Have we really come that far since the days of Negative Pressure Ventilation?Have we really come that far since the days of Negative Pressure Ventilation?

Prolonged Mechanical Prolonged Mechanical VentilationVentilation

Weaning Strategies in the ICUWeaning Strategies in the ICU

When is MV Prolonged?When is MV Prolonged?

Numerous DefinitionsNumerous Definitions NAMDRC Consensus StatementNAMDRC Consensus Statement

>21 consecutive days for >6 h/d >21 consecutive days for >6 h/d (recommendation #1)(recommendation #1)

Estimated 5% of MV patients will require PMV Estimated 5% of MV patients will require PMV (Pierson et al.)(Pierson et al.)

But, nearly 34% of patients intubated for >48 But, nearly 34% of patients intubated for >48 hours will require extended intubationshours will require extended intubations

Patient TypePatient Type

OlderOlder Comorbid ConditionsComorbid Conditions Underlying Obstructive Lung DiseaseUnderlying Obstructive Lung Disease

Ventilator DependenceVentilator Dependence SystemicSystemic

Chronic comorbid conditionsChronic comorbid conditions Chronic HypercapniaChronic Hypercapnia Organ Failure (Renal failure especially can Organ Failure (Renal failure especially can

dramatically increase the mortality rate)dramatically increase the mortality rate) MechanicsMechanics

Increased Work of BreathingIncreased Work of Breathing Decreased Respiratory Muscle CapacityDecreased Respiratory Muscle Capacity Intrinsic PEEPIntrinsic PEEP Airway Patency (eg. tracheal stenosis)Airway Patency (eg. tracheal stenosis)

IatrogenicIatrogenic Unrecognized withdrawal potentialUnrecognized withdrawal potential Inappropriate vent settingsInappropriate vent settings MEDS (Suppress drive and muscle weakness)MEDS (Suppress drive and muscle weakness)

Long-term hospital stayLong-term hospital stay Infection (VAP, Sepsis/SIRS—decrease O2 uptake)Infection (VAP, Sepsis/SIRS—decrease O2 uptake) Recurrent Aspiration Recurrent Aspiration DVTDVT

PsychPsych SedationSedation DepressionDepression AnxietyAnxiety

Dependence/Failure to WeanDependence/Failure to Wean

Additional FeaturesAdditional Features• Cardiovascular FunctionCardiovascular Function

• IschemiaIschemia• Heart FailureHeart Failure

• Metabolic DerangementsMetabolic Derangements• HypophosphatemiaHypophosphatemia• HypocalcemiaHypocalcemia• HypomagnesemiaHypomagnesemia• Hypothyroidism (severe)Hypothyroidism (severe)

• NutritionNutrition• Poor—protein catabolismPoor—protein catabolism• Overfeeding—excess CO2Overfeeding—excess CO2

• DeconditioningDeconditioning

Complications of PMVComplications of PMV InfectionInfection

• Bacterial PneumoniaBacterial Pneumonia• Line sepsisLine sepsis• C. DiffC. Diff

Volume OverloadVolume Overload Laryngeal EdemaLaryngeal Edema PneumothoraxPneumothorax Tracheal BleedingTracheal Bleeding Renal FailureRenal Failure IleusIleus GI BleedingGI Bleeding DVTDVT Additional Complications if Tracheostomy is necessaryAdditional Complications if Tracheostomy is necessary

WeaningWeaning Start as soon as possibleStart as soon as possible Success depends generally on Success depends generally on

1) Strength of Respiratory muscles1) Strength of Respiratory muscles2) Load Applied 2) Load Applied 3) Drive to Breath3) Drive to Breath

Has the problem which led to intubation been Has the problem which led to intubation been resolved? Is there a new problem? resolved? Is there a new problem?

Identify those factors contributing to Identify those factors contributing to dependence that are potentially reversible dependence that are potentially reversible (NAMDRC Rec #4)(NAMDRC Rec #4)

Sedative-based depression of respiratory drive Sedative-based depression of respiratory drive can lead to inappropriately prolonged can lead to inappropriately prolonged dependence on MVdependence on MV

Initiate Weaning Initiate Weaning

When there is:When there is:1.1. Adequate OxygenationAdequate Oxygenation

A)A) PaO2/FiO2 >150-200PaO2/FiO2 >150-200

B)B) Vent Settings: PEEP <8 and FiO2 <0.5Vent Settings: PEEP <8 and FiO2 <0.5

2.2. pH >7.25pH >7.25

3.3. Hemodynamic stablilityHemodynamic stablility

4.4. Ability to Initiate an Inspiratory EffortAbility to Initiate an Inspiratory Effort

5.5. Sedation (esp. with resp-depressing Sedation (esp. with resp-depressing drugs) has itself been weaneddrugs) has itself been weaned

