# Pulse Oximetry Histogram Profiles Before and After Red Blood Cell Transfusion in Very Preterm Infants: A Prospective Observational Cohort

## TL;DR

RBC transfusions in very preterm infants improved anemia but had limited effects on oxygenation stability, with variations seen in higher-risk groups.

## Contribution

This study introduces SpO2 histograms as a potential tool to assess heterogeneous oxygenation responses after RBC transfusion in preterm infants.

## Key findings

- RBC transfusion increased hemoglobin but did not significantly improve oxygenation stability in preterm infants.
- Higher-risk subgroups like BPD and low birth weight infants showed persistent oxygenation instability.
- SpO2 histograms showed modest discrimination for predicting outcomes like ROP and BPD.

## Abstract

What are the main findings?
Continuous SpO2 histogram monitoring showed only modest, non-significant shifts in hypoxemia, target-range oxygenation, and hyperoxemia over 72 h after RBC transfusion in very preterm infants.Despite a substantial hemoglobin increase after transfusion, oxygenation instability persisted and varied across higher-risk subgroups (BPD and birth weight < 1000 g).

Continuous SpO2 histogram monitoring showed only modest, non-significant shifts in hypoxemia, target-range oxygenation, and hyperoxemia over 72 h after RBC transfusion in very preterm infants.

Despite a substantial hemoglobin increase after transfusion, oxygenation instability persisted and varied across higher-risk subgroups (BPD and birth weight < 1000 g).

What are the implications of the main findings?
RBC transfusion should not be assumed to consistently normalize bedside oxygenation patterns; SpO2 histograms may provide a practical adjunct for assessing heterogeneous responses beyond hemoglobin values alone.Early post-transfusion histogram profiles may be useful for hypothesis generation and future risk-stratification studies for outcomes such as BPD and ROP, warranting validation in larger cohorts.

RBC transfusion should not be assumed to consistently normalize bedside oxygenation patterns; SpO2 histograms may provide a practical adjunct for assessing heterogeneous responses beyond hemoglobin values alone.

Early post-transfusion histogram profiles may be useful for hypothesis generation and future risk-stratification studies for outcomes such as BPD and ROP, warranting validation in larger cohorts.

Background/Objectives: Red blood cell (RBC) transfusion is frequently used to treat anemia of prematurity, yet bedside metrics that capture its short-term impact on oxygenation stability are limited. We assessed whether pulse oximetry histogram-derived oxygen saturation (SpO2) exposure changes after transfusion and whether responses differ across clinical subgroups. Methods: This prospective observational cohort included preterm infants born <32 weeks’ gestation who received a standardized RBC transfusion (15 mL/kg). Continuous SpO2 histograms quantified the percentage of monitored time spent in hypoxemia (<85%), normoxemia (86–95%), and hyperoxemia (≥96%) during four intervals: 24 h pre-transfusion and 24, 48, and 72 h post-transfusion. Repeated-measures and subgroup analyses (BPD, sex, birth weight < 1000 g) were performed. Results: Thirty-three infants were analyzed (gestational age 29.4 ± 2.1 weeks; birth weight 1220.6 ± 316.9 g). Hemoglobin increased from 8.6 ± 1.1 to 11.7 ± 1.0 g/dL (p < 0.001). Cohort-level histogram shifts were modest: normoxemia increased from 68.4 ± 12.1% to 72.6 ± 11.4% at 24 h (p = 0.18), hypoxemia decreased from 10.3 ± 6.5% to 6.6 ± 4.8% (p = 0.09), and hyperoxemia remained stable (21.3 ± 9.2% to 20.8 ± 8.5%; p = 0.44). Infants with BPD and those <1000 g showed persistently higher hypoxemia and/or hyperoxemia at 72 h compared with counterparts. Exploratory ROC analyses showed modest discrimination of 24 h hypoxemia for ROP (AUC 0.71) and 72 h hyperoxemia for BPD (AUC 0.74). Conclusions: RBC transfusion corrected anemia but did not produce a consistent cohort-level improvement in SpO2 histogram stability. Histogram metrics may help characterize heterogeneous oxygenation responses and support hypothesis generation for individualized monitoring strategies.