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Diaphragmatic activity and ventilation in preterm infants. I. The effects of sleep state
F J Reis1, D B Cates, L V Landriault
1Department of Pediatrics, University of Manitoba, Winnipeg, Canada.
Insights
Sleep significantly impacts diaphragmatic activity and ventilation in preterm infants. Diaphragmatic electrical activity decreases during REM sleep, while ventilation increases, suggesting altered breathing control mechanisms.
Area of Science:
- Neonatal Physiology
- Respiratory Control
Background:
- Sleep state influences respiratory control in infants.
- Understanding diaphragmatic activity during sleep is crucial for preterm infant respiratory management.
Purpose of the Study:
- To investigate the effects of sleep state (quiet vs. REM sleep) on diaphragmatic electrical activity and ventilation in preterm infants.
Main Methods:
- Measured surface and esophageal diaphragmatic electromyograms (EMGdi) and ventilation in 10 preterm infants.
- Analyzed diaphragmatic activity for phasic and tonic components.
- Correlated diaphragmatic activity with ventilation parameters (minute and alveolar ventilation, tidal volume, frequency, inspiratory time).
Main Results:
- Decreased total phasic, expiratory phasic activity, and expiratory to total phasic activity ratio in both surface and esophageal EMGdi from quiet to REM sleep.
- Substantial decrease in tonic activity from quiet to REM sleep in surface EMGdi; rarely observed in esophageal EMGdi.
- Increased minute and alveolar ventilation during REM sleep, primarily due to increased frequency (shorter inspiratory time), with minimal change in tidal volume.
Conclusions:
- Sleep state significantly modulates diaphragmatic electrical activity and ventilation in preterm infants.
- The decrease in tonic activity suggests it may originate from chest wall postural muscles rather than the diaphragm.
- Altered breathing patterns during REM sleep are linked to changes in diaphragmatic drive and inspiratory timing.
Abstract:
To determine the effects of sleep on diaphragmatic activity and ventilation we studied 10 preterm infants (birth weight 1,840 +/- 50 g, gestational age 33 +/- 0.6 weeks, and postnatal age 9.4 +/- 1.4 days). We measured surface and esophageal diaphragmatic electromyograms (EMGdi). Ventilation was measured using a nasal flowmeter and a flow-through system. Diaphragmatic activity was analyzed for total phasic activity, expiratory phasic activity, the expiratory to total phasic activity ratio, and the presence of 'tonic' activity. The latter was defined by the presence of electrical activity and the end of expiration. There was a decrease in the average total phasic activity (1.25 vs. 0.71 s, p = 0.001), expiratory phasic activity (0.67 vs. 0.21 s, p = 0.002), the expiratory to total phasic activity ratio (0.51:0.27 s, p = 0.001) and tonic activity (51 to 5%, p = 0.01) from quiet to REM sleep in the surface EMGdi. Similar changes were found in the esophageal EMGdi, except that tonic activity was rarely observed. In parallel with these changes in electrical activity of the diaphragm, minute ventilation and alveolar ventilation increased from quiet to REM sleep. This increase was primarily related to an increase in frequency with a negligible change in tidal volume. The increase in frequency was primarily due to shortening of inspiratory time. The findings that tonic activity recorded via surface electrodes decreased substantially from quiet to REM sleep and was not observed in the esophageal EMGdi suggests that this tonic activity may represent electrical activity of the postural muscles of the chest wall rather than the diaphragm.