Read advanced assessment handout.PDF text version

2/18/2009

Learning Objectives:

Advanced Assessment Techniques in Critical Care

Arthur Jones, EdD, RRT

http://www.geocities.com/jonesapjr/index.html

ÙDescribe techniques for measuring and optimizing ventilatory mechanics. ÙInterpret common ventilator wave form abnormalities. ÙExplain the significance of end-tidal CO2 measurements.

Purposes For Monitoring Mechanics

ÙDetermine appropriate ventilator settings utidal volume uPEEP uinspiratory flow rate/time upressure support

Lung Mechanics

Purposes For Monitoring Mechanics ÙAssess condition of lungs

uconsolidation usurfactant deficiency ubronchospasm

Purposes For Monitoring Mechanics ÙEvaluate therapeutic effects

ubronchodilators urecruitment maneuvers usurfactant uweaning modes

ÙDetermine when to wean or discontinue support

Copyright 2009 AP Jones

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Parameters Monitored

ÙDynamic compliance (CDYN) includes elastic recoil and resistance to flow ÙStatic compliance (CST) - elastic recoil of lung and thorax ÙInspiratory/expiratory resistance to flow ÙTotal PEEP

Parameters Monitored

ÙTotal PEEP - imposed (set) PEEP + intrinsic PEEP (PEEPi)

uPEEPi - end-expiratory pressure in lung that may exceed set PEEP, esp. with high rates obstructive disease active exhalation

Parameters Monitored

ÙPEEPi

ucontinuous monitoring possible at tip of ETT umeasurement requires endexpiratory pause and absence of active exhalation to measure usignificance of PEEPi impairs triggering causes hyperinflation

Parameters Monitored

ÙIntratracheal pressure - GE Engstrom Carestation Spirodynamics(TM)

2 mm OD sensor tube ETT > 6.5 mm Images courtesy GE Healthcare

Click to visit GE Engstrom Carestation web site

http://www.gehealthcare.com/euen/respiratory-care/products/engstrom-carestation/index.html

Parameters Monitored

ÙIntratracheal pressure

umeasured at distal end of ETT umore closely reflects alveolar pressure

Parameters Monitored

ÙIntratracheal pressure - GE Engstrom Carestation Spirodynamics(TM)

intratracheal sensor

Image courtesy GE Healthcare

ventilator wye

Copyright 2009 AP Jones

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Parameters Monitored

ÙIntratracheal pressure - GE Engstrom Carestation Spirodynamics(TM) ueasy detection of total PEEP

Parameters Monitored

ÙIntratracheal pressure - GE Engstrom Carestation Spirodynamics(TM) uCompliance values calculated at three points along VP curve: 5 -15%, 45-55%, and 85-95% of the inspiratory phase. uInflection points readily discernable

PEEP TOT

AL

FYI - click to download article: Practical assessment of respiratory mechanics http://bja.oxfordjournals.org/cgi/content/full/91/1/92

Measuring Compliance/Resistance

ÙStabilize patient- tachypnea, active expiration will confound results by increasing intrinsic PEEP ÙMeasure:

uexhaled TV upeak inspiratory pressure (PIP) uPEEP (total) uplateau pressure (Ppt)- for volume control mode uinspiratory flow

Measuring Compliance/Resistance

ÙIn pressure control mode, including pressure control with volume guarantee, the peak pressure is also the plateau pressure. ÙChanging to volume control enables measuring plateau; but, mechanics will not be the same. ÙUse dynamic compliance for mechanics.

Measuring Compliance/Resistance

ÙSimple calculation

uPEEPtotal = (PEEP + PEEPintrinsic) udynamic compliance = tidal volume/(PIP - PEEP) ustatic compliance = tidal volume/(Ppt - PEEP) uresistance = (PIP - Ppt)/flow

FYI - Click for article on monitoring mechanics during ventilation http://www.medscape.com/viewarticle/417584_6

Measuring Compliance/Resistance

ÙUnits of measurement:

uCompliance- V/P -- Liters/cm H2O normal - > .06 L/cm H2O very low - .02 L/cm H2O uResistance- P/flow -- cm H2O/L/sec normal - 5 cm H2O/L/sec high - > 10 cm H2O/L/sec

Copyright 2009 AP Jones

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Measuring Compliance/Resistance

ÙChanges in lung mechanics for an individual patient are more revealing than absolute numbers. ÙEveryone must measure by same technique. ÙSystem must be leak-free ÙExamine trends and pre- posttherapy values.

