Weaning from mechanical ventilation is a critical process involving the gradual withdrawal of mechanical support as patients regain spontaneous breathing capability after recovering from their acute condition. Successful weaning necessitates careful evaluation of clinical, ventilatory, and oxygenation criteria, with various modes and trials employed to assess readiness for extubation. Challenges such as weaning failure can arise due to respiratory muscle fatigue or increased airflow resistance, and ethical considerations are pivotal in cases of terminal weaning.

1. WEANING FROM
MECHANICAL VENTILATION
Presenter : Dr. Md. Majidul Islam
Phase-B Resident, CVTS
National Institute of Cardiovascular
Diseases (NICVD)

2. • Weaning is the process of withdrawing
mechanical ventilatory support and
transferring the work of breathing from
the ventilator to the patient.

3. • Before weaning, the patient should have recovered from
the acute phase of the disease leading to mechanical
ventilation and be able to assume adequate spontaneous
breathing.
• Weaning is gradually started after evaluating the patient’s
clinical condition, pulmonary and cardiovascular status.
• Depending upon these parameters patient may be given
spontaneous breathing trials on air and extubated.
• If SBT unsuccessful patient is taken back on partial
ventilatory support or pressure support and gradually the
settings reduced and SBT repeated.

4. VENTILATORY MODES USED FOR WEANING
• Conventional Modes used –
 Pressure support ventilation
 Continuous positive airway pressure
 Synchronised Intermittent Mandatory Ventilation
• Advanced Modes used –
 Volume support
 Volume-assured pressure support
 Mandatory minute ventilation
 Airway pressure-release ventilation
 Automatic tube compensation

5. Weaning criteria
• Weaning criteria are used to evaluate the
readiness of a patient for a weaning trial and
the likelihood of weaning success.
Clinical criteria
Ventilatory criteria
Oxygenation criteria
Pulmonary reserve and measurements

6. Clinical criteria
• Resolution of acute phase of disease
• Adequate cough
• Absence of excessive secretions
• Cardiovascular and hemodynamic stability

7. Ventilatory criteria
f= Frequency of breaths , VT = Tidal Volume

8. Oxygenation criteria
Qs/Qt = intrapulmonary shunt , P(A-a)O2= alv. art. O2 tension gradient

9. Pulmonary Reserve & Measurements

10. Weaning Procedure
• Weaning can be done using : –
Spontaneous breathing trials
Pressure support Ventilation
Synchronised Mandatory Intermittent
Ventilation (SIMV)– Not Recommended alone

11. Weaning Procedure
• Spontaneous breathing trial (SBT): An evaluation of a
patient’s readiness for weaning from mechanical
ventilation and extubation.
• SBT is the major diagnostic test to determine if patients
can be successfully extubated and weaned from
mechanical ventilation.
• Spontaneous breathing may be augmented with low-
level (≤ 8 cm H2O) of pressure support, CPAP, or
automatic tube compensation (ATC).
• SBT may last up to 30 minutes.

12. SBT Steps

13. SBT Failure

14. Rapid shallow breathing index (RSBI):
RSBI is used to evaluate the spontaneous breathing pattern
Rapid shallow breathing index (RSBI): The RSBI (f/VT index) is calculated by dividing the
spontaneous breathing frequency (breaths/min) by the average spontaneous VT (L).
Absence of rapid shallow breathing, as defined by an f/VT ratio of less than 100
breaths/ min/L, is an accurate predictor of weaning success.

15. • When the RSBI or f/VT index is greater than
100 breaths/min/L, it correlates with weaning
failure.
• On the other hand, absence of rapid shallow
breathing (f/VT ratio ,100 breaths/min/L), is
an accurate predictor of weaning success.

16. Weaning using PSV

17. Weaning using SIMV
Based on the results of the sixth International Consensus Conference on Intensive Care
Medicine, synchronized intermittent mandatory ventilation (SIMV) should be avoided as a
stand-alone weaning modality (Boles et al., 2007). However, SIMV remains an effective tool
in providing partial ventilatory support during continuous mechanical ventilation.

18. Termination criteria: Spontaneous frequency >35/min for 5 min; SpO2 <90%;Heart rate >140/min or 120%
of baseline; Systolic pressure >180 mmHg or <90 mm Hg; Signs of anxiety or use of accessory muscles.

19. • Weaning success is defined as absence of ventilatory
support 48 hours following the extubation.
• Weaning in progress is an intermediate category
(between weaning success and weaning failure) for
patients who are extubated but continue to receive
ventilatory support by noninvasive ventilation (NIV).
• Weaning failure- Failure of spontaneous breathing
trial (SBT) or the need for reintubation within 48
hours following extubation.

20. Weaning Failure
Early signs of weaning failure include: tachypnea, use of accessory muscles and
paradoxical abdominal movements, dyspnea, chest pain, chest-abdomen asynchrony
and diaphoresis.

22. Causes of Weaning Failure
• Weaning failure is generally related to
(1) increase of airflow resistance
(2) decrease of compliance
(3) respiratory muscle fatigue.

23. Increase of Airflow Resistance
• Normal subjects using an endotracheal (ET) tube have an
increase of 54% to 240% in the work of breathing,
depending on the size of the ET tube and ventilator flow
rate.
• An 8-mm ET tube has a cross-sectional area of 50 mm2,
which is slightly smaller than adult glottis (66 mm2), the
narrowest part of the airway .
• To minimize this ET tubes of larger size should be used
when it is appropriate to the patient’s size & the ET tube
may be cut to about an inch from the patient’s lips.

24. • Other strategies for decreasing airway resistance
Periodic monitoring of the ET tube for kinking or
obstructions by secretions, or other devices attached
to the ET tube such as a continuous suction catheter,
heat and moisture exchanger, or end-tidal CO2
monitor probe.
Endotracheal suctioning to remove retained
secretions and use of bronchodilators to relieve
bronchospasm

25. Decrease of compliance

26. Respiratory Muscle Fatigue
Causes are :
o Low lung or thoracic compliance , increased airway resistance
o Muscle disuse may lead to respiratory muscle dysfunction and
diaphragmatic atrophy.
o Mechanical ventilation-induced oxidative stress  ventilator
induced proteolysis and contractile dysfunction.
o Inadequate oxygen delivery (low O2 content or cardiac output),
o Insufficient nutrition
o Electrolyte imbalance, especially hypokalemia, hypophosphatemia,
hypocalcemia, and hypomagnesemia.
• Retraining of atrophied muscles may be accomplished by short
T-tube trials that improve respiratory muscle strength. Pressure
support ventilation may also be tried as it increases diaphragmatic
endurance .

27. Terminal Weaning
• Terminal weaning is defined as withdrawal of mechanical ventilation that
results in the death of a patient who is terminally ill or brain dead.
• Different from “EUTHANASIA” or mercy killing as disease is allowed to take its
natural course to death.
• Ethical and moral concerns and legal issues arise before ending mechanical
ventilatory support.
• Only done after detailed discussion with family members and taking their
consent and patient’s consent (conscious patients)when medical intervention
is futile or hopeless in treating the illness.
• In India, terminal weaning only legalised in brain dead or patient in persistent
vegetative state . (On 7 March 2011 Supreme court of India made this decision
as part of verdict in case of Aruna Shanbaug as rarest of rare cases).
• As still there is no clear legislation , such a move requires the permission of
High Court.

28. THANK YOU