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. 2021 Jul;90(1):125-130.
doi: 10.1038/s41390-021-01428-3. Epub 2021 Mar 25.

Vital sign metrics of VLBW infants in three NICUs: implications for predictive algorithms

Amanda M Zimmet  1 , Brynne A Sullivan  2 , Karen D Fairchild  3 , J Randall Moorman  1 , Joseph R Isler  4 , Aaron W Wallman-Stokes  4 , Rakesh Sahni  4 , Zachary A Vesoulis  5 , Sarah J Ratcliffe  6 , Douglas E Lake  1
Affiliations

Vital sign metrics of VLBW infants in three NICUs: implications for predictive algorithms

Amanda M Zimmet et al. Pediatr Res. 2021 Jul.

Erratum in

Abstract

Background: Continuous heart rate (HR) and oxygenation (SpO2) metrics can be useful for predicting adverse events in very low birth weight (VLBW) infants. To optimize the utility of these tools, inter-site variability must be taken into account.

Methods: For VLBW infants at three neonatal intensive care units (NICUs), we analyzed the mean, standard deviation, skewness, kurtosis, and cross-correlation of electrocardiogram HR, pulse oximeter pulse rate, and SpO2. The number and durations of bradycardia and desaturation events were also measured. Twenty-two metrics were calculated hourly, and mean daily values were compared between sites.

Results: We analyzed data from 1168 VLBW infants from birth through day 42 (35,238 infant-days). HR and SpO2 metrics were similar at the three NICUs, with mean HR rising by ~10 beats/min over the first 2 weeks and mean SpO2 remaining stable ~94% over time. The number of bradycardia events was higher at one site, and the duration of desaturations was longer at another site.

Conclusions: Mean HR and SpO2 were generally similar among VLBW infants at three NICUs from birth through 6 weeks of age, but bradycardia and desaturation events differed in the first 2 weeks after birth. This highlights the importance of developing predictive analytics tools at multiple sites.

Impact: HR and SpO2 analytics can be useful for predicting adverse events in VLBW infants in the NICU, but inter-site differences must be taken into account in developing predictive algorithms. Although mean HR and SpO2 patterns were similar in VLBW infants at three NICUs, inter-site differences in the number of bradycardia events and duration of desaturation events were found. Inter-site differences in bradycardia and desaturation events among VLBW infants should be considered in the development of predictive algorithms.

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Conflict of interest statement

Disclosure Statement

RM and DL have equity shares in Medical Predictive Science Corporation, Charlottesville, VA. RM is an officer and owns equity in Advanced Medical Predictive Devices, Diagnostics, and Displays. SR has received consulting fees from Airway Therapeutics. The other authors declare no conflicts of interest.

Figures

Figure 1:
Figure 1:. HR and SpO2 Trends of VLBWs at Three NICUs.
Daily mean HR (left) and SpO2 (right) are shown for VLBW infants at the three NICUs through the first six weeks from birth. Thin dotted lines indicate the 95% confidence interval. Asterisks indicate a statistically significant difference on that day compared to one other site (small asterisk) or both other sites (large asterisk). Y-axis limits are the 10th and 90th percentiles.
Figure 2:
Figure 2:. Bradycardia and Desaturation Events by Site.
Mean number of bradycardia (A) and desaturation (B) events per day of data are shown for the first six weeks from birth for VLBW infants at UVA, CU, and WUSTL. Mean event duration in seconds is shown in the bottom panels (C,D). Dotted lines indicate the 95% confidence interval. Asterisks indicate a statistically significant difference on that day compared to one other site (small asterisk) or both other sites (large asterisk). Y-axis limits are the 10th and 90th percentiles.
Figure 3:
Figure 3:. Magnitude of Statistical Significance of Site Differences in HR, PR, and SpO2 metrics.
For each metric shown on the left y axis, the number of zeros preceding the p-value for inter-site differences each day shown on the x axis is depicted as a heat map. Black boxes indicate no significant difference between sites (adjusting for 42 comparisons, p<0.05/42 or approximately p<0.001). Progressively darker shades of blue indicate more leading zeros in the p-value for inter-site differences. * = computed using ten minute averages. SD = standard deviation, XC = cross-correlation, HR = ECG heart rate.
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