Pulmonology · ICU and Critical Care
Alveolar–Arterial Oxygen Gradient calculator
Enter the published formula inputs below to calculate and interpret this score.
Clinical inputs
Allowed range: 0.21–1 fraction
Allowed range: 10–150 mmHg
Allowed range: 20–600 mmHg
Allowed range: 500–780 mmHg
Use local barometric pressure (760 mmHg at sea level).
Allowed range: 40–50 mmHg
Allowed range: 0.7–1 ratio
Respiratory quotient; 0.8 is standard unless measured.
Result
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Clinical inputs
- aagradient fio2 fractionAccepted range: 0.21 to 1
- aagradient paco2 mmhgAccepted range: 10 to 150
- aagradient pao2 mmhgAccepted range: 20 to 600
- aagradient barometric pressure mmhgAccepted range: 500 to 780
- aagradient water vapor pressure mmhgAccepted range: 40 to 50
- aagradient respiratory quotient (ratio)Accepted range: 0.7 to 1
Primary source
Alveolar gas equation as used in arterial blood gas interpretation. DOI: 10.1164/ajrccm.158.1.9711041. PMID: 9655694. Scope: calculates P(A–a)O₂ as (PB − PH₂O) × FiO₂ − PaCO₂/RQ − PaO₂ for adult arterial blood gas assessment. (1998)
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