weaning a patient from mechanical ventilation.
A. Assessment for Weaning
1. Arterial blood gases should show adequate ventilation and oxygenation (PCO2, PO2).
2. Bedside pulmonary function.
a. VT >5 ml/kg.
b. VC > 10 mL/kg (2 X VT).
c. f 8-20 breaths per min.
d. minute ventilation <10L/min.
e. MIP/NIF > - 20 cm H2O.
f. MEP > 40 cm HzO.
g. RSBI < 100.
Rapid Shallow Breathing Index = Respiratory Rate /VT (L).
3. Clinicalmeasurements.
a. A-a DO2 < 300 mm Hg.
b. Qs/Qt <20%
c. VD/VT < 60%.
d. Pulse and blood pressure normal.
4. Verify that underlying disease process has been reversed.
B. Decreasing Ventilator Settings
1. lf assessment of the patient indicates that the patient can begin weaning then the first step is to decrease the ventilator settings (f, FrO2,
PEEP).
2. Ventilation can be decreased by using the IMV/SIMV mode and turning down the mandatory rate as the patient can tolerate it.
3. Oxygen therapy is decreased by first decreasing the FrOz setting to a level below 60%.
4. Once the FrOz is below 60%, then PEEP levels are reduced 2 - 5 cm HzO at a time.
5. The lowest settings on the ventilator prior to extubation are as follows:
SIMV/lMV 4 breaths per minute.
FiO2- 0.40.
PEEP-5 cm H2O.
6. Some patients will be able to come off the ventilator quickly depending on how well they respond.
These patients may remain intubated and placed on a heated aerosol with oxygen for a while.
7. ABG should approximate patient's pre-ventilatory blood gases, especially for patients with COPD.
C. Weaning Methods
1. Methods used for weaning:
a. Traditional method/Trial and error/T-piece trial. The patient is taken completely off the ventilator.
b. IMV/SIMV - decreasing the ventilator rate and allowing the patient to breathe spontaneously.
c. Pressure Support Ventilation (PSV) - to support inspiration when the patient is having difficulty with weaning. PSV can be used with
IMV/SIMV.
2. Best to attempt weaning when adequate personnel are available to work with the patient.
3. Drugs that suppress ventilation should be stopped.
4. The patient should be aware of what is happening.
5. Weaning should be done during the day and the patient allowed to rest at night.
D. Assessment of the patient during weaning.
1. Heart and lungs.
a. lf the heart rate increases 20 beats or more from baseline, then stop weaning and resume mechanical ventilation.
b. lf the heart rate increases less than 20 beats, continue weaning and observe closely, may increase the FrOz while off the ventilator.
c. Blood pressure, respirations, V1, VC should be assessed every 20 minutes for any problems.
2. Sensorium.
a. Patient should be alert and responsive.
b. Any change in the mental status or level of consciousness would indicate the need to resume mechanical ventilation.
c. The therapist should observe the patient for anxiety, confusion, combativeness, lethargy, unresponsiveness, or loss of consciousness.
3. Other assessments.
a. An ABG should be drawn after 20 - 30 min off of mechanical ventilation to assess the patient's ventilation and oxygenation status.
b. Continuous observation for signs and/or symptoms of any problems.
c. Auscultation of breath sounds and checking the position / patency of the artificial airway is appropriate.
d. Monitor urine output (40 - 60 ml/hr).
e. Recommend IPPB or SMI to prevent atelectasis.
4. Summary of adverse conditions.
a. Increase in heart rate by > 20 beats/minute.
b. Change in blood pressure by 10 - 20 mm Hg.
c. Increased PaCO2 by > '10 torr.
d. Respiratory rate increases by > 10 or is > 30 b/min.