Choosing a mode

• Controlled- patients who aren't generating breaths. PC, VC. Most common mode at initiation of MV.

• SIMV- patient generating some breaths, but still needs significant mechanical support.

• Spontaneous- not frequently used at initiation, but can be used for patients with airway obstruction and preserved lung function.

How to set initial parameters

• TV (6-8 mL/ kg predicted body weight) [lung protective ventilation]

• RR 10-14

• FiO2 often start at 100%, but quickly weaned unless severely hypoxic

• Inspiratory:expiratory ratio typically 1:2

• Flow- typically set @ 60L/min, can increase if the patient is in distress or has a high minute ventilation

How to adjust parameters based on arterial blood gas results

• Low PaO2 (low arterial oxygen content)- increase FiO2, increase mean airway pressure

• Markedly elevated PaO2 (hyperoxia)- decrease FiO2

• Low PaCO2 (low arterial carbon dioxide concentration)- decrease TV or RR

• High PaCO2 (high arterial carbon dioxide concentration)- increase TV or RR

*For more details, check out these resources: 

Lectures: Critical Care: Respiratory Failure

Lectures: Critical Care: Vents

Other principles of mechanical ventilation

• VAP bundle- elevated head of bed, oral care

• Daily awakening and spontaneous breathing trials