Predicting SuccessPredicting Success

A number of criteria have been A number of criteria have been proposedproposed

Vital CapacityVital Capacity Tidal Volume (using a cutoff of 4 mL/Kg) Tidal Volume (using a cutoff of 4 mL/Kg)

• PPV 0.67, NPV 0.85PPV 0.67, NPV 0.85 PaO2/FiO2PaO2/FiO2 Max Insp. PressureMax Insp. Pressure RR/VT (Rapid Shallow Breathing Index)RR/VT (Rapid Shallow Breathing Index)

RSBIRSBI

First described by Yang and Tobin in First described by Yang and Tobin in 19911991

Simply the f/VTSimply the f/VT Observation that those who fail Observation that those who fail

weaning trials decrease their tidal weaning trials decrease their tidal volumes and increase their ratevolumes and increase their rate

Threshold <105Threshold <105• PPV: 0.78 and NPV: 0.95PPV: 0.78 and NPV: 0.95

In PMVIn PMV Even with these indices predicting Even with these indices predicting

weaning success in this population is weaning success in this population is difficult. difficult.

Some attempts have been madeSome attempts have been made Success has been correlated with number of Success has been correlated with number of

comorbid diagnoses as well as length of MVcomorbid diagnoses as well as length of MV Scheinhorn et al used A-a gradient, gender, and BUN Scheinhorn et al used A-a gradient, gender, and BUN

(recognizing the increased mortality when renal (recognizing the increased mortality when renal failure was involved) to attempt to score the failure was involved) to attempt to score the likelihood of successful weaning. Unfortunately this likelihood of successful weaning. Unfortunately this has shown limited success in repeat studies.has shown limited success in repeat studies.

Additionally, the up and coming use of Additionally, the up and coming use of post-ICU weaning facilities has improved post-ICU weaning facilities has improved weaning outcome.weaning outcome.

Methods of WeaningMethods of Weaning

Synchronized Intermittent Mandatory Synchronized Intermittent Mandatory Ventilation (SIMV)Ventilation (SIMV)

Pressure Support Ventilation (PSV)Pressure Support Ventilation (PSV) SBTSBT

No SupportNo Support CPAPCPAP PSPS

NB: These methods are the same used with acute patients. NB: These methods are the same used with acute patients. The important difference is PMV patients generally require The important difference is PMV patients generally require a more gradual weaning coursea more gradual weaning course

SIMVSIMV Breaths are either spontaneous (+/- pressure support) or Breaths are either spontaneous (+/- pressure support) or

mandatory vent-controlled. Mandatory breaths are synchronized mandatory vent-controlled. Mandatory breaths are synchronized with patient’s own effortswith patient’s own efforts

Allows for a gradual decrease in ventilator-provided support and a Allows for a gradual decrease in ventilator-provided support and a gradual increase in the patient’s respiratory workloadgradual increase in the patient’s respiratory workload

Rate is Reduced Progressively (2 breaths every 1-2 hours)Rate is Reduced Progressively (2 breaths every 1-2 hours) Blood gasses are checkedBlood gasses are checked Patient is monitored for ability to accept increased work of breathing (HR, Patient is monitored for ability to accept increased work of breathing (HR,

RR, Sats, clinical signs)RR, Sats, clinical signs)

But, studies have shown that respiratory muscles are unable to But, studies have shown that respiratory muscles are unable to rest during the mandatory ventilator breaths (the respiratory rest during the mandatory ventilator breaths (the respiratory center fails to adapt to the intermittent support).center fails to adapt to the intermittent support).

Can delay weaning by contributing to the development of Can delay weaning by contributing to the development of respiratory muscle fatigue and therefore can delay extubationrespiratory muscle fatigue and therefore can delay extubation

Esteban A, Frutos F, Tobin MJ, et al. A comparison of four methods of weaning patients from mechanical ventilation. Spanish lung failure collaborative group. N Engl J Med 1995; 332:345-350

Pressure Support VentilationPressure Support Ventilation All breaths are spontaneous. But when PS is high All breaths are spontaneous. But when PS is high

relative to patient effort, support is almost fully relative to patient effort, support is almost fully from MV from MV

Enough PS is given with each breath to ensure an Enough PS is given with each breath to ensure an adequate Vadequate VTT..

