Weaning Modes and Protocol. Causes of Ventilator Dependence Assessment for Discontinuation Trial...

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Transcript of Weaning Modes and Protocol. Causes of Ventilator Dependence Assessment for Discontinuation Trial...

Weaning Modesand Protocol

• Causes of Ventilator Dependence• Assessment for Discontinuation Trial• Spontaneous Breathing Trial (SBT)

– Extubation Criteria

• Failure of SBT• Weaning Modes• Weaning Protocols• Role of Tracheostomy• Long-term Facilities

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Stages of Mechanical Ventilation

Causes of Ventilator Dependence

Who is the “ventilator dependent’?

• Mechanical ventilation > 24 h

or• Failure to respond during discontinuation

attemps

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Causes Description

Neurologic controller Central drivePeripheral nerves

Respiratory system Mechanical loadsVentilatory muscle propertiesGas exchange properties

Cardiovascular system Cardiac tolerance of ventilatory muscle workperipheral oxygen demands

Psychological issues

Causes of Ventilator Dependence

Assessment for Discontinuation Trial

Criteria for discontinuation trial:

• Evidence for some reversal of the underlying cause for respiratory failure

• Adequate oxygenation and pH• Hemodynamic stability; and• The capability to initiate an inspiratory

effort

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Extubation failure• 8-fold higher odds ratio for nosocomial

pneumonia

• 6-fold to 12-fold increased mortality risk

• Reported reintubation rates range from 4 to 23% for different ICU populations

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Assessment for Discontinuation Trial

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Criteria Used in Weaning/Discontinuation in different studies

Assessment for Discontinuation Trial

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Measurements used To Predict the Outcome of a Ventilator Discontinuation Effort in More Than One Study

Assessment for Discontinuation Trial

• Formal discontinuation assessments should be performed during spontaneous breathing

• An initial brief period of spontaneous breathing can be used to assess the capability of continuing onto a formal SBT.

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Spontaneous Breathing Trial

• How to assess patient tolerance?– the respiratory pattern– the adequacy of gas exchange– hemodynamic stability, and – subjective comfort.

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Spontaneous Breathing Trial

Criteria Used in Several Large Trials To Define Tolerance of an SBT*

*HR heart rate; Spo2 hemoglobin oxygen saturation.

Spontaneous Breathing Trial

• The tolerance of SBTs lasting 30 to 120 min should prompt consideration for permanent ventilator discontinuation

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Spontaneous Breathing Trial

Frequency of Tolerating an SBT in Selected Patients and Rate of Permanent Ventilator Discontinuation

Following a Successful SBT*

*Values given as No. (%). Pts patients.†30-min SBT.‡120-min SBT.

Spontaneous Breathing Trial

Do Not Wean To Exhaustion

Weaning to Exhaustion

• RR > 35/min• Spo2 < 90%• HR > 140/min• Sustained 20% increase in HR• SBP > 180 mm Hg, DBP > 90 mm Hg• Anxiety• Diaphoresis

Daily SBT

<100

Mechanical Ventilation

RR > 35/minSpo2 < 90%HR > 140/minSustained 20% increase in HRSBP > 180 mm Hg, DBP > 90 mm HgAnxietyDiaphoresis

30-120 min

PaO2/FiO2 ≥ 200 mm HgPEEP ≤ 5 cm H2OIntact airway reflexesNo need for continuous infusions of vasopressors or inotrops

RSBI

ExtubationNo

> 100

Rest 24 hrs

Yes

Stable Support StrategyAssisted/PSV

24 hours

Low level CPAP (5 cm H2O), Low levels of pressure support (5 to 7 cm H2O)“T-piece” breathing

Ability to protect upper airway– Effective cough– Alertness

Improving clinical condition

Adequate lumen of trachea and larynx– “Leak test” to identify patients who are at risk

for post-extubation stridor

Extubation Criteria

Post Extubation Stridor • The Cuff leak test during MV:

– Set a tidal Volume 10-12 ml/kg

– Measure the expired tidal volume

– Deflated the cuff

– Remeasure expired tidal volume (average of 4-6 breaths)

– The difference in the tidal volumes with the cuff inflated and deflated is the leak

• A value of 130ml 85% sensitivity

95% specificity

Extubation Criteria

Post Extubation Stridor • Cough / Leak test in spontaneous breathing

– Tracheal cuff is deflated and monitored for the first 30 seconds for cough.

