title: Persistence of the biphasic ventilatory response to hypoxia in preterm infants.
abstract: 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Pediatrics, Western Reserve University School of Medicine, Cleveland, Ohio 44106-6010, USA.
authors.forename: R J
authors.initials: RJ
authors.lastname: Martin
authors.forename: J M
authors.initials: JM
authors.lastname: DiFiore
authors.forename: L
authors.initials: L
authors.lastname: Jana
authors.forename: R L
authors.initials: RL
authors.lastname: Davis
authors.forename: M J
authors.initials: MJ
authors.lastname: Miller
authors.forename: S K
authors.initials: SK
authors.lastname: Coles
authors.forename: T E
authors.initials: TE
authors.lastname: Dick
mesh_terms: D001049:Apnea / Q000503:physiopathology*; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology; D007223:Infant; D007231:Infant, Newborn; D007234:Infant, Premature / Q000254:growth & development / Q000502:physiology*; D008297:Male; D010100:Oxygen / Q000097:blood / Q000502:physiology*; D012123:Pulmonary Ventilation / Q000502:physiology*; D012121:Respiration, Artificial; D013990:Tidal Volume / Q000502:physiology
chemical_list: D010100:Oxygen