Role of Pulse Oximetry as a Screening Tool for the Detection of Congenital Heart Disease in Newborn Babies

Abstract

Congenital heart disease (CHD) is one of the commonly seen malformations, with incidence varying from 7 to 8/1000 live birth. Causes are multifactorial. Routine examination of neonates may miss more than 50% of cases. Pulse oximetry is a simple, noninvasive, bedside test which estimates the percentage of oxygen bound to hemoglobin (oxygen saturation [SpO2]). Detection of critical CHD (CCHD) has been possible with SpO2 screening. Many countries included SpO2 as part of newborn screening due to this. As a primary approach, both pre- and post-ductal extremity SpO2 is measured after 24 h of life. Echocardiography (ECHO) will be done on neonates with SpO2 readings <95%. Neonates born in high-altitude regions, studies have suggest to use adjusted threshold values. In India, there are limited studies. The aim of this study was to determine the usefulness of pulse oximetry as a screening tool for early detection of CHD in otherwise asymptomatic newborns. To determine, the accuracy of SpO2 for detecting clinically unrecognized CCHD in newborns. This is a prospective observational study done in the department of pediatrics in a tertiary hospital. The study was conducted over 12 months. During the study period, all neonates born who fulfilled the inclusion criteria were included in the study. After 24 h of life, neonates were examined clinically and the pre- and post-ductal SpO2 was measured. Neonates with SpO2 <90% in room air were excluded from the study. If the SpO2 was between 90% and 94%, clinical examination was repeated, if suspicious of CHD, they were referred for ECHO. If there was no suspicion of CHD, SpO2 was repeated after 6 h and ECHO was done if SpO2 ≤95. The difference of SpO2 >3% between the right upper limb and right lower limb was considered positive. Positive neonates were evaluated with two-dimensional echocardiograph. Inclusion criteria - All hemodynamically stable neonates were born during the study period. Exclusion criteria (1) Antenatally diagnosed cardiac anomalies, (2) Outborn neonates, (3) Parents/guardians are not willing to participate in the study and/or further investigation, (4) Sick neonates and those with SpO2 <90% at birth. 1117 (83.7%) were eligible for the study out of 1333 neonates born. 669 (59.9%) were born by cesarean section and 448 (40.1%) by vaginal delivery. 996 (89.2%) were born at term (≥37 weeks of gestation) and 121 (10.8%) were preterm (<37 weeks of gestation). The male-to-female ratio was 1.03:1. The mean birth weight of the neonates was 2.91 ± 0.46 kg (mean ± standard deviation). The mean SPO2 in the right upper limb was 96.62 ± 1.73, in the right lower limb was 96.87 ± 1.76, in the left upper limb was 96.59 ± 1.90, and in the left lower limb was 97.06 ± 1.74. The average SPO2 difference between the right upper limb and right lower limb was 1.04 ± 1.07. Based on SpO2, 858 (76.8%) cases were not suspected of having CHD and 259 (23.3%) were suspected of having CHD and were evaluated with ECHO. Six (0.5%) neonates had CHD in whom echo was done. In our study, for detecting CCHD, SPO2 cutoff value of ≤90% showed 90% sensitivity, 99.94% specificity, 75% positive predictive value, and 99.98% negative predictive value. This study emphasizes noninvasive SPO2 as reliable and feasible, with good negative predictive value screening for CHD in neonates.