– Only cough associated with respiratory gurgling (heard without a stethoscope and related to secretions) is taken into account.

– The tube is then obstructed with a finger while the patient continues to breath.

– The ability to breathe around the tube is assessed by the auscultation of a respiratory flow.

Extubation Criteria

• The risk of postextubation upper airway obstruction increases with

– the duration of mechanical ventilation– female gender– trauma, and – Repeated or traumatic intubation

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Extubation Criteria

Failure of SBT

• Correct reversible causes for failure– adequacy of pain control– the appropriateness of sedation– fluid status– bronchodilator needs– the control of myocardial ischemia, and – the presence of other disease processes

• Subsequent SBTs should be performed every 24 h

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:

:

:

Failure of SBT

Respiratory Increased resistanceDecreased complianceIncreased WOB and exhaustionAuto-PEEP

Cardiovascular Backward failure: LV dysfunctionForward heart failure

Metablic/Electrolytes Poor nutritional statusOverfeedingDecreased Mg and PO4 levelsMetabolic and respiratory alkalosis

Infection/fever

Major organ failure

Stridor

• Left Heart Failure:– Increased metabolic demands– Increases in venous return and pulmonary

edema

• Appropriate management of cardiovascular status is necessary before weaning will be successful

Failure of SBT

Failure of SBT

Factors affecting ventilator demands

Failure of SBTTherapeutic measures to enhance weaning progress

Weaning Modes

• Patients receiving mechanical ventilation for respiratory failure who fail an SBT should receive a stable, nonfatiguing, comfortable form of ventilatory support

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Modes of Partial Ventilator Support

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*SIMV synchronized intermittent mandatory ventilation; PSV pressure support ventilation; VS volume support; VAPS(PA) volume assured pressure support (pressure augmentation); MMV mandatory minute ventilation; APRV airway pressure release ventilation.

Weaning Modes

PSV: Pressure Support• Gradual decrease in the level of PSV on

regular basis (hours or days) to minimum level of 5-8 cm H2O

• PSV that prevents activation of accessory muscles

• Once the patient is capable of maintaining the target ventilatory pattern and gas exchange at this level, MV is discontinued

Weaning Modes

SIMV: synchronized intermittent mandatory ventilation

• Gradual decrease in mandatory breaths• It may be applied with PSV• Has the worst weaning outcomes in

clinical trials• Its use is not recommended

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Weaning Modes

New Modes• VS, Volume support• Automode• MMV, mandatory minute ventilation• ATC, automatic tube compensation• ASV, adaptive support ventilation

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Weaning Modes

• With the assisted modes, to achieve patient comfort and minimize imposed loads, we should consider:– sensitive/responsive ventilator-triggering

systems– applied PEEP in the presence of a triggering

threshold load from auto-PEEP– flow patterns matched to patient demand, and – appropriate ventilator cycling to avoid air

trapping are all important to

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Weaning Protocols

• Weaning protocols– Developed by multidisciplinary team– Implemented by respiratory therapists and

nurses to make clinical decisions– Results in shorter weaning times and shorter

length of mechanical ventilation than physician-directed weaning

• Sedation protocols should be developed and implemented

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Weaning Protocols

Role of Tracheotomy

• Candidates for early tracheotomy:

– High levels of sedation– Marginal respiratory mechanics– Psychological benefit– Mobility may assist physical therapy efforts.

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• The benefits of tracheotomy include:– improved patient comfort– more effective airway suctioning– decreased airway resistance– enhanced patient mobility– increased opportunities for articulated speech– ability to eat orally, and – more secure airway

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Role of Tracheotomy

• Concerns:

– Risk associated with the procedure– Long term airway injury– Costs

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Role of Tracheotomy

Long-term Facilities

• Unless there is evidence for clearly irreversible disease (e.g., high spinal cord injury or advanced amyotrophic lateral sclerosis), a patient requiring prolonged mechanical ventilatory (PMV) support for respiratory failure should not be considered permanently ventilator-dependent until 3 months of weaning attempts have failed.

