2Causes of Ventilator Dependence Assessment for Discontinuation Trial Spontaneous Breathing Trial (SBT)Extubation CriteriaFailure of SBTWeaning ModesWeaning ProtocolsRole of TracheostomyLong-term Facilities
3Stages of Mechanical Ventilation The six stages are defined in table 1 and are as follows: 1) treatment of acute respiratory failure (ARF); 2) suspicion that weaning may be possible; 3) assessment of readiness to wean; 4) spontaneous breathing trial (SBT); 5) extubation; and possibly 6) reintuba-tion.weaning process represents 40–50% of the total duration of mechanical ventilation2
4Causes of Ventilator Dependence Who is the “ventilator dependent’?Mechanical ventilation > 24 horFailure to respond during discontinuation attempsIn patients requiring mechanical ventilation for 24 h, a search for all the causes that may be contributing to ventilator dependence should be undertaken. This is particularly true in the patient who has failed attempts at withdrawing the mechanical ventilator.
5Causes of Ventilator Dependence DescriptionCausesCentral drivePeripheral nervesNeurologic controllerMechanical loadsVentilatory muscle propertiesGas exchange propertiesRespiratory systemCardiac tolerance of ventilatory muscle workperipheral oxygen demandsCardiovascular systemPsychological issuesVentilatory muscle properties: inherent strength/endurance; metabolic state/nutrients/oxygen delivery and extractionGas exchange properties: vascular properties and ventilation/perfusion matching
6Assessment for Discontinuation Trial Criteria for discontinuation trial:Evidence for some reversal of the underlying cause for respiratory failureAdequate oxygenation and pHHemodynamic stability; andThe capability to initiate an inspiratory effortOxegenation: (eg, PaO2/Fio2 ratio 150 to 200; requiring positive end-expiratory pressure [PEEP] 5 to 8 cmH2O; Fio to 0.5)pH (eg, 7.25);, hemodynamic stability is defined by the absence of active myocardial ischemia and the absence of clinically significant hypotension (ie, a condition requiring no vasopressor therapy or therapy with only low-dose vasopressors such as dopamine or dobutamine, 5 g/kg/min)
7Assessment for Discontinuation Trial Extubation failure8-fold higher odds ratio for nosocomial pneumonia6-fold to 12-fold increased mortality riskReported reintubation rates range from 4 to 23% for different ICU populations
8Assessment for Discontinuation Trial Criteria Used in Weaning/Discontinuation in different studies
9Assessment for Discontinuation Trial Measurements used To Predict the Outcome of a Ventilator Discontinuation Effort in More Than One Study
10Spontaneous Breathing Trial Formal discontinuation assessments should be performed during spontaneous breathingAn initial brief period of spontaneous breathing can be used to assess the capability of continuing onto a formal SBT.the initial few minutes of an SBT should be monitored closely before a decision is made to continue (this is often referred to as the “screening”phase of an SBT)CPAP, however, conceivably could enhance breath triggering in patients with significant auto-PEEP
11Spontaneous Breathing Trial How to assess patient tolerance?the respiratory patternthe adequacy of gas exchangehemodynamic stability, andsubjective comfort.
12Criteria Used in Several Large Trials To Define Tolerance of an SBT* Spontaneous Breathing TrialCriteria Used in Several Large Trials To Define Tolerance of an SBT**HR heart rate; Spo2 hemoglobin oxygen saturation.
13Spontaneous Breathing Trial The tolerance of SBTs lasting 30 to 120 min should prompt consideration for permanent ventilator discontinuation
14Spontaneous 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.
16Weaning to Exhaustion RR > 35/min Spo2 < 90% HR > 140/min Sustained 20% increase in HRSBP > 180 mm Hg, DBP > 90 mm HgAnxietyDiaphoresis
17Mechanical Ventilation > 100Rest 24 hrsPaO2/FiO2 ≥ 200 mm HgPEEP ≤ 5 cm H2OIntact airway reflexesNo need for continuous infusions of vasopressors or inotropsRSBIDaily SBT<100YesStable Support StrategyAssisted/PSV24 hoursLow level CPAP (5 cm H2O),Low levels of pressure support (5 to 7 cm H2O)“T-piece” breathingRR > 35/minSpo2 < 90%HR > 140/minSustained 20% increase in HRSBP > 180 mm Hg, DBP > 90 mm HgAnxietyDiaphoresisminOther causes of failure next slideExtubationNo
18Extubation Criteria Ability to protect upper airway Effective coughAlertnessImproving clinical conditionAdequate lumen of trachea and larynx“Leak test” to identify patients who are at risk for post-extubation stridor
19Post Extubation Stridor Extubation CriteriaPost Extubation StridorThe Cuff leak test during MV:Set a tidal Volume ml/kgMeasure the expired tidal volumeDeflated the cuffRemeasure expired tidal volume (average of 4-6 breaths)The difference in the tidal volumes with the cuff inflated and deflated is the leakA value of 130ml 85% sensitivity95% specificity
20Post Extubation Stridor Extubation CriteriaPost Extubation StridorCough / Leak test in spontaneous breathingTracheal 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.
