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Weill Cornell Medicine — Pediatric Critical Care Medicine

Ventilation Index

All calculations should be independently verified prior to clinical use. These calculators are intended to supplement, not replace, clinical judgment.

Calculate the ventilation index (VI) from respiratory rate, peak inspiratory pressure, PEEP, and PaCO2. VI reflects the ventilatory burden required to achieve a given level of CO2 elimination and is used alongside the oxygenation index to assess ECMO candidacy.

breaths/min
cmH2O
cmH2O
torr

The ventilation index quantifies the overall ventilatory load by combining respiratory rate, the amplitude of pressure swing applied to the airway, and the resulting arterial CO2:

VI = RR × ( PIP − PEEP ) × PaCO2 ÷ 1000

The (PIP − PEEP) term is the driving pressure — the pressure amplitude actually delivered to the lung with each breath. Dividing by 1000 scales the result to a convenient range. Unlike the Oxygenation Index, which assesses the oxygen side of gas exchange, VI assesses the CO2 side: a higher VI indicates that more ventilatory work is being done to achieve (or despite) a given PaCO2.

Clinical severity reference (VI thresholds):

VI Interpretation
< 20 Mild ventilatory impairment
20 – 40 Moderate ventilatory impairment
40 – 60 Severe ventilatory impairment; consider ECMO evaluation
> 60 Critical ventilatory failure; ECMO candidacy threshold used in many paediatric centres (Ortiz et al. 1987)

VI and OI are often used together: an OI > 40 with a VI > 60 provides stronger support for ECMO candidacy than either index alone. Individual centre protocols and patient factors should always guide clinical decision-making.

See also the Oxygenation Index, A-a Gradient, and Alveolar Gas Equation calculators.

References

  1. Ortiz RM, Cilley RE, Bartlett RH. Extracorporeal membrane oxygenation in pediatric respiratory failure. Pediatr Clin North Am. 1987;34(1):39–46.
  2. Trachsel D, McCrindle BW, Nakagawa S, Bohn D. Oxygenation index predicts outcome in children with acute hypoxemic respiratory failure. Am J Respir Crit Care Med. 2005;172(2):206–211.
  3. Bartlett RH. Extracorporeal Life Support: The ELSO Red Book. 5th ed. ELSO; 2017.