MethodMethod Gradually decrease the amount of PS (transferring the work Gradually decrease the amount of PS (transferring the work

to the patient)to the patient) Once PS approaches 5-6 cmHOnce PS approaches 5-6 cmH22O extubation can be O extubation can be

consideredconsidered Reduces the work of breathingReduces the work of breathing Can be used in conjunction with SIMV during Can be used in conjunction with SIMV during

weaningweaning Reduces the likelihood of reintubation but was Reduces the likelihood of reintubation but was

shown to be only slightly better than SIMV in shown to be only slightly better than SIMV in duration of weaningduration of weaning

SBT—Sink or SwimSBT—Sink or Swim

ApplicationsApplications Extubation readiness—a 90 minute test (though at Extubation readiness—a 90 minute test (though at

least one study—Esteban et al—suggested that only least one study—Esteban et al—suggested that only 30 min may be necessary) 30 min may be necessary)

Weaning• Length of SBT is increased daily• Periods of ventilation are alternated with these trials• T-piece TrialsT-piece Trials

Requires removing patient from vent and providing Requires removing patient from vent and providing supplemental humidified Osupplemental humidified O22 to their airway to their airway (through a tube that looks like a T.)(through a tube that looks like a T.)

These trials can also now be done with the patient These trials can also now be done with the patient still directly connected to the vent which allows still directly connected to the vent which allows closer observation (and all the bells and whistles closer observation (and all the bells and whistles that the vent provides)that the vent provides)

Types of SBTsTypes of SBTs

1.1. No Vent SupportNo Vent Support

2.2. Low level of CPAP—closing pressureLow level of CPAP—closing pressure

3.3. Low Level of PS—airway resistanceLow Level of PS—airway resistance

No controlled studies have demonstrated superiority of any of these modes. No controlled studies have demonstrated superiority of any of these modes. However, in certain patient populations such as those with marginal left However, in certain patient populations such as those with marginal left ventricular function, a low level of CPAP and the subsequent increase in ventricular function, a low level of CPAP and the subsequent increase in intrathoracic pressure can help prevent heart failure. But, its removal, may intrathoracic pressure can help prevent heart failure. But, its removal, may lead to acute heart failure following extubation secondary to increased LV lead to acute heart failure following extubation secondary to increased LV preload and LVEDPpreload and LVEDP

TrialTrial 30-90 minutes30-90 minutes Once daily Once daily

A number of studies have demonstrated equivalent results A number of studies have demonstrated equivalent results between multiple daily tests and once daily testsbetween multiple daily tests and once daily tests

Following each SBT evaluate for possible Following each SBT evaluate for possible extubationextubation

BP, RR, HR, ABG should all be consideredBP, RR, HR, ABG should all be considered Level of sedationLevel of sedation

SBTs are superior to both IMV and PS in duration SBTs are superior to both IMV and PS in duration of weaning and likelihood of success after of weaning and likelihood of success after weaningweaning

In patients on PMV, daily trials may be required In patients on PMV, daily trials may be required for a longer period of time.for a longer period of time.

Seminal Study (Esteban et al)Seminal Study (Esteban et al)

546 Patients546 Patients All underwent a 2-hr SBT to evaluate for All underwent a 2-hr SBT to evaluate for

extubationextubation

• 130 had respiratory distress during the SBT 130 had respiratory distress during the SBT and were not extubatedand were not extubated

• These pts were randomized to 1 of 4 groupsThese pts were randomized to 1 of 4 groups• SIMV—initial rate of 10.0 breaths per minute, then SIMV—initial rate of 10.0 breaths per minute, then

decreased at least twice a day, by 2 to 4 bpm (29)decreased at least twice a day, by 2 to 4 bpm (29)• PSV—initially set at 18.0 cm HPSV—initially set at 18.0 cm H22O then reduced by 2 to O then reduced by 2 to

4 cm H4 cm H22O at least twice a day (37)O at least twice a day (37)• Once a day SBT (31)Once a day SBT (31)• Multiple daily SBTs (33)Multiple daily SBTs (33)

ConclusionConclusion

A once-daily SBT led to extubation A once-daily SBT led to extubation about three times more quickly than about three times more quickly than IMV and about twice as quickly as IMV and about twice as quickly as PSV. Multiple daily SBTs were equally PSV. Multiple daily SBTs were equally successful.successful.

Weaning ProtocolWeaning Protocol Improve overall outcomeImprove overall outcome Example:Example:

1.1. Is patient is a candidate for weaning?Is patient is a candidate for weaning?i)i) PaOPaO22 > 60mmHg > 60mmHgii)ii) FFiiOO22 <0.5 <0.5iii)iii) PEEP < 8 cm HPEEP < 8 cm H22OO

2.2. Screen for readiness—RSB TrialScreen for readiness—RSB Triali)i) SBT for one minute to calculate RSBISBT for one minute to calculate RSBI

3.3. Ensure intact airway reflexesEnsure intact airway reflexesi)i) Coughing during suctioningCoughing during suctioning

4.4. Patient can now be subject to SBTsPatient can now be subject to SBTsi)i) PS, CPAP, or T-piecePS, CPAP, or T-pieceii)ii) Up to 120 minutesUp to 120 minutes

