Laryngeal stimulation by an acid solution in the pre-term lamb

Area of Science:

• Neonatal physiology
• Respiratory control
• Gastroenterology

Background:

• Laryngeal chemoreflexes (LCR) protect mature airways but cause apnea/bradycardia in neonates.
• Acid gastro-oesophageal reflux is implicated in infant life-threatening events and SIDS.
• Previous studies suggested LCR are consistently mature in full-term lambs.

Purpose of the Study:

• To investigate if premature birth alters LCR compared to full-term lambs.
• To determine the impact of acid reflux on LCR in preterm neonates.
• To assess the developmental trajectory of LCR in preterm lambs.

Main Methods:

• Laryngeal chemoreflexes were triggered using saline and hydrochloric acid (HCl) in preterm and full-term lambs.
• Responses including apnea, bradycardia, and oxygen desaturation were monitored.
• Experiments were conducted at different postnatal ages (D7 and D14) in preterm lambs.

Main Results:

• Preterm lambs exhibited significantly more pronounced LCR to HCl than full-term lambs.
• Life-threatening events (apnea >90s, severe desaturation, bradycardia) occurred in preterm lambs at D7.
• LCR responses were significantly blunted in preterm lambs by D14.

Conclusions:

• Acid reflux triggers potentially dangerous LCR in preterm lambs at D7.
• Altered LCR in preterm infants may contribute to apnea, bradycardia, and desaturation.
• These findings are relevant before preterm infants reach full-term post-conceptional age.