Mechanical Ventilation in the ICU

Initial Ventilator Mode Selection

The American Thoracic Society recommends starting with volume-cycled assist-control (AC) ventilation set to deliver 6 mL/kg predicted body weight with a plateau pressure limit of ≤30 cmH₂O, as this provides complete ventilatory support while minimizing ventilator-induced lung injury 1
Volume control (VC) mode should be the default initial setting when starting mechanical ventilation in the ICU, as it guarantees a set number of mandatory breaths per minute while allowing patient-triggered breaths, all delivering the same preset tidal volume 1
VC mode is particularly advantageous because it ensures consistent alveolar ventilation even when lung compliance or airway resistance changes, which is critical in the acute phase of respiratory failure 2

Calculate tidal volume using predicted body weight (PBW), NOT actual body weight: Men = 50 + 2.3 × (height in inches - 60); Women = 45.5 + 2.3 × (height in inches - 60) 1
Set initial tidal volume at 6 mL/kg PBW to reduce mortality in ARDS and sepsis-induced respiratory failure—this represents a strong recommendation with high-quality evidence 1, 3
Avoid exceeding 8-10 mL/kg PBW under any circumstances, as higher volumes increase mortality risk 1, 3

Maintain plateau pressure (Pplat) ≤30 cmH₂O in obstructive airway disease and most conditions to prevent alveolar overdistension and ventilator-induced lung injury 1, 3, 4
Monitor plateau pressure by performing an inspiratory hold maneuver (0.5-1 second pause at end-inspiration) to measure static pressure 4, 5

Set respiratory rate at 10-15 breaths/min for adults with obstructive disease to allow adequate expiratory time and prevent air trapping 4, 6
Adjust inspiratory-to-expiratory (I:E) ratio to 1:2 or 1:3 in obstructive disease to prolong expiratory time and limit gas trapping 4, 7

Start with PEEP of 3-5 cmH₂O in patients without lung injury as a physiologic baseline 3
Avoid setting PEEP levels that exceed intrinsic PEEP (iPEEP) in obstructive disease, as this may worsen hyperinflation 4

Volume control is preferred initially because it compensates for air leaks and ensures consistent tidal volume delivery despite changes in compliance or resistance 2, 8
In obese patients, volume control is associated with lower peak airway pressures and less dead space ventilation compared to pressure control 7

Maintain strict adherence to 6 mL/kg PBW and Pplat ≤30 cmH₂O regardless of gas exchange—this is a strong recommendation that reduces mortality 1, 5
Accept permissive hypercapnia with pH as low as 7.2 if necessary to maintain pressure limits 4

Use lower respiratory rates (10-15/min) and longer expiratory times to prevent dynamic hyperinflation 4
Avoid attempting to normalize PaCO₂ rapidly—higher target PaCO₂ levels are acceptable based on pre-morbid bicarbonate levels 4

Continuously monitor delivered tidal volume, plateau pressure, and auto-PEEP throughout mechanical ventilation 3, 4
Perform regular inspiratory hold maneuvers to measure plateau pressure, especially after any ventilator adjustments 4, 5
Adjust FiO₂ to maintain SpO₂ 88-94% in most patients (except asthma, where >96% is recommended) 4, 7