis 134:61;1986Marini: Prob Crit Care 4:184;1990,影響病人WOB的決定因素,在輔助通氣主要影響病人呼吸作功的因素是最大吸氣流速(peak flow)在低流速時(shí)病人呼吸功達(dá)到總吸氣作功的65%當(dāng)

11、送氣流速增加時(shí)WOB 減少 Ward, et al.: Anaesthesiology 69:29;1988Sassoon, et al.: Chest 93:571;1988,呼吸作功,什么功? 如何測(cè)量?,呼吸作功,“WOB 在床邊肺功能留下一個(gè)沒解決的難題”From: Monitoring of Pulmonary Functionsin Goldschmidt: Assisted Ventilation of th

12、e Neonate 1996WOB是熱量和氧的消耗 大約 70% 是消耗在克服彈力，30%對(duì)抗管道阻力。,WOB 測(cè)量,P,A,,,,,,,,B,C,D,E,V,WOB = ∫0 ti P x Vdt彈性功: ABCA阻力功吸氣: ADCA呼氣: ACEA,,,WOB的測(cè)量,WOB = ∫0 ti P x VdtPaw: 呼吸機(jī)作功: 機(jī)械力推動(dòng)氣體進(jìn)入肺，表現(xiàn)為呼吸系統(tǒng)作功總量。（病人+呼吸機(jī)） Peso: 病人

13、作功: 呼吸肌作功, 表現(xiàn)為肺的呼吸功 。Paw—Ptr:克服支氣管阻力的功。,WOB意義,病人作功是呼吸機(jī)依賴最敏感的指標(biāo)。比較呼吸機(jī)和病人的功在脫機(jī)過程中非常有用。順應(yīng)性和阻力變化 、吸氣努力、壓力支持水平、PEEP、不適合的吸氣時(shí)間、靈敏度的改變模式的變化WOB可以改變。 WOB提高提示脫機(jī)過程有不當(dāng)。,,,P-V 環(huán)和 WOB,P,,,V,,,,,P,,,V,,,,P,,,V,,,,,,順應(yīng)性和阻力正常,順應(yīng)性正常阻力增

14、加,順應(yīng)性降低阻力正常,Methods of Rrs Measurement,同容量法 (Krieger)彈性減小法 (Neergard)被動(dòng)呼氣法 (Comroe)峰呼氣法 (Jonson)呼氣時(shí)間常數(shù)法 (Bergman)加力振動(dòng)法 (Goldman)吸氣壓 / 流速 法 (Suter),評(píng)價(jià)靜態(tài) P-V 曲線,用一個(gè)大的注射器逐步膨脹肺，分次測(cè)定個(gè)容量時(shí)的壓力 .耗時(shí)操作麻煩難以標(biāo)準(zhǔn)化病人必須肌松，連接特殊設(shè)備

15、冒低氧血癥的風(fēng)險(xiǎn),,Volume,Pressure,,,,,,,,,,,機(jī)械通氣,機(jī)械通氣的基本原理遵循了流體力學(xué)的原則。通氣支持的過程及目的是改變肺容量，包括氣體的流量及壓力輸送到病人的氣道增加肺容量。氣體在一個(gè)特定環(huán)境中運(yùn)動(dòng)用流體力學(xué)的原則去研究可以用上述三個(gè)參數(shù)來描述，因?yàn)榱髁繀?shù)中包含了時(shí)間的概念，所以描述呼吸機(jī)送氣、氣體在呼吸管路中的運(yùn)動(dòng)、病人氣道和肺組織對(duì)送入氣體的反應(yīng)涉及上述四個(gè)參數(shù)既壓力（P）、容量（V）、流量（F

16、）和時(shí)間（t）。,,,,,,,,,,,容量變化,時(shí)間,正壓通氣,氣流增加,壓力差,Key-words,PressureFlowTimeVolume,術(shù)語: PIP & MAP,術(shù)語: PEEP, I:E Ratio,術(shù)語: Flow and Volume,Minute Ventilation = Tidal Volume x Breath Rate,Pressure,,,,,,,,,,,Flow,,Time,Tidal V

17、olume,,,,壓力,壓力應(yīng)該包括呼吸機(jī)的送氣壓力、呼吸回路內(nèi)的壓力、病人氣道內(nèi)的壓力。上述管路的口徑不同，即使在相同壓力下流速也不同，在相同的時(shí)段經(jīng)過的容量不同。目前還不能檢測(cè)氣道內(nèi)的參數(shù)，只能檢測(cè)近人工氣道的參數(shù)。近氣道的參數(shù)來反映病人氣道對(duì)氣流的反應(yīng)以及肺泡對(duì)壓力和容積的反應(yīng)。從而可以推測(cè)肺通氣功能的狀態(tài)。,壓力,把不同時(shí)段壓力變化的軌跡連接起來就形成一條壓力曲線，通過它可以了解大氣道不同時(shí)相和時(shí)段的壓力。同樣的方法可以得

