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Influence of upper airway negative pressure reflex on response to airway occlusion in sleeping infants
B T Thach1, G L Schefft, D L Pickens
1Edward Mallinckrodt Department of Pediatrics, Children's Hospital, Washington University School of Medicine, St. Louis, Missouri.
Insights
Infants possess an upper airway reflex that responds to inspiratory pressure. This reflex, triggered by negative airway pressure, influences breathing mechanics in infants.
Area of Science:
- Pediatric Respiratory Physiology
- Neuroscience
- Infant Breathing Dynamics
Background:
- Artificial upper airway suction is known to inhibit diaphragmatic activity in animals and infants.
- The impact of spontaneously generated upper airway suction on human infant breathing remains largely uncharacterized.
Purpose of the Study:
- To investigate the effects of spontaneously generated upper airway suction on diaphragmatic activity and inspiratory mechanics in human infants.
- To determine the threshold for the upper airway reflex response to inspiratory pressure.
Main Methods:
- Studied nine tracheostomized infants during quiet sleep.
- Briefly occluded the tracheostomy airway at end expiration to create suction in either the upper and lower airways or the lower airway only.
- Measured peak airway pressure, rate of pressure decrease, and inspiratory pressure waveform characteristics.
Main Results:
- Peak airway pressure was less negative and the rate of pressure decrease was slower during combined upper and lower airway occlusions compared to lower airway occlusions alone.
- The threshold for this inhibitory response was found to be less than or equal to 4 cmH2O suction pressure.
- A decrease in the slope of the inspiratory pressure waveform was more pronounced with combined occlusions.
Conclusions:
- Infants exhibit an upper airway reflex response to negative inspiratory pressure.
- This reflex alters the peak, slope, and overall shape of the inspiratory pressure waveform.
- The findings elucidate a novel mechanism influencing infant respiratory control.
Abstract:
Artificially produced upper airway suction inhibits the diaphragm in animals and infants; however, the effects of spontaneously generated suction in humans are unknown. We studied nine tracheostomized infants because separation of the upper from the lower airway allowed us to channel suction created by an occluded inspiratory effort to both upper and lower airways (upper + lower airway occlusions) or to the lower airway only (lower airway occlusion). The tracheostomy airway was briefly occluded at end expiration during quiet sleep. In upper + lower airway occlusions, peak airway pressure of the first occluded breath was less negative and rate of pressure decrease slower than that of lower airway occlusions, indicating that upper airway suction inhibits thoracic inspiratory muscles. The threshold for this response was less than or equal to 4 cmH2O suction pressure. The effect on inspiratory time was variable. A decrease in slope of the inspiratory pressure waveform occurring at approximately 0.12 s after inspiration onset was more marked in upper + lower airway occlusions. We conclude that infants have an upper airway reflex response to inspiratory pressure that alters not only the peak and slope but also the shape of the inspiratory pressure waveform.