Weaning From Mechanical Ventilation Created By Sebastian Benavides (2012) Updated by Melanie Kusonruksa (2016)

Objective Identify patients who are ready to wean from mechanical ventilation Understand weaning parameters Identify when patients are ready for extubation

Discontinuing Mechanical Ventilation Two step process: 1. Readiness testing: Purpose is to identify patients who should start weaning 2. Weaning: Process of decreasing the amount of support a patient receives from the ventilator Readiness Testing: patients have to meet certain criteria before they even begin weaning process Weaning: progressive decrease of support a patient receives from the vent with patient assuming greater portion of their ventilation

Readiness Testing Required Clinical Criteria: Cause of the respiratory failure has improved Adequate oxygenation Arterial pH > 7.25 Hemodynamic stability Able to initiate respiratory effort ADEQUATE OXYGENATION: -O2 sat ≥ 90% while on FIO2 ≤ 40 to 50% and PEEP ≤5 to 8. Can also use P/F ratio ≥ 150 HEMODYNAMIC STABILITY: -SBP >90 and <180 mmHg -can be on minimal vasopressors (how much can depend on the institution) -At UCI: levophed <5 mcg/min, dopamine <5 mcg/kg/min, and dobutamine < 5mcg/kg/min

Readiness Testing Optional Criteria: Hb: ≥7 to10 mg/dL Core temperature: ≤38 to 38.5°C Mental status: awake and alert or easily arousable Patients should be screened daily whether they meet criteria to start weaning ANEMIA: -previously, any degree of anemia was considered a contraindication to weaning because it reduces oxygen carrying capacity. However, only severe anemia is currently contraindicated AFEBRILE: -rationale for this is that fever increases minute ventilation and thus the load on respiratory system MENTAL STATUS: -considered optional because even though awake or easily arousable patient is ideal for weaning, an abnormal mental status (GCS <8 or inability to follow simple commands) does not appear to be associated with higher rate of extubation failure. -as long as patient can protect airway, abnormal mental status does not preclude extubation

Methods of Weaning Spontaneous Breathing Trial (SBT) When patient spontaneously breaths through ETT for a set period of time (30-120 min) Ventilator set to PSV 5 cmH2O and PEEP 5 cmH2O Pressure Support Ventilation (PSV) Progressive decrease in pressure support (2 to 4 mmH2O daily) Alternative to patients who do not tolerate SBTs SBT is the recommended method PSV is an alternative to those who cannot tolerate SBT. Amount of pressure support is set to ensure adequate tidal volume then progressively decreases as patient tolerates.

Weaning Trial Failure If patient develops the following during SBT: Respiratory rate <6 or >35 Heart rate <50 or >120 Systolic BP >180 or <90 Hypoxia not corrected by raising FIO2 (max FIO2 50%) Marked diaphoresis or agitation Deterioration in mental status End SBT and put patient back on prior vent mode Taken from SBT protocol created by UCI. Used by RT as parameters to end SBTs.

Weaning Parameters Predictors: Rapid Shallow Breathing Index (RSBI): RR/Vt < 105 Negative Inspiratory Force (NIF): ≤ -30mmHg H20 Minute ventilation: RR x Vt <10 to 15L/min Spontaneous volume: ≥ 5 ml/kg These parameters are predictors of weaning success or failure RSBI: respiratory rate divided by tidal volume. -Most studied of the weaning parameters -The faster you breathe with small volumes the higher the number NIF: (or MIP – maximal inspiratory pressure) -global assessment of strength of respiratory muscles MINUTE VENTILATION: respiratory rate x tidal volume -estimates demand on the respiratory system. Normal is 5-6L/min in healthy adults. -increased CO2 production from fever, hypermetabolic state, hypoxemia, etc will increase minute ventilation

Extubation Prior to extubation: Confirm minimal FIO2 and PEEP Evaluate upper airway complications Check cuff leak Check that cough and gag are present Have equipment ready NC/facemask/bipap Suction secretions Extubate! AIRWAY PROTECTION: cough strength and mental status AIRWAY PATENCY: -cuff leak is checked to make sure there is no significant airway edema (deflate cuff and measure the difference between inspired and expired tidal volume) Should be at least 110cc

Case 59 year old male is admitted to the ICU and intubated for respiratory failure secondary to aspiration pneumonia Five days later he is hemodynamically stable, no longer on vasopressors, and has O2 sat of 94% on FIO2 of 35% He tolerates PEEP of 5 and PSV of 5 for 90 minutes Weaning parameters shows NIF of -50, RR of 34, and Vt of 200cc

Case What would be the appropriate plan of action? A) Extubate patient B) Place patient back on volume control AC and reassess with next SBT C) Increase sedation to decrease respiratory rate D) Continue the patient on PSV of 5 and PEEP of 5 until he can no longer tolerate it

Case Answer: B Given high respiratory rate and low tidal volume, patient is not ready for extubation. RSBI in this case is 170 which predicts extubation failure. Even though patient is not in marked respiratory distress during the SBT and is able to complete the trial, he should be placed back on an assist- control mode in order to rest his respiratory muscles until the next SBT, which in general is the next day.

Summary Remember that patients must meet clinical criteria in order to start weaning Know your weaning parameters RSBI, NIF, minute ventilation, spontaneous tidal volume Use your judgment and ask yourself if the patient looks ready to be extubated Even in planned extubations, 12-14% of patients fail and require reintubation. Make sure to frequently reassess patients after extubation.