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Control of laryngeal muscle activity in preterm infants
Insights
Control of laryngeal muscles (LAR) and diaphragm (DIA) impacts infant breathing. LAR muscle activity precedes diaphragm activity, influencing airflow and respiratory responses to CO2 and airway occlusion.
Area of Science:
- Respiratory Physiology
- Neonatal Medicine
- Neuroscience
Background:
- Upper airway muscle control, particularly laryngeal (LAR) muscles, is crucial for optimizing airflow during respiration.
- Understanding the coordination between upper airway and chest wall muscles is vital for infant respiratory health.
Purpose of the Study:
- To investigate the electromyographic (EMG) activity of laryngeal (LAR) and diaphragm (DIA) muscles in sleeping preterm infants.
- To examine the influence of chemical (CO2) and mechanical (airway occlusion) feedback on respiratory muscle activity and timing.
Main Methods:
- Recorded esophageal and skin electrode electromyograms (EMGs) of laryngeal (LAR) and diaphragm (DIA) muscles in 12 unsedated sleeping preterm infants.
- Introduced controlled changes in chemical feedback (4% CO2 inhalation) and mechanical feedback (end-expiratory occlusion).
- Analyzed the temporal relationships between LAR EMG, DIA EMG, and inspiratory airflow.
Main Results:
- Phasic inspiratory LAR EMG onset preceded DIA EMG and inspiratory airflow.
- Inhalation of 4% CO2 increased peak LAR and DIA EMGs without altering temporal relationships.
- End-expiratory occlusion prolonged both LAR and DIA EMGs, affecting mechanical inspiratory time.
- Laryngeal muscle activity was linked to expiratory flow braking and the onset of subsequent inspirations.
Conclusions:
- Respiratory activity of laryngeal muscles is modulated by both chemical and mechanoreceptor stimulation.
- Simultaneous recording of LAR and DIA EMGs indicates distinct roles for upper airway and chest wall muscles in shaping infant expiratory flow patterns.
Abstract:
Control of upper airway muscles, such as those in the larynx, appears important for optimizing airflow patterns during normal respiration. Electromyograms (EMGs) of the laryngeal (LAR) area and diaphragm (DIA) were recorded with esophageal and skin electrodes, respectively, in 12 unsedated sleeping preterm infants during changes in chemical and mechanical feedback. Onset of phasic inspiratory LAR EMG preceded both DIA EMG and inspiratory airflow by 70 +/- 60 and 180 +/- 80 ms, respectively. Inhalation of 4% CO2 increased both peak LAR and DIA EMGs but did not alter their temporal relationships. End expiratory occlusion prolonged both LAR (600 +/- 120 to 930 +/- 290 ms, p less than 0.05) and DIA EMGs (690 +/- 180 to 940 +/- 270 ms, p less than 0.005) as well as mechanical inspiratory time. Early braking of expiratory flow was accompanied by persistence of DIA EMG into the expiratory phase, while termination of mid- to late expiratory braking was associated with onset of the LAR EMG of the subsequent inspiration. We conclude that respiratory activity of the LAR EMG is altered by both chemical and mechanoreceptor stimulation. Furthermore, simultaneous recording of LAR and DIA EMGs suggests that upper airway and chest wall muscles have different effects on expiratory flow patterns in human infants.