21Extubation CriteriaThe risk of postextubation upper airway obstruction increases withthe duration of mechanical ventilationfemale gendertrauma, andRepeated or traumatic intubation
22Failure of SBT Correct reversible causes for failure adequacy of pain controlthe appropriateness of sedationfluid statusbronchodilator needsthe control of myocardial ischemia, andthe presence of other disease processesSubsequent SBTs should be performed every 24 hif the patient still meets the criteria for SBTstrong evidence that twice-daily SBTs offer no advantage over a single SBT and, thus, would serve only to consume unnecessary clinical resources
23Failure of SBT : Increased resistance Decreased compliance Increased WOB and exhaustionAuto-PEEPRespiratoryBackward failure: LV dysfunctionForward heart failureCardiovascularPoor nutritional statusOverfeedingDecreased Mg and PO4 levelsMetabolic and respiratory alkalosisMetablic/ElectrolytesInfection/feverMajor organ failureStridor:
24Failure of SBT Left Heart Failure: Increased metabolic demandsIncreases in venous return and pulmonary edemaAppropriate management of cardiovascular status is necessary before weaning will be successful
25Failure of SBTFactors affecting ventilator demands
26Failure of SBTTherapeutic measures to enhance weaning progress
27Weaning ModesPatients receiving mechanical ventilation for respiratory failure who fail an SBT should receive a stable, nonfatiguing, comfortable form of ventilatory support
28Modes of Partial Ventilator Support Weaning ModesModes of Partial Ventilator Support*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.
29Weaning Modes PSV: Pressure Support Gradual decrease in the level of PSV on regular basis (hours or days) to minimum level of 5-8 cm H2OPSV that prevents activation of accessory musclesOnce the patient is capable of maintaining the target ventilatory pattern and gas exchange at this level, MV is discontinued
30Weaning Modes SIMV: synchronized intermittent mandatory ventilation Gradual decrease in mandatory breathsIt may be applied with PSVHas the worst weaning outcomes in clinical trialsIts use is not recommended
31Weaning Modes New Modes VS, Volume support Automode MMV, mandatory minute ventilationATC, automatic tube compensationASV, adaptive support ventilationBecause none of these studies offer evidence that gradual support strategies are superior to stable support strategies between SBTs, theclinical focus for the 24 h after a failed SBT should be on maintaining adequate muscle unloading, optimizing comfort (and thus sedation needs), and avoiding complications, rather than aggressive ventilatory support reductionNPPV is recently used to facilitate the discontinuation
32Weaning ProtocolsWith the assisted modes, to achieve patient comfort and minimize imposed loads, we should consider:sensitive/responsive ventilator-triggering systemsapplied PEEP in the presence of a triggering threshold load from auto-PEEPflow patterns matched to patient demand, andappropriate ventilator cycling to avoid air trapping are all important to
33Weaning Protocols Weaning protocols Developed by multidisciplinary teamImplemented by respiratory therapists and nurses to make clinical decisionsResults in shorter weaning times and shorter length of mechanical ventilation than physician-directed weaningSedation protocols should be developed and implementedtwo-step protocol driven by HCPs using a daily screening procedure followed by an SBT in those who met the screening criteriaIn the context of emerging data about the benefits of NPPV and the substantial roles of HCPs in providing this treatment, there should be efforts made to develop HCP-driven protocols for this modalitynot be used to replace clinical judgment, but rather to complement it.Dynamic tool can be modefiedinstitutions must be prepared to commit the necessary resources to develop and implement protocols. For instance, adequate staffing
34Role of Tracheotomy Candidates for early tracheotomy: High levels of sedationMarginal respiratory mechanicsPsychological benefitMobility may assist physical therapy efforts.Marginal mechanics: in whom a tracheostomy tube having lower resistance might reduce the risk of muscle overloadpsychological benefit from the ability to eat orally, communicate by articulated speech, and experience enhanced mobility
35Role of Tracheotomy The benefits of tracheotomy include: improved patient comfortmore effective airway suctioningdecreased airway resistanceenhanced patient mobilityincreased opportunities for articulated speechability to eat orally, andmore secure airway
36Role of Tracheotomy Concerns: Risk associated with the procedure Long term airway injuryCostsPresently, no data support the competing contentions that early tracheotomy either decreases or increases the risk of ventilator-associated pneumoniaMore recent studies, however, have established that standard surgical tracheotomy can be performed with an acceptably low risk of perioperative complicationsthe risk of tracheal stenosis after tracheotomy is not clearly higher than the risks of subglottic stenosis from prolonged translaryngeal intubationthe cost of tracheotomy can be lowered if it is performed in the ICUEven when tracheotomy is performed in an operating room, the cost may be balanced by cost savings if a ventilator-dependent patient can be moved from an ICU setting after the placement of a tracheostomy
37Long-term FacilitiesUnless 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.
