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Ventilatory response to 100% and 15% O2 during wakefulness and sleep in preterm infants
Insights
Preterm infants show intact peripheral chemoreceptor activity during wakefulness and sleep, responding to oxygen changes. However, a late decrease in ventilation during hypoxia is absent in non-rapid eye movement sleep.
Area of Science:
- Neonatal Physiology
- Respiratory Control
- Sleep Medicine
Background:
- Preterm infants exhibit unique cardiorespiratory control mechanisms.
- Understanding ventilatory responses to oxygen is crucial for preterm infant care.
Purpose of the Study:
- To investigate the ventilatory response to hyperoxia (100% O2) and hypoxia (15% O2) in preterm infants during wakefulness, REM sleep, and N-REM sleep.
- To assess peripheral chemoreceptor function in preterm infants across different sleep-wake states.
Main Methods:
- Studied eleven preterm infants (birthweight 1770 ± 102 g; gestational age 32 ± 1 weeks).
- Measured ventilatory (Ve) and arterial carbon dioxide partial pressure (PaCO2) responses to 100% and 15% O2.
- Defined sleep-wake states using EEG, EOG, ECG, and body movements.
Main Results:
- 100% O2 caused immediate decreases followed by late increases in ventilation across all states; PaCO2 decreased.
- Apnea duration after 100% O2 administration was similar across states.
- 15% O2 induced a late decrease in ventilation during wakefulness and REM sleep, but a sustained increase during N-REM sleep; PaCO2 decreased significantly only in N-REM sleep.
Conclusions:
- Peripheral chemoreceptor activity appears qualitatively intact in preterm infants during wakefulness and sleep.
- The absence of a late ventilatory decrease during hypoxia in N-REM sleep suggests state-dependent respiratory control differences.
Abstract:
To examine the ventilatory response to 100% and 15% O2 during wakefulness and sleep, we studied eleven preterm infants birthweight 1770 +/- 102 g; gestational age 32 +/- 1 weeks; postnatal age 31 +/- 5 days) on two occasions each. Wakefulness (W) was present around feeding time and was defined by open eyes for more than 2 min plus presence of purposeful movements. Rapid eye movement (REM) and non-rapid eye movement (N-REM) sleep were defined using electroencephalogram (EEG), electrooculogram (EOG), electrocardiogram (ECG), and body movements. During 100% O2 breathing, immediate (30 s) decreases of 28, 39 and 37% followed by late (5 min) increases in ventilation (Ve) of 42, 49 and 27% were observed during W, REM and N-REM sleep (P greater than 0.05 between states). PaCO2 decreased significantly towards the end of 5 min of breathing 100% O2 in W, REM and N-REM sleep (P greater than 0.05). Average duration of apnea following sudden administration of 100% O2 was 8.5, 11.1 and 8.8 s during W, REM and N-REM sleep (P greater than 0.05 between states). During inhalation of 15% O2, there was a late decrease in ventilation of 19 and 23% during wakefulness and REM sleep, and a sustained increase in Ve of 17% during N-REM sleep (P less than 0.05). PaCO2 at the end of hypoxia (5 min) was significantly decreased in N-REM sleep only (P less than 0.05). We suggest that (i) peripheral chemoreceptor activity is qualitatively intact during W and sleep, as reflected by (a) the immediate changes in Ve during inhalation of high and low O2, and (b) apnea following administration of 100% O2. (ii) The late decrease in ventilation with hypoxia is absent in N-REM sleep.