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PATIENT VENTILATOR INTERACTION TRIGGERING AND FLOW PROBLEMS

PATIENT VENTILATOR INTERACTION TRIGGERING AND FLOW PROBLEMS. Dr Sait Karakurt Marmara University Pulmonary and Critical Care Medicine. Patient - ventilator asynchrony - Trigger and flow problems. Trigger Asynchrony ( muscular effort without ventilator trigger ). Flow Asynchrony

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PATIENT VENTILATOR INTERACTION TRIGGERING AND FLOW PROBLEMS

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  1. PATIENT VENTILATOR INTERACTIONTRIGGERING AND FLOW PROBLEMS Dr Sait Karakurt Marmara University PulmonaryandCriticalCareMedicine

  2. Patient-ventilatorasynchrony-Triggerandflowproblems TriggerAsynchrony (musculareffortwithoutventilatortrigger) FlowAsynchrony (ventilatorflowdoes not matchthepatientflow) • Ineffectivetriggering • Doble /tripletriggering • Auto-triggering • Volum-controlledventilation • Pressure-controlledventilation

  3. Mechanicalventilation- breathingtypes

  4. Triggersensitivity • Triggersensitivity • Pressure -0.5 to –1.5 cm H2O • Flow 2 L/mindecrease in flowduring 5-20 L/mincontinueflow in system

  5. Patient-ventilatorasynchrony-Triggerandflowproblems TriggerAsynchrony (musculareffortwithoutventilatortrigger) FlowAsynchrony (ventilatorflowdoes not matchthepatientflow) • Ineffectivetriggering • Double /tripletriggering • Auto-triggering • Volum-controlledventilation • Pressure-controlledventilation

  6. Ineffectivetriggering

  7. Ineffectivetriggering

  8. Ineffectivetriggering

  9. Ineffectivetriggering patient factors ventilator factors • low respiratory drive • weak inspiratory muscles • partially blocked ETT or tracheostomy • alkaline pHandincreasedbicarbonatelevels • dynamic hyperinflation resulting in intrinsic PEEP • high level of pressure support or high tidal volume causing gas trapping and intrinsic PEEP • expiratory asynchrony with delayed opening of exhalation valve • Theuse of in-linenebulizers • Hightriggersensitivity

  10. Oto PEEP

  11. Dynamichyperventilation LUNG VOLUME normal lung Vtrap FRC İnsp. Exp. time

  12. oto-PEEP normal patient Oto PEEP inspiration time(sn) Flow(L/min) } expiration

  13. A B 10 0 0 Oto PEEP andtriggering pressure pressure 10 0 time time

  14. Therapy of dynamichyperventilation • Decreaseminuteventilation (pH>7.20) • DecreaseVt • Decreaserespiratory rate • Prolongexpiratory time • increaseflow • no plato • Reduceairwayresistance • medikal Tx (bronchodilators, steroid) • remoresecretion • tubepatency

  15. Doubletriggering Doubletriggering is thedelivery of 2 consecutiveventilatorcyclesseparatedby a veryshortexpiratory time, withthefirstcyclebeingpatienttriggered.

  16. Doubletriggering • Patient’sventilatorydemand is highandtheinspiratory time set on theventilator is tooshort. • That is, doubletriggeringoccurswhentheventilatorinspiratory time is shorterthanthepatient’sinspiratory time. Thepatient’seffort is not completed at theend of thefirstventilatorcycleandtriggers a secondventilatorcycleandthusoccursmorecommonly in modeswithfixedinspiratoryflowtimes, suchassist-controlventilation.

  17. Doubletriggering • PaO2/FiO2ratio is lowerandpeakinspiratorypressure is higherthan in patientswithoutthisasynchrony. • Thissituation is commonlyseen in patientswithacutelunginjuryoracuterespiratorydistresssyndrome. • Thus, as patientswithacutelunginjuryoracuterespiratorydistresssyndromeareoptimallyventilated, doubletriggering can deliver volumesmuchhigherthantheintendedvolumeprescriptionandthus can potentiallyresult in worseoutcomes.

