Weaning Modes and 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

Stages 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 ventilation 2

Causes of Ventilator Dependence Who is the “ventilator dependent’? Mechanical ventilation > 24 h or Failure to respond during discontinuation attemps In 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.

Causes of Ventilator Dependence Description Causes Central drive Peripheral nerves Neurologic controller Mechanical loads Ventilatory muscle properties Gas exchange properties Respiratory system Cardiac tolerance of ventilatory muscle work peripheral oxygen demands Cardiovascular system Psychological issues Ventilatory muscle properties: inherent strength/endurance; metabolic state/nutrients/oxygen delivery and extraction Gas exchange properties: vascular properties and ventilation/perfusion matching

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 Oxegenation: (eg, PaO2/Fio2 ratio 150 to 200; requiring positive end-expiratory pressure [PEEP] 5 to 8 cmH2O; Fio2 0.4 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)

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. 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

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

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

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.

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

Mechanical Ventilation > 100 Rest 24 hrs PaO2/FiO2 ≥ 200 mm Hg PEEP ≤ 5 cm H2O Intact airway reflexes No need for continuous infusions of vasopressors or inotrops RSBI Daily SBT <100 Yes Stable Support Strategy Assisted/PSV 24 hours Low level CPAP (5 cm H2O), Low levels of pressure support (5 to 7 cm H2O) “T-piece” breathing RR > 35/min Spo2 < 90% HR > 140/min Sustained 20% increase in HR SBP > 180 mm Hg, DBP > 90 mm Hg Anxiety Diaphoresis 30-120 min Other causes of failure next slide Extubation No

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 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

Post Extubation Stridor 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

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 if the patient still meets the criteria for SBT strong evidence that twice-daily SBTs offer no advantage over a single SBT and, thus, would serve only to consume unnecessary clinical resources

Failure of SBT : Increased resistance Decreased compliance Increased WOB and exhaustion Auto-PEEP Respiratory Backward failure: LV dysfunction Forward heart failure Cardiovascular Poor nutritional status Overfeeding Decreased Mg and PO4 levels Metabolic and respiratory alkalosis Metablic/Electrolytes Infection/fever Major organ failure Stridor :

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

Modes of Partial Ventilator 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 Because none of these studies offer evidence that gradual support strategies are superior to stable support strategies between SBTs, the clinical 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 reduction NPPV is recently used to facilitate the discontinuation

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 two-step protocol driven by HCPs using a daily screening procedure followed by an SBT in those who met the screening criteria In 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 modality not be used to replace clinical judgment, but rather to complement it. Dynamic tool can be modefied institutions must be prepared to commit the necessary resources to develop and implement protocols. For instance, adequate staffing

Role of Tracheotomy Candidates for early tracheotomy: High levels of sedation Marginal respiratory mechanics Psychological benefit Mobility may assist physical therapy efforts. Marginal mechanics: in whom a tracheostomy tube having lower resistance might reduce the risk of muscle overload psychological benefit from the ability to eat orally, communicate by articulated speech, and experience enhanced mobility

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 Presently, no data support the competing contentions that early tracheotomy either decreases or increases the risk of ventilator-associated pneumonia More recent studies, however, have established that standard surgical tracheotomy can be performed with an acceptably low risk of perioperative complications the risk of tracheal stenosis after tracheotomy is not clearly higher than the risks of subglottic stenosis from prolonged translaryngeal intubation the cost of tracheotomy can be lowered if it is performed in the ICU Even 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

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 ICU patients receiving PMV can be discontinued effectively and safely from ventilation when they are transferred to units dedicated to that activity

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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 Value Evaluation of ventilatory drive: P 0.1 < 6 cm H2O Ventilatory muscle capability: Vital capacity Maximum inspiratory pressure > 10 mL/kg < -30 cm H2O Ventilatory performance Minute ventilation Maximum voluntary ventilation Rapid shallow breathing index Respiratory rate < 10 L/min > 3 times VE < 105 < 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 High airway resistance Low compliance 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

Gradient -5 -5

Gradient Auto PEEP +10 -5 -15

PEEP 10 Gradient Auto PEEP +10 5 -5

Preparation: Factors Affecting Ventilatory Demand

The 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.

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.

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