18、到流速曲線和容量曲線。把上述除時(shí)間參數(shù)以外的參數(shù)兩兩組合在二維坐標(biāo)中，可以得到壓力容積曲線、容積流速曲線、壓力流速曲線。,環(huán),,,,,,Pressure,Volume,Volume,Flow,,,,,Insp.,Expir.,Insp.,Expir.,,,壓力-時(shí)間曲線,,波形各段意義,A/ 觸發(fā):病人 (assisted)呼吸機(jī) (controlled)B/ 限制:流速壓力C/ 切換:容量時(shí)間,,,,A,B,C,,,

19、,切換與限制,在吸氣相所記錄的測(cè)量值,,圖2. 在吸氣相和呼氣相中所評(píng)估的變量,二、壓力—時(shí)間曲線 壓力通常在呼吸機(jī)回路（如丫形管處，吸氣端或呼氣端）中測(cè)量。雖然氣管插管的管子在總氣管內(nèi)分隔出來，但壓力仍與氣道壓力有關(guān)，壓力傳感器可測(cè)至150cmH2O，而且應(yīng)是抗?jié)窕挂后w或病人的分泌物。 壓力—時(shí)間曲線的臨床應(yīng)用：區(qū)分呼吸類型，計(jì)算平臺(tái)壓，評(píng)估吸氣觸發(fā)所作功，評(píng)估整個(gè)呼吸時(shí)相，調(diào)節(jié)峰流速，計(jì)算靜態(tài)

20、呼吸動(dòng)力學(xué)的參數(shù)。,,,,,,,,,,,,,,,,,,,,,,,,,,,,1,2,3,4,5,6,30,-10,P,aw,cmH,2,0,Sec,,壓力-時(shí)間曲線,,,,,,,,,,,,,,,,,,,,Pressure Time Curve,,Volume,Expiration,,,,,,,,,,,,,,,,1,2,3,4,5,6,30,P,aw,cmH,2,0,Sec,,,,,,Volume,,壓力-時(shí)間曲線,V,.,Expirati

21、on,,,,,,,,,,,,,,,,Pressure Time Curve,,Volume,Expiration,,,,,,,,,,,,,,,,1,2,3,4,5,6,30,P,aw,cmH,2,0,Sec,,,,,,Volume,,,,Pressure,Inspiration,,壓力-時(shí)間曲線,,,V,.,,,,,,,,,,,,,,,,Pressure Time Curve,Expiration,,,,,,,,,,,,,,,,,1,2

22、,3,4,5,6,30,P,aw,cmH,2,0,Sec,,,Volume,,Pressure,,壓力-時(shí)間曲線,V,.,,,,,,,,Inspiratory Time,,,,,,,,,,,,,,,,Pressure Time Curve,Expiration,,,,,,,,,,,,,,,,,1,2,3,4,5,6,30,-10,P,aw,cmH,2,0,Sec,,,,Volume,,Pressure,Expiration,,壓力-時(shí)間

23、曲線,,,壓力曲線的臨床應(yīng)用,,壓力-時(shí)間曲線的臨床意義,區(qū)別各種通氣模式和特殊通氣方式估計(jì)觸發(fā)的做功計(jì)算吸-呼時(shí)比，估計(jì)呼氣時(shí)間是否充足。估計(jì)是否達(dá)到充分的平臺(tái)壓觀察壓力上升速度估計(jì)所用吸氣流速是否適合測(cè)定靜態(tài)呼吸力學(xué)參數(shù)顯示壓力波型形態(tài),,,,,,,,,控制通氣,Volume Ventilation,Pressure Ventilation,,,,Pressure,Flow,time,,,,Pressure,Flow,t

24、ime,,,,,,,,,,,,,,,,Assist/Control,SIMV + Pressure Support,Pressure supported spontaneous + Patient, or machine-initiated mandatory breaths,,,Paw,,,,,,,,,,,,,,,,CPAP,,,,,,Synchronized IMV,,,,,,,,,,,,,,,,,,,,,,,,,,,,A/C 5

25、 bpm,SIMV 5 bpm,,,12 sec,,,,,,,,,,,,,,,,,SIMV vs. Assist/Control,,,,,,,,,,,,,,,,Pressure,Time,如何影響 MAP,A = á PIP,C = á BaseLine,B = á Rise Time,D = á Frequency,流速-時(shí)間曲線,,,,,,,,,,,,,,,,,,,,,,

26、,,,,,1,2,3,4,5,6,SEC,V,.,LPM,120,120,EXH,,,,,,流速-時(shí)間曲線,INSP,吸氣,,,,,,,,,,,,,,,,,,,,,,,,,,,,,1,2,3,4,5,6,SEC,V,.,LPM,120,120,EXH,,,INSP,Inspiration,,,,,,,,流速-時(shí)間曲線,,,,,,,,,,,,,,,,,,,,,,,,,,1,2,3,4,5,6,SEC,V,.,LPM,120,120,EXH

27、,,,,,,流速-時(shí)間曲線,,,,,,,Insp. Pause,,Expiration,INSP,,流速-時(shí)間曲線的臨床意義,吸氣流速和呼氣流速呼吸類型的鑒別判別是否存在內(nèi)源性PEEP觀察患者對(duì)支氣管擴(kuò)張劑的反應(yīng)選擇PCV時(shí)合適的吸氣時(shí)間發(fā)現(xiàn)漏氣及速度顯示流速波形的形態(tài),,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,1,2,3,4,5,6,SEC,V,.,LPM,120,120,,,,,,,,峰流速相同遞減流速

