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Updated: Aug 15, 2026

A Swine Model of Neonatal Asphyxia
Published on: October 11, 2011
Persistence of the biphasic ventilatory response to hypoxia in preterm infants
R J Martin1, J M DiFiore, L Jana
1Department of Pediatrics, Western Reserve University School of Medicine, Cleveland, Ohio 44106-6010, USA.
Insights
The biphasic ventilatory response to hypoxia in preterm infants persists into the second month of life. This response involves a transient increase in tidal volume and a sustained decrease in respiratory frequency, impacting neonatal apnea vulnerability.
Area of Science:
- Neonatal physiology
- Respiratory control
Background:
- Preterm infants exhibit unique respiratory control patterns.
- Understanding ventilatory responses to hypoxia is crucial for preterm infant care.
Purpose of the Study:
- To characterize the postnatal maturation of the biphasic ventilatory response to hypoxia in preterm infants.
- To determine if this response persists beyond the initial weeks of life.
- To assess the roles of respiratory frequency and tidal volume in this response.
Main Methods:
- Stable preterm infants were studied at two postnatal ages: 2-3 weeks and 4-8 weeks.
- Infants were exposed to hypoxic conditions (15% or 13% inspired oxygen).
- Ventilation, oxygen saturation, end-tidal partial pressure of carbon dioxide, and heart rate were continuously monitored.
Main Results:
- A biphasic ventilatory response to hypoxia was observed at both postnatal ages.
- Tidal volume transiently increased, peaking at 1 minute.
- Respiratory frequency decreased due to prolonged expiratory time, irrespective of periodic breathing.
Conclusions:
- The biphasic ventilatory response to hypoxia is present in preterm infants up to the second month of postnatal life.
- This sustained response may relate to the increased risk of neonatal apnea in these infants.
Objective:
To characterize postnatal maturation of the biphasic ventilatory response to hypoxia in order to determine whether it persists beyond the first weeks of life in preterm infants, and the contributions of respiratory frequency and tidal volume to this response.
Methods:
Stable preterm infants were studied at two postnatal ages, 2 to 3 weeks (n = 12) and 4 to 8 weeks (n = 12), before hospital discharge at 35 weeks (range, 33 to 38 weeks) of postconceptional age. Infants were exposed to 5 minutes of 15% (or 13%) inspired oxygen; ventilation, oxygen saturation, end-tidal partial pressure of carbon dioxide, and heart rate were simultaneously recorded.
Results:
Minute ventilation exhibited a characteristic biphasic response to hypoxia at both postnatal ages, regardless of the development of periodic breathing. At both ages there was a transient increase in tidal volume, which peaked at 1 minute, accompanied by a sustained decrease in respiratory frequency as a result of significant prolongation of expiratory time.
Conclusion:
The characteristic biphasic ventilatory response to hypoxia persists into the second month of postnatal life in preterm infants. We speculate that this finding is consistent with the prolonged vulnerability of such infants to neonatal apnea.
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