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Difficult Weaning
Dr. Hanaa El Gendy
Lecturer Of Anesthesia and Intensive care
Learning Objectives:
1) The epidemiology of weaning problems.
2) The pathophysiology of weaning failure.
3) The usual process of initial weaning from the
ventilator.
4) Is there a role for different ventilator modes in
difficult weaning?
5) How should patients with prolonged weaning failure
be managed?
Definition Of Weaning
-
Gradual reduction of ventilatory support
condition is improving.
from pts. whose
- 80% of patients requiring temporary mechanical ventilation do
not require a slow withdrawal process and can be
disconnected within hours or days of initial support.
- 20 % of all initial weaning attempts in mechanically ventilated
ICU patients failed.
- Prolongation of mechanical ventilation is associated with
weaning failure.
Schematic Representation of the Different Stages Occurring in a
Mechanically Ventilated Patient
Martin J. Tobin
2001
Definition of the different stages, from initiation to mechanical ventilation to weaning
Stages
Definitions
Treatment of ARF
Period of care and resolution of the disorder that caused respiratory failure and
prompted mechanical ventilation
Suspicion
The point at which the clinician suspects the patient may be ready to begin the
weaning process
Assessing readiness to wean
Daily testing of physiological measures of readiness for weaning (NIF, fR/VT) to
determine probability of weaning success
Spontaneous breathing trial
Assessment of the patient’s ability to breathe spontaneously
Extubation
Removal of the endotracheal tube
Reintubation
Replacement of the endotracheal tube for patients who are unable to sustain
spontaneous ventilation
Weaning tends to be delayed
-Exposing the patient to unnecessary discomfort
-Increased risk of complications
-Increasing the cost of care and mortality 12% vs 27% .
Time spent in the weaning process →40–50% of the total
duration of mechanical ventilation
The incidence of unplanned extubation ranges → 0.3–16%.
In most cases (83%), the unplanned extubation is initiated by the
patient, while 17% are accidental
Almost half of patients with self-extubation during the
weaning period do not require reintubation
Definitions of Weaning Success and Failure
Weaning success is defined as
Extubation and the absence of ventilatory support 48 hs following the
extubation.
Weaning in progress: Requirement of NIV after extubation
Weaning failure is defined as one of the following:
1)Failed SBT
2) Reintubation and/or resumption of ventilatory support 48 hs
following successful extubation; or
3) Death within 48 hs following extubation.
Classification of Patients According to the Weaning Process
Group
(1)Simple
weaning
(2) Difficult
weaning
Definition
Patients who proceed from
initiation of weaning to
successful extubation on the
first attempt without
difficulty
Patients who fail initial
weaning and require up to
three SBT or as long as 7
days from the first SBT to
achieve successful weaning
Frequency
ICU
mortality
Hospital
mortality
69%
5%
12%
16%
25%
(3) Prolonged
weaning
Patients who fail at least
three weaning attempts or
require  7 days of weaning
after the first SBT
15%
Boles, et al. Eur Respir J 2007
The Pathophysiology of Weaning Failure
Respiratory load
Cardiac load
Neuropsychological
causes
Neuromuscular
causes
Metabolic
DIFFICULT WEANING
Nutrition
Thorough &
Systematic search for
these
potentially
reversible
pathologies
Anaemia
Common Pathophysiologies which may Impact on the Ability to Wean a
Patient from Mechanical Ventilation
Pathophysiology
Consider
Respiratory load
Increased work of breathing: inappropriate ventilator settings
Reduced compliance: pneumonia (ventilator-acquired); cardiogenic or noncardiogenic oedema; pulmonary fibrosis;
pulmonary haemorrhage; diffuse pulmonary infiltrates
Airway bronchoconstriction
Increased resistive load
During SBT: endotracheal tube
Post-extubation: glottic oedema; increased airway secretions; sputum retention
Cardiac load
Cardiac dysfunction prior to critical illness
Increased cardiac workload leading to myocardial dysfunction; increased metabolic demand; unresolved sepsis
Brain natriuretic peptide (BNP) -elevation is associated with weaning failure
>712 ==> weaning failure
>864 ==> reintubation
transthoracic echocardiography
(TTE) - detects decreased left ventricular ejection fraction during SBT Schifelbain LM et al 2011
Neuromuscular
Depressed central drive: metabolic alkalosis; mechanical ventilation; sedative/hynotic medications
Central ventilatory command: failure of the neuromuscular respiratory system
Peripheral dysfunction: primary causes of neuromuscular weakness; CINMA
Neuropsychological
Delirium 22-80%
Anxiety, depression 30-75 %
Metabolic
Metabolic disturbances
Role of corticosteroids
Hyperglycaemia
Nutrition
Overweight ( body mass index  25 kg/m2)
Malnutrition (body mass index  20 kg/m2) 40 %
Ventilator-induced diaphragm dysfunction
Anaemia
Hb < 8 gm/dl (8-10 gm/dl)
.
