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Effect of periodic or regular respiratory pattern on the ventilatory response to low inhaled CO2 in preterm infants
Insights
The ventilatory response to low carbon dioxide (CO2) in preterm infants depends on their resting breathing pattern, not their sleep state. Periodic breathing shows increased breathing frequency, while regular breathing shows increased tidal volume when exposed to CO2.
Area of Science:
- Neonatal Physiology
- Respiratory Control
Background:
- The ventilatory response to carbon dioxide (CO2) is crucial for maintaining homeostasis.
- Understanding this response in preterm infants is vital due to their immature respiratory systems.
Purpose of the Study:
- To investigate if the ventilatory response to low CO2 concentrations in preterm infants is measurable without changes in end-tidal partial pressure of carbon dioxide (PETCO2).
- To determine if this response is dependent on sleep state or dictated by the resting respiratory pattern.
Main Methods:
- 11 preterm infants (gestational age 32 ± 1 wk) were studied during both active and quiet sleep states.
- Infants received 0.5–1.5% CO2 after a control period of breathing 21% O2.
- Infants were categorized based on their resting respiratory pattern (periodic or regular breathing).
Main Results:
- In both sleep states, inhaled CO2 increased ventilation and end-tidal partial pressure of carbon dioxide (PETCO2).
- The ventilatory response was characterized by an increase in breathing frequency for infants with periodic breathing.
- The ventilatory response was characterized by an increase in tidal volume for infants with regular breathing.
- The observed responses were not significantly affected by sleep state.
Conclusions:
- The ventilatory response to low inhaled CO2 in preterm infants is fundamentally dependent on their baseline respiratory pattern (periodic vs. regular).
- Sleep state does not appear to significantly influence this CO2-driven ventilatory response in preterm infants.
Abstract:
We wanted to know whether the ventilatory response to low concentrations of CO2 is measurable in the absence of change in alveolar PCO2, is sleep state dependent, and is dictated by the resting respiratory pattern. Therefore, we gave 11 preterm infants (birth weight, 1,565 +/- 122 g; gestational age, 32 +/- 1 wk; postnatal age, 28 +/- 5 days) 0.5 to 1.5% CO2 after a control period of breathing 21% O2. They were studied on 2 or 3 occasions, the aim being to have 5 infants in each of 2 categories, periodic to regular breathing, and regular to regular breathing, after administration of CO2 in both sleep states (n = 20). In both sleep states, when low CO2 increased ventilation, alveolar PCO2 also increased. The increase in ventilation was primarily due to an increase in breathing frequency if breathing was periodic, and to an increase in tidal volume if breathing was regular. This response was not affected by sleep state. We conclude that changes in respiratory pattern with low inhaled CO2 are fundamentally dependent on whether the baseline respiration is periodic or regular.