End-tidal carbon monoxide (CO), corrected for ambient CO (ETCOc), is a quick, non-invasive test that detects and quantifies hemolysis by measuring CO in exhaled breath and can provide valuable information for treating hemolytic disease of the fetus and newborn (HDFN), according to a study recently published in Seminars in Fetal and Neonatal Medicine.
Elevated CO levels indicate that red blood cells (RBCs) are breaking down at an abnormal rate, releasing hemoglobin, which leads to jaundiceJaundice A common symptom of HDFN, jaundice is caused by excess bilirubin and is characterized by a yellow tint to the skin or eyes. and anemiaAnemia A condition that occurs when the body doesn’t have enough healthy red blood cells to carry oxygen to its tissues. In HDFN, anemia occurs when maternal antibodies destroy fetal red blood cells. if unmanaged. This test provides important information for treating HDFN by assessing the severity and duration of the disease. Since this condition can cause serious complications in infants, early identification and monitoring of hemolysis are essential.
Measuring ETCOc is particularly helpful in diagnosing unexplained jaundice or anemia in newborns. This breath test can differentiate between hemolytic and non-hemolytic jaundice, guiding appropriate interventions such as phototherapyPhototherapy A treatment that uses special blue light to help newborns break down bilirubin and prevent kernicterus.. In the case of hemolytic jaundice, more intensive treatments may be necessary, as CO levels will remain elevated, signaling ongoing RBC breakdown. This can also help doctors determine the root cause of the jaundice, be it due to immune response or a genetic condition affecting the RBCs, which is vital for effective and timely treatment.
ETCOc testing during pregnancy and after birth
ETCOc testing is not only beneficial post-birth; it can also be used to monitor at-risk pregnancies. Research suggests that fetuses experiencing hemolysis release enough CO to be detectable in the mother’s exhaled breath. This monitoring helps doctors anticipate complications and prepare for treatments at birth, especially in pregnancies where fetal anemia is likely to develop after the 34th week when standard ultrasoundUltrasound An imaging test that uses sound waves to monitor fetal growth, development and signs of complications during pregnancy. tests are less effective.
Read more about the testing and diagnosis of HDFN
After birth, neonates diagnosed with HDFN undergo weekly ETCOc monitoring to measure how long hemolysis persists. Tracking CO levels over time gives healthcare providers a clear picture of when the disease has resolved, reducing the need for more invasive tests and offering reassurance to parents. In many cases, this method provides a more personalized approach to neonatal care, allowing families to understand their infant’s progress.
Hospitals also find ETCOc testing useful in managing phototherapy in jaundiced newborns. For instance, a study conducted in a newborn nursery found that infants with elevated ETCOc levels required longer and earlier phototherapy sessions. This early intervention is critical, as it can prevent severe jaundice from progressing to dangerous levels, minimizing the need for emergency readmissions post-discharge.
Some hospitals now include ETCOc screening as part of their standard jaundice management program to prevent readmission for severe hyperbilirubinemiaHyperbilirubinemia A common cause of jaundice, this refers to higher than normal bilirubin levels in the blood.. “We also encourage clinical and academic groups to study these and other potential perinatal uses of ETCOc, and to publish their findings, adding to the growing literature on recognizing and quantifying hemolysis in the fetus and neonate,” the authors stated.
