logo

Aa Gradient

A-a Gradient Calculator

Patient age* : (*Will be used to calculate normal A-a gradient based on age)
PB (Local barometric pressure) in mmHg: mmHg
PaO2 (partial pressure of arterial O2) from ABG: mmHg
PaCO2 (partial pressure of arterial CO2) from ABG: mmHg
FiO2 (fraction of inspired oxygen):
   Program Information

Results

A-a Gradient =
Normal A-a gradient for age entered above:
(Normal A-a gradient = (Age+10) / 4)

References

  Crapo RO, Jensen RL, Hegewald M, Tashkin DP.  Arterial blood gas reference values for sea level and an altitude of 1,400 meters. Am J Respir Crit Care Med. 1999 Nov;160(5 Pt 1):1525-31.

D'Alonzo GE, Bower JS, DeHart P, Dantzker DR. The mechanisms of abnormal gas exchange in acute massive pulmonary embolism. Am Rev Respir Dis. 1983 Jul;128(1):170-2.

Giannella-Neto A, Paoletti P, Fornai E, Giuntini C. Estimates of mean alveolar gas in patients with chronic airways obstruction. Eur Respir J. 1989 May;2(5):451-60.

Helmholz HF Jr.   The abbreviated alveolar air equation.
Chest. 1979 Jun;75(6):748

Hopkins SR, McKenzie DC. Hypoxic ventilatory response and arterial desaturation during heavy work.  J Appl Physiol. 1989 Sep;67(3):1119-24.

Maya Martinez M, Carrion Valero F, Diaz Lopez J, Marin Pardo J.  [Barometric pressure and respiratory quotient for estimating the alveolar-arterial oxygen gradient]. An Med Interna. 2000 May;17(5):243-6

McFarlane MJ, Imperiale TF.  Use of the alveolar-arterial oxygen gradient in the diagnosis of pulmonary embolism.   Am J Med. 1994 Jan;96(1):57-62.

Stein PD, Goldhaber SZ, Henry JW. Alveolar-arterial oxygen gradient in the assessment of acute pulmonary embolism.
Chest. 1995 Jan;107(1):139-43.

St Croix CM, Cunningham DA, Kowalchuk JM, McConnell AK, Kirby AS, Scheuermann BW, Petrella RJ, Paterson DH. Estimation of arterial PCO2 in the elderly. J Appl Physiol. 1995 Dec;79(6):2086-93.

Story DA. Alveolar oxygen partial pressure, alveolar carbon dioxide partial pressure, and the alveolar gas equation.
Anesthesiology. 1996 Apr;84(4):1011. 

Torda TA. Alveolar-arterial oxygen tension difference: a critical look.  Anaesth Intensive Care. 1981 Nov;9(4):326-30.

Disclaimer

All calculations must be confirmed before use. The authors make no claims of the accuracy of the information contained herein; and these suggested doses are not a substitute for clinical judgement. Neither GlobalRPh Inc. nor any other party involved in the preparation of this program shall be liable for any special, consequential, or exemplary damages resulting in whole or part from any user's use of or reliance upon this material.PLEASE READ THE DISCLAIMER CAREFULLY BEFORE ACCESSING OR USING THIS SITE. BY ACCESSING OR USING THIS SITE, YOU AGREE TO BE BOUND BY THE TERMS AND CONDITIONS SET FORTH IN THE DISCLAIMER.   Read the disclaimer
more Career Center image description
Medical Calculators - A thru Z
Lab Values - A thru Z