Weaning from mechanical ventilation.pptx

anesthesia

1. Weaning from mechanical ventilation MODERATORS : DR SHAMSHAD BEEGUM DR MOHSINA

2. Weaning from mechanical ventilation is the process of reducing ventilatory support, ultimately resulting in a patient breathing spontaneously and being extubated. This process can be achieved rapidly in 80% of patients when the original cause of the respiratory failure has improved.

3. 3 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 success is defined as absence of ventilatory support 48 hours following the extubation W eaning failure is defined as either the failure of spontaneous breathing trial (SBT) or the need for reintubation within 48 hours following extubation . Patients who fail the SBT exhibit clinical signs: tachypnea , tachycardia, hypertension, hypotension, hypoxemia, acidosis, or arrhythmias. Physical signs of SBT failure may include : agitation, distress, diminished mental status, diaphoresis and increased work of breathing

4. 4 Factors associated with successful weaning ( i ) has the underlying condition improved? (ii) is the patient’s general condition optimal? (iii) have potential airway problems been identified and remedied? (iv) is breathing adequate?

5. I) Has the underlying condition improved? cause of their respiratory failure has to be resolved to a reasonable level. II) General optimization : Patients who are re-intubated in general have worse outcomes. Common causes of weaning failure are: 1. Central drive : reduced by: Sedatives, Direct insults to the respiratory centre Metabolic alkalosis (commonly exacerbated by hypokalaemia ) Loss of hypoxic drive (COPD)

6. 6 2. Neuromuscular : Primary neurological disorders: Guillain–Barre´ syndrome Myasthenia Gravis, Botulism Critical illness polyneuropathy (more common with steroids and neuromuscular blocking agents) Critical cases of myopathy/malnutrition Electrolyte abnormalities : Hypokalaemia, Hypophosphatemia Hypomagnesaemia, Hypocalcaemia, Hypothyroidism 3 . Increased respiratory load: Increased resistance : Bronchospasm, Increased or thick secretions Reduced compliance : Pneumonia, Pulmonary oedema, Pleural effusions, Pneumothorax, Paralytic ileus or abdominal distension Increased ventilation: Hypermetabolism (sepsis is a common cause) Overfeeding, Metabolic acidosis, Shock, Pulmonary embolism

7. 7

8. 8 WEANING CRITERIA

9. 9 PaO2/FIO2: The arterial oxygen tension to inspired oxygen concentration (PaO2/FiO2) or P/F index is a simplified method for estimating the degree of intrapulmonary shunt. QS/QT : The physiologic shunt to total perfusion (QS/QT) ratio is used to estimate how much pulmonary perfusion is wasted. physiologic shunt of 10% or less - normal. Shunt of 10% to 20% - mild physiologic shunt shunt of 20% to 30% - significant physiologic shunt. Greater than 30% - critical / severe shunt

10. III) Airway problems resolved or not the artificial airway needs to be removed. Good upper airway reflexes, including an adequate cough and minimal secretions. An adequate conscious level is required for airway maintenance after extubation . Airway (particularly laryngeal) oedema may be a cause of difficulty in breathing after extubation . risk factors : traumatic or difficult intubation, history of self extubation , overinflated tracheal tube cuff intubation for extended periods. The ability to breathe around a deflated endotracheal tube cuff, or cuff leak >130 ml during volume cycled ventilation - to predict an adequate airway diameter. In those patients at risk, corticosteroids can be used Post- extubation stridor may be ameliorated by epinephrine nebulizers

11. 11 General preconditions for commencement of weaning: Reversal of primary problem causing need for ventilation Patient awake and responsive Good analgesia, ability to cough Reducing or minimal doses of inotropic support Ideally—functioning bowels, absence of abdominal distension Normalizing metabolic status Adequate hemoglobin concentration

12. 12 Minute ventilation <10 liter /min Vital capacity/weight >10 ml /kg Respiratory frequency <35bpm Tidal volume/weight >5ml /kg Maximum inspiratory pressure < 25cmH 2 O Numerical indices used to predict successful weaning

13. 13 IV) Assessing adequacy of breathing : Spontaneous breathing trial is the traditional approach to weaning patients from mechanical ventilation. When patients are considered ready to wean, the best way to assess whether they will breathe on their own is by undertaking an SBT. This involved disconnecting the patient from the ventilator and connecting T-piece. Others include continuous positive airway pressure (CPAP), which may maintain the functional residual capacity, and low level variable pressure support ventilation (PSV) to overcome the resistance to breathing through an endotracheal tube (often called tube compensation). Assessing whether a patient is ready for extubation : SBTs of increasing duration can be used to aid the weaning process and can be performed without disconnecting the patient from the ventilator. Patients successfully completing an SBT may proceed to extubation . Those who fail SBTs may require a slower form of weaning involving SBTs of a gradually increasing duration. Consideration may also be given to the formation of a tracheostomy.

14. 14 RAPID SHALLOW BREATHING INDEX (RSBI) Rapid shallow breathing is quantified as the f (number of breaths per minute) divided by the VT in liters . T his breathing pattern induces inefficient, deadspace ventilation. When the RSBI or f/VT index > 100 breaths/min/L = weaning failure. A bsence of rapid shallow breathing (f/VT ratio <100 breaths/min/L), is an accurate predictor of weaning success

15. 15 The spontaneous breathing trial (SBT) is the major diagnostic test to determine if patients can be successfully extubated and weaned from mechanical ventilation. Low level pressure support (PS), continuous positive airway pressure (CPAP), or automatic tube compensation (ATC) may be used along with SBT to augment a patient’s spontaneous breathing efforts T he patient may be discontinued from full ventilatory support and placed on a spontaneous breathing mode via the ventilator or T-tube (Brigg’s adaptor) for up to 30 minutes. The criteria for passing an SBT : normal respiratory pattern (i.e. absence of rapid shallow breathing), adequate gas exchange, and hemodynamic stability. SPONTANEOUS BREATHING TRIAL (SBT)

16. 16 Patients failing the spontaneous breathing trial The ventilatory choices for these patients include the following: ( i ) T-piece trials (ii) synchronized intermittent mandatory ventilation (SIMV) (iii) pressure support ventilation (PSV).

17. 17 PRESSURE SUPPORT VENTILATION Weaning with PSV is done by starting the pressure support level at 5 to 15 cmH2O and adjusting it gradually (up to 40 cm H2O) until a desired spontaneous VT (10 to 15 mL/kg) is obtained

18. 18 AUTOMATIC TUBE COMPENSATION . Automatic tube compensation (ATC) is a mode in the Evita 4 ventilator (Dräger Medical) that reduces the airflow resistance imposed by artificial airway (endotracheal or tracheostomy tube). It allows the patient to have a breathing pattern as if breathing spontaneously without an artificial airway This type of compensation may facilitate breathing efficacy and reduce the work of breathing throughout the weaning process.

19. 19 SYNCHRONIZED INTERMITTENT MANDATORY VENTILATION (SIMV)

20. 20 WEANING PROTOCOL *Termination criteria: Spontaneous frequency > 35/min for 5 min; SpO 2 < 90%, Heart rate > 140/min or 20% of baseline; Systolic pressure > 180 mmHg or < 90 mm Hg; Signs of anxiety or use of accessory muscles.

21. 21 SIGNS OF WEANING FAILURE Early signs of weaning failure include tachypnea, use of accessory muscles and paradoxical abdominal movements Other indications : dyspnea , chest pain, chest-abdomen asynchrony, diaphoresis, and delirium