HOW TO WEAN AND WHEN?

A patient is considered fit for weaning from ventilator when he is conscious responsive and hemodynamically stable and when the pathology which necessitated mechanical ventilation has been resolved adequately.Improved patient outcomes and decreased costs are two benefits of implementing a protocol for early weaning from ventilator.A simplified approach to weaning off ventilator is described below.

1).Criteria to determine whether a patient can be given a trial of spontaneous breathing.
Repiratory criteria:

• PaO2 > 60 mmHg on Fio2 40-50% and peep less than 5-8 cmH2O
• PaCO2 normal or baseline
• Adequate inspiratory effort

Cardiovascular criteria:

• No evidence of myocardial ischemia
• Heart rate less than 140/mt.
• Blood pressure normal without inotrops or minimal inotropic support eg: dopamine <5 mic/kg/mt

Adequate mental status:

• GCS >13 and arousable

Absence of correctable comorbid conditions:

• Afebrile
• No significant electrolyte abnormalities

2) Criteria to determine whether patients can tolerate spontaneous breathing trial

• Tidal volume               5-7 ml/kg                  threshold    >4-6 ml/kg
• Respiratory rate          10-18beats/mt          threshold    <30/mt.
• RR/VT ratio                20-40 /LTR                threshold 100/LTR
• Max insp. pressure     -90to -120 cm H2O     threshold  -15 to -30 cm H2O

The RR/VT ratio or rapid shallow breathing index is a useul predictor. Value above 105/LT, 95% of the attempts are successfull.