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Diaphragmatic activity and ventilation in preterm infants. II. The effects of inhalation of 3% CO2 and abdominal
F J Reis1, D B Cates, L V Landriault
1Department of Pediatrics, University of Manitoba, Winnipeg, Canada.
Insights
Inhaled CO2 increased diaphragmatic electrical activity intensity in preterm infants during sleep. Abdominal loading altered diaphragmatic activity patterns but not overall ventilation.
Area of Science:
- Neonatal Physiology
- Respiratory Control
- Sleep Studies
Background:
- Preterm infants often experience respiratory challenges during sleep.
- Understanding diaphragmatic responses to stimuli is crucial for respiratory support.
Purpose of the Study:
- To investigate the impact of inhaled carbon dioxide (CO2) and abdominal loading on diaphragmatic electromyography (EMGdi) and ventilation in preterm infants during sleep.
Main Methods:
- Studied 10 preterm infants, measuring surface and esophageal diaphragmatic activity (EMGdi) and ventilation.
- Analyzed EMGdi parameters including duration, expiratory to total ratio, and tonic activity.
- Administered 3% inhaled CO2 and applied abdominal loading with sandbags during quiet and REM sleep.
Main Results:
- Inhaled CO2 increased EMGdi intensity but did not alter its duration or pattern.
- 3% CO2 increased ventilation in both quiet and REM sleep due to changes in tidal volume and frequency.
- Abdominal loading increased the duration and ratio of expiratory diaphragmatic activity and tonic activity in REM and quiet sleep.
- Abdominal loading did not significantly affect overall ventilation or breath structure.
Conclusions:
- Inhaled CO2 stimulates diaphragmatic electrical activity intensity in preterm infants.
- Abdominal loading modifies diaphragmatic muscle activation patterns during sleep without altering ventilation.
- These findings provide insights into respiratory control mechanisms in preterm neonates.
Abstract:
To determine the effects of inhaled CO2 and abdominal loading on diaphragmatic electromyography (EMGdi) and ventilation during sleep, we studied 10 preterm infants (birth weight 1,840 +/- 50 g; gestational age 32 +/- 0.6 weeks and postnatal age 10.4 +/- 1.4 days). We measured surface and esophageal diaphragmatic activity. Ventilation was measured using a nasal flowmeter and a flow-through system. Diaphragmatic activity was analyzed for the duration of total phasic and expiratory activities, the expiratory to total phasic activity ratio and the presence of tonic activity (defined by the presence of electrical activity of the diaphragm at the end of expiration). With 3% CO2 in quiet and REM sleep, the intensity of EMGdi increased, but the duration of total phasic activity, the expiratory to total phasic activity ratio and tonic activity did not change. During quiet sleep with 3% CO2, ventilation increased (0.392 +/- 0.028 to 0.616 +/- 0.058 l/min; p = 0.001) due to an increase in tidal volume and frequency. Similar changes occurred in REM sleep. Abdominal loading with sandbags increased the duration of total phasic activity (0.68-0.78 s; p = 0.03), expiratory phasic activity (0.21-0.32 s; p = 0.01), the expiratory to total phasic activity ratio (0.28-0.39; p = 0.03) and diaphragmatic tonic activity (20-60%; p = 0.04) as measured with surface electrodes in REM sleep. It also increased the expiratory to total phasic activity ratio and tonic activity, as measured with surface electrodes in quiet sleep. Abdominal loading did not alter ventilation or the structure of the average breath in either sleep state.(ABSTRACT TRUNCATED AT 250 WORDS)