Abnormal Cst

ÙDecreased Cst (CDYN if resistance is constant)

uARDS, ALI uExtrathoracic restriction obesity ascites, distension uThoracic restriction uVolume-occupying lesions pneumothorax pleural effusion

Implications- Decreased Cst

ÙIncreased work of breathing (WOB) ÙIncreased ventilation pressure requirement s==> uExcessive shear forces on lung tissue, causing inflammation uHyperinflation of compliant lung units, causing volutrauma

Implications- increased Cst

ÙAppropriate PEEP setting ÙResolution of pathology

Benefits of PEEP in ARDS

ÙPrevents alveolar collapse (AKA de-recruitment) ÙRe-recruits collapsed alveoli ÙReduces shear forces required to ventilate collapsed alveoli- prevents atelectrauma ÙIncreases ventilation-perfusion matching- improves oxygenation

PEEP Therapy

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Adverse Effects of PEEP

Ùincreased pulmonary vascular resistance (PVR) Ùincreased alveolar dead space (VDA) - hypercapnia, hypoxemia Ùdecreased venous return udecreased cardiac output (QT) udecreased mixed venous saturation (SvO2) udecreased urine output

Adverse Effects of PEEP

Ùhyperinflation- volutrauma Ùright-to-left shunt with patent foramen ovale (PFO) uPFO present in 15-25% normal adults uincreasing PEEP decreases PaO2

Optimal PEEP

ÙDefined- level of PEEP that imposes favorable volume-pressure relationship on the majority of lung units ==> ugreatest Cst ugreatest SvO2 uimproved ventilation-perfusion (VQ) matching ureduced shear forces required for ventilation

Optimal PEEP

ÙMethods for determination

ulower inflection point of PV curve ustepwise incremental Cst measurement ustepwise decremental Cst measurement ualternative method (Mercat, et al) uvolume-oriented - FRC measurement

Optimal PEEP

ÙMethods for determination ulocate lower inflection point (LIP) of PV curve uOptimal PEEP = LIP + 2-3 cm H2O

Optimal PEEP

Ùlower inflection point (LIP) of PV curve udisagreement among observers ucontroversy over significance of LIP

Volume

LIP Pressure

Copyright 2009 AP Jones

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Stepwise Decremental Technique

ÙAdjust TV to desired level (<8 ml/kg IBW) ÙAdjust FIO2 to 1.0 ÙIncrease PEEP by 5, up to 20 cm H2O umonitor vital signs umonitor SpO2 ÙAdjust FIO2 for SpO2 90-95%

Stepwise Decremental Technique

ÙDecrease PEEP by 2 cm H2O uQ3 min, or until stabilized umonitor SpO2, SvO2, vital signs umeasure Cst ÙOptimal PEEP = level with greatest Cst, SvO2 ÙMonitored/adjusted each shift

Alternative technique

ÙMethods: uAdjust TV to 6 mL/kg IBW uIncrease PEEP to achieve Ppt 2830 cm H2O ÙTrial findings uno change in mortality udecreased duration of ventilation and organ failure

Volume - oriented PEEP

ÙGoal of PEEP - adjust FRC ÙDirect FRC measurement uBody plethysmograph - PFT laboratory uCT scan - gold standard uHe dilution uN2 washin-washout - available on Engstrom Carestation(TM)

Click for more information on Carestation(TM) FRC measurement

http://www.gehealthcare.com/euen/respiratory- care/products/engstrom carestation/inview - frc.html -

Volume - oriented PEEP

ÙFRC measurement rationale uassess effects of PEEP and recruitment maneuvers umonitor lung recruitment status udetection of overdistension

Optimal PEEP

ÙSelect a procedure that works and make sure that EVERYONE follows it precisely; that is, standardize. ÙOptimal PEEP changes with changes in pathology- adjust at least every shift and with changes in patient status. ÙA level of PEEP that is optimal one day might be detrimental the next day.

FYI - Click for abstract of comparative study on FRC methods http://ccforum.com/content/12/6/R150/abstract

Copyright 2009 AP Jones

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Applications For Graphics

ÙAssess lung mechanics uresistance ucompliance uWOB ÙDetect ventilation problems uPEEPi ulung overdistension upatient/ventilator asynchrony

Ventilator Graphics Analysis

Applications For Graphics

ÙEvaluate interventions ubronchodilator therapy uventilator settings

primary mode tidal volume, drive pressure PEEP ventilation times trigger level rise time expiratory flow limit (PSV)

Graphic Types

Ùwaves upressure-time uflow-time uvolume-time

Graphic Types

Ùwaves

upressure -time

Graphic Types

Ùwaves

uflow-time

Courtesy Newport Medical

Courtesy Newport Medical

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Graphic Types

Ùwaves- comparing volume, vs. pressure control (PRVC, etc. = pressure control)

Graphic Types

Ùwaves

uvolume-time

Courtesy Newport Medical

Courtesy Newport Medical

Graphic Types

Ùloops

upressure -volume

mandatory breath

Graphic Types

Ùloops

upressure -volume

spontaneous breath

Courtesy Newport Medical

Courtesy Newport Medical

Graphic Types

Ùloops

uflow-volume

mandatory breath

Graphic Types

Ùloops

uflow-volume

mandatory breath

Courtesy Newport Medical

Courtesy Newport Medical

Copyright 2009 AP Jones

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Compliance- pressure volume curve

ÙLower inflection point (LIP) - opening of atelectatic units ÙUpper inflection point (UIP) hyperinflation

