Side-by-side comparison helps you choose the right calculator for a specific clinical question.
Clinical
Estimate PaO₂ from SpO₂ pulse oximetry using the oxygen-hemoglobin dissociation curve. SpO₂ 98%≈100 mmHg, 95%≈80, 90%≈60 (critical threshold). Useful when ABG is unavailable.
Formula
Approximation based on the oxygen-hemoglobin dissociation curve (Severinghaus equation)
Inputs
Clinical
Calculate the alveolar-arterial oxygen gradient to evaluate the cause of hypoxemia. Differentiates lung pathology from hypoventilation.
Formula
A-a gradient = [FiO₂ × (Patm − 47) − PaCO₂/0.8] − PaO₂
Inputs