Assessment of upper airway stabilizing forces with the use of phrenic nerve stimulation in conscious humans.
Phrenic nerve stimulation (PNS) applied at end-expiration allows the investigation of passive upper airway (UA) dynamic during wakefulness. Assuming that phasic UA dilating/stabilizing forces should modify the UA properties when twitches are applied during inspiration, we compared the UA dynamic responses to expiratory and inspiratory twitches (2 s and 200 ms after expiratory and inspiratory onset, respectively) in nine men (mean age 28 yr). This procedure was repeated with a 2-cm mouth opening provided with a closed mouthpiece. The percentage of flow-limited (FL) twitches was significantly higher when PNS was realized during expiration than during inspiration. Maximal inspiratory flow (Vi(max)) of FL twitches was significantly higher for inspiratory twitches (1,383 +/- 42 and 1,185 +/- 40 ml/s). With mouth aperture, Vi(max) decreased with an increase in the corresponding pharyngeal resistance values, and the percentage of twitch with a FL regimen increased but only for inspiratory twitches. We conclude that 1) UA dynamics are significantly influenced by the inspiratory/expiratory timing at which PNS is applied, 2) the improvement in UA dynamic properties observed from expiratory to inspiratory PNS characterizes the overall inspiratory stabilizing effects, and 3) mouth aperture alters the stability of UA structures during inspiration.
Sériès
Frédéric
F
Centre de Recherche, Hôpital Laval, Institut Universitaire de Cardiologie et de Pneumologie de l'Université Laval, Québec, Canada G1V 4G5. frederic.series@med.ulaval.ca
Ethier
Germain
G
D000328:Adult; D004558:Electric Stimulation; D006801:Humans; D007013:Hypopharynx; D001239:Inhalation; D008280:Magnetics; D008297:Male; D009055:Mouth / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology; D010609:Pharyngeal Muscles / Q000502:physiology*; D010791:Phrenic Nerve / Q000502:physiology*; D011312:Pressure; D012123:Pulmonary Ventilation; D015656:Respiratory Mechanics; D013997:Time Factors