Mechanical Ventilation Basics And Ventilator Modes
Indications ...

Mechanical Ventilation Basics And Ventilator Modes

Indications for Intubation:

 • Failure of NIPPV: No clinical improvement (Intensive Care Med 2001;27:1718)

 • Cannot ventilate: PaCO2 >60 with severe acidemia (COPD or other obstruction, sedation, NM disease, respiratory muscle fatigue, trauma)

 • Cannot oxygenate: Worsening P:F ratio (PNA, pulmonary edema, ARDS, PE)

 • Airway protection/instability: Unconsciousness, AMS, shock, facial/head trauma, nausea/vomiting/UGIB, severe secretions, severe bronchospasm/anaphylaxis

 • Persistent increased work of breathing: Severe bronchospasm, airway obstruction, inability to compensate for severe acidemia

 • Hemodynamic instability: unstable arrhythmia, HoTN

Ventilator Modes:

AC/VC - Assist Control/Volume Control

 • Delivers a breath until set tidal volume is reached

 • Pros: ↑control over ventilation (fixed VT prevents barotrauma or atelectrauma, e.g., ARDSNet)

 • Cons: fixed inspiratory flow regardless of effort, ↑ pt-vent dyssynchrony

AC/PC - Assist Control/Pressure Control

 • Delivers a breath until set pressure is reached

 • Pros: variable flow (and variable VT) during inspiration to satisfy patient demand, ↓ dyssynchrony

 • Cons: can cause volutrauma as compliance or pt effort changes

PSV - Pressure Support Ventilation

 • Delivers a set pressure triggered by patient’s spontaneous breathing

 • Pros: better tolerated, less sedation required, used as trial setting prior to extubation (i.e. SBT of 0/0)

 • Cons: less control over respiratory parameters, volutrauma possible, no fixed RR (only backup rate)

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