5.5. SBT can be terminated if patient:SBT can be terminated if patient:i)i) Successfully tolerates the SBT from 30-120 minutesSuccessfully tolerates the SBT from 30-120 minutesii)ii) Shows s/sx of failureShows s/sx of failure

Weaning FailureWeaning Failure HR >140 bpm or a sustained increase of

>20% RR >35 breaths/min for >5 min O2 Sats <90% for >30s HR with a sustained decrease of >20% SBP>180 for > 5 min SBP<90 for > 5 min Clinical features: Anxiety, agitation,

diaphoresis NB: May not be due to weaning failure and should be

treated appropriately

Problems with FailureProblems with Failure

Failing can put significant stress on Failing can put significant stress on the respiratory systemthe respiratory system

Inspiratory effort can increase 4-6 Inspiratory effort can increase 4-6 times following a failed SBT (Jubran times following a failed SBT (Jubran et al.)et al.)

Protocols are driven by RT and/or nursesProtocols are driven by RT and/or nurses

Studies have shown that protocol-driven Studies have shown that protocol-driven weaning by these individuals is superior to weaning by these individuals is superior to independent physician-directed weaning independent physician-directed weaning (Horst et al.)(Horst et al.)

Sending PMV patients to institutions Sending PMV patients to institutions dedicated specifically to weaning improves dedicated specifically to weaning improves outcomes (ie, Long-Term Assisted Care outcomes (ie, Long-Term Assisted Care facilities) facilities)

Who should run the Trial?Who should run the Trial?

The FutureThe Future Automatic Tube CompensationAutomatic Tube Compensation

Compensates for pressure drop across ET tubeCompensates for pressure drop across ET tube Delivers the exact amount of pressure to overcome the Delivers the exact amount of pressure to overcome the

resistive load of the tube given the flow across the tube resistive load of the tube given the flow across the tube measured at that instant (variable pressure support)measured at that instant (variable pressure support)

Studies by Cohen and others have demonstrated that ATC Studies by Cohen and others have demonstrated that ATC improves weaning outcome compared to PSV and CPAPimproves weaning outcome compared to PSV and CPAP

No studies as of yet have compared ATC vs. T-pieceNo studies as of yet have compared ATC vs. T-piece Proportional-Assist VentilationProportional-Assist Ventilation

Ventilator adjusts airway pressure in proportion to patients Ventilator adjusts airway pressure in proportion to patients instantaneous effort. This occurs from breath-to-breath and instantaneous effort. This occurs from breath-to-breath and continuously through each inspirationcontinuously through each inspiration

No set tidal volume, pressure, or flow rate.No set tidal volume, pressure, or flow rate. The patient’s work of breathing remains constant despite The patient’s work of breathing remains constant despite

changing effort or demandchanging effort or demand Computer-Driven ProtocolsComputer-Driven Protocols

Using knowledge-based algorithmsUsing knowledge-based algorithms Decreased MV duration from 12 to 7.5 days in a recent trial Decreased MV duration from 12 to 7.5 days in a recent trial

(Lellouche et al.)(Lellouche et al.) Used automatic gradual reduction in pressure supportUsed automatic gradual reduction in pressure support Automatic Performance of SBTsAutomatic Performance of SBTs

Outcomes in PMV PatientsOutcomes in PMV Patients

Population is very diversePopulation is very diverse• Results are therefore difficult to generalizeResults are therefore difficult to generalize• For example, patients who require PMV post-For example, patients who require PMV post-

operatively generally do significantly better than operatively generally do significantly better than patients with COPDpatients with COPD

LTAC facilitiesLTAC facilities• Scheinhorn et al.(2007)Scheinhorn et al.(2007) Large, Large,

multicenter trial evaluating outcomes in multicenter trial evaluating outcomes in post-ICU PMV patients at 23 LTAC post-ICU PMV patients at 23 LTAC facilities.facilities.

Scheinhorn et al (2007)Scheinhorn et al (2007)

1,419 patients1,419 patients 23 sites from 3/2002-2/200323 sites from 3/2002-2/2003 Excluded: End-of-life care; terminal Excluded: End-of-life care; terminal

weaning, or considered incapable of weaning, or considered incapable of weaning at the time of admissionweaning at the time of admission

One-Year Mortality: 52%One-Year Mortality: 52% 25% died in the weaning hospital25% died in the weaning hospital 27% died after discharge27% died after discharge

Survival to Discharge: 67%Survival to Discharge: 67% Cost: $3968/day Cost: $3968/day

ReferencesReferences Cohen JD, Shapiro M, et al. Automatic tube compensation-assissted respiratory rate to tidal volume ratio improves the

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