Weaning from Mechanical Ventilation. Dr Azmin Huda Abdul Rahim

Transcription

1 Weaning from Mechanical Ventilation Dr Azmin Huda Abdul Rahim

2 Content Definition Classification Weaning criteria Weaning methods Criteria for extubation

3 Introduction Weaning comprises 40% of the duration of mechanical ventilation 20% to 30% of patients are difficult to wean from invasive mechanical ventilation. Undue delay leads to excess stay, iatrogenic lung injury, unnecessary sedation, and even higher mortality

4 Stages of Mechanical Ventilation 2 EUROPEAN RESPIRATORY JOURNAL

5 Definition Weaning can be considered once the underlying process necessitating mechanical ventilation is resolving Weaning is the process of liberation from, or discontinuation of mechanical ventilatory support ( weaning per se is not always required, liberation may be a better term!) American Journal of respiratory and Critical care

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7 Classification Simple Weaning ventilator discontinued after the first assessment Difficult Weaning ventilator discontinued from 2 7d after initial assessment Prolonged Weaning ventilator discontinued in >7d after initial assessment RESPIRATORY CARE OCTOBER 2012 VOL 57 NO 10

8 CAUSE OF DIFFICULT WEANING ICU Protocol 2012

9 ICU Protocol 2012

10 ICU Protocol 2012

11 CLINICAL CRITERIA PULMONARY CRITERIA WEANING CRITERIA VENTILATORY CRITERIA PULMONARY RESERVE OXYGENATION CRITERIA

12 Assessment for weaning Clinical Criteria Evidence for some reversal of the underlying cause for respiratory failure Adequate oxygenation and ph Hemodynamic stability The capability to initiate an inspiratory effort 12

13 VENTILATORY CRITERIA PaCO2 Spontaneous Tidal Volume Spontaneous Frequency Minute Ventilation

14 PaCO2 PaCO2 is a reliable indicator for weaning Weaning can be attempted when PaCO2 is less than 50mmhg Patients with COAD, the acceptable PaCO2 may be slightly higher and the ph slightly lower, depending on the patient s baseline normal values prior to mechanical ventilation

15 Spontaneous Frequency The spontaneous frequency should be less than 35/min while the corresponding PaCO2 should be less than 50 mm Hg. A frequency of greater than 35/min is associated with rapid shallow breathing. This breathing pattern increases dead space ventilation and is highly ineffective for gas exchange during spontaneous breathing.

16 Oxygenation Criteria PaO2 and SaO2 PaO2/FIO2

17 Accepted oxygenation weaning criteria include a PaO2 of greater than 60 mm Hg (or SaO2. 90%) on an FIO2 of 0.40 or less.. A PaO2/FIO2 of > mm Hg suggests acceptable physiologic shunt and compatible to successful weaning trial.

18 Pulmonary Reserve Vital Capacity Maximum Inspiratory Pressure P100

19 PULMONARY RESERVE VC measures the maximum amount of lung volume that the patient can exhale following maximal inspiration.

20 Maximum Inspiratory Pressure The maximum inspiratory pressure (also called negative inspiratory force) is the amount of negative pressure that the patient can generate when inspiring against an occluded measuring device The MIP is considered a measure of ventilatory muscle strength, and weaning will likely be successful if the patient can generate an MIP of at least -20 cmh2o

21 P100 or P0.1 The P100 is the most negative pressure that the patient can generate against a closed system during the first one hundred miliseconds of a spontaneous effort. P100 can be used as an indicator of the level of central respiratory drive. Value of less than 2 cm h2o in normal subjects.

22 Pulmonary Measurements Static Compliance Airway Resistance

23 Static Compliance The static lung compliance is measured by dividing the patient s tidal volume by the difference in the plateau pressure and the PEEP. The lower the compliance, the greater the work of breathing. The minimal compliance value consistent with successful weaning is 30 ml/cm H2O or greater.

