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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 (Partial Pressure  of inspired oxygen):
   Program Information

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.