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Ventilator Parameters Calculator

OI, OSI, MAP, HFOV

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1 What is the Ventilator Parameters Calculator?

The Ventilator Parameters Calculator is a multi-tab NICU tool covering conventional ventilation, high-frequency oscillatory ventilation (HFOV), and non-invasive CPAP support. It calculates oxygenation indices used to grade the severity of hypoxaemic respiratory failure and to help decide when to escalate or de-escalate respiratory support. The tool covers Mean Airway Pressure (MAP), the Oxygenation Index (OI) and Oxygen Saturation Index (OSI), HFOV-specific DCO2 (CO2 diffusion) calculations, and CPAP/high-flow weaning indices (SOPI, S/F ratio, ROX index).

2 When to use it

  • Grading severity of hypoxaemic respiratory failure in a ventilated neonate via the Oxygenation Index (OI), or the non-invasive Oxygen Saturation Index (OSI) when an arterial line is unavailable
  • Calculating Mean Airway Pressure (MAP) from ventilator settings (PIP, PEEP, inspiratory time, rate) to feed into OI/OSI
  • Setting and adjusting HFOV parameters (frequency, MAP, tidal volume) and tracking CO2 elimination via DCO2
  • Deciding whether to escalate to HFOV, inhaled nitric oxide, or ECMO referral based on OI severity banding
  • Assessing readiness to wean CPAP or high-flow support using SOPI, the S/F ratio, or the ROX index

3 Formula & method

OI = (MAP x FiO2%) / PaO2, or equivalently OI = (MAP x FiO2 x 100) / PaO2 when FiO2 is entered as a decimal — both give identical results. OSI substitutes SpO2 for PaO2: OSI = (MAP x FiO2%) / SpO2, with an approximate correlation of OI ~ (2.3 x OSI) - 4. MAP = [K x (PIP - PEEP) x (Ti/Ttotal)] + PEEP, where K is a waveform constant (Square 1.0, Sine 0.64, Triangular 0.5). In HFOV mode, DCO2 = VThf^2 x f (tidal volume squared x frequency), and target DCO2 = current DCO2 x (current PaCO2 / target PaCO2). For CPAP/non-invasive support: SOPI = (CPAP x FiO2) / SpO2, S/F ratio = SpO2 / FiO2, and the ROX index = (SpO2/FiO2) / respiratory rate.

4 Frequently asked questions

What is the Oxygenation Index (OI) used for?

OI combines Mean Airway Pressure, FiO2, and PaO2 into a single number used to grade severity of hypoxaemic respiratory failure. The app bands OI as Mild (<5), Moderate (5-15), Severe (16-25), Very Severe (26-40), or a range where ECMO should be considered (>40-60).

What's the difference between OI and OSI?

OI uses PaO2 from an arterial blood gas, while OSI substitutes pulse-oximetry SpO2 so it can be tracked non-invasively. The tool cross-checks the two using OI approximately equal to (2.3 x OSI) - 4.

Which waveform constant (K) should I use for the MAP formula?

The calculator offers Square (K=1.0, the default for most conventional pressure-control/SIMV ventilators), Sine (K=0.64, used for HFOV and some sine-flow volume-controlled modes), and Triangular (K=0.5, decelerating/ramp flow patterns) — pick the one matching the ventilator's actual pressure waveform.

When does the tool suggest considering ECMO?

The severity table flags ECMO evaluation when OI exceeds 40 on maximum support (HFOV plus inhaled nitric oxide) for more than 4-6 hours, or at any time OI exceeds 60.

What does the ROX index tell me?

ROX = (SpO2/FiO2) / respiratory rate is presented in the CPAP/non-invasive tab as a weaning predictor, with a value greater than 4.88 at 2 hours associated with high-flow nasal cannula (HFNC) success.

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ESPGHAN 2022
For qualified clinicians. This page and the PediAid app are a clinical aid only. Calculations and reference data must be verified against the patient's clinical context, the source guideline and your local protocols before any treatment decision is made.