Mechanical ventilation ventilator variables

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Mechanical ventilation Microchapters


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Ventilator variables

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Syed Hassan A. Kazmi BSc, MD [2]


Ventilator variables modulate the oxygenation achieved. They can be adjusted according to the clinical condition of the patient and to achieve specific goals of management. The variables include fraction of inspired oxygen (FiO2), tidal volume (Vt), respiratory rate (f), positive end expiratory pressure (PEEP), inspiratory time, inspiratory flow rate, peak inspiratory pressure (PIP) and plateau pressure (Pplateau). Tailoring the ventilator settings can help achieve specific goals, for example, to improve oxygenation, option include increasing the FiO2 and PEEP and to improve ventilation, the tidal volume (Vt), inspiratory pressure and respiratory rate (f) may be increased (this follows the basic principle of minute ventilation = Tidal volume x respiratory rate).

Variables variables

The following are the various variables on a ventilator:[1][2][3][4]


  • Fraction of inspired air that is oxygen

Tidal volume (Vt)

  • Volume of breath delivered
  • Target should be lung protective: goal of less than equal to 6 cc/Kg

Repiratory rate (f)

  • Rate is set by ventilator
  • f may be lower than respiratory rate if breaths are patient triggered

Positive end expiratory pressure (PEEP)

Inspiratory time

  • Normally inspiratory to expiratory ratio (I:E) is 1:2
  • Can be used to alter flow rate
  • Used in pressure-control mode

Inspiratory flow rate

Peak inspiratory pressure (PIP)

Plateau pressure (Pplat)

Ventilator variables,


  1. Mejhert M, Linder-Klingsell E, Edner M, Kahan T, Persson H (September 2002). "Ventilatory variables are strong prognostic markers in elderly patients with heart failure". Heart. 88 (3): 239–43. PMC 1767337. PMID 12181213.
  2. Huhle R, Pelosi P, de Abreu MG (March 2016). "Variable ventilation from bench to bedside". Crit Care. 20: 62. doi:10.1186/s13054-016-1216-6. PMC 4791785. PMID 26979175.
  3. Sassoon CS, Gruer SE (February 1995). "Characteristics of the ventilator pressure- and flow-trigger variables". Intensive Care Med. 21 (2): 159–68. PMID 7775698.
  4. Sassoon CS (September 1992). "Mechanical ventilator design and function: the trigger variable". Respir Care. 37 (9): 1056–69. PMID 10145700.

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