Differences in CO2 threshold of respiratory muscles in preterm infants

Academic Article


  • Because neonatal apnea is frequently associated with airway obstruction, we compared relative changes in activity between various upper airway muscles and the diaphragm during hypercapnic stimulation. The technique of hyperoxic CO rebreathing was employed in 17 healthy, sleeping preterm infants studied at a postnatal age of 32 ± 12 days. Surface diaphragm (DIA) electromyograms (EMGs) were recorded in all infants, and noninvasive measurements of posterior cricoarytenoid (PCA), genioglossus (GG), and alae nasi (AN) EMGs were analyzed in 11, 9, and 8 infants, respectively. During the control period, consistent phasic EMGs were recorded from the DIA in all infants and from the PCA in 8 infants, but from the GG and AN each in only one infant. During CO rebreathing, minute ventilation and end-tidal CO increased linearly as CO rose from 31 ± 5 to 51 ± 5 Torr. DIA and PCA EMGs also had proportional and comparable increases throughout rebreathing. In contrast, both GG and AN responses differed from the DIA and PCA (P < 0.001) and exhibited minimal or absent responses at low levels of hypercapnia. Consistent GG and AN EMGs appeared at comparable levels of end-tidal CO (47 ± 5 and 45 ± 5 Torr, respectively) and subsequently increased linearly in most infants. We conclude that during CO rebreathing the initially delayed and subsequently linear responses of the GG and AN EMGs indicate a high CO threshold for these muscles. 2 2 2 2 2 2 2
  • Authors

    Digital Object Identifier (doi)

    Author List

  • Carlo WA; Martin RJ; Difiore JM
  • Start Page

  • 2434
  • End Page

  • 2439
  • Volume

  • 65
  • Issue

  • 6