Can alveolar—arterial oxygen gradient predict severity of pulmonary embolism?

• Published in: The Egyptian Journal of Bronchology Vol. 13; no. 2; pp. 273 - 279
• Main Authors: Abdelghany, Elham Abdelhady, Othman, Ashraf M., Abdelfatah, Rasha Abdelraof, Magdy, Mohammed-Elhoseany, Abd Elghany, Hosny S., Higazi, Mahmoud M.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-04-2019; Wolters Kluwer India Pvt. Ltd; Springer Nature B.V; SpringerOpen
• Subjects: alveolar–arterial oxygen gradient; Medical imaging; Medicine & Public Health; Original Article; Oxygen saturation; Pulmonary arteries; pulmonary artery obstructive index; pulmonary embolism; Pulmonary embolisms; Tomography; alveolar–arterial oxygen gradient; pulmonary embolism; pulmonary artery obstructive index; alveolar-arterial oxygen gradient
• ISSN: 1687-8426; 2314-8551
• DOI: 10.4103/ejb.ejb_62_18

Background
The perceived risk for pulmonary embolism (PE) can be assessed by oxygenation and calculation of the alveolar–arterial (A-a) oxygen (O
2
) gradient. We attempt to evaluate the efficacy of A-a O
2
gradient for the diagnosis of PE and if it can predict the degree of severity of PE.
Patient and methods
This study is a prospective study conducted on 70 patients presented by signs or symptoms of suspected acute PE. Arterial-blood gases including arterial partial pressure of oxygen (PaO
2
), partial pressure of carbon dioxide (PaCO
2
), and arterial oxygen saturation (SaO
2
) and computed tomography pulmonary angiography were done on admission.
Results
Fifty patients proved to have PE by computed tomography pulmonary angiography. The patients were divided into (a) nonhigh-risk and (b) high-risk groups. There was a significant difference between the two groups regarding pulmonary artery obstructive index. Although A-a gradients were high in all studied patients with positive PE in comparison to negative PE patients, there was no significant difference between high-risk and nonhigh-risk groups regarding PaO
2
(mmHg), arterial oxygen saturation, %, A-a O
2
, PaCO
2
. In addition, no significant relationship was detected between arterial-blood gas parameters regarding PaO
2
and SaO
2
with pulmonary artery obstructive index; also PaCO
2
and A-a O
2
gradients were nonsignificant.
Conclusion
The A-a O
2
gradient values are clinically important in the diagnosis of patients with PE because it is easy to perform and is a bedside test. However, it may be incapable of detection of severity of PE.