A hyperoxia test is a test that is performed—usually on an infant—to determine whether the patient's

cyanosis Cyanosis is the change of body tissue color to a bluish-purple hue as a result of having decreased amounts of oxygen bound to the hemoglobin in the red blood cells of the capillary bed. Body tissues that show cyanosis are usually in locations ...

is due to lung disease or a problem with blood circulation. It is performed by measuring the

arterial blood gases An arterial blood gas (ABG) test, or arterial blood gas analysis (ABGA) measures the amounts of arterial gases, such as oxygen and carbon dioxide. An ABG test requires that a small volume of blood be drawn from the radial artery with a syringe an ...

of the patient while they breathe room air, then re-measuring the blood gases after the patient has breathed 100% oxygen for 10 minutes.^:141^:141 If the cause of the cyanosis is poor oxygen saturation by the lungs, allowing the patient to breathe 100% oxygen will augment the lungs' ability to saturate the blood with oxygen, and the

partial pressure In a mixture of gases, each constituent gas has a partial pressure which is the notional pressure of that constituent gas as if it alone occupied the entire volume of the original mixture at the same temperature. The total pressure of an ideal gas ...

of oxygen in the arterial blood will rise (usually above 150

mmHg A millimetre of mercury is a manometric unit of pressure, formerly defined as the extra pressure generated by a column of mercury one millimetre high, and currently defined as exactly pascals. It is denoted mmHg or mm Hg. Although not an SI ...

). However, if the lungs are healthy and already fully saturating the blood that is delivered to them, then supplemental oxygen will have no effect, and the partial pressure of oxygen will usually remain below 100 mmHg. In this case, the cyanosis is most likely due to blood that moves from the systemic veins to the systemic arteries via a

right-to-left shunt A right-to-left shunt is a cardiac shunt which allows blood to flow from the right heart to the left heart. This terminology is used both for the abnormal state in humans and for normal physiological shunts in reptiles. Clinical Significance A ...

without ever going through the lungs.^:141

References

Pediatrics Cardiology Pulmonology {{Cardiology-stub