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Apnea threshold and breathing rhythmicity in newborn lambs
E Canet1, J P Praud, J M Laberge
1Centre Jeremy Rill, Département de Pédiatrie, Faculté de Médecine, Université de Sherbrooke, Quebec, Canada.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|June 1, 1993
Summary
Newborn lamb breathing control is sensitive to chemical stimuli. Hypoxia and carotid body integrity significantly influence the apnea threshold, impacting respiratory stability.
Area of Science:
- Neonatal Physiology
- Respiratory Control
- Chemoreception
Background:
- Breathing rhythmicity in newborns is crucial for survival.
- Chemical stimuli, like carbon dioxide and oxygen levels, are key regulators.
- Understanding the apnea threshold is vital for assessing respiratory vulnerability.
Purpose of the Study:
- To investigate how removing chemical stimuli affects breathing in newborn lambs.
- To determine the specific threshold of arterial carbon dioxide (PaCO2) at which breathing stops (apnea threshold).
Main Methods:
- Utilized graded extracorporeal CO2 removal with apneic oxygenation.
- Studied three groups of lambs based on age (<2 days vs. 12 days) and carotid body (CB) integrity (intact vs. denervated).
- Assessed breathing patterns under varying oxygenation levels (hyperoxia, normoxia, hypoxia).
Main Results:
- Chemical drive suppression consistently led to apnea across all groups.
- The PaCO2 apnea threshold was higher in younger lambs, indicating less mature respiratory control.
- Hypoxia lowered the apnea threshold, making lambs more susceptible to respiratory cessation.
- Carotid body denervation (CBD) resulted in a higher apnea threshold, showing the CB's importance.
Conclusions:
- Postnatal maturation, oxygen levels, and carotid body status are critical determinants of the PaCO2 apnea threshold.
- 12-day-old CBD lambs exhibited breathing patterns close to their apnea threshold, highlighting their vulnerability.