Pathogenesis of apneas in hypersomnia-sleep apnea syndrome
ABSTRACT To define the pathogenesis of apneas, eight patients with hypersomnia-sleep apnea syndrome were studied during nocturnal sleep. Diaphragmatic and genioglossal electromyograms quantitated as moving time average activity showed parallel periodic fluctuations resembling the pattern of Cheyne-Stokes breathing. Hypopneas and occlusive apneas occurred at the nadir of these cyclic changes, and mixed apneas represented an extreme of this periodicity with no inspiratory activity at the nadir of the cycle. Tracings of central apneas were compatible with an extremely prolonged expiratory phase. Electromyogram activity of both muscles showed an inversely linear relationship with oxygen saturation but genioglossal activity at the resolution of upper airway occlusion was increased out of proportion to the increase in diaphragmatic activity and the degree of oxygen desaturation. These results indicated that occlusive and mixed apneas result from an instability of ventilatory control during sleep, which seems to be an exaggeration of periodic breathing observed at sleep onset.
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- "As outlined above, considerable research and clinical interest has centered on the GG and more specifically, on the " phasic inspiratory " activities of this muscle (Berry et al., 1997; Hudgel and Harasick, 1990; Hudgel et al., 1984; Onal et al., 1982; Pillar et al., 2001). By the same token, studies conducted by White and colleagues drew attention to the " tonic " component and the potential for this " background " activity that persists through inspiration and expiration to contribute to airway patency in the presence of an anatomically compromised airway (Fogel et al., 2001; Fogel et al., 2005; McGinley et al., 2008; Mezzanotte et al., 1992; Tangel et al., 1992; Tangel et al., 1991; Wiegand et al., 1991). "
ABSTRACT: Upper airway muscles play an important role in regulating airway lumen and in increasing the ability of the pharynx to remain patent in the face of subatmospheric intraluminal pressures produced during inspiration. Due to the considerable technical challenges associated with recording from muscles of the upper airway, much of the experimental work conducted in human subjects has centered on recording respiratory-related activities of the extrinsic tongue protudor muscle, the genioglossus (GG). The GG is one of eight muscles that invest the human tongue (Abd-El-Malek, 1939). All eight muscles are innervated by the hypoglossal nerve (cranial nerve XII) the cell bodies of which are located in the hypoglossal motor nucleus (HMN) of the caudal medulla. Much of the earlier work on the respiratory-related activity of XII motoneurons was based on recordings obtained from single motor axons dissected from the whole XII nerve or from whole muscle GG EMG recordings. Detailed information regarding respiratory-related GG motor unit activities was lacking until as recently as 2006. This paper examines key findings that have emerged from the last decade of work conducted in human subjects. Wherever appropriate, these results are compared with results obtained from in vitro and in vivo studies conducted in non-human mammals. The review is written with the objective of facilitating some discussion and some new thoughts regarding future research directions. The material is framed around four topics: (a) motor unit type, (b) rate coding and recruitment, (c) motor unit activity patterns, and (d) a compartment based view of pharyngeal airway control.Respiratory Physiology & Neurobiology 04/2011; 179(1):14-22. DOI:10.1016/j.resp.2011.04.018 · 1.97 Impact Factor
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ABSTRACT: The pathophysiology of obstructive sleep apnoea (OSA) is complex and incompletely understood. A narrowed upper airway is very common among OSA patients, and is usually in adults due to nonspecific factors such as fat depo- sition in the neck, or abnormal bony morphology of the upper airway. Functional impairment of the upper airway dilating muscles is particularly impor- tant in the development of OSA, and patients have a reduction both in tonic and phasic contraction of these muscles during sleep when compared to normals. A variety of defective respiratory control mechanisms are found in OSA, including impaired chemical drive, defective inspiratory load responses, and abnormal upper airway protective reflexes. These defects may play an important role in the abnor- mal upper airway muscle responses found among patients with OSA. Local upper airway reflexes mediated by surface receptors sensitive to intrapharyngeal pressure changes appear to be important in this respect. Arousal plays an important role in the termination of each apnoea, but may also contribute to the development of further apnoea, because of a reduction in respi- ratory drive related to the hypocapnia which results from postapnoeic hyperventi- lation. A cyclical pattern of repetitive obstructive apnoeas may result. A better understanding of the integrated pathophysiology of OSA should help in the development of new therapeutic techniques.
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ABSTRACT: Chronic inflammatory processes frequently lead to the abnormal replacement of normal tissue elements by increased numbers of fibroblasts and fibrous connective tissue, i.e., fibrosis. Since the growth of fibroblasts requires that these cells be attached to an extracellular support, the current study was designed to determine if the interaction between the fibroblast attachment factor fibronectin and the C1q component of complement could support fibroblast attachment and growth and thus could form a basis for the attachment of fibroblasts in abnormal tissue locations in those inflammatory states where C1q is bound. Fibronectin purified from human plasma supported attachment of both Chinese hamster ovary cells and of normal fetal lung fibroblasts (HFL-1) to C1q coated substrates. The attachment activity was approximately twice that of attachment to collagen, and was specific, as no attachment occurred to albumin coated substrates. Cells attached to C1q substrates demonstrated characteristic 'spreading' similar to those on collagen. Moreover, the C1q substrate resembled collagen in its ability to support fibroblast growth. Further, the ability of the interaction between C1q and fibronectin to mediate attachment of fibroblasts to immune complexes was demonstrated by the formation of fibroblast-red blood cell-immune complex rosettes, a process that was dependent on both fibronectin and C1q. Thus, the interaction between fibronectin and C1q could serve as the basis for fibroblast attachment and growth in abnormal tissue sites where immune complexes are formed and could be a contributing factor to the development of fibrosis.Clinical & Experimental Immunology 11/1983; 54(1):239-47. · 3.04 Impact Factor