Related Experiment Video
Updated: Mar 29, 2026
Preoxygenation Techniques for Tracheal Intubation in Critically Ill Adults Utilizing Oxygen Mask and Noninvasive Ventilation
Published on: December 5, 2025
Influence of pulmonary factors on pulse oximeter saturation in preterm infants
J G Jones1, G G Lockwood2, N Fung3
1Department of Anaesthesia, Addenbrookes Hospital, Cambridge, UK.
Insights
Oxygen saturation stability (SpO2%) in infants with bronchopulmonary dysplasia (BPD) varies significantly. Higher SpO2 targets are more stable, with steep slopes below 90% potentially explaining low oxygen flow dependence in BPD infants.
Area of Science:
- Neonatal Medicine
- Pediatric Pulmonology
- Respiratory Physiology
Background:
- Bronchopulmonary dysplasia (BPD) is a chronic lung disease in infants.
- Oxygen saturation (SpO2%) stability is crucial for managing BPD.
- Understanding SpO2% variability informs clinical practice.
Purpose of the Study:
- To quantify the stability of SpO2% in infants with BPD.
- To analyze SpO2% variability across different inspired oxygen concentrations (FIO2).
- To correlate SpO2% stability with gas exchange parameters in BPD.
Main Methods:
- Studied clinically stable infants with BPD.
- Measured SpO2% at varying FIO2 levels.
- Utilized a computer model to calculate the SpO2% vs. FIO2 curve slope (SpO2 stability) between 85%-95% SpO2.
Main Results:
- Dominant impairment was low ventilation/perfusion ratio (VA/Q).
- SpO2% stability varied significantly between infants.
- Steeper slopes observed at lower SpO2% (85%-95%), especially in less severe BPD.
Conclusions:
- SpO2% stability in BPD infants shows considerable inter-infant variation.
- Higher SpO2% targets are inherently more stable.
- Steep SpO2% slopes below 90% may explain dependence on low oxygen flows.
Aim:
To describe how the stability of oxygen saturation measured by pulse oximetry (SpO2%) varies within and between infants with bronchopulmonary dysplasia (BPD).
Methods:
Clinically stable infants with BPD had SpO2 measured at different inspired oxygen concentrations (FIO2 expressed as %). A computer model of gas exchange, that is, ventilation/perfusion ratio (VA/Q) and shunt, plotted the curve of SpO2 versus FIO2 best fitting these data. The slope of this curve is the change in SpO2 per % change in FIO2, hence SpO2 stability, calculated at each SpO2 from 85% to 95%.
Results:
Data from 16 infants with BPD previously described were analysed. The dominant gas exchange impairment was low VA/Q (median 0.35, IQR, 0.16-0.4, normal 0.86). Median shunt was 1% (IQR, 0-10.5; normal <2%). Slope varied markedly between infants, but above 95% SpO2 was always <1.5. In infants with least severe BPD (VA/Q ≈0.4, shunt ≤2%) median slope at 85% SpO2 was 5.1 (IQR, 3.7-5.5). With more severe BPD (VA/Q ≤0.3) slope was flatter throughout the SpO2 range. The highest FIO2 for 90% SpO2 was in infants with the lowest VA/Q values.
Conclusions:
In infants with BPD, there was large variation in the slope of the curve relating SpO2% to inspired oxygen fraction in the SpO2 range 85%-95%. Slopes were considerably steeper at lower than higher SpO2, especially in infants with least severe BPD, meaning that higher SpO2 target values are intrinsically much more stable. Steep slopes below 90% SpO2 may explain why some infants appear dependent on remarkably low oxygen flows.
Related Concept Videos
01:24Pulse Oximetry
Purpose
Average SpO2 values are greater than 95%. If the readings fall below 90%, it indicates that...
01:19Special considerations while measuring oxygen saturation
Ensuring accuracy in vital sign recordings while prioritizing patient comfort and minimizing anxiety is...
01:19Guidelines For Measuring Vital Signs
Before taking a patient's vital signs, a nurse would consider and assess the patient's comfort level and ensure appropriate equipment is available.
01:19Factors Affecting Pulmonary Ventilation
Alveolar Surface Tension
The alveolar fluid lines the luminal surface of the alveoli and exerts a force called surface tension. This force is caused by the polar water molecules in the liquid being more strongly attracted to each...
01:17Assessment of Diffusion and Perfusion
The Role of Diffusion in Respiration
Diffusion is the process by which molecules move from an area of higher concentration to an area of lower concentration. In the respiratory system, this...
01:19Respiratory Assessment: Purpose and Indications
Objectives and Importance:
The primary goal of respiratory assessment is to evaluate patients at early risk of clinical deterioration. Since respiratory distress often precedes other signs of declining health, breathing patterns and sounds become a...