Abstract
The biphasic respiratory response (hyperpnea followed by hypoventilation) of the newborn human has been attributed to central hypoxic depression of the respiratory centers. Recently, we have shown that, in the absence of hypoxia, the excitatory effect of continued carotid sinus nerve (CSN) stimulation fatigues in piglets 4-14 days of age (The Physiologist 23:140, 1980). To study maturation of the excitatory effects of the CSN without confounding blood gas changes, we compared changes in respiratory output (RO=f × neural tidal volume) during electrical CSN stimulation in young and older piglets (7 piglets 4-14 days; 7 piglets 20-34 days). The piglets were anesthetized, vagotomized, paralyzed and ventilated (FIO2=1.0). End-tidal CO2 was kept constant with a servo-controller (mean end-tidal CO2=30.2mmHg). RO was quantified by moving average of the rectified phrenic neurogram. The RO of all piglets increased (p<.01) at the onset of CSN stimulation due to change in both frequency and neural tidal volume. However, by 50-60s, the average RO had decreased to 54±7% (±SEM) of peak RO in young piglets whereas in the 7 older piglets respiratory output was 78±5% of peak. This difference was significant (p<.025). Again, change in both frequency and neural tidal volume accounted for the changes in RO. These findings demonstrate that central neural mechanisms control the biphasic respiratory response to hypoxia. We conclude that neural maturation during the first 4 weeks of life permits the more sustained response seen in the older animals.
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Lawson, E., Haddad, A., Long, W. et al. 1351 CENTRAL NEURAL MATURATION OF THE EXCITATORY RESPONSE TO CAROTID SINUS NERVE STIMULATION. Pediatr Res 15 (Suppl 4), 668 (1981). https://doi.org/10.1203/00006450-198104001-01380
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DOI: https://doi.org/10.1203/00006450-198104001-01380