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Centre de Recherche, Hôpital Laval, Institut Universitaire de Cardiologie et de Pneumologie de l'Université Laval, Québec, Canada G1V 4G5
Upper airway (UA) dynamics can be evaluated during wakefulness
by using electrical phrenic nerve stimulation (EPNS) applied at
end-expiration during exclusive nasal breathing by dissociating twitch
flow and phasic activation of UA muscles. This technique can be used to
quantify the influence of nonphasic electromyographic (EMG) activity on
UA dynamics. UA dynamics was characterized by using EPNS when
increasing tonic EMG activity with CO2 stimulation in six
normal awake subjects. Instantaneous flow, esophageal and nasopharyngeal pressures, and genioglossal EMG activity were recorded during EPNS at baseline and during CO2 ventilatory
stimulation. The proportion of twitches presenting an inspiratory-flow
limitation pattern decreased from 100% at baseline to 78.7 ± 21.4% (P = 10
4) during CO2
rebreathing. During CO2 stimuli, maximal inspiratory twitch
flow (
Imax) of flow-limited twitches
significantly rose, with the driving pressure at which flow limitation
occurred being more negative. For the group as a whole, the increase in
Imax and the decrease in pressure were
significantly correlated with the rise in end-expiratory EMG activity.
UA stability assessed by EPNS is dramatically modified during
CO2 ventilatory stimulation. Changes in tonic genioglossus
EMG activity significantly contribute to the improvement in UA stability.
electromyographic tonic activity; diaphragm twitch; electrical phrenic nerve stimulation
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