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The hyperoxia-hyperventilation test (aka 100% Oxygen Challenge test) is used to differentiate the cause of central cyanosis in the sick neonate. The majority of neonatal cyanosis is caused by either cardiac or respiratory pathology.
Classically the test is performed as follows:
1. An ABG is obtained with the neonate breathing room air
2. The patient is placed on 100% FiO2 for 10 minutes
3. A repeat ABG is performed looking for an increase in PaO2 to >150 mmHg
- If the hypoxia is secondary to a respiratory cause, the PaO2 should increase to >150 mmHg.
- If the hypoxia is secondary to a congenital cardiac lesion (i.e. secondary to a right-to-left cardiac shunt) the PaO2 is not expected to rise significantly.
In practice, many physicians instead use pulse oximetry and monitor the SpO2 pre and post administration of 10 minutes of 100% FiO2.
- If after 10min of 100% FiO2, if SpO2 is not ? 95% (some resources use 85%) then the central cyanosis is likely secondary to intracardiac shunt.
- When this occurs, presume the sick neonate is symptomatic from a congenital cardiac lesion and initiate prostaglandin E-1 (PGE1) at 0.05-0.01 mcg/kg/min. Use caution as PGE1 may cause apnea.