Weaning and discontinuation

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OBJECTIVES Rationale for weaning Predictors of Weaning success or failure Methods of weaning Weaning failure

WEANING The transition process from total ventilatory support to spontaneous breathing trial.

This period may take many forms ranging from abrupt withdrawal to gradual withdrawal from ventilatory support.


WHEN SHOULD WEANING COMMENCE ? Evaluation of weanability should commence with decision to intubate, ventilate. Patient should be tested for reduced support when it is safe. Physicians must relay on clinical judgement. Consider when the reason for IPPV is stabilized and the patient is improving and haemodynamically stable Daily screening may reduce the duration of MV and ICU cost

Double edged sword !!!! Unnecessary delays in this discontinuation process increase the complication rate from mechanical ventilation (e.g., pneumonia, airway trauma) as well as the cost!! Premature discontinuation carries its own set of problems, including difficulty in re-establishing artificial airways and compromised gas exchange.

Daily screening Resolution/improvement of patients underlying problem Patient able to initiate an inspiratory effort. Normal state of consciousness Absence of fever, temperature < 38C Correction of metabolic and electrolyte disorders Adequate hemoglobin concentration, > 8-10 g/dl

Physiological parameters

Patients receiving MV for respiratory failure should undergo a formal assessment of discontinuation potential if the criteria are satisfied.

Reversal of cause, adequate oxygenation, haemodynamic stability, capability to initiate respiratory effort. The decision must be individualized.

Search for all the causes that may contribute to ventilator dependence in all patients with longer than 24hrs of MV support, particularly who has fail attempts. Reversing all possible causes should be an integral part of discontinuation process.

Predictors of the outcome of weaningPatient parameters Awake, alert and cooperative Haemodynamically stable RR < 30/min No effect of sedation/neuromuscular blockade Minimal secretions Nutritional status goodBurton GG Respir Care 1997, Caruso P 1999 Chest Girault C. 1994 Monaldi Arch Chest Dis, TobinMJ. 1990 Eur Respir J, Yang KL.1991 N Engl J Med

Ventilator parametersSpontaneous TV > 5 - 8 ml/kg , VC > 10 - 15 ml/kg , PEEP requirement < 5 mm of H2OStatic compliance > 30 ml/cm of H2OMV < 10 LVD/VT < 60 %MIP < -30 cm H2ONIFBurton GG Respir Care 1997, Caruso P 1999 Chest Girault C. 1994 Monaldi Arch Chest Dis, TobinMJ. 1990 Eur Respir J, Yang KL.1991 N Engl J Med

Oxygenation criteria PaCO2 < 50 mm of Hg with Normal pH PaO2 > 60 at FiO2 0.4 or less SaO2 > 90 % at FiO2 0.4 or less PaO2/FiO2 > 200 Qs/QT < 20 % P(A-a)O2 < 350 mm of Hg at FiO2 of 1.0

Burton GG Respir Care 1997, Caruso P 1999 Chest Girault C. 1994 Monaldi Arch Chest Dis, TobinMJ. 1990 Eur Respir J, Yang KL.1991 N Engl J MedNone of the variables demonstrate more than modest accuracy in predicting weaning outcome

The removal of the artificial airway from a patient who has successfully been discontinued from ventilatory support should be based on assessment of airway patency and the ability of the patient to protect the airway.

Parameters that assess airway patency and protection

Maximal expiratory pressurePeak expiratory flow rateCough strengthSecretion volume

Suctioning frequencyCuff leak test Neurological function (GCS)

methods of weaning

Spontaneous breathing with t-pieceSIMVNewer ModesPSV


No data available

Most trials have used sudden weaning using Spontaneous breathing trial with T-piece, PSV or CPAP

However if a patient fails recurrent weaning attempts gradual weaning strategy is advocated

Respir Care 2002; 47: 69-90

spontaneous breathing trial Communicate with patient, weaning is about to begin, allow patient to express fear whenever possible Obtain baseline value and monitoring clinical parameters; vital signs, distress, gas exchange, arrhythmia Ensure a calm atmosphere, avoid sedation Fit T-tube with adequate flow, observe for 2 hrs.

Esteban et al compared a 30 min to a 120min T-piece trial

The criteria to assess patient tolerance during SBTs are respiratory pattern, gas exchange, hemodynamics stability and patient comfort. The tolerance of SBTs lasting 30 to 120 minutes should prompt for permanent ventilator discontinuation.

Pressure support protocolEsteban et al compared 2-h trials of unassisted breathing using PS of 7 cm H2O v/s a T-pieceA smaller proportion of patients in the PS group (14%) failed to tolerate the weaning and to achieve extubation at the end of the 2-h trial than in the T-pieceReintubation rates were similar

A superior weaning technique among the threemost popular modes, T-piece, pressure support ventilation, or synchronized intermittent mandatory ventilation cannot be identifiedSIMV may lead to a longer duration of the weaning process than either T-piece or PSVThe most effective mode of ventilation for weaning still needs to be determined and more work is required in this area.

Failed to wean

Patients receiving MV who fail an SBT should have the cause determined. Once causes are corrected, and if the patient still meets the criteria , subsequent SBTs should be performed every 24 hours.

Signs and symptoms of weaning failureRR > 10 breaths/minHR > 20 beats/minSPB > 30 mmHg

Associated with intrinsic lung disease Associated with prolonged critical illness Incidence approximately 20% Increased risk in patient with longer duration of mechanical ventilation Increased risk of complications, mortality

Patients receiving MV for respiratory failure who fail an SBT should receive a stable, non fatiguing, comfortable form of ventilatory support.


Tracheostomy should be considered after period of stabilization on the ventilator when it becomes apparent that the patient will require prolonged MV. Tracheostomy should be performed when the patient appears likely to gain one or more benefits from the procedure

Improved patient comfort More effective airway suctioning Decreased airway resistance Enhanced patient mobility Increased opportunities for articulated speech Ability to eat orally, a more secure airway Accelerated weaning from mechanical ventilation Ability to transfer ventilator-dependent patients from ICU

Unless there is evidence for clearly irreversible disease, a patient requiring prolonged MV should not be considered permanently ventilator-dependent until 3 months of weaning attempts have failed.

SUMMARY The ventilator discontinuation process is a critical component of ICU care. Daily wean screen and subsequent SBT should be done in all patients recovering from respiratory failure. Early extubation with backup ventilation of NIPPV is usefull especially in COPD Role of newer modes unclear require more studies.Managing the patients who fails the SBT - determine the reasons for failure.

REFERENCENeil R. Maclntyre, Mechanical Ventilation: 2nd edition; Chapter 18, Discontinuing Mechanical Ventilation; pg.no. 317-322.Lynelle N. B. Pierce, Management of the mechanically ventilated Patient: 2nd edition; Chapter 11, Weaning from Mechanical Ventilation; pg.no. 378-398.Susan P. Pilbeam, Mechanical Ventilation: 5th edition; Part 7: Discontinuation from Ventilation and Long term Ventilation; pg.no. 402 452