From the Guidelines
In congenital heart diseases, a preductal and postductal oxygen saturation difference of ≥3% is considered significant, and the lower limit of an acceptable oxygen saturation should be ≥95% in both measurements, as recommended by the American Academy of Pediatrics (AAP) in their 2025 clinical report 1. The AAP's endorsement of a new simplified CCHD screening algorithm emphasizes the importance of accurate oxygen saturation measurements. Key points from the algorithm include:
- Lower limit of an acceptable oxygen saturation should be ≥95% in both pre- and post-ductal measurements
- Only one retest following an indeterminate result
- Newborn should not be on supplemental oxygen
- Use of the recommended minimum dataset for data collection The significance of the preductal and postductal oxygen saturation difference lies in its ability to indicate ductal-dependent lesions, such as coarctation of the aorta, interrupted aortic arch, or hypoplastic left heart syndrome. To measure this difference, pulse oximetry should be performed simultaneously on the right hand (preductal) and either foot (postductal), as stated in the AAP's clinical report 1. If a significant difference is detected, immediate cardiology consultation is warranted, and prostaglandin E1 may be needed to maintain ductal patency until definitive intervention. Regular monitoring of these saturations is essential in neonates suspected of having critical congenital heart disease, as emphasized by the AAP's recommendations 1. The AAP's algorithm also highlights the importance of education and identification of disease other than CCHD, as well as enhanced efforts to use health information technology and optimization of electronic health records 1.
From the Research
O2 Saturation Difference in Congenital Heart Diseases
- The difference in O2 saturation between preductal and postductal measurements is an important aspect of screening for critical congenital heart disease (CCHD) 2.
- A study published in Pediatrics in 2013 found that the mean difference between pre- and postductal saturation was -0.29% (95% CI: -0.31 to -0.27) with P < .00005 in asymptomatic newborns 2.
- The same study found that the postductal saturation was equal to preductal saturation in 38% and greater than preductal saturation in 40% of the screens 2.
- Another study published in Congenital Heart Disease in 2018 found that a difference higher than 3% in preductal saturation and postductal saturation can be used as a positive screening criterion for CHD 3.
Preductal and Postductal Saturation Values
- The mean preductal saturation was 98.29% (95% CI: 98.27-98.31) and the mean postductal saturation was 98.57% (95% CI: 98.55-98.60) in asymptomatic newborns 2.
- At high altitude, the mean preductal saturation was 92.76% (SD ± 3) and the postductal saturation was 93.76% (SD ± 4.7) in term newborns 3.
Clinical Relevance
- The clinical relevance of the difference in O2 saturation between preductal and postductal measurements remains to be determined 2.
- Pulse oximetry can be a useful tool for the early detection of critical congenital heart disease, especially at high altitude 3.
- However, new cutoff points in saturation values may be necessary to identify critical cardiac anomalies in cities at high altitude 3.