Skip to Main Content

Table Graphic Jump Location
Favorite Table | Download (.pdf) | Print
Tidal volume (VT)
  • Initially choose 8–10 mL/kg IBW
  • Avoid high volumes to prevent barotrauma
  • VT = ↑ MV and ↓ Paco2 and ↑ pH
  • If ARDS/ALI is present, use 6 mL/kg IBW
Respiratory rate (RR)
  • 12–14 breaths/min usually adequate
  • ↑ RR = ↑ MV and ↓ Paco2 and ↑ pH, but beyond a certain point, dead space ventilation and risk of breath stacking
Fraction of inspired oxygen (FiO2)Start at 1.0 and taper down quickly to achieve a goal Pao2 of >60 mm Hg and O2 saturation of >90%
Inspiratory flow
  • Usually 40–60 L/min
  • ↑ Flow = ↓ inspiratory time and ↑ expiratory time, thus ↓ I:E ratio
  • Useful in obstructive airways disease to decrease auto-PEEP, be careful though about the increase in peak airway pressure
Positive end-expiratory pressure (PEEP)
  • Typically set at 5 cm H2O
  • ↑ PEEP (up to 20–24 cm H2O) = ↑ oxygenation in ALI/ARDS
  • May lead to decreased venous return/hypotension, increased plateau pressure/barotrauma, may increase ICP (in theory)

IBW, ideal body weight; ARDS, acute respiratory distress syndrome; ALI, acute lung injury; I:E ratio, inspiratory to expiratory ratio; ICP, intracranial pressure.


  • Trigger: What signals the ventilator to initiate the inspiration?
    • Time or patient effort (pressure or flow)
  • Target (limit): What limits/governs the airflow during inspiration?
    • Pressure or flow or volume (not time)
  • Termination (cycle): What signals the ventilator to stop the inspiration?
    • Time or pressure or flow or volume


  • Mandatory—The machine triggers and/or cycles the breath
  • Spontaneous—Patient triggered and cycled (the patient determines the VT); may be assisted or unassisted
  • Assisted—The patient triggers the spontaneous breath and the machine does at least some of the work. The airway pressure rises above the baseline pressure (e.g., pressure support ventilation)


Image not available.


  • Volume-cycled ventilation:
    • Controlled mechanical ventilation (CMV)—rarely used nowadays in the ICU
      • Time triggered, preset RR and VT, the patient cannot trigger any extra breaths
      • The patient should be heavily sedated/paralyzed
    • Assist control/volume control (AC/VC)—most common mode

      Time and patient triggered, preset RR and VT. Patients can trigger additional set tidal volumes; they do not necessarily need to be sedated or paralyzed. Beware of hyperventilation and respiratory alkalosis.

    • Intermittent mandatory ventilation (IMV)/synchronized intermittent mandatory ventilation (SIMV)—may also be used as a weaning mode (not routinely used today, may actually prolong the weaning process)

      IMV: time-triggered mandatory breaths, preset RR and VT. In between breaths, the patient can take additional spontaneous assisted breaths with a chosen pressure support (the VT varies with the effort).

      May lead to breath stacking (mandatory breath on top of a spontaneous breath).

      SIMV: similar to IMV, but the mandatory breaths are machine (time) or patient triggered, providing synchrony with the patient's effort and eliminating breath stacking.


  • Flow-cycled ventilation: ...

Want remote access to your institution's subscription?

Sign in to your MyAccess profile while you are actively authenticated on this site via your institution (you will be able to verify this by looking at the top right corner of the screen - if you see your institution's name, you are authenticated). Once logged in to your MyAccess profile, you will be able to access your institution's subscription for 90 days from any location. You must be logged in while authenticated at least once every 90 days to maintain this remote access.


About MyAccess

If your institution subscribes to this resource, and you don't have a MyAccess profile, please contact your library's reference desk for information on how to gain access to this resource from off-campus.

Subscription Options

AccessAnesthesiology Full Site: One-Year Subscription

Connect to the full suite of AccessAnesthesiology content and resources including procedural videos, interactive self-assessment, real-life cases, 20+ textbooks, and more

$995 USD
Buy Now

Pay Per View: Timed Access to all of AccessAnesthesiology

24 Hour Subscription $34.95

Buy Now

48 Hour Subscription $54.95

Buy Now

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.