1) The epidemiology of weaning 2) Evidence-based weaning guidelines 3) The pathophysiology of weaning failure 4) Is there a role for different ventilator modes in weaning?

1. Weaning and Discontinuing
Ventilatory Support
Hanaa A. El Gendy
Assistant Professor of Anesthesia
and ICU (ASUH(

2. Learning Objectives:
1(The epidemiology of weaning
2(Evidence-based weaning guidelines
3(The pathophysiology of weaning failure
4(Is there a role for different ventilator modes in weaning?

3. ᵜProcess of gradual withdrawal of mechanical
ventilatory support that transfers the work of breathing
from ventilator to the patient
ᵜThis period may take many forms ranging from abrupt
to gradual withdrawal from ventilatory support
Definition Of Weaning

4. ᵜ75% of mechanically ventilated patients are easy to be
weaned off the ventilator with simple process
ᵜ10-15% patients require use of a weaning protocol over a
period of 24-72 hours
ᵜ5-10% require a gradual weaning over longer time
ᵜ1% of patients become chronically dependent on ventilator
ᵜOut of the total time that a patient spends on ventilator,
40% of the time is spent on weaning process

5. Why Wean
early???
Increased
risk of VAP
Increased ICU
length of stay
Increased hospital
length of stay
Increased morbidity
& mortality
Increased cost
Decreases the
availability of ICU
beds
Can adversely
affect the
patient outcome
Re-intubation is not required in 50% of self-extubations

6. REINTUBATION VAP WEANING
FAILURE
6-8 FOLD
INCREASED RISK

7. HOW DOES LATENT MYOCARDIAL DYSFUNCTION
BECOME MANIFEST DURING WEANING?
PPV  SPONTANEOUS
 MYOCARDIAL O2 CONSUMPTION
- VE INTRATHORACIC PRESS. 
VENOUS RETURN
 LV AFTERLOAD

8. Latent
ischaemia
Manifest
ischaemia
 LV
Compliance
 WOB – Weaning
failure
Decreased lung
compliance
Pulmonary
edema
SBT

9. 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

10. Schematic Representation of the Different Stages Occurring in a
Mechanically Ventilated Patient
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
Martin J. TobinMartin J. Tobin
20012001

11. The Pathophysiology of Weaning Failure

13. Cardiac load
Respiratory load
Neuromuscular
causes
DIFFICULT WEANING
Neuropsychological
causes
Metabolic
AnaemiaNutrition Thorough &
Systematic search for
these
potentially
reversible
pathologies

14. 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.

15. Classification of Patients According to the Weaning Process
Group Definition Frequency
ICU
mortality
Hospital
mortality
(1(Simple
weaning
Patients who proceed from
initiation of weaning to
successful extubation on the
first attempt without
difficulty
69% 5% 12%
(2(Difficult
weaning
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
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

16. Evidence-based weaning guidelines

17. Evidence-based weaning
guidelines
Recommendations from the ACCP/ AARC/ ACCM
1) Pathology of ventilator dependence
2) Assessment of readiness using evaluation
criteria.
3) Assessment during spontaneous breathing.
4) Removal of the artificial airway.
5) SBT failure.

18. Evidence-based weaning
guidelines
6) Maintaining ventilation with SBT failure.
7) Anesthesia and sedation strategies.
8) Weaning protocols.
9) Role of tracheostomy in weaning.
10) Long-term care facilities for patients requiring
prolonged ventilation.
11) Clinician familiarity with long-term care facilities

19. Evidence-based weaning
guidelines
Recommendation 1: Pathology of
ventilator dependence
– If mechanical ventilation >24 hours, search
for all causes that may be contributing to
ventilator dependence.
Recommendation 2:
– Assessment of readiness using evaluation
criteria:

20. Evidence-based weaning
guidelines
Physiological parameters for weaning & extubation
A-Ventilatory performance and muscle strength
– VE 10 to 15 L/min˂
– VT > 4 to 6 mL/kg (IBW)
– F < 35 breaths/ min
– f/VT RSBI < 105 breaths/ min/ L(spontaneously breathing pt)
– Ventilatory pattern synchronous and stable
– Maximal inspiratory pressure (MIP)(NIF) (the maximum
pressure that can be generated against an occluded airway
beginning at functional residual capacity (FRC). up to 20
second ) < -20 to -30 cm H2O Total PEEP-max Paw drop
B- Measurement of drive to breathe P0.1> -2cm H2O

21. RSBI ( Rapid shallow breathing index)
 Index of rapid and shallow breathing f/Vt
 RSBI<105 predicts successful weaning attempts
 The RSBI measurement is performed with minimal
ventilatory support with the patient still intubated and
spontaneously breathing for 1 min
 More accurate predictor of weaning success than any
other parameter studied
 RSBI > 105: 95% extubations failed


22. Evidence-based weaning
guidelines
Measurements of drive to Breath
 Airway occlusion pressure (P0.1 [or P100]).
 P100 is the pressure generated during the first 100
milliseconds of inspiratory effort against an occluded
airway.
 A measurement of the neural output from the
medullary centers, it is effort independent.
 The normal range is 0 to -2 cm H2O.
 The minimum of 4 repeat measurements were required
to obtain valid results

