title: Increased load on the respiratory muscles in obstructive sleep apnea.
abstract: We wished to quantify, in patients with obstructive sleep apnoea (OSA), the activity of the respiratory muscles in relation to upper airway occlusion and patency in sleep. We hypothesized that particular levels of neuromuscular activation are directly associated with upper airway patency. 21 patients with previously diagnosed OSA and 21 healthy control subjects underwent respiratory muscle testing and polysomnography. Neural respiratory drive, as measured by the electromyogram of the diaphragm (EMG(di)) was elevated in the obese OSA patients, awake and supine (13.1(5.6)%max), compared to normal subjects (mean (SD) 8.1(2.3)%max, p<0.01). During unobstructed breathing in sleep (stage N2) normal subjects had an EMG(di) of 7.7(3.9) compared to 22.8(19.2)%max in the OSA group (p<0.001). Prior to airway occlusion, EMG(submandibular) and EMG(di) dropped markedly, and then, following occlusion, increased progressively to their highest levels at airflow onset. Patients with OSA require specific and increased levels of neural respiratory drive to sustain ventilation in sleep.
authors.affiliation: King's College London School of Medicine, London, UK. joerg.steier@kcl.ac.uk
authors.forename: Joerg
authors.initials: J
authors.lastname: Steier
authors.forename: Caroline J
authors.initials: CJ
authors.lastname: Jolley
authors.forename: John
authors.initials: J
authors.lastname: Seymour
authors.forename: Katie
authors.initials: K
authors.lastname: Ward
authors.forename: Yuan M
authors.initials: YM
authors.lastname: Luo
authors.forename: Michael I
authors.initials: MI
authors.lastname: Polkey
authors.forename: John
authors.initials: J
authors.lastname: Moxham
mesh_terms: D000328:Adult; D000403:Airway Resistance / Q000502:physiology; D000704:Analysis of Variance; D004576:Electromyography / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology; D017286:Polysomnography / Q000379:methods; D012123:Pulmonary Ventilation / Q000502:physiology*; D012132:Respiratory Muscles / Q000503:physiopathology*; D020181:Sleep Apnea, Obstructive / Q000473:pathology* / Q000503:physiopathology*