When a baby is born, the heart rate (HR) is used to assess the efficiency of spontaneous breathing and the need for interventions such as positive pressure ventilation. HR is the most important and sensitive indicator in neonatal resuscitation; thus, interventions are initiated based on HR, and increase in HR to the normal range is the first sign of a resuscitation response [1,2]. Therefore, fast and accurate estimation of HR is important in neonatal resuscitation. Neonatal resuscitation guidelines recommending a stethoscope and pulse oximetry (PO) ± electrocardiogram (ECG) assessment for HR determination are weak, based on limited, very low-quality evidence [1–4]. A stethoscope is initially useful in traditional resuscitation, but ongoing resuscitation requires a tool that continuously and accurately monitors HR.

Several studies suggest that ECG is faster and more accurate for HR assessment at birth relative to PO [5–8]. However, ECG monitoring is unavailable in many hospitals because the guideline does not specify such methods in the delivery room environment. Therefore, our study assessed the use of a nearby standard ECG monitor with standard newborn three-lead gel electrodes during high-risk deliveries. The primary outcome of the study was to examine the efficiency of HR assessment using ECG compared to PO in high-risk newborn resuscitation.

During the study period, 83 cases were classified as high-risk births, 23 were vaginally delivered, and 18 were twins; all of these were excluded from the study. Consent was obtained in all remaining cases, one of which was excluded because the video was obscured. Finally, 41 cases were analyzed in the study (Table 1).

Eleven newborns needed positive pressure ventilation, and one infant was intubated. None of the patients required chest compressions. The average Apgar score was 7 (interquartile range [IQR], 6–8) at 1 minute and 9 (IQR, 8–9) at 5 minutes. All studied infants were discharged alive.

The median time for both PO and ECG placement from birth was 22 seconds. The median time for PO and ECG HR detection after placement was 125 and 30 seconds, respectively. Time from ECG placement to HR detection was significantly faster than time from PO placement to HR detection (P<0.001). Initial HR with ECG detection was significantly lower than initial HR with PO detection (134.0 [IQR, 112.0–148.0] vs. 150.0 [IQR, 130.0–163.5], P<0.001) (Table 2 and Fig. 1).

When the study population was divided into three GA groups (<32, 32–35, and ≥36 weeks), the median time for ECG HR detection after placement was significantly fastest in the youngest GA group (19 seconds, P=0.039) (Table 2 and Fig. 2).

In this study, HR detection in high-risk infants at birth was faster with ECG monitoring than with PO. HR in preterm infants younger than GA 32 weeks who needed more frequent resuscitation at birth was more effectively evaluated by ECG than by PO monitoring.

The timing of HR detection by ECG or PO in the study cohort was comparable to that of other studies. In our study, time from PO placement to HR detection was 125 seconds (IQR, 100–175 seconds), while a study conducted by Katheria et al. [6], which included 40 preterm infants (mean GA, 28 weeks), showed a PO HR detection time of 114±39 seconds. Mizumoto et al. [7] studied 20 newborn infants (mean GA, 36 weeks), finding a PO HR detection time of 122 seconds (IQR, 101–146 seconds), similar to our study results. Furthermore, their study showed an ECG HR detection time as 38 seconds (IQR, 34–43 seconds). A study including 30 very-low-birth weight infants (mean GA, 27 weeks), 28 of whom required resuscitation, reported a median ECG HR detection time of 26 seconds (IQR, 17–41 seconds) [5]. Another study, which included a large number of preterm and term newborn infants (n=334), reported a median ECG HR detection time of 29 seconds (IQR, 5–60 seconds) [8]. In our study, the ECG HR detection time was 30 seconds (IQR, 20–43.5 seconds), similar to those of the aforementioned studies.

Preterm infants younger than GA 32 weeks showed the fastest HR detection. Gulati et al. [8] conducted a study similar to ours, and the results showed significantly faster ECG HR detection in preterm infants younger than GA 31 weeks than that in infants with GA 31 weeks and above (10 seconds [IQR, 2–40 seconds] vs. 30 seconds [IQR, 5–60 seconds]). Low-GA infants without skin vernix may not move excessively, decreasing motion artifacts. With increasing GA, thick skin vernix appears, attributing to the insufficient drying of infants, delaying HR detection by ECG.

The initial HR detection by ECG was significantly lower, as well as faster, than that of the PO in our study, which suggests that ECG is better at detecting lower HR than PO. A study by van Vonderen et al. [9], which monitored 53 term and preterm infants simultaneously with ECG and PO after birth, showed significantly lower PO HR than ECG HR, implying that PO underestimates HR compared to ECG in the first minutes after birth. In addition, Iglesias et al. [10] monitored 29 episodes of bradycardia in the delivery room of preterm infants (mean GA, 29.5 weeks) and found PO to detect the start and recovery of bradycardia events slower and less accurately than ECG during stabilization at birth. The discrepancy between PO and ECG may be due to hemodynamic instability and hypoperfusion interfering with PO function. Because of the relative superiority of ECG over PO in HR detection just after delivery, ECG seems to decrease intubation frequency and increase cardiac compression frequency [11], while a randomized controlled study showed that ECG monitoring did not reduce time to stabilization during preterm resuscitation [12]. The outcomes of ECG monitoring during newborn resuscitation need to be further studied.

Recently, new interfaces for ECG monitoring including dry-electrode ECG was introduced for rapid HR detection [13–15]. ECG monitoring with classical gel electrodes is sometimes difficult due to the damp skin of newborn infants. Thus, dry-electrode ECG was suggested for fast HR detection. In addition, a new ECG algorithm study reported rapid HR detection [16]. Instead of the usual ECG monitor algorithm, which requires time for analysis of several beats before displaying HR, a novel ECG algorithm using statistical techniques to buffer HR values showed shortened HR detection time. However, in many hospitals, there is a practical inability to utilize advanced ECG devices, despite the recommendation of ECG by the NRP guidelines. Furthermore, the NRP guidelines do not provide specific methods for ECG in the delivery room environment. In the study cohort, a domestically manufactured ECG monitor, readily available as a defibrillator in a cardiopulmonary resuscitation cart, was used with standard newborn three-lead gel electrodes. The study methodology aims to improve the accessibility of ECG monitoring in the delivery room environment for newborns requiring resuscitation.

One limitation of the study was the low resuscitation rate. However, resuscitation rate was higher in neonates younger than GA 32 weeks, in whom HR detection by ECG was more effective. The other limitation of the study is that the sample size was small, and the distribution of infants was not even according to GA. Thus, effectiveness of ECG HR detection for high-risk deliveries should be further evaluated with larger numbers of preterm and term infants who require resuscitation from a larger, multicenter study.

In conclusion, ECG provided earlier HR detection than PO, and the HR of preterm infants younger than GA 32 weeks was more effectively evaluated by ECG than by PO monitoring. The study findings support the use of any conventional ECG for high-risk preterm deliveries.