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Synergistic behavior of inspiratory muscles after diaphragmatic fatigue in the newborn
Insights
In newborn infants, diaphragmatic muscle fatigue can lead to apnea. However, recruiting intercostal muscles can prevent this, highlighting synergistic respiratory muscle function in neonates.
Area of Science:
- Neonatal physiology
- Respiratory mechanics
Background:
- Diaphragmatic fatigue is a concern in newborns.
- Understanding compensatory mechanisms is crucial for infant respiratory health.
Purpose of the Study:
- To investigate diaphragmatic and intercostal muscle activity post-diaphragmatic fatigue in neonates.
- To identify patterns of rib cage and abdominal motion during respiratory distress.
Main Methods:
- Studied 15 newborn infants using magnetometers for motion and electromyograms (EMG) for muscle activity.
- Analyzed EMG frequency spectrum to identify diaphragmatic and intercostal muscle fatigue.
- Observed two distinct response patterns to diaphragmatic fatigue.
Main Results:
- Twelve infants experienced 66 episodes of muscle fatigue.
- Five infants recruited intercostal muscles, normalizing diaphragmatic EMG and preventing clinical deterioration.
- Seven infants showed no intercostal recruitment, and diaphragmatic fatigue led to apnea.
Conclusions:
- Synergistic action between diaphragm and intercostal muscles enhances respiratory performance in newborns.
- Intercostal muscle recruitment is a key compensatory mechanism that can prevent apnea in neonates experiencing diaphragmatic fatigue.
Abstract:
We studied diaphragmatic and intercostal muscle activity and the pattern of motion of rib cage and abdomen after diaphragmatic muscle fatigue in 15 newborn infants (birth wt 1,251 +/- 424 g, mean +/- SD). Rib cage and abdominal motion were monitored with magnetometers and intercostal and diaphragmatic electromyograms (EMG's) with surface electrodes. Twelve infants showed a total of 66 episodes of muscle fatigue identified by EMG frequency spectrum analysis. Two patterns of responses to fatigue were observed. In the first case, five infants consistently recruited their intercostal muscles; this was followed by a normalization of the diaphragmatic frequency spectrum. In these infants, recruitment of intercostal muscles successfully prevented any clinical deterioration. In the second, seven infants showed no change in their intercostal muscle activity, and diaphragmatic fatigue was followed by apnea. We conclude that in newborn infants the synergistic behavior of the diaphragm and intercostal muscles can maximize the performance of these muscles and, in some infants, seems to prevent development of apnea.