Metabolic and
endocrine factors
Role in difficult
weaning needs
further clarification
Hypophosphatemia
Hypomagensemia
Hypokalemia
Hypothyroidism
Hypadrenalism
Muscle
weakness
Corticosteroids
Clycemic control
Difficult weaning
VAP
REINTUBATION
6-8 FOLD
INCREASED
RISK
WEANING
FAILURE
HOW DOES LATENT MYOCARDIAL DYSFUNCTION
BECOME MANIFEST DURING WEANING ?
PPV  SPONTANEOUS
 MYOCARDIAL O2 CONSUMPTION
- VE INTRATHORACIC PRESS. 
VENOUS RETURN
 LV AFTERLOAD
Latent
ischaemia
Manifest
ischaemia
 LV
Compliance
SBT
 WOB – Weaning
failure
Decreased lung
compliance
Pulmonary
edema
CRITICAL ILLNESS OXIDATIVE STRESS
Loss of diaphragm force-generating capacity that is specifically
related to use of controlled mechanical ventilation
Mitochondrial swelling, myofibril damage and increased lipid vacuoles.
Oxidative modifications noted within 6 h
Muscle atrophy
Structural injury
Fibre remodeling
The Usual Process of Initial Weaning from the Ventilator
As EARLY as possible < 72 hs
Underestimate the ability of patients to be successfully weaned
Discontinuation of sedation is a critical step ( dexmetedomedine might
be a good choice)
2 step strategy
Assessment readiness for weaning / extubation
Spontaneous breathing trial (SBT)
Considerations for Assessing Readiness to Wean
Clinical assessment
Adequate cough Absence of excessive thick tracheobronchial secretion
Resolution of disease acute phase for which the patient was intubated
Objective measurements
Clinical stability
Stable cardiovascular status (i.e. fC  140 beats/min, systolic BP 90–160
mmHg, no or minimal vasopressors)
Stable metabolic status Negative fluid balance adequate nutrition
Adequate oxygenation
SaO2  90% on  FIO2 0.4 (or PaO2/FIO2  150 mmHg)
PEEP  5 -8 cmH2O
P(A-a)O2 < 350 on FIO2 = 1.0
SvO2 > 60%
P(a/A)O2 > .35
Oxygen index = FIO2 x MAP x 100/ PaO2
very good < 5
medium 10 – 20
poor > 25
Adequate pulmonary function
fR  34 breaths/min Vd?Vt < 0.6 (0.25-0.4)
NIF  -20– -25 cmH2O
VT  5 mL/kg
CROP weaning index ≥ 13
VC  10 mL/kg
fR/VT 60-105 breaths/min/L Or ≤130→ age > 65
No significant respiratory acidosis
Adequate mentation
No sedation or adequate mentation on sedation (or stable neurologic patient)
RSBI = respiratory frequency (fR) / VT
Predicts successful SBT: sensitivity 0.97 & specificity 0.65
Spontaneous Breathing Trial
T-tube trial
Low levels of pressure support (PS)
6~8 cmH2O in adults, 10 cmH2O in pediatrics
3-14 cmH2O inspiratory pressure is needded to overcome
resistance of endotracheal tube
CPAP
AUTOMATIC TUBE COMPENSATION (ATC)
Designed to reduce work associated with ET resistance
Duration: Esteban et al. AJRCCM, 1999
Patients who fail an SBT do so within first ~20 min
Success rate for an initial SBT is similar for a 30-min
compared with a 120-min trial
Reintubation rate:
Passing SBT  13%; Do not receive SBT  40%
Low levels PEEP:
≤5 cmH2O PEEP during an SBT
COPD More likely to pass 30-min SBT with 5~7.5
cmH2O CPAP Reissmann et al, ICM, 2000
Passing
SBT
Respiratory pattern
Gas exchange
Haemodynamic stability
Subject comfort
Tobin. Principles and Practice of Mechanical Ventilation, McGrawHill, 1994, s1192
Failed SBT
Repeated frequently (daily) SBT
Unnecessary prolongation of a failed SBT can result in muscle fatigue,
hemodynamic instability, discomfort or worsening gas exchange.
