Aimsandobjec5ves TheBasicsofMechanical Ven5la5on January2012 Whyweven5latepeople Terms,acronymsandotherconfusingthings Basicven5latorseFngs/modes Thosewavylinestheyaskyouaboutinthe exam ThisisNOTanencyclopediclectureon complexven5la5on! 1
Confusingscreens Whydoweusemechanicalven5la5on? Respiratoryfailure Howdowenormallybreathe? Physiological=nega5vepressureven5la5on IntraNpostNopera5ve Intubatedcri5callyillpa5ents(sepsis,shock, neuro,airway,etc..) Invasivemechanicalven5la5oneliminatesthemetaboliccostof breathing(i.e.!vo 2 ) HayekOscillator 2
Earlyintensivecareunits Howdomostven5latorswork..? Posi5vepressure: NonNphysiological Inflammatoryresponse Barotrauma Uncomfortable The Iron%lung Airwaydevices Physiologyofven5la5on The-goal-of-ven1la1on-is-to-maintain-normal-PaO 2 -and-paco 2- Minute-ven1la1on-(V E ):- Minutevolume=Respratex5dalvolume(V T ) Totalvolumeofgasexhaledperminute( normal =80N100ml/kg) Minutevolumecomprisedoftwofactors: Alveolarven5la5on(V A ) Deadspaceven5la5on(V D ) V D /V T =0.33 Respira1on-in-the-cri1cally-ill:- IncreasedCO 2 produc5on Pyrexia,sepsisinflamma5on, IncreasedV D (V/Q'mismatch) Atelectasis,pneumonia,ARDSpulmonaryembolism 3
Componentsofanar5ficialbreath Trigger- Cycle- Inspira5on(ac/ve) Expira5on(passive) Triggering(exp4insp) Cycling(insp4exp) Inspira5on:expira5on(I:E)ra5o Posi5veendNexpiratorypressure(PEEP) Volumecontrolven5la5on Pressure Volume Flow Tidalvolumepreset(e.g.500ml) 8N10ml/kgisfine(ideal'body'weight) Lessin damaged lungs(6n8ml/kg) Airwaypressurewillvary compliance' Sethighairwaypressurealarms(e.g. 30cmH 2 O) 4
Pressurecontrolven5la5on Inspiratorypressurepreset (e.g.15cmh 2 O) Tidalvolumewillvary CHECKTIDALVOLUME 5
Triggering Theparameterchosentoini5ateabreathand cycletoinspira5on: Time:preNsetfrequency(mandatoryvent) Pressure:todetectspontaneousbreaths (N0.5N2.0cmH 2 O) Flow:todetectspontaneousbreaths Cycling Parameterusedtodictatetheendofthe inspiratoryphase,cyclingtoexpira5on: Time-:-mandatoryvent;setinsp5me(Ti) Flow:inpressuresupport;preNdetermined% ofpeakinspflow(e.g.25%) Volume:whensetvolumereached,noend insppause I:Era5o(5mecycled) Pressureorvolumecontrol?? Mandatoryven5la5on Alterinspiratory5me(Ti) T I or T H I:E or T H:T L T E or T L 8-00204 Takeyourpick. Volume:shortNterm, healthylungs,constantmv RR=10andTi=2seconds Tewillbe4secondsandI:E=1:2 ARDS:1:1,2:1,3:1(rememberPCO 2 ) Pressure:longNterm, reducedairwaypressure, variablemv 6
WhatisPEEP? S5ckyourheadoutofacarwindow Raisedbaselinerespiratorypressure PhysiologicalPEEPisaround5cmH 2 O; resistanceofexpiratoryairflowthroughglofs Whenintubated,lossofphysiologicalPEEP providedbythelarynxandvocalcords Deliveredthroughouttherespiratorycycleand issynonymoustocpap,butintheintubated pa5ent PEEP Preventsalveolarcollapse Improvesoxygena5on Howhigh? Fixedregimens? PressureNvolumecurve inflec5onpoints? Don t forget that the peak airway pressure will also include the PEEP that is added 7
Don t forget that the peak airway pressure will also include the PEEP that is added Modesofven5la5on Mandatory Synchronisedintermiqentmandatory ven5la5on(simv) Spontaneouse.g.pressuresupport Unsupportedspontaneousi.e.CPAP Mandatory-(controlled)-ven1la1on- - SIMV Deviceterminologyvaries Threetypesofbreath: Mandatory(5med) Supported(spontaneous) Assisted(addi5onalspontaneous) Commonly: Mandatorysupported=volumee.g.500ml Assisted=pressure,e.g.16cmH 2 O MinimumRRset 8
7 C HAPTER Synchronous intermittent mandatory ventilation (SIMV) 7 30/01/2012 SIMV is a mixed ventilatory mode that allows both mandatory and spontaneous breaths. The mandatory breaths can be volumeor pressure-based, and the spontaneous breaths can be pressureassisted (for example, when pressure support is in effect). You can select pressure- or flow-triggering in SIMV. The SIMV algorithm is designed to guarantee one mandatory breath each SIMV breath cycle. This mandatory breath is either a patient-initiated mandatory (PIM) breath (also called an assisted breath) or a ventilator-initiated mandatory (VIM) breath (in case the patient's inspiratory effort is not sensed within the breath cycle). As Figure 7-1 shows, each SIMV breath cycle (Tb) has two parts: the first part of the cycle is the mandatory interval (Tm) and is reserved for a PIM. If a PIM is