Prolonged partial upper airway obstruction during sleep - an underdiagnosed phenotype of sleep-disordered breathing

Abstract

Obstructive sleep apnea syndrome (OSAS) is a well-recognized disorder conventionally diagnosed with an elevated apnea-hypopnea index. Prolonged partial upper airway obstruction is a common phenotype of sleep-disordered breathing (SDB), which however is still largely underreported. The major reasons for this are that cyclic breathing pattern coupled with arousals and arterial oxyhemoglobin saturation are easy to detect and considered more important than prolonged episodes of increased respiratory effort with increased levels of carbon dioxide in the absence of cycling breathing pattern and repetitive arousals. There is also a growing body of evidence that prolonged partial obstruction is a clinically significant form of SDB, which is associated with symptoms and co-morbidities which may partially differ from those associated with OSAS. Partial upper airway obstruction is most prevalent in women, and it is treatable with the nasal continuous positive pressure device with good adherence to therapy. This review describes the characteristics of prolonged partial upper airway obstruction during sleep in terms of diagnostics, pathophysiology, clinical presentation, and comorbidity to improve recognition of this phenotype and its timely and appropriate treatment.

Keywords: UARS; flow limitation; increased respiratory resistance; non-apneic snoring; prolonged partial upper airway obstruction; simple snoring; sleep; sleep apnea.

Fig. 1

Example of overnight PtcCO₂ and SaO₂ profile with expanded view of normal steady breathing, prolonged flow limitation and hypopnea sequence. Note the association between breathing type and PtcCO₂ (15). (Reproduced with permission from Respir Physiol Neurobiol). PtcCO₂=transcutaneous carbon dioxide; SaO₂=arterial oxyhemoglobin saturation.

Fig. 2

Example of a 5-min polysomnography period. At the beginning of the sheet, respiratory movements are stable; flow channel shows slight flow limitation and mouth breathing. Negative esophageal pressure is increased up to −30 cm H₂O. Emfit high-frequency channel shows multiple spikes. At the middle of sheet (marked with a black arrow) is a short arousal with opening of upper airway, normalizing esophageal pressure values and cease of spiking. Gradually breathing effort starts to increase again. Channels from top: thoracic and abdominal belts, flow by nasal pressure transducer, esophageal pressure, Emfit high-frequency channel, Emfit low-frequency channel, arterial oxyhemoglobin saturation, snoring, and pulse.

Fig. 3

The three-dimensional figures demonstrate that the associations are non-linear and suggest that in women (left-hand panel) there is a consistently increasing susceptibility for prolonged partial upper airway obstruction after 65 years of age over the entire BMI range, whereas in men (right-hand panel) partial obstruction associates with the combination of high age–high BMI (51). (Reproduced with permission from Respir Physiol Neurobiol).