Nonfatiguing mode of mechanical ventilation (A/C or PSV) 
ESTEBAN et al. AJRCCM 2000: Weaning method
PS 36%, SIMV 5%, SIMV + PS 28%, intermittent SBT 17% & daily SBT 4%
ESTEBAN et al. JAMA 2002: Weaning trial
Once-daily SBT in 89%: T-tube 52%, CPAP 19%, PS 28%
Termination of SBT
-RR > 30 for 5 min
-SpO2 < 90% for 30 sec
-20% change in HR for > 5 min
-P SYS > 180 or < 90 for 1 min
-Anxiety, agitation or diaphoresis
for 5 min
Extubation:
Neurological status
Although depressed mentation is frequently considered a contra-indication to
extubation, a low reintubation rate (9%) in stable brain-injured patients with a
Glasgow coma score 4 COPLIN et al. 2001
KOH et al. 2005 GCS did NOT predict extubation failure
Excessive secretions
KHAMIEES et al. 2006 Poor cough strength and excessive
secretions were common in patients who failed extubation
following a successful SBT.
Airway obstruction
Positive leak test is adequate before proceeding with extubation.A
successful cuff leak test does not guarantee that post-extubation
difficulties will not arise.
Criteria for extubation failure
-fR >25 breaths/min for 2 h
-HR >140 beats/min or sustained increase or decrease of > 20%
-Clinical signs of respiratory muscle fatigue or increased work of
breathing
-SpO2 < 90%; PaO2 <80 mmHg on FiO2 ≥0.50
-Hypercapnia (PaCO2 > 45 mmHg or ≥ 20% from pre-extubation),
pH < 7.33
Weaning Protocol
Standardising process of weaning
Protocol-directed daily screening of resp. function & SBT
Advantage:
↓ % of patients who required weaning from 80 to 10%
↓ time required for extubation
↓ incidence of self-extubation
↓ incidence of tracheostomy
↓ ICU costs
↓ incidence of VAP and death (Dries et al, 2004)
No increase or even a decrease in incidence of reintubation
Less likely effective
Majority of patients are rapidly extubated
Physicians do not extubate following a successful SBT
When the quality of critical care is already high
Neil et al. Evidence-Based Guidelines for Weaning and Discontinuing Ventilatory
Support. Chest 2001, 120:S375-395
Is there a role for different ventilator modes in
difficult weaning ?
DIFFICULT WEANING-MODE OF VENTILATION
Maintainence of a favourable balance
between respiratory system capacity and
load
Attempt to avoid diaphragm muscle
atrophy
Aid in the weaning process
Pressure support ventilation
Noninvasive ventilation
Continuous positive airway pressure
Automatic tube compensation
Proportional assist ventilation
Servo-controlled ventilation (ASV/Smartcare)
PSV: should be favoured
-As a weaning mode after initial failed SBT (group 2)
Brochard et al. CCM 1995
-May be helpful after several failed attempts at SBT
(group 3) Vittaca et al. AJRCCM 2000
NIV:
-Selected patients, esp. hypercapnic respiratory failure
( COPD)
-Should NOT be routinely used as in the event of
extubation failure
-Its use CANNOT be recommended for all patients failing
a SBT Keenan et al, 2002 & Esteban et al, 2004
-Group 2 & 3: NO firm recommendations
CPAP:
- No clear improvement in outcomes (compared to
T-piece)
-May be effective in preventing hypoxic resp.
failure after major surgery Squadrone et al, 2005
-Group 1: CPAP may be an alternative modes
- Group 2 & 3: NOT been clearly evaluated
ATC:
-As successful as simple T-tube or low-level PS
-Lack of trials in groups 2 and 3
PAV:
NOT been investigated thoroughly in weaning trials
ASV:
2 non-randomised trials & 1 randomised trial:
Post-cardiac surgery patient
Earlier extubation & fewer ventilator adjustments
Reduced need for ABG & high-pressure alarms
ASV was compared with SIMV (the worst mode)
Smartcare
-Maintain a patient in the comfort zone more successfully than
clinician-directed adjustments
-Additional studies needed to evaluate weaning efficacy
Management of patients with prolonged
weaning failure
-31.2% of ICU admissions
-Significant amount of the overall ICU patient-days and 50% of financial
resources
-20% of MICU patients remained dependent on MV after 21 days
VALLVERDU et al 1995 reported that weaning failure occurred in as many
as 61% of COPD patients, in 41% of neurological patients and in 38% of
hypoxaemic patients
Reversible factors?