28、延長吸氣時(shí)間,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,1,2,3,4,5,6,SEC,,,,,,,,1,2,3,4,5,6,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

29、,,,,,,,,,,,,,,,,,,,,,,,600 cc,-20,120,120,SEC,,,,,0,,,,,450cc,,,,,,,Pressure,Flow,流速不足,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,壓力通氣,恒定的壓力 .遞減, 可變的流量時(shí)間切換: (A)Pressure Control流速切換: (B)Pressure Support,,,,Pressure,Flow

30、,A,B,,,,,,,,,,,,,Time Cycled,,Flow Cycled,壓力通氣波形,,,,,,,Flow,Pressure,,,,,,Tinsp.,,PIP,,,,,,,,,,Peak Flow,25%,Pressure Control,Pressure Support,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,1,2,3,4,5,6,60,P,aw,cmH,2,0,Sec,,,,,,,,,,,,,

31、,,,,,,,What is this?,,,,,,,,,,,,,,,,,,,,,,,,,,,,1,2,3,4,5,6,60,P,aw,cmH,2,0,Sec,,,,,,,,,,,,,,,,,,,壓力過沖伴反沖,,,,,,,,,,,,,,,,,,,,,,,,,,,,1,2,3,4,5,6,SEC,V,.,LPM,120,120,,,Expiration starts before inspiratory flow returns to

32、 zero,,呼氣靈敏度設(shè)置15 %,,壓力支持,,,,,,,,呼氣靈敏度,,,Flow,Peak Flow (100%),,,,Time,,,TS 5%,,,,,Leak,,,Set (max) Tinsp.,,Tinsp. (eff.),,,,,,,容積-時(shí)間曲線,,,,,,,,,,,,,,,,,,,,,,,,2,3,4,5,6,SEC,VT,800 ml,,,,,,,,,,,,,,,,,1,,,,,容量-時(shí)間曲線,,,,,,,,,

33、,,,,,,,,,,,,,,2,3,4,5,6,SEC,VT,800 ml,,1,,,,,Inspiration,,容量-時(shí)間曲線,,,,,,,,,,,,,,,,,,,,,,,2,3,4,5,6,SEC,VT,800 ml,,1,,,,,,Expiration,,容量-時(shí)間曲線,容量-時(shí)間曲線的臨床意義,肺內(nèi)氣體陷閉呼吸回路漏氣,壓力-容積環(huán),水平軸描述壓力，縱軸描述容量,,,,,,,,,,,,,壓力-容量環(huán),,,Volume,Pre

34、ssure,,,,,,,Volume,Pressure,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,最佳PEEP,,,,,V,P,,,V,P,,,,,,Changing Lung Volume in CV:,Paw = Lung Volume,,臨床應(yīng)用：,計(jì)算吸氣面積計(jì)算順應(yīng)性計(jì)算阻力評(píng)估肺泡過度膨脹衡量壓力支持水平及其做功,典型的P-V環(huán),,,Volum

35、e,Pressure,,,Volume,Pressure,,,,Volume,Pressure,,,,,Controlled Assisted Spontaneous,評(píng)估吸氣流速,Volume,Volume,Pressure,Pressure,Normal,Insufficient Flow,Pressure Volume Loops,,Cusping,,,,,,

36、,,過度膨脹,Overdistension occurs when the volume limit of some components of the lung has been exceededAbrupt decrease in compliance at the termination of inspirationResults in a terminal “Beaking” of the P/V Loop,,,,,,,,V

37、olume,Pressure,,,,,Volume,Pressure,Zone ofOverdistention,“Safe”Window,Zone ofDerecruitmentand Atelectasis,Injury,Injury,最佳肺容量（安全窗）,膨脹過度肺泡痿陷,Mean Airway pressure 25 cm H2O,CT Scan :ARDS pig model 30 kg,,Optimized Lu

38、ng Volume Strategy:,Mean Airway Pressure 40 cm H2O,CT Scan :ARDS pig model 30 kg,,Optimized Lung Volume Strategy:,,CDP= FRC,,,,,CT 1,CT 2,CT 3,Paw = CDP,ContinuousDistendingPressure,,急性呼衰時(shí)V-P曲線拐點(diǎn)的意義,上拐點(diǎn)提示：壓力導(dǎo)致局部肺泡過度膨

39、脹下拐點(diǎn)代表：使肺泡開始打開的最小壓力,,Volume,Pressure,,,,LPIflex,UPIflex,,,,,,,,容積-流速環(huán),,流速-容量環(huán),Volume,Flow,,,,,Volume,Flow,,,,,臨床應(yīng)用,評(píng)價(jià)支氣管擴(kuò)張劑的療效評(píng)估是否漏氣評(píng)估吸氣阻力和呼氣流速受阻,,,,F,V,,,,V,F,氣道阻塞,重度阻塞,漏氣,,,Volume,,,,,,,,,Pressure,,,,,,Volume,Flow,V