23. C-Estimation of WOB
– Dynamic compliance>25 mL/cm H2O
– VD/VT<0.6 VD/VT = (PaCO2 – PECO2)/PaCO2
D-Measurement of adequacy of oxygenation
– PaO2>60 mmHg (FiO2 <0.5)
– PEEP<5 to 8 cm H2O
– PaO2/FiO2>150 - 250 mmHg.
– PaO2/PAO2>0.35
– P(A-a)O2<350mmHg (FiO2=1)
– Oxygen index = FIO2 x MAP x 100/ PaO2
very good < 5 medium 10 – 20 poor > 25
Evidence-based weaning
guidelines
PAO2 = ( FiO2 * (Patm – PH2O)) – (PaCO2 / RQ)
MAP = (PIP * %IT) + (PEEP * %ET).

24. Recommendation 3:
Assessment during spontaneous breathing
1) Rspiratory pattern.
2) Adequacy of gas exchange.
3) Hemodynamic stability.
4) Subjective comfort. SBT of 30 to 120 minutes.
N.B. Unnecessary prolongation of a failed SBT can result in muscle
fatigue, hemodynamic instability, discomfort or worsening gas
exchange.
Evidence-based weaning guidelines

25. PassingPassing
SBTSBT
Respiratory pattern
Gas exchange
Haemodynamic stability
Subject comfort

26. Tobin. Principles and Practice of Mechanical Ventilation, McGraw-
Hill, 1994, s1192

27. Recommendation 4:
Removal of the artificial airway:
 In most cases, discontinuation of venilatory support
and extubation are a single process.
 This decision is based on assessment of:
- Airway patency.
- Ability to protect the airway.
Ex;upper airway burns or copious secretions & weak
cough)
Evidence-based weaning guidelines

28. Postextubation difficulties:
 Hoarseness, sore throat, and cough.
 ↑ WOB: subglottic edema,,secretions, airway obstruction, laryngospasm.
Postextubation glottic edema can → partial airway obstruction,
causing stridor.
TTT; aerosol oxygen,nebulized epinephrine or budesonide .
The recommended dose is 0.5mL/kg of 1:1,000 up to a maximum dose
of 5 mL
Prior to extubation dexamethasone 0.3- 0.5 mg/kg/dose
Evidence-based weaning
guidelines

29. The cuff leak
The expired tidal volume is measured with the cuff inflated on
Assist Control mode, The cuff is then deflated , four to six
consecutive breaths are used to compute the average value for the
expiratory tidal volume.
The difference in the tidal volumes with the cuff inflated and
deflated is the leak.
A value of < 110 ml (10 -12 % of expiratory tidal volume) gave a
sensitivity of 85% and a specificity of 95% to identify patients with an
increased risk of post extubation stridor.
A low value for cuff leak can also be caused by encrusted
secretions around the tube rather than by a narrowed upper airway

30. Noninvasive positive pressure ventilation
after extubation:
 Transition from invasive ventilation to
spontaneous breathing.
Benefits:
Lowers the mortality rate
Reduces the risk of nosocomial pneumonia.
Evidence-based weaning
guidelines

31. NIPPV:
-Selected patients, esp. hypercapnic respiratory failure
( COPD(
-Should NOTNOT be routinely used as in the event of
extubation failure
-Its use CANNOTCANNOT be recommended for all patients failing
a SBT Keenan et al, 2002 & Esteban et al, 2004Keenan et al, 2002 & Esteban et al, 2004
-Group 2 & 3: NONO firm recommendations

32. Recommendation 5: SBT failure
Any ventilation mode without machine-triggered
breaths
30 minutes is as good as 2 hour
A failed SBT often reflects……….persistent
mechanical abnormalities of the respiratory
system…….a problem not likely to reverse
quickly.
Evidence-based weaning
guidelines

33. Termination of SBTTermination 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

34. Criteria for extubation failureCriteria 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

35. Recommendation 6: Maintaining ventilation with
SBT failure
 Patients who fail in SBT should receive a stable,
nonfatiguing, comfortable form of ventilatory support.
Recommendation 7: Anesthesia and sedation
strategies and protocols
 Anesthesia and sedation strategies and ventilator
management should be aimed at early extubation for
surgical pts.
Recommendation 8: Weaning protocols:
 Protocols for weaning should be developed and
implemented by intensive care units.
Evidence-based weaning
guidelines

36. Weaning ProtocolWeaning Protocol
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(

38. Recommendation 9: Role of tracheostomy in weaning
– Considered when it becomes apparent that pt. needs prolonged ventilation.
Timing: within 7 days or sooner in neurologically impaired patients
Indications:
– Pts.requiring high levels of sedation to tolerate ETs.
– Marginal respiratory mechanics.
– High Raw.
Benefits
– Reduce the risk of muscle fatigue.
– Gain psychological benefit from the ability to eat, talk, and have greater
mobility.
– Less WOB , Vd and better secretion removal.
The most important beneficial outcome of a tracheostomy is
facilitation of the discontinuation of mechanical ventilatory
support.
Evidence-based weaning
guidelines
Percutaneous TracheostomyPercutaneous Tracheostomy::
Cost-effective & Fewer complication; NO diff. in outcomeCost-effective & Fewer complication; NO diff. in outcome
Percutaneous TracheostomyPercutaneous Tracheostomy::
Cost-effective & Fewer complication; NO diff. in outcomeCost-effective & Fewer complication; NO diff. in outcome

