Mechanical ventilation
Formal Definition
A form of life support in which a machine (ventilator) delivers breaths to a patient who cannot breathe adequately on their own; modes include assist-control (full breaths set, patient can trigger additional), SIMV (set rate with patient-triggered breaths), and pressure support; settings include tidal volume, respiratory rate, PEEP, and FiO2, adjusted to maintain oxygenation and ventilation while minimizing lung injury.
How It's Used on the Ward
On the vent or mechanically ventilated or intubated and on the ventilator — the patient has a breathing tube connected to a machine that is breathing for them.
Example
"ARDS patient with PaO2 62 on FiO2 70%, PEEP 10: lung-protective strategy: tidal volume 6 mL/kg ideal body weight (IBW: 56kg → 336 mL), RR 24 to maintain minute ventilation, plateau pressure 28 cmH2O (goal <30), FiO2 weaned as PaO2 allows. Daily sedation holiday and SBT readiness assessment."
Clinical Context
Modes: AC (assist-control) — every breath is same size, patient can trigger more; SIMV — set rate + patient-triggered breaths; PSV (pressure support) — patient triggers all breaths at set pressure. Key settings: TV (6 mL/kg IBW for lung protection), RR (15-30), FiO2 (titrate to SpO2 >88-92%), PEEP (recruit alveoli, prevent atelectasis; higher PEEP in severe ARDS per protocol). Complications: VILI (ventilator-induced lung injury — volutrauma, barotrauma, atelectrauma), VAP (ventilator-associated pneumonia), muscle atrophy from prolonged sedation and disuse. Liberation: daily spontaneous breathing trial (SBT) — patient on T-piece or low pressure support for 30 minutes, assess readiness (FiO2 ≤50%, PEEP ≤8, MAP ≥60, no continuous infusions, following commands).