delivered, the Tm interval ends and the ventilator switches to the second part of the cycle, the spontaneous interval (Ts), which is reserved for spontaneous breathing throughout the remainder of the breath cycle. At the end of an SIMV breath cycle, the cycle repeats. If a PIM is not delivered, the ventilator delivers a VIM at the end of the mandatory interval, then switches to the spontaneous interval. SIMV Synchronised-intermiEent-mandatory-ven1la1on(SIMV)-- Tb = SIMV breath cycle (includes Tm and Ts ) Tb Tm Ts Tm = Mandatory interval (reserved for a PIM breath) Ts = Spontaneous interval (VIM) delivered if no PIM delivered during Tm) 8-00055 Figure 7-1. SIMV breath cycle (mandatory and spontaneous intervals) 4-075609-00 Rev. G (10/06) 840 Ventilator System Technical Reference TR 7-1 TR 7 Synchronous intermittent mandatory ventilation (SIMV) Figure 7-2 shows an SIMV breath cycle where a PIM is delivered within the mandatory interval. PIM (Subsequent trigger efforts during Ts yield spontaneous breaths) Tm transitions to Ts when a PIM is delivered Tm Ts Tb SIMV TR 7 Synchronous intermittent mandatory ventilation (SIMV) SIMV 8-00056 Figure 7-2. SIMV breath cycle, PIM delivered within mandatory interval Figure 7-3 shows an SIMV breath cycle where a PIM is not delivered within the mandatory interval. Figure 7-2 shows an SIMV breath cycle where a PIM is delivered within the mandatory interval. VIM PIM (Subsequent trigger efforts during Ts yield spontaneous breaths) VIM delivered at end of Tm if no PIM delivered during Tm Tm transitions to Ts when a PIM is delivered Tm Tm Ts Ts Tb Tb 8-00057 8-00056 Figure 7-2. SIMV breath cycle, PIM delivered within mandatory interval Figure 7-3. SIMV breath cycle, PIM not delivered within mandatory interval 7.1 Figure 7-3 shows an SIMV breath cycle where a PIM is not delivered within the mandatory interval. Mandatory breaths in SIMV are identical to mandatory breaths in A/C mode, and spontaneous breaths in SIMV are identical to spontaneous breaths in SPONT mode. Patient triggering must meet the requirements for flow and pressure sensitivity. VIM VIM delivered at end of Tm if no PIM delivered during Tm Tm Breath delivery in SIMV Ts Tb 8-00057 Figure 7-3. SIMV breath cycle, PIM not delivered within mandatory interval 7.1 840 Ventilator System Technical Reference 4-075609-00 Rev. G (10/06) TR 7-2 Breath delivery in SIMV Mandatory breaths in SIMV are identical to mandatory breaths in A/C mode, and spontaneous breaths in SIMV are identical to spontaneous breaths in SPONT mode. Patient triggering must meet the requirements for flow and pressure sensitivity. 9 840 Ventilator System Technical Reference TR 7-2 4-075609-00 Rev. G (10/06)
Spontaneousven5la5on Constantpressureaboveatmospheric maintained Pressuresupportven5la5on Some5mesknownas Assistedspontaneous Breaths (ASB) Partofweaningprocess/improvesmuscle strength Decreasesworkofspontaneousbreathing Pa5entcontrolledRR,TiandI:E=comfortable lessseda5on Fa5guepossible Apnoeapossible 1.Pressure-support-ven1la1on-(PSV)- Ven5latorprovidesinsp.assistancetoeach pa5enteffort(flowncycled) - 2.Con1nuous-posi1ve-airways-pressure-(CPAP)- Spontaneous-ven1la1on-(pressure-support)- - Spontaneous-ven1la1on-(CPAP)- - 10
Pressure Support Ventilation Othermodes Airwaypressurereleaseven5la5on(APRV) Pressureregulatedvolumecontrol(PRVC) Propor5onalAssistVen5la5on(PAV) Automa5cTubeCompensa5on(ATC) BiLevel FORGET%ABOUT%THEM%!!% Patient Patient Complica5onsofven5la5on Barotrauma:-Pressureburstsalveoliandsmallair passagesandinpar5cularburstsalveoliinto adjacentbronchovascularsheath Volutrauma:-abnormalstretchingoflung5ssue disrup5ngarchitecture;alsocausesreleaseof cytokinesandfeedsinflammatoryprocess Atelectotrauma:-areasofclosedlungforcefully reopenedinasitua5onoflowsurfactantleading totraumatothealveolarwalls(opennclose) Howmuchoxygen? Normoxaemiaisdesirable HigherFIO 2 ifunknowngasexchange capability AlterFIO 2 toachievetarget Oxygentoxicity 11
CommonseFngs MODE Inspiratoryphase(pressure/volume) Desiredpressure/volume RR I:E FIO 2 Alarms Pressure Volume Pressure Spontaneous- PEEP- Volume Need-for- ven1la1on- Mandatory- SIMV- Pressure Volume CPAP Basic Ventilatory Modes: Summary CMV PSV PEEP SIMV PSV Mandatory Overlap Spontaneous 12