Neuromuscular and chest wall disorders:
Less likely to be weaned completely but also less mortality
COPD: highest mortality
Tracheostomy
Specialized
weaning units
Home
ventilation
Rehabilitation
Terminal care
30-day mortality rate
Pneumonia
Accidental Extubation
Nolength
Advantage
ICU
of stay
Little evidence to guide optimal timing
Need for better predictors
Timing of Tracheostomy
Outcome
Longer duration of MV & ICU & hospital stay
Engoren et al, 2004: poor survival & functional outcomes
North Carolina Medicare database:
Rate of tracheostomy increased
25% died in hospital
23% discharged to a skilled-nursing facility
35% discharged to rehabilitation or long-term care units
8% discharged home
Long Term Outcome  Study? Study? Study?
Percutaneous Tracheostomy:
Cost-effective & Fewer complication; NO diff. in outcome
Rehabilitation
Spitzer et al, 1992:
62% of difficult-to-wean pts had neuromuscular disease
severe enough to account for ventilator dependency
Lack of studies demonstrating an impact of rehabilitation on the
prevention or reversal of weaning failure or other outcomes.
Efforts to prevent / treat respiratory muscle weakness might
have a role in reducing weaning failure.
Specialized Weaning Units
‘‘Bridge to home’’
Relieve pressure on ICU beds
2 types:
Step-down / respiratory care units in acute care hospitals
Regional weaning centres that serve acute care hospitals
34–60% in SWU can be weaned successfully
Successful weaning can occur up to 3 months after admission
Long-term mortality rate is not adversely affected by transfer
Sucessfully weaned patients in SWU  70% (50~94%) discharged home alive
1-YSR 38–53%  only 5–25% of patients admitted to SWU can be expected to be
ventilator independent and alive at home 1 yr after their initial respiratory failure
Specialized Weaning Units (SWU)
Weaning successful rate:
Post-operative patients (58%)
Acute lung injury (57%)
COPD or neuromuscular disease (22%)
Outcomes of care between SWUs & ICUs: Few studies
SWUs may be cost-effective alternatives to acute ICUs
In difficult-to-wean patients, the use of clearly defined
protocols, independent of the mode used, may result in
better outcomes than uncontrolled clinical practice.
Admission criteria:
Two documented failed weaning trials
Presence of a tracheostomy tube
Clinical stability & potential to benefit from rehabilitation
Minimum operating standards & staff qualifications
Acceptable nurse/patient ratios (1:2)
Requirement for a supervising pulmonary physician
Qualifications of respiratory therapists
Presence of certain specialised staff members (e.g.
nutritionists, psychologists, etc.)
Home Ventilation
Cleveland (OH, USA):
ARDS, cardiothoracic surgery or COPD
9% were discharged home with partial ventilatory support
1% using NIV & 8% requiring partial MV via tracheostomy
Schönhofer et al: COPD
75% discharged home from an SWU
31.5% required home NIV
UK study:
35% required further home ventilation, mostly NIV
Terminal care for
Ventilator-Dependent Patients
-Poor Quality of Life
& Low survival
rates
-Withdrawal of mechanical
ventilation ?
-Full disclosure of prognostic data
-Routine palliative care or ethics
consultation can improve the
quality of decision making in the
acute ICU setting.
Recommendations
Evaluate readiness for weaning early
Be aggressive and search for reversible causes in difficult to wean
patients
DIFFICULT TO WEAN PROTOCOL ‐ Most valuable physicians should
adhere to standardised weaning guidelines.
PSV – Preferred mode in difficult to wean. T‐ piece trials also
appropriate. Do not use SIMV.
NIV – Select subgroups. “Weaning in progress”
Thank You