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25 Airway Resistance The airway resistance can be estimated by dividing the difference in the peak inspiratory pressure and the plateau pressure (H2O) by the constant inspiratory flow (L/sec). The normal range for airway resistance is cm H2O/L/sec and higher for ventilated patients because of the associated pathological conditions (e.g., bronchospasm) and tubing resistance

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28 Therapeutic measures to enhance weaning progress

29 Weaning Methods

30 Spontaneous Breathing Trial SBT can be conducted while the patient connected to a ventilator circuit or Allow breathing through an independent source of oxygen via a T piece. 1. SBT through Ventilator: Use PSV. PS 5-7 cm h20 plus low PEEP(5cmh20) 2. SBT through T-piece- deliver oxygen enriched gas at high flow rates. RESPIRATORY CARE OCTOBER 2012 VOL 57 NO 10

31 Frequency of Tolerating an SBT in Selected Patients and Rate of Permanent Ventilator Discontinuation Following a Successful SBT*

32 ICU Protocol 2012

33 Anaesthesia, Critical Care & Pain Volume 5 Number

34 ICU Protocol 2012

35 Rapid Shallow Breathing Index (RSBI) Failure of weaning may be related to the development of a spontaneous breathing pattern that is rapid (high frequency) and shallow (low tidal volume). Rapid shallow breathing is quantified as the f (number of breaths per minute) divided by the VT in liters. When the RSBI or f/vt index is greater than 100 breaths/min/l, it correlates with weaning failure. RESPIRATORY CARE OCTOBER 2012 VOL 57 NO 10

36 Mechanical Ventilation Rest 24 hrs PaO2/FiO2 200 mm Hg PEEP 5 cm H2O Intact airway reflexes No need for continuous infusions of vasopressors or inotrops RSBI > 100 Stable Support Strategy Assisted/PSV 24 hours <100 Daily SBT min Low level CPAP (5 cm H2O), Low levels of pressure support (5 to 7 cm H2O) T-piece breathing Yes RR > 35/min Spo2 < 90% HR > 140/min Sustained 20% increase in HR SBP > 180 mm Hg, DBP > 90 mm Hg Anxiety Diaphoresis No Extubation

37 Weaning Failure Weaning failure is defined as the failure to pass a spontaneousbreathing trial or the need for reintubation within 48 hours following extubation. Predicting success is important to reduce rates of reintubation. RESPIRATORY CARE OCTOBER 2012 VOL 57 NO 10

38 Anaesthesia, Critical Care & Pain Volume 5 Number

39 Weaning failure Reintubation is associated with a 7-11x increase in hospital mortality. Reintubation rates of 5% to 20% are acceptable for most well-run ICUs (a target of 0% is unrealistic and would lead to prolonged ventilation) RESPIRATORY CARE OCTOBER 2012 VOL 57 NO

40 A-Airway/Lung compliance B- Brain Dysfunction C- Cardiovascular D-Drugs/diaphragm E-Electrolytes/endocrine

41 SBT Failure Correct reversible causes for failure adequacy of pain control the appropriateness of sedation fluid status bronchodilator needs the control of myocardial ischemia, and the presence of other disease processes Subsequent SBTs should be performed every 24 H RESPIRATORY CARE OCTOBER 2012 VOL 57 NO

42 SBT failure Left Heart Failure: Increased metabolic demands Increases in venous return and pulmonary edema Appropriate management of cardiovascular status is necessary before weaning will be successful RESPIRATORY CARE OCTOBER 2012 VOL 57 NO

43 Extubation Criteria Ability to protect upper airway Effective cough Alertness

44 Improving clinical condition Adequate lumen of trachea and larynx Leak test to identify patients who are at risk for postextubation stridor RESPIRATORY CARE OCTOBER 2012 VOL 57 NO

45 Cuff Leak Test in MV Set a tidal Volume ml/kg Measure the expired tidal volume Deflated the cuff Remeasure expired tidal volume (average of 4-6 breaths) RESPIRATORY CARE OCTOBER 2012 VOL 57 NO

46 The difference in the tidal volumes with the cuff inflated and deflated is the leak A value of 130ml 85% sensitivity 95% specificity RESPIRATORY CARE OCTOBER 2012 VOL 57 NO

47 Cough / Leak test in spontaneous breathing Tracheal cuff is deflated and monitored for the first 30 seconds for cough. Only cough associated with respiratory gurgling (heard without a stethoscope and related to secretions) is taken into account. RESPIRATORY CARE OCTOBER 2012 VOL 57 NO

48 The risk of post extubation upper airway obstruction increases with the duration of mechanical ventilation female gender trauma repeated or traumatic intubation RESPIRATORY CARE OCTOBER 2012 VOL 57 NO

49 Weaning a tracheostomised patient ICU Protocol 2012

50 Conclusion Weaning is an essential component in mechanical ventilation. Patients receiving ventilatory support should be assessed on a daily basis for their suitability for weaning. Consider weaning if, the gas exchange is adequate with low PEEP/FIO2 requirements,hemodynamics are stable without a need for pressors, and capable to initiate spontaneous breaths Resolve causes of weaning failure to avoid prolonged ventilation.

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