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
Causes of Ventilator Dependence Who is the “ventilator dependent’? • Mechanical ventilation > 24 h or • Failure to respond during discontinuation attemps
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
Assessment for Discontinuation Trial 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
Assessment for Discontinuation Trial Criteria Used in Weaning/Discontinuation in different studies
Assessment for Discontinuation Trial Measurements used To Predict the Outcome of a Ventilator Discontinuation Effort in More Than One Study
Spontaneous Breathing 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.
Spontaneous Breathing Trial • How to assess patient tolerance? • the respiratory pattern • the adequacy of gas exchange • hemodynamic stability, and • subjective comfort.
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
Frequency of Tolerating an SBT in Selected Patients and Rate of Permanent Ventilator DiscontinuationFollowing a Successful SBT* Spontaneous Breathing Trial *Values given as No. (%). Pts patients. †30-min SBT. ‡120-min SBT.
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
Rest 24 hrs PaO2/FiO2 ≥ 200 mm Hg PEEP ≤ 5 cm H2O Intact airway reflexes No need for continuous infusions of vasopressors or inotrops > 100 RSBI <100 Stable Support Strategy Assisted/PSV Daily SBT 24 hours 30-120 min RR > 35/min Spo2 < 90% HR > 140/min Sustained 20% increase in HR SBP > 180 mm Hg, DBP > 90 mm Hg Anxiety Diaphoresis Extubation No Yes Mechanical Ventilation Low level CPAP (5 cm H2O), Low levels of pressure support (5 to 7 cm H2O) “T-piece” breathing
Extubation Criteria • 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
Post Extubation Stridor Extubation Criteria • 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
Post Extubation Stridor Extubation Criteria • 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
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
Failure of SBT • : • : • :
Failure of SBT • 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 Factors affecting ventilator demands
Failure of SBT Therapeutic 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
Weaning Modes Modes 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.
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
Weaning Modes New Modes • VS, Volume support • Automode • MMV, mandatory minute ventilation • ATC, automatic tube compensation • ASV, adaptive support ventilation
Weaning Protocols • 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
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
Role of Tracheotomy • Candidates for early tracheotomy: • High levels of sedation • Marginal respiratory mechanics • Psychological benefit • Mobility may assist physical therapy efforts.
Role of Tracheotomy • 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
Role of Tracheotomy • Concerns: • Risk associated with the procedure • Long term airway injury • Costs
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.
Long-term Facilities • 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
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
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
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 BriefPeriod of Spontaneous Breathing That Have Been Shown to Have Statistically Significant LRs To Predict theOutcome of a Ventilator Discontinuation Effort in More Than One Study*