38Long-term FacilitiesCritical-care practitioners should familiarize themselves with specialized facilities in managing patients who require prolonged mechanical ventilationPatients who failed ventilator discontinuation attempts in the ICU should be transferred to those facilities
39Long-term FacilitiesWeaning strategies in the PMV patient should be slow-paced and should include gradually lengthening SBTsPsychological support and careful avoidance of unnecessary muscle overload is important for these types of patientsICU patients receiving PMV can be discontinued effectively and safely from ventilation when they are transferred to units dedicated to that activity
41Introduction75% of mechanically ventilated patients are easy to be weaned off the ventilator with simple process10-15% of patients require a use of a weaning protocol over a hours5-10% require a gradual weaning over longer time1% of patients become chronically dependent on MV
42Readiness To Wean Improvement of respiratory failure Absence of major organ system failureAppropriate level of oxygenationAdequate ventilatory statusIntact airway protective mechanism (needed for extubation)
43Oxygenation StatusPaO2 ≥ 60 mm HgFiO2 ≤ 0.40PEEP ≤ 5 cm H2O
44Ventilation StatusIntact ventilatory drive: ability to control their own level of ventilationRespiratory rate < 30Minute ventilation of < 12 L to maintain PaCO2 in normal rangeFunctional respiratory muscles
45Intact Airway Protective Mechanism Appropriate level of consciousnessCooperationIntact cough reflexIntact gag reflexFunctional respiratory muscles with ability to support a strong and effective cough
46Function of Other Organ Systems Optimized cardiovascular functionArrhythmiasFluid overloadMyocardial contractilityBody temperature1◦ degree increases CO2 production and O2 consumption by 5%Normal electrolytesPotassium, magnesium, phosphate and calciumAdequate nutritional statusUnder- or over-feedingOptimized renal, Acid-base, liver and GI functions
47Predictors of Weaning Outcome ValueEvaluation of ventilatory drive:P 0.1< 6 cm H2OVentilatory muscle capability:Vital capacityMaximum inspiratory pressure> 10 mL/kg< -30 cm H2OVentilatory performanceMinute ventilationMaximum voluntary ventilationRapid shallow breathing indexRespiratory rate< 10 L/min> 3 times VE< 105< 30 /min
48Maximal 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)
49Frequency/Volume Ratio Index of rapid and shallow breathing RR/VtSingle study results:RR/Vt> % wean attempts unsuccessfulRR/Vt< % successfulOne of the most predictive bedside parameters.
50Measurements 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*
51Weaning to Exhaustion RR > 35/min Spo2 < 90% HR > 140/min Sustained 20% increase in HRSBP > 180 mm Hg, DBP > 90 mm HgAnxietyDiaphoresis
52Work-of-Breathing High airway resistance Low compliance Pressure= Volume/compliance+ flow X resistanceHigh airway resistanceLow complianceAerosolized bronchodilators, bronchial hygiene and normalized fluid balance assist in normalizing compliance, resistance and work-of-breathing
53Auto-PEEP Increases the pressure gradient needed to inspire Use of CPAP is needed to balance alveolar pressure with the ventilator circuit pressureStart at 5 cm H2O, adjust to decrease patient stressInspiratory changes in esophageal pressure can be used to titrate CPAP
59The frequency to tidal volume ratio (or rapid shallow breathing index, RSBI) is a simple and useful integrative indicator of the balance between power supply and power demand. A rapid shallow breathing index < 100 generally indicates adequate power reserve. In this instance, the RSBI indicated that spontaneous breathing without pressure support was not tolerable, likely due in part to the development of gas trapping.Even when the mechanical requirements of the respiratory system can be met by adequate ventilation reserve, congestive heart failure, arrhythmia or ischemia may cause failure of spontaneous breathing.
61Measured Indices Must Be Combined With Clinical Observations
62Three 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.