weaning and discontinuation

WEANING AND DISCONTINUATIO

N Presented byAnn Mary Jose,

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.

CATEGORIES• First SBT trial successful, extubation successful.

SIMPLE WEANING

• Fails first SBT, requires upto 3 SBTs before successful (7 days or less from 1st SBT to successful SBT)

DIFFICULT WEANING

• Fails atleast 3 SBTs or requires > 7 days from 1st SBT to successful SBT

PROLONGED WEANING

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 patient’s 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

Ventilatory performance and muscle strength

VC > 15mL/kg

VE < 10 to 15 l/min

VT > 4 to 6 ml/kg

f < 35 breaths per minf/VT < 60 to105 breaths/min/L

PImax < -20 to -30 cm H2O

Measure of drive to breath

P0.1 > -6cm H20

Measure and estimation of WOB

WOB < 8J/L

Cdyn > 25mL/cm H2O

VD/VT < 0.6

CROP index > 13 mL/breaths/min

Measurement of adequacy of oxygenationPaO2 > 60 mm Hg

PEEP < 5 to 8 cm H2OPaO2/FiO2 > 250 mm

HgPaO2/PAO2 > 0.47

P(A-a)O2 < 350 mm Hg

%QS/QT < 20% to 30%

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 WEANING

Patient parameters Awake, alert and cooperative Haemodynamically stable RR < 30/min No effect of sedation/neuromuscular blockade Minimal secretions Nutritional status good

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 Med

Ventilator parameters Spontaneous TV > 5 - 8 ml/kg , VC > 10 - 15 ml/kg , PEEP requirement < 5 mm of H2O

Static compliance > 30 ml/cm of H2O MV < 10 L VD/VT < 60 %

MIP < -30 cm H2O NIF

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 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 1.0Burton 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

None 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

1. Maximal expiratory pressure

2. Peak expiratory flow rate

3. Cough strength

4. Secretion volume

5. Suctioning frequency

6. Cuff leak test

7. Neurological function (GCS)

METHODS OF WEANING

Spontaneous

breathing with t-

piece

SIMV

Newer Modes

PSV

GRADUAL V/S SUDDEN

WEANING ??? 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

No reported difference in the rate of re-intubation

between groups.

Patients who were randomized to the

shorter T-piece trial benefited from

statistically significant reductions in ICU and

hospital lengths of stay (2 days and 5 days

shorter, respectively)

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 PROTOCOL

Esteban 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 identified

SIMV may lead to a longer duration of the weaning process than either T-piece or PSV

The 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.

Early detection

Record vs. physical

exam

Obtain an ABG if

possible

Put back previous settings

Identify causes

SIGNS AND SYMPTOMS OF WEANING FAILURE

Subjective Indices

• Agitation and anxiety• Diaphoresis • Cyanosis • Accessory muscle use• Facial sign of distress• Dyspnea

Objective Measurements• PaO2 ≤50-60 mmHg on FiO2 ≥ 0.5

• SaO2 < 90%• PaCO2 > 50mm Hg• pH < 7.3• f/Vt > 105 breaths/min/L• RR > 35bpm• SBP ≥ 180mmHg or increase of

≥ 20%• SBP < 90mmHg• Cardiac arrhythmias

RR > 10 breaths/min

HR > 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.

Rest 24 hours

Correct the causes

Retry weaning

Retry with gradual modes

Tracheostomy long term ventilation

ROLE OF TRACHEOSTOMY

Click icon to add picture

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.

REFERENCE1. Neil R. Maclntyre, Mechanical Ventilation: 2nd edition; Chapter 18,

Discontinuing Mechanical Ventilation; pg.no. 317-322.

2. Lynelle N. B. Pierce, Management of the mechanically ventilated Patient: 2nd edition; Chapter 11, Weaning from Mechanical Ventilation; pg.no. 378-398.

3. Susan P. Pilbeam, Mechanical Ventilation: 5th edition; Part 7: Discontinuation from Ventilation and Long term Ventilation; pg.no. 402 – 452

THANK YOU