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• Critical-care practitioners should familiarize themselves with specialized facilities in managing patients who require prolonged mechanical ventilation

• Patients who failed ventilator discontinuation attempts in the ICU should be transferred to those facilities

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Long-term Facilities

• Weaning strategies in the PMV patient should be slow-paced and should include gradually lengthening SBTs

• Psychological support and careful avoidance of unnecessary muscle overload is important for these types of patients

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Long-term Facilities

Thank You

Introduction

• 75% of mechanically ventilated patients are easy to be weaned off the ventilator with simple process

• 10-15% of patients require a use of a weaning protocol over a 24-72 hours

• 5-10% require a gradual weaning over longer time

• 1% of patients become chronically dependent on MV

Readiness To Wean

• Improvement of respiratory failure• Absence of major organ system failure• Appropriate level of oxygenation• Adequate ventilatory status• Intact airway protective mechanism (needed

for extubation)

Oxygenation Status

• PaO2 ≥ 60 mm Hg

• FiO2 ≤ 0.40

• PEEP ≤ 5 cm H2O

Ventilation Status

• Intact ventilatory drive: ability to control their own level of ventilation

• Respiratory rate < 30

• Minute ventilation of < 12 L to maintain PaCO2 in normal range

• Functional respiratory muscles

Intact Airway Protective Mechanism

• Appropriate level of consciousness• Cooperation• Intact cough reflex• Intact gag reflex• Functional respiratory muscles with ability to

support a strong and effective cough

Function of Other Organ Systems

• Optimized cardiovascular function– Arrhythmias– Fluid overload– Myocardial contractility

• Body temperature– 1◦ degree increases CO2 production and O2 consumption by 5%

• Normal electrolytes– Potassium, magnesium, phosphate and calcium

• Adequate nutritional status– Under- or over-feeding

• Optimized renal, Acid-base, liver and GI functions

Predictors of Weaning Outcome

PredictorPredictor ValueValueEvaluation of ventilatory drive:Evaluation of ventilatory drive:

P 0.1P 0.1 < 6 cm H2O< 6 cm H2O

Ventilatory muscle capability:Ventilatory muscle capability: Vital capacityVital capacity Maximum inspiratory pressureMaximum inspiratory pressure

> 10 mL/kg> 10 mL/kg < -30 cm H< -30 cm H22OO

Ventilatory performanceVentilatory performance Minute ventilationMinute ventilation Maximum voluntary ventilationMaximum voluntary ventilation Rapid shallow breathing indexRapid shallow breathing index Respiratory rateRespiratory rate

< 10 L/min< 10 L/min > 3 times V> 3 times VEE

< 105< 105 < 30 /min< 30 /min

Maximal Inspiratory Pressure

• Pmax: Excellent negative predictive value if less than –20 (in one study 100% failure to wean at this value)

An acceptable Pmax however has a poor positive predictive value (40% failure to wean in this study with a Pmax more than –20)

Frequency/Volume Ratio

• Index of rapid and shallow breathing RR/Vt• Single study results:

– RR/Vt>105 95% wean attempts unsuccessful– RR/Vt<105 80% successful

• One of the most predictive bedside parameters.

Measurements Performed Either While Patient Was Receiving Ventilatory Support or During a Brief

Period of Spontaneous Breathing That Have Been Shown to Have Statistically Significant LRs To Predict the

Outcome of a Ventilator Discontinuation Effort in More Than One Study*

Weaning to Exhaustion

• RR > 35/min• Spo2 < 90%• HR > 140/min• Sustained 20% increase in HR• SBP > 180 mm Hg, DBP > 90 mm Hg• Anxiety• Diaphoresis

Work-of-Breathing

• Pressure= Volume/compliance+ flow X resistance

• High airway resistance• Low compliance• Aerosolized bronchodilators, bronchial

hygiene and normalized fluid balance assist in normalizing compliance, resistance and work-of-breathing

Auto-PEEP

• Increases the pressure gradient needed to inspire

• Use of CPAP is needed to balance alveolar pressure with the ventilator circuit pressure

• Start at 5 cm H2O, adjust to decrease patient stress

• Inspiratory changes in esophageal pressure can be used to titrate CPAP

0

-5

Gradient

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0

Auto PEEP +10

-5

Gradient

-15

PEEP10

Auto PEEP +10

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Gradient

-5

Preparation: Factors Affecting Ventilatory Demand

Integrative Indices Predicting Success

Measured Indices Must Be Combined With Clinical Observations

Three Methods for Gradually Withdrawing Ventilator Support

Although the majority of patients do not require gradual withdrawal of ventilation, those that do tend to do better with graded pressure supported weaning than with abrupt transitions from Assist/Control to CPAP or with SIMV used with only minimal pressure support.

Thank You