Forced oscillation measurements do not affect upper airway muscle tone or sleep in clinical studies

• Published in: The European respiratory journal Vol. 18; no. 2; pp. 335 - 339
• Main Authors: Badia, J.R, Farre, R, Rigau, J, Uribe, M.E, Navajas, D, Montserrat, J.M
• Format: Journal Article
• Language: English
• Published: Leeds Eur Respiratory Soc 01.08.2001; Maney
• Subjects: Airway Obstruction - diagnosis; Airway Obstruction - physiopathology; Biological and medical sciences; Electroencephalography; Electromyography; Female; Humans; Investigative techniques of respiratory function; Investigative techniques, diagnostic techniques (general aspects); Male; Medical sciences; Middle Aged; Respiratory Function Tests - adverse effects; Respiratory Function Tests - methods; Respiratory Muscles - physiopathology; Severity of Illness Index; Sleep Apnea Syndromes - diagnosis; Sleep Apnea Syndromes - physiopathology; Human; Measurement; Evaluation; Sleep apnea syndrome; Upper respiratory tract; Respiratory disease; Sleep disorder; Exploration; Obstruction; Sleep; Respiratory muscle; Forced oscillation; Muscular tonus
• ISSN: 0903-1936; 1399-3003
• DOI: 10.1183/09031936.01.00085001

Upper airway obstruction in the sleep apnoea/hypopnoea syndrome (SAHS) can be easily assessed by measuring respiratory impedance with the forced oscillation technique (FOT). This methodology has been proposed as a useful clinical tool both for the diagnosis of sleep breathing disorders and for continuous positive airway pressure (CPAP) titration. However, previous studies suggest that the application of high-frequency pressure oscillation to the upper airway may induce changes in the electroencephalogram (EEG) or upper airway muscle function. The effect of FOT measurements on upper airway muscle tone and EEG in clinical sleep studies was examined. Seven patients with moderate SAHS were included (age: 54+/-11 yrs; apnoea/hypopnoea index: 43+/-21 events x h(-1); body mass index: 30+/-2 kg x m(-2)). Genioglossus surface electromyogram activity (EMGgg) and EEG signal were analysed with and without FOT application (frequency: 5 Hz and 30 Hz; peak-to-peak pressure oscillation: 1 cmH2O) during stable sleep. Measurements were carried out in two different situations. Step 1: applying FOT during episodes of obstructive events or flow limitation; and step 2: during prolonged periods of normal breathing at optimal CPAP. The root mean square of EMGgg activity and fast Fourier analysis (alpha and delta bands) of the EEG signal were performed. The application of FOT did not increase EMGgg activity in any of the situations studied. In addition, no evidence of the effects on EEG was found: alpha/delta relationship: awake:0.70, baseline sleep:0.13, FOT(5 Hz):0.18, FOT(30 Hz):0.11. The presented results suggest that the use of forced oscillation technique over the ranges of frequency and amplitude proposed for clinical sleep studies does not induce changes in upper airway muscle activity and neurological variables in patients with sleep apnoea/hypopnoea syndrome.