Miscellaneous Calculators

Estimating Pmus from P0.1 (1)

Equation: Pmus = – 2.99 x (P0.1) + 0.53

Reference: Estimating actual inspiratory muscle pressure from airway occlusion pressure at 100 msec

Estimating Pmus from P0.1 (2)

Equation: Pmus = 3.95 (P0.1) – 2.05

Reference: Estimation of inspiratory muscle effort using three common indices in various respiratory models, a bench study

Estimating Pmus from Pocclusion

Equation: Pmus = 1.11 (Pocc) + 0.82

Reference: Estimation of inspiratory muscle effort using three common indices in various respiratory models, a bench study

Estimating Pmus from PMI

(Not for obstructive cases with high resistance)

Equation: Pmus = 1.53 (PMI) + 0.61

Reference: Estimation of inspiratory muscle effort using three common indices in various respiratory models, a bench study

Oxygenation Index

Equation: OI = (FiO2 x MAP) / PaO2

Reference: Oxygenation index predicts outcome in children with acute hypoxemic respiratory failure

Oxygenation Stretch Index

Equation: OSI = PaO2 / (FiO2 x DP)

Reference: Partition of respiratory mechanics in patients with acute respiratory distress syndrome and association with outcome: a multicenter clinical study

Dead Space

Equation: Dead space volume = VD = VT x (PaCO2 – PeCO2) / PaCO2

Reference: Physiology, Lung Dead Space

Alveolar Minute Ventilation

Equation: Alveolar minute ventilation = (Total VT – Alveolar VT) X RR

Reference: Physiology, Tidal volume

Ventilation-Perfusion Ratio (V/Q)

Equation: Ventilation-Perfusion ratio (V/Q) = Alveolar ventilation / Pulmonary blood flow (cardiac output)

Reference: Physiology, Pulmonary ventilation and perfusion

Ventilation Ratio

Equation: Ventilation Ratio = minute ventilation (ml/min) × Pa_CO2 (mm Hg)]/(predicted body weight × 100 × 37.5)

Reference: Physiologic Analysis and Clinical Performance of the Ventilatory Ratio in Acute Respiratory Distress Syndrome 

ROX Index

Equation: ROX Index = SpO₂/FiO₂ / Respiratory rate

Reference: Predicting success of high-flow nasal cannula in pneumonia patients with hypoxemic respiratory failure: The utility of the ROX index