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Ventilatory response and stability of oxygen saturation during a hypoxic challenge in very preterm infants
Emanuela Zannin1,2, Benjamin Stoecklin3,4, Jane Y Choi3,5
1Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Milan, Italy.
Insights
Very preterm infants, even without bronchopulmonary dysplasia (BPD), show unstable breathing and oxygen saturation (SpO2) during mild hypoxia. This study reveals significant individual variability in ventilatory responses to low oxygen levels.
Area of Science:
- Neonatal Physiology
- Respiratory Medicine
- Pediatric Pulmonology
Background:
- Preterm infants possess immature respiratory control and compromised gas exchange.
- Bronchopulmonary dysplasia (BPD) may further impair ventilatory responses and oxygen saturation (SpO2) stability.
- Hypoxic challenges in preterm infants can reveal underlying respiratory vulnerabilities.
Purpose of the Study:
- To investigate the ventilatory and SpO2 responses to a mild hypoxic challenge in very preterm infants.
- To determine if infants with bronchopulmonary dysplasia (BPD) exhibit a blunted ventilatory response or increased SpO2 instability compared to those without BPD.
- To characterize the patterns of respiratory and SpO2 variability during hypoxia in this population.
Main Methods:
- Fifty-seven very preterm infants (36 weeks postmenstrual age) were studied, categorized by BPD severity (none, mild, moderate-to-severe).
- Fraction of inspired oxygen (FiO2) was incrementally reduced to maintain SpO2 between 86-95%.
- Respiratory signals were recorded using plethysmography to calculate respiratory rate, tidal volume, minute ventilation, and respiratory drive; SpO2 variability was quantified.
Main Results:
- A mild hypoxic challenge induced significant individual variability in minute ventilation (VE) response, with some infants decreasing VE and others increasing it.
- Approximately 35% of infants developed periodic breathing, associated with increased SpO2 variability and lower SpO2 minima.
- An additional 28% exhibited oscillatory patterns in VE and SpO2, irrespective of BPD severity.
Conclusions:
- Mild hypoxic challenges in very preterm infants can lead to reduced ventilation and increased SpO2 variability, including periodic breathing.
- These respiratory and SpO2 instabilities occur across the spectrum of BPD severity, highlighting general vulnerabilities in preterm infants.
- The findings underscore the complex and variable respiratory control in preterm infants, even under mild hypoxic conditions.
Background:
Preterm infants have immature control of breathing and impaired pulmonary gas exchange. We hypothesized that infants with bronchopulmonary dysplasia (BPD) have a blunted ventilatory response and peripheral oxygen saturation (SpO2 ) instability during a hypoxic challenge.
Methods:
We evaluated the response to hypoxia in 57 very preterm infants (38 no BPD, 10 mild BPD, 9 moderate-to-severe BPD) at 36 weeks' postmenstrual age. The fraction of inspired oxygen (FI O2 ) was reduced stepwise at 5-min intervals to achieve peripheral SpO2 between 86% and 95%. The lowest permissible FI O2 and SpO2 were 0.14% and 86%. We recorded SpO2 , FI O2 , and the respiratory signal (respiratory inductive plethysmography). We calculated respiratory rate (RR), tidal volume (VT ), minute ventilation (VE ), and respiratory drive (ratio between VT and inspiratory time, VT /TI ). SpO2 variability was expressed as the interquartile range (IQR).
Results:
FI O2 was reduced from a median (Q1, Q3) of 0.21 (0.21, 0.21) to 0.17 (0.17, 0.18). We observed a marked individual variability in the ventilatory response to the hypoxic challenge, regardless of BPD severity. At the lowest permissible FI O2 , 37 (65%) infants reduced their VE , and 20 (35%) increased minute ventilation; 20 infants (35%) developed periodic breathing associated with increased SpO2 IQR and lower SpO2 minima, and 16 (28%) exhibited an oscillatory pattern in VE and SpO2 without end-expiratory pauses, regardless of BPD severity.
Conclusion:
In very preterm infants, a mild hypoxic challenge reduced ventilation, increased SpO2 variability and periodic breathing regardless of BPD severity.
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