Weaning from the ventilator

Doctor ChadPulmCrit.com

Questions to answer before attempted weaning● What is the cause of the respiratory

failure, and has it been reversed?● Is the patient capable of performing

an SBT?● How will the SBT be performed, and

what is considered passing?● How will the patient be managed

after failing an SBT?● What is the role of tracheostomy?

Requirements to meet before SBT● Minimal vent settings: ie Oxygenation (PaO2 >

60 on FiO2 ≤ 50%, and positive end-expiratory pressure [PEEP] ≤ 8).

● Do not have copious secretions/can manage their own secretions

● pH ≥ 7.25 (metabolic acidosis increases respiratory rate [RR] and places a “load” on the patient).

● Hemodynamic stability (i.e., no active malignant arrhythmias, cardiac ischemia, or critical hypoperfusion).

● Patient is initiating spontaneous breaths.● Presence of cough and gag reflexes

(SBT/weaningparameters can be obtained without this).

RSBI - Rapid shallow breathing indexRSBI= RR/TVThreshold value < 105 bpm is “positive” and indicates a likelihood of weaning success.RSBI sensitivity in multiple trials is about 70–90% in predicting successful liberation.However, false positives are the concern and the positive predictive value is about 80%, and specificity of 11–64% (i.e., those who pass but require reintubation or fail their SBT).

Other measures of successful weaning ● PImax aka negative inspiratory force (NIF) aka

maximum inspiratory pressure (MIP) o Measures pressure generated by patient from

functional residual capacity (FRC), and requires patient effort.

o Poor indicator of success or failure of extubation.

● Minute ventilation (VE): ie TVx RR. Values <10 L/min thought to be an indicator of liberation successo Values >15–20 L/min helped identify those

likely to fail.o Several large trials found this to be a poor

predictor of outcome.● TAKE AWAY: If in doubt, do a SBT!!

HOW IS AN SBT PERFORMED?WHAT IS CONSIDERED “PASSING”?SBT involves one of three methods: CPAP 5 cmH2O; pressure support (PS) of 5 or 7 cmH2O over PEEP; Removing the ventilator and using a T-piece.• Disadvantage of the T-piece method is the lack of respiratory monitoring (ventilator waveforms, VT, alarms). • Monitoring is most important during the initial fewminutes, as this is when most patients fail.• If the patient does not fail (see below) within thefirst few minutes, then a trial of 30–120 minutes isattempted.• If the patient passes an SBT, extubation is successful≥80–90% of the time (assuming that the endotrachealtube [ETT] is no longer needed for other problems)● Cuff leak test

How do you define success in SBT?

How do you define success in SBT?● SpO2 ≥ 85–90% or PaO2 ≥ 50–60● pH ≥ 7.32, increase in PaCO2 ≤ 10● Hemodynamic stability● Not requiring significant

vasopressors● Heart rate (HR) < 120–140 bpm,

change < 20%● SBP < 180–200, but > 90, and no

change > 20%● Breathing patternRR ≤ 30–35 Not

increased by >50%

Subjective measures of success● No mental status changes

(agitation, anxiety, lethargy, or somnolence)

● No visible discomfort● No diaphoresis● No signs of dramatically increased

work of breathing (accessory muscles, abdominal paradox, respiratory alternans)

Recent literature on weaning...● Multicenter, unblinded randomized controlled trial 304 patients to either a BNP or physician-driven strategy of fluid management during weaning of mechanical ventilation weaning.

● Patients included were hemodynamically stable on a PEEP of 8 or less and FiO2 50% or less,

● Control group physicians were blinded to BNP assay results and other treatments were per

usual care with no explicit protocol.

When daily BNP was >/= 200 pg/ml, BNP-guided physicians followed a protocol that

included restricting fluid intake and administering furosemide to meet target urine output

goal. BNP-guided strategy was continued for at least 24 hours post-extubation.

● Authors predefined three subgroups of interest: COPD, LV dysfunction and neither

● Patients in the BNP-guided group received more diuretics and had a more negative fluid

balance during weaning.

● BNP guided therapy resulted in faster time to extubation (statistically significant), faster

removal of non-invasive ventilation (not quite statistically significant) and more ventilator-

free days. This effect was strongest in the group with left ventricular dysfunctionMekontso-Dessap A et al. Natriuretic-peptide driven fluid management during ventilator weaning: a randomized controlled trial. Am J Respir Crit Care Med2012;186(12):1256-63.

What approach should I take to wean?● Two large randomized trials have evaluated the

weaningprocess .

● Majority of patients considered for weaning are already sufficiently recovered so as to be ready for extubation.

● For the minority of patients who fail an SBT, alternate modes were compared (T-piece vs. PS vs. SIMV).

● In one trial, T-piece was found to be best, while in the

other, PS was superior. Both trials found SIMV to delay weaning.● Weaning protocols (nurse or respiratory

therapist-driven) lead to shorter duration of mechanical ventilation.

T-piece

Can’t get my patient of the vent. What about TRACHEOSTOMY?Possible benefits include:● Improved patient comfort● Effective airway suctioning● Decreased airway resistance● More secure airway● Ability for speech, eating● Mobility● More rapid weaning from ventilator

• No data clearly support that tracheostomy reducesrisk of ventilator-associated pneumonia.

Tracman TrialDuncan Young et al. Effect of Early vs Late Tracheostomy Placement on Survival in Patients Receiving Mechanical Ventilation: The TracMan Randomized Trial.

To test whether early vs late tracheostomy would be associated with lower mortality in adult patients requiring mechanical ventilation in critical care units. An open multicentered randomized clinical trial conducted - 909 vented adult patients for less than 4 days and identified by the treating physician as likely to require at least 7 more days of mechanical ventilation. Randomized 1:1 to early tracheostomy (within 4 days) or late tracheostomy (after 10 days if still indicated).

Primary outcome measure was 30-day mortality and the analysis was by intention to treat.

92% of the early-group patients received a tracheostomy, while only 45% in the late group did.

Late group- surviving patients didn’t need a tracheostomy by day 10 because they were

successfully extubated.

No proven difference between groups in 30-day mortality (30.8% early vs. 31.5% late, primary

outcome), nor in any other outcome including 2-year mortality. Patients getting early

tracheostomies required fewer days of sedation, and there was a suggestion of a reduction of -

1.7 ventilator days with early trach (mean 13.6 days vs 15.2 days, p=0.06). However, ICU stays

were exactly equal at a median 13 days. JAMA 2013;309(20):2121-2129.

TAKE AWAY Start SBT trials early once patients meet

criteria (an RT driven protocol works best)

A reintubation rate of 10% is acceptable Diurese if you can - a dry lung is a happy

lung NIFs & MIFs are poor predictors of

successful extubation. Consider only in patients with neuromuscular diseases leading to respiratory failure

Early trachs will reduce ventilator time and sedation needs but ICU LOS is unchanged