Clinical Applications For Graphics

Compliance- pressure volume curve

1000 UIP Volume mL greatest complianc e LIP Pressure cm H2O 50

Qualitative assessment of compliance

Volume mL

normal CL

decreased CL

Detecting intrinsic peep

Ùzero end-expiratory flow (EEF) ==> zero PEEPi

Detecting intrinsic PEEP during expiratory hold

Ùmeasured during absence of patient effort

flow 0 zero EEF flow 0 non-zero EEF

pressure 5

7

0 total PEEP

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Lung overdistension

Patient/ventilator asynchrony

volume

Scooping on the upswing of the flow waveform

"beak"

Significant pressure drop at the onset of patient effort

Courtesy Newport Medical

pressure

Inspiratory flow/rise- pressure wave

Expiratory flow-cycling (PSV)

Linear or bowed upward rise in pressure after trigger on the pressure wave Slow rise in pressure, concave shape of the pressure wave Courtesy Newport Medical

Patient expiratory effort

Late termination

Inability to trigger

Courtesy Newport Medical

Spontaneous WOB

spontaneous breaths

VT

LITERS

Bronchodilator effectiveness

VT

LITERS

0.6

0.6

WOB

WOB

Paw

cmH 2 O/ mbar

Inspiration

Expiration

Increased WOB

Courtesy Newport Medical

Copyright 2009 AP Jones

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Applications

ÙConfirm ETT placement- reliable ÙEstimate PaCO2- unreliable ÙMonitor changes in PaCO2unreliable ÙEstimate dead space- reliable for finding dead space/tidal volume (Vd/Vt) ÙDetect pulmonary embolismreliable

End-Tidal CO2 Monitoring

Applications

ÙEvaluate chest compressions ÙCompare condition of lungs during independent lung ventilation ÙPredict weaning failure

Interpretation- PetCO2

ÙNormal difference between PaCO2- PetCO2 = 2-5 torr ÙIncreased P(a-et)CO2 ==> dead space; e.g.: upulmonary embolus uexcessive PEEP ÙBohr equation: Vd/Vt = PaCO2- P ECO2 PaCO2 FYI - Link to capnography case studies

http://www.oridion.com/global/english/clinical_solutions/educational_resources/case_studies.html#CARE

Interpretation- PetCO2

ÙDecreased PetCO2- ominous sign during resuscitation ulow perfusion uembolization ÙIncreased PetCO2 uhypoventilation uadministration of NaHCO3

Summary and Review

ÙPulmonary mechanics upurposes for measurement uimplications umeasurement ÙOptimal PEEP uimplications utechniques for determination

Copyright 2009 AP Jones

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Summary and Review

ÙVentilator graphics utypes unormal waveforms uabnormal waveforms ÙETCO2 monitoring uapplications uinterpretation of P(a-et)CO2

END

References

ÙChiumello D, Cressoni M, Chierichetti M, Tallarini F, Botticelli M, Berto V, Mietto C, Gattinoni L. Nitrogen washout/washin, helium dilution and computed tomography in the assessment of end expiratory lung volume. Crit Care. 2008 Dec 1;12(6):R150. ÙMacnaughton PD. New ventilators for the ICU-usefulness of lung performance reporting. Br J Anaesth 2006 Jul;97(1):57-63. ÙMercat A, et al. Positive End- Expiratory Pressure Setting in Adults With Acute Lung Injury and Acute Respiratory Distress Syndrome: Randomized Controlled Trial. JAMA. 2008;299(6):646-655. ÙPepe PE, Hudson LD, Carrico CJ. . Early application of positive end-expiratory pressure in patients at risk for the adult respiratory-distress syndrome. N Engl J Med. 1984 Aug 2;311(5):281-6.

References

ÙPinsky MR. Cardiovascular issues in respiratory care. Chest 2005;128:5925-75. ÙCujec B, Polasek P, Mayers I, Johnson D.. Positive endexpiratory pressure increases the right -to-left shunt in mechanically ventilated patients with patent foramen ovale. Annals Int Med 1993 Nov 1;119(9):887-94. ÙRouby JJ, Lu Q, Goldstein I. .Selecting the right level of positive end-expiratory pressure in patients with acute respiratory distress syndrome. Am J Respir Crit Care Med. 2002 Apr 15;165(8):1182-6. ÙMaggiore SM, Jonson B, Richard JC, Jaber S, Lemaire F, Brochard L. .Alveolar derecruitment at decremental positive end-expiratory pressure levels in acute lung injury: comparison with the lower inflection point, oxygenation, and compliance. Am J Respir Crit Care Med. 2001 Sep 1;164(5):795-801

References

ÙGirgis K, Hamed H, Khater Y, Kacmarek RM. A Decremental PEEP Trial Identifies the PEEP Level That Maintains Oxygenation After Lung Recruitment. Respir Care 2006;51:1132-38. ÙStenqvist, O. Practical assessment of respiratory mechanics. Br. J. Anaesth 2003;91:92-105.

Copyright 2009 AP Jones

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