Weaning from mechanical ventilation
- 1. WEANING FROM MECHANICAL VENTILATION Moderator – Dr. Arvind Khare Presented by – Dr. Aji Kumar JLN Medical College, Ajmer
- 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.
- 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
- 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.
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