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Developmental changes in sequential activation of laryngeal abductor muscle and diaphragm in infants
E C Eichenwald1, R G Howell, P C Kosch
1Department of Pediatrics, Harvard Medical School, Boston, Massachusetts.
Insights
Newborn infants often show disrupted respiratory muscle coordination. Maturation and aminophylline treatment improve the sequence of posterior cricoarytenoid muscle (PCA) and diaphragm (DIA) activity for better airflow control.
Area of Science:
- Neonatal Physiology
- Respiratory Control
Background:
- Upper airway muscle activity typically precedes diaphragm activity in adults and animals.
- The coordination of respiratory muscles is crucial for effective airflow control, especially in newborns.
Purpose of the Study:
- To investigate the interplay between the posterior cricoarytenoid muscle (PCA) and diaphragm (DIA) in newborn infants.
- To assess how maturation affects the sequence of respiratory muscle activation in neonates.
Main Methods:
- Electromyograms (EMG) of DIA and PCA, along with tidal volume and airflow, were recorded in full-term, premature, and premature infants with apnea.
- Analysis focused on the timing of PCA and DIA EMG onset relative to each other and to inspiratory airflow.
Main Results:
- The typical sequence of PCA activity preceding DIA activity was frequently disrupted, with 'lag breaths' observed in all infants.
- Lag breaths, where PCA onset followed DIA onset, were more common in premature infants compared to full-term infants.
- Premature infants treated with aminophylline showed a reduced frequency of lag breaths, indicating improved coordination.
Conclusions:
- The coordination between PCA and DIA muscle activation is often disrupted in newborn infants.
- Both physiological maturation and respiratory stimulation with aminophylline can enhance the coordination of PCA and DIA activity, improving respiratory control.
Abstract:
In animals and human adults, upper airway muscle activity usually precedes inspiratory diaphragm activity. We examined the interaction of the posterior cricoarytenoid muscle (PCA), which abducts the larynx, and the diaphragm (DIA) in the control of airflow in newborn infants to assess the effect of maturation on respiratory muscle sequence. We recorded tidal volume, airflow, and DIA and PCA electromyograms (EMG) in 12 full-term, 14 premature, and 10 premature infants with apnea treated with aminophylline. In most breaths, onset of PCA EMG activity preceded onset of DIA EMG activity (lead breaths). In all subjects, we also observed breaths (range 6-61%) in which PCA EMG onset followed DIA EMG onset (lag breaths). DIA neural inspiratory duration and the neuromechanical delay between DIA EMG onset and inspiratory flow were longer in lag than in lead breaths (P < 0.05 and P < 0.01, respectively). The frequency of lag breaths was greater in the premature infants [33 +/- 4% (SE)] than in either the full-term infants (21 +/- 3%, P < 0.03) or the premature infants with apnea treated with aminophylline (16 +/- 2%, P < 0.01). We conclude that the expected sequence of onset of PCA and DIA EMG activity is frequently disrupted in newborn infants. Both maturation and respiratory stimulation with aminophylline improve the coordination of the PCA and DIA.