Critical Care

Mechanical Ventilation: Principles & Management

Added by Dr. Andrew · Last updated 2024-01-15

Overview

Mechanical ventilation provides respiratory support for patients with respiratory failure. Key goals are to maintain adequate gas exchange while minimizing ventilator-induced lung injury (VILI). Understanding modes, settings, and weaning is essential for every intensivist.

Key Points

1Volume-controlled (VC) vs pressure-controlled (PC) ventilation: VC guarantees tidal volume, PC guarantees pressure
2Key settings: FiO₂, PEEP, tidal volume (6 ml/kg PBW), RR, I:E ratio
3Plateau pressure ≤30 cmH₂O; driving pressure (Pplat − PEEP) <15 cmH₂O
4PEEP: prevents alveolar collapse, improves oxygenation, reduces FiO₂ requirement
5Weaning: daily spontaneous breathing trials (SBT) with T-piece or low PS
6Extubation criteria: SBT passed, GCS adequate, secretions manageable, cough present

Clinical Pearls

Auto-PEEP (intrinsic PEEP) occurs in obstructive disease — detect by end-expiratory hold
Permissive hypercapnia: accept PaCO₂ up to 60–80 if pH >7.20 to allow lung protection
Pressure support ventilation (PSV) is the most common weaning mode
RSBI (f/VT) <105 predicts successful extubation
Ventilator asynchrony worsens outcomes — optimize trigger sensitivity and flow

Board High-Yield

Exam Focus

Driving pressure = Pplat − PEEP; strongest predictor of ARDS mortality
Auto-PEEP in COPD/asthma: decrease RR, increase expiratory time, bronchodilators
RSBI = respiratory rate / tidal volume (L); <105 = likely to extubate successfully
SIMV is inferior to PSV for weaning (Brochard trial)
Daily SAT + SBT bundle reduces ICU LOS and mortality (ABC trial)

Key Articles

Ventilation with Lower Tidal Volumes as Compared with Traditional Tidal Volumes for Acute Lung Injury and the Acute Respiratory Distress Syndrome (ARMA / ARDSNet)

New England Journal of Medicine, 2000

ABIM Exam Weight

15%

Critical Care Medicine represents approximately 15% of the PCCM certification exam.