title: Acute and chronic responses of the upper airway to inspiratory loading in healthy awake humans: an MRI study.
abstract: We assessed upper airway responses to acute and chronic inspiratory loading. In Experiment I, 11 healthy subjects underwent T(2)-weighted magnetic resonance imaging (MRI) of upper airway dilator muscles (genioglossus and geniohyoid) before and up to 10 min after a single bout of pressure threshold inspiratory muscle training (IMT) at 60% maximal inspiratory mouth pressure (MIP). T(2) values for genioglossus and geniohyoid were increased versus control (p<0.001), suggesting that these airway dilator muscles are activated in response to acute IMT. In Experiment II, nine subjects underwent 2D-Flash sequence MRI of the upper airway during quiet breathing and while performing single inspirations against resistive loads (10%, 30% and 50% MIP); this procedure was repeated after 6 weeks of IMT. Lateral narrowing of the upper airway occurred at all loads, whilst anteroposterior narrowing occurred at the level of the laryngopharynx at loads > or =30% MIP. Changes in upper airway morphology and narrowing after IMT were undetectable using MRI.
authors.affiliation: Centre for Sports Medicine and Human Performance, School of Sport and Education, Brunel University, Uxbridge, Middlesex UB8 3PH, UK.
authors.forename: Stephen C
authors.initials: SC
authors.lastname: How
authors.forename: Alison K
authors.initials: AK
authors.lastname: McConnell
authors.forename: Bryan J
authors.initials: BJ
authors.lastname: Taylor
authors.forename: Lee M
authors.initials: LM
authors.lastname: Romer
mesh_terms: D000328:Adult; D000403:Airway Resistance / Q000502:physiology*; D001945:Breathing Exercises; D005260:Female; D006801:Humans; D001239:Inhalation / Q000502:physiology*; D008279:Magnetic Resonance Imaging; D008297:Male; D009058:Mouth Breathing; D012132:Respiratory Muscles / Q000502:physiology; D012143:Respiratory Physiological Phenomena; D012137:Respiratory System / Q000033:anatomy & histology*; D013997:Time Factors; D014851:Wakefulness / Q000502:physiology*