  18. Doubletriggering • Increasingtheinspiratory time orincreasingthetidalvolumesmayhelpwithdoubletriggering. • Ifthepatient has a variablerespiratorydrivesuchthatsetting a flow on a fixedmode of flowdelivery is not adequate, changingto a variableflow (eg, pressure-controlventilation) or a dual-controlmodemay be helpful. • Sedationadjustmentsmayneedto be madeifallthesemeasures fail. • Ifthepatient’sventilatoryneed is highor has suddenlychanged, it is importanttodeterminethecause of thischange (eg, stroke, pulmonaryembolus) whenmakingtheseadjustments.

  19. Autotriggering

  20. Autotriggering • Autotriggeringmay be causedby • fluid in thecircuit, • circuitleaks, • chesttubeleaks, • vibration of theventilatortubing (as mightoccurduringinsufflationsandexsufflations of thelungswithpoorcompliance). • Autotriggering can alsooccur in thefollowingclinicalsettings:  • Lowrespiratory rate, lowrespiratorydrive, andapneatesting - Allowforlowflow in thecircuitsuchthatanynoise in thesystem (eg, cardiacoscillations) maytrigger a breath • Highcardiac-outputstates, valvularheartdisease,andcardiomegaly

  21. Patient-ventilatorasynchrony-Triggerandflowproblems TriggerAsynchrony (musculareffortwithoutventilatortrigger) FlowAsynchrony (ventilatorflowdoes not matchthepatientflow) • Ineffectivetriggering • Double /tripletriggering • Auto-triggering • Volum-controlledventilation • Pressure-controlledventilation

  22. Flowproblems • Flow can be delivered in thefollowing 3 forms: • Fixedflow (eg, A/CMV, SIMV) • Variableflow (eg, pressure-controlventilation) • Combinedfixedandvariableflows (dualmodes, eg, volume-assuredpressuresupportandpressureaugmentation)

  23. FLOW TYPES SQUARE DESCENDING SINUSOIDAL ASCENDING

  24. Flow • Generally 60L/min • Highflow rate • Decrease in inspiratory time • Increase in expiratory time • Decrease in dynamichyperventilation • Increse in CO2 elemination • Lowflow rate • Increse in inspiratory time • Goodoxygenationfor severe hypoxemicpatients

  25. Inadequateinspiratoryflow-pressurecontrolledventilation NORMAL INADEQUATE INSPIRATORY FLOW

  26. Inadequateinspiratoryflow- volumecontrolledventilation "scooped-out" appearance

  27. Patienteffort Inadequate inspiratory flow Normal Abnormal time (sn) Flow (L/min)

  28. Fixflowandasynchrony Flow rate–relatedasynchrony Flowpattern–relatedasynchrony Inadequateflow Inadequateflowratesmaycauseundueprolongation of theinspiratory time, leadingtoshortenedexpiratorytimes, which, in turn, mayleadtoauto-PEEP andineffectivetriggering. Excessiveflow Excessiveflow can be identified on thepressurewaveformbythe presence of acute "takeoff" of theascendinglimp of thepressurecurvealongwith a pressurespike at thebeginning of thecurve. • Certainpatterns of flowareused in certainclinicalsituations. Forexample, in patientswithchronicobstructivepulmonarydisease, thedescending-rampflowpatternorvariableflowassociatedwithpressure-controlventilation has beenshownto be preferable. • Flow-patternchangescould be accompaniedby a prolonging of inspiratorytimeswithshortenedexpiratorytimes, resulting in auto-PEEP.

  29. Variableflowandasynchrony Duringpressure-controlventilation, theflow is variable. Theflowdepends on variousvariablessuch as respiratorysystemcompliance, set targetpressure, andpatienteffort.Whentherise time is adequate, therepresentativepressurewaveform has a roundedfrontendand a plateau body.Excessive (rapid) rise time prematurebreathtermination doubletriggeringInadequaterise time prolongation of inspiration, insufficientexpiratory time neuralasynchrony auto-PEEP triggeringasynchrony.

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