Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_4586_Библиотеки_им_академика_М_И_Перельмана

scale of respiratory disturbance, in contrast to the all-or-nothing event detection approach [45]. In the same line, in-depth visual analysis was proposed, given inspira­tory ow limitation is a hallmark feature of pharyngeal narrowing. Genta etal. described different airow shapes observed among OSA patients [46]. Flow shape was classied according to the degree of negative effort dependence (NED), dened as the percent reduction in inspiratory ow from peak to mid- inspiratory ow (the plateau phase) with increasing respiratory effort [(Peak ow- Plateau ow)/Peak ow]×100 [46]. NED is a reection of the dynamic compliance of the structure responsible for collapse, with greater NED implying a more compliant airway or structure [46]. Epiglottis collapse was associated with severe NED (89%) and abrupt discontinuities in inspiratory ow, while moderate NED was found among patients with isolated palatal collapse (45%) and lateral wall collapse (50%). Tongue-related obstruction was associated with only a small amount of NED (19%). Moreover, epi­glottic collapse often occurred suddenly and produced another ow shape dened as an abrupt discontinuity, characterized by a rapid and severe reduction in airow (>25% reduction per 50ms) followed by either constant low or immediate airow recovery (Fig.7.3). The epiglottis can be considered as an unstable structure that would sometimes reopen/close repeatedly during inspiration, causing a jagged ow (that can be quantied by the discontinuity and jaggedness indices) [47]. This feature was present among 76% of the ow-limited breaths exhibiting epiglottic collapse [46]. From this it follows that a at ow limitation pattern (small NED) is indicative of tongue-related obstruction, whereas a scooped- out ow limitation pattern (large NED) suggests that the collapse is due to one of the other pharyngeal structures. Altogether, careful assessment of ow shape may prove to be an inexpensive and noninvasive tool of determining the structure causing upper airway collapse. This approach may be helpful in selecting OSA therapy and allow individualized decision making. In 2019, Mann etal. developed and validated a tool that combines ow shape features across multiple known domains (attening, scooping, timing, utter­ing) to estimate airow obstruction objectively across a continuum of severities, using the nasal pressure signal as a clinically applicable means to quantify obstruc­tion [48]. The technique is ready for application to routine clinical PSG, given use of nasal pressure did not yield a substantial deterioration in performance compared to pneumotachography as the physiological gold standard.