Clinical reference support
A–a gradient calculator
Calculate estimated alveolar oxygen and the A–a oxygen gradient from simultaneous arterial values. The result is transparent arithmetic, not a diagnosis or treatment recommendation.
Scope and limits
- Requires PaO₂ and PaCO₂ from the same arterial sample; do not substitute venous values.
- Uses FiO₂, local barometric pressure, PH₂O 47 mmHg, and respiratory quotient 0.8 as explicit calculation assumptions.
- Does not apply a normal range, identify a pulmonary condition, direct treatment, or retain results.
Source and formula
The veterinary alveolar gas equation is PAO₂ = FiO₂ × (barometric pressure − PH₂O) − PaCO₂/RQ; A–a gradient is PAO₂ − PaO₂. The Association of Veterinary Anaesthetists proceedings and veterinary research document this form. This implementation fixes PH₂O at 47 mmHg and RQ at 0.8; it does not infer clinical meaning from the result.
Formula audit trail
The formula trail appears after valid values are entered.
Sources: Veterinary alveolar-gas equation references. Reviewed July 2026.