Ventilator Weaning

1. Pathophysiology
   1. Ventilated for less than 2 weeks
      1. Respiratory muscles do not decondition significantly
      2. Exceptions
         1. Comorbid condition or
         2. Severe increased VO2 with negative nitrogen balance
   2. Majority of patients do not need Ventilator Weaning
      1. Either need the Ventilator or they do not
2. Indications for weaning
   1. Prolonged debilitated state, deconditioning or weakness
   2. Chronic Obstructive Pulmonary Disease
   3. Severe Congestive Heart Failure
   4. Catabolic State
      1. Results from high dose Corticosteroids
      2. Results in weak chest muscles
3. Preparation for weaning: Nutritional Status
   1. Early nutritionist consultation
   2. Low Carbohydrate Diet if increased VCo2
   3. Avoid negative nitrogen balance
   4. Use a working GI Tract to provide early nutrition
      1. Place Dobbhoff NG tube (check placement with XRay)
      2. Select a supplement (e.g. FS Pulmocare)
      3. Measure q4 hour Residual Volumes
         1. Consider prokinetic agent for >50 cc residuals
            1. Metoclopramide (Reglan) 10 mg PO qid
            2. Erythromycin 250 to 500 mg PO qid
4. Preparation for weaning: Pulmonary Status
   1. Maximize bronchodilation if bronchospasm
      1. Consider Inhaled Corticosteroids over systemic
   2. Avoid Respiratory Acidosis
      1. Adjust pCO2 to premorbid level
5. Preparation for weaning: Psychosocial Status
   1. Alleviate anxiety
   2. Reassure of support
   3. Encourage optimism. and discourage discouragement
   4. Try not to convey frustration
6. Preparation for weaning: Cardiac Status
   1. Coronary Artery Disease
      1. Consider Anti-Anginal medications (Nitroglycerin)
      2. Check Electrocardiogram
         1. Baseline
         2. After a failed weaning trial
   2. Congestive Heart Failure
      1. Maximize volume status
      2. Reduce Afterload
      3. Use inotropic agents as needed (Dopamine, Dobutamine)
7. Concept of Respiratory Muscle training
   1. Methods
      1. IMV
      2. Pressure Support (favored by some pulmonologists)
      3. T-Tube trials
      4. CPAP
   2. Principles
      1. Give respiratory muscles a nightly rest
         1. "Marathon runners do not train around the clock"
         2. Full Ventilatory support at night
         3. Maximize sleep at night
            1. Give sedative at bedtime (e.g. Ativan, Ambien)
            2. Sleep orders: do not disturb, lights out
      2. Use Daily standard screening assessment tool
         1. Completed by Respiratory Therapist
         2. Reduces intubation time (4.5 versus 6 days)
         3. Fewer complications (20% versus 41%)
         4. Reference
            1. Ely (1996) N Engl J Med 335:1864-9
8. Extubation Criteria
   1. Are weaning parameters in an acceptable range?
      1. Respiratory Rate
      2. Blood Pressure
      3. Pulse
      4. Ventilator Parameters: Ve, Vc Vt
   2. Are secretions controlled?
   3. Can the patient protect their airway?
   4. Is cough reflex adequate?
   5. Is the patient alert?
9. Extubation Technique
   1. Patient is placed in reverse Trendelenburg
      1. Head up
      2. Legs up
   2. Monitoring prior to extubation
      1. Vital Signs
      2. Arterial Blood Gas
10. Post extubation support
    1. Pressure Support from 0800 - 2230
       1. PEEP: 5,
       2. Pressure support: begin at 15 and wean
       3. Weaning parameters
          1. Respiratory Rate <30
          2. Tidal Volume > 250 cc
          3. Patient comfortable
          4. Arterial Blood Gas when Pressure Support 3 for 1h
    2. AC from 2230-0800
       1. PEEP: 5
       2. AC: 12
       3. Maximize sleep and respiratory rest as above
    3. Intermittent Rest throughout the day as needed
       1. PEEP: 5
       2. AC: 12
11. Reference
    1. Mickman (1995) Lecture, Fairview-Riverside, Minneapolis