Quantification of Pharyngeal Patency in Patients with Sleep-Disordered Breathing

Abstract

Many techniques are available for the assessment of pharyngeal characteristics in sleep-disordered breathing (SDB). However, most of the reported techniques are invasive to some extent and/or hard to perform during sleep studies. The focus of this concept paper is on the forced oscillation technique (FOT) to quantify pharyngeal patency in patients with SDB. In a pilot study, the potential of FOT for non-invasive and continuous assessment of pharyngeal patency during different types of respiratory events was studied in 8 patients with an established diagnosis of a sleep apnea-hypopnea syndrome. During polysomnography, FOT was applied using a 5-Hz pressure oscillation signal. The respiratory impedance was determined and considered as a marker for pharyngeal patency. The results demonstrate that FOT allows detection of the complete pharyngeal occlusion during obstructive sleep apnea. In addition, we found that central sleep apnea can be associated with pharyngeal closure. We also demonstrated that during the flow-limited breath preceding obstructive apnea, almost complete upper airway closure can occur during either the expiratory or the inspiratory phase. FOT is a suitable method to assess pharyngeal patency continuously and non-invasively during sleep. Furthermore, this technique has the potential to contribute substantially to our knowledge of upper airway physiology in SDB.

Upper Airway Mechanics

“…This was also seen in the UA imaging studies [24]. We recently used the forced oscillation technique (FOT) to study the airway impedance during sleep in OSA patients [25,26,27,28]. The impedance often rises during inspiration but always drops during the following expiration until collapse occurs during the end of an expiration (with Zrs amounting to the level observed during the apnoea).…”

Evaluation of upper airway patency during Cheyne–Stokes breathing in heart failure patients

“…More recently, VANDERVEKEN et al [12] applied FOT in eight patients with predominantly OSA and demonstrated variable increases in |Z| during a small number of central apnoeas. However, to our knowledge, ours is the first study to assess upper airway calibre with FOT in a group consisting of exclusively stable CHF patients with predominantly central events.…”

“…Upper airway closure has previously been reported to occur in some forms of both spontaneous and experimentally induced central apnoea [7,[12][13][14][15].…”

Complex sleep apnoea syndrome

“…The exclusion of these factors is especially important for patients with a history of coronary heart disease, hypertension, and/or atrial fibrillation [29]. It must also be emphasised that airway obstruction, especially in the supine position, can mimic central apnoea [30], while the high prevalence of supine dependency of CompSAS by THOMAS et al [27] was intended, as patients were examined predominantly in the supine position [27]. Overall, the prevalence of CompSAS in clinical settings remains somewhat hazy, while the multitude of pathways leading to CompSAS results in a dynamic phenotype, with the improvement or disappearance of CompSAS activity in some patients, and de novo appearance in others.…”