39. Recommendation 10: Long-term care facilities for
patients requiring prolonged ventilation:
 Unless evidence of irreversible disease is present (i.e.,
high spinal cord injury, advanced lateral sclerosis),
prolonged M.V. should not be considered permanently
ventilator dependent until 3 months of weaning attempts
have failed.
Recommendation 11: Clinician familiarity with long-
term care facilities
 Failure of weaning attempts in ICU → long-term ventilation
care facilities when Pts. are medically stable.
Evidence-based weaning
guidelines

40. Terminal care forTerminal care for
Ventilator-Dependent PatientsVentilator-Dependent Patients
-Poor Quality of Life & Low survival
rates
-Withdrawal of mechanical
ventilation ?XXX
-Full disclosure of prognostic data
-Routine palliative care or ethics
consultation can improve the quality
of decision making in the acute ICU
setting.

41. Is there a role for different ventilator modes
in weaning?

42. DO NOT WEAN TO EXHAUSTION

43. Weaning modes
Methods of weaning from M.V.:
 Synchronized intermittent mandatory
ventilation (SIMV)
 Pressure support ventilation.
 T-piece weaning.
 Closed loop ventilation.

44. Synchronized Intermittent Mandatory
Ventilation
(SIMV)
Weaning procedure
• Reduce the mandatory rate progressively→1-2
breaths/min at a pace that matches the patient's
improvement.
• Pressure support (PS) ~ 5 to 10cm H2O.
• PEEP: 3 to 5 cm H2O
-Has the worst weaning outcomes in clinical trials
-Its use is not recommended

45. Pressure Support Ventilation
• Patient triggered, pressure limited, flow cycled.
• Pt. control rate, timing, depth of each breath.
Weaning procedure
A. PS INITIAL SETTING:
 1st.method
– Setting pressure level: → a reasonable ventilatory pattern for
the patient. ( 5 to 20 cm H2O)
 2nd. method
– Setting pressure level: → reestablish a patient's baseline
respiratory rate (15 to 25 breaths/min) and VT (300 to
600mL/min).

46. Pressure Support Ventilation
B. WEANING OF PS.:
 PS level ▼ (2cmH2O/ 2-4Hrs.)as long as:
 an appropriate spontaneous respiratory rate and VT are evident
 distress is not evident.
 When PS ≈5 cm H2O, level of PS is sufficient to overcome the work
imposed by the ventilatory system.
PSV: should be favoured
-As a weaning mode after initial failed SBT ((group 2group 2)) Brochard et al. CCMBrochard et al. CCM
19951995
-May be helpful after several failed attempts at SBT ((group 3group 3)) Vittaca etVittaca et
al. AJRCCM 2000al. AJRCCM 2000

47. T-tube weaning
 Patients less likely to tolerate T-piece weaning include:
Severe heart disease, severe muscle weakness,panic
because of psychological problems ,preexisting chronic
lung conditions.

48. Goals of Advanced Modes of
Ventilation
-Limit the duration of invasive ventilation
-Prevent patient ventilator asynchrony
-Be applicable to a wide variety of patients and
automatically adapt to changes in lung and
respiratory mechanics

50. Closed loop ventilation
Idea:
A set variable is compared with a
measured control variable.
The ventilator adjusts some parameters
based on the results of the compared
variables.

58. ADAPTIVE SUPPORT VENTILATION (ASV(
• Patient-centered closed loop that increases or
decreases ventilatory support based on monitored
patient parameters.
• Pressure-limited breaths that target a volume and
rate.
• Monitors pressure, flow, inspiratory and expiratory
time, compliance, resistance to ensure delivery of an
acceptable VE based on practitioner settings.
• Settings: Ideal body weight,PEEP, FiO2, rise time,
flow cycle, and percentage of predicted VE desired.

59. -Height of the patient (based on this, the vent will automatically calculate
ideal body weight and dead space(
-Gender
-%Min Vol: 25-350%
Normal 100%, Asthma 90%, ARDS 120%, Others 110%
-Trigger: flow trigger of 2 L/min
-Expiratory trigger sensitivity: Start with 25% and 40% in COPD
-Tube resistance compensation: Set to 100%
-High pressure alarm limit
-PEEP
-FiO2
ASV vent settings

60. Automatic Tube Compensation
Compensates for the resistance of ETT
Facilitates “ electronic weaning “ i.e pt during ATC mimic
their breathing pattern as if extubated
∆P=RVE
As the flow ↑ / ETT dia ↓, the P support needs to be ↑to ↓WOB
∆P (P support( α (L / r4
( α flow α WOB

61. Pressure drop due to ET tube resistance
Higher circuit pressure
Lower carina pressure
AUTOMATIC TUBE COMPENSATION (ATC(