Regional velopharyngeal compliance in the rat: influence of tongue muscle contraction

Zutphen, Cornelius Van; Janssen, P. L.; Hassan, Mahmood Ul; Cabrera, R.; Bailey, E. Fiona; Fregosi, Ralph F.

doi:10.1002/nbm.1129

Cited by 14 publications

(15 citation statements)

References 46 publications

(61 reference statements)

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“…As soft tissue is not compressible, contraction of the GG probably enabled enlargement of the pharynx by caudal displacement of soft tissue outside the maxilo-mandibular bony enclosure, as described by TSUIKI et al [11]. While compliance may decrease at the level of the oropharynx during GG stimulation [15], we did not find a change in compliance at the level of the velopharynx, confirming previous observations in humans [7,15], as well as in animals studied with MRI [14,25]. This finding supports the notion that GG stimulation alters velopharyngeal patency primarily by its effect on the surrounding external pressure [26].…”

Section: Sleep-related Disorders Y Dotan Et Alsupporting

confidence: 89%

Parameters affecting pharyngeal response to genioglossus stimulation in sleep apnoea

Dotan¹,

Golibroda²,

Oliven³

et al. 2010

European Respiratory Journal

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Chronic stimulation of the hypoglossus nerve may provide a new treatment modality for obstructive sleep apnoea (OSA). In previous studies we observed large differences in response to stimulation of the genioglossus (GG). We hypothesised that both individual patient characteristics and the area of the GG stimulated are responsible for these differences.In the present study, we compared the response to GG electrical stimulation at the anterior area (GGa-ES), which activates the whole GG and the posterior area (GGp-ES), which activates preferentially the longitudinal fibres. Studies were performed in 14 propofol-sedated OSA patients. The parameters evaluated included cephalometry, pressure-flow relationship and pharyngeal shape and compliance assessed by pharyngoscopy.Compared with GGa-ES, GGp-ES resulted in significantly larger decreases in the critical value of end-expiratory pressure (Pcrit) (from 3.8¡2.2 to 2.9¡3.3 and -2.0¡3.9 cmH 2 O, respectively (p,0.001)). Both tongue size and velopharyngeal shape (anteroposterior to lateral ratio) correlated significantly with the decrease in Pcrit during respectively; p,0.05). In the patients with the larger tongue size (n57), the decrease in Pcrit reached 8.0¡2.2 cmH 2 O during GGp-ES.We conclude that directing stimulation to longitudinal fibres of the GG improves the flowmechanical effect. In addition, patients with large tongues and narrow pharynx tend to respond better to GGp-ES.

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Section: Sleep-related Disorders Y Dotan Et Alsupporting

confidence: 89%

Parameters affecting pharyngeal response to genioglossus stimulation in sleep apnoea

Dotan¹,

Golibroda²,

Oliven³

et al. 2010

European Respiratory Journal

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“…Indeed, the upper airway was kept open and a progressive intratracheal negative pressure was applied to promote the reduction of the inspiratory flow (flow limitation) but without reaching full airway collapse [12,13]. A similar approach has recently been used to study the intraluminal volume changes in response to negative and positive pressures by means of magnetic resonance imaging [15]. Given that this technique demands the continuous application of positive or negative pressure over an extended period of time for image acquisition, the fastcycling dynamics characterising the upper airway events in OSA could not be mimicked.…”

Section: Discussionmentioning

confidence: 99%

“…In contrast, the model used in the present work was able to simulate the mechanical stress experienced in OSA, since the sequence of mechanical events applied to the upper airway was induced by a dynamic pattern mimicking breathing. Another advantage of this experimental setting was that it allowed the direct measurement of Pcrit (intraluminal pressure causing closure) of the upper airway instead of extrapolating data from partial collapse conditions using a Starling-resistor model, or by introducing catheters into the upper airway [12,13,15].…”

Section: Discussionmentioning

confidence: 99%

Upper airway collapse and reopening induce inflammation in a sleep apnoea model

Almendros

Carreras²,

Ramírez³

et al. 2008

European Respiratory Journal

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The upper airway of obstructive sleep apnoea patients is subjected to recurrent negative pressure swings promoting its collapse and reopening. The aim of the present study was to ascertain whether this mechanical stress induces upper airway inflammation in a rat model.The upper airway of Sprague-Dawley rats was subjected to a periodic pattern of recurrent negative (-40 cmH 2 O, 1 s) and positive (4 cmH 2 O, 2 s) pressures inducing collapse and reopening for 5 h. Rats that were instrumented but not subjected to negative pressure swings were used as controls. The gene expression of the pro-inflammatory biomarkers macrophage inflammatory protein (MIP)-2, tumour necrosis factor (TNF)-a, interleukin (IL)-1b and P-selectin in the soft palate and larynx tissues was assessed by real-time PCR.A marked overexpression of MIP-2, TNF-a, IL-1b and P-selectin (,40-, 24-, 47-and 7-fold greater than controls, respectively) was observed in the larynx tissue; similar results were found in the soft palate tissue (,14-, 7-, 35-and 11-fold greater than controls, respectively).Recurrent upper airway collapse and reopening mimicking those experienced by obstructive sleep apnoea patients triggered an early local inflammatory process. These results could explain the inflammation observed in the upper airway of obstructive sleep apnoea patients.

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confidence: 99%

“…However, we know little about the influence of tongue muscle contraction on VP volume changes in either human subjects or animal models, and recent studies suggest that the VP is a complex pharyngeal region that does not behave uniformly along its length in cats or rats (7,52). For example, the VP in the adult rat is only ϳ10 mm long, but it shows differences in compliance between its most rostral and caudal regions (52). This observation suggests that volume changes evoked by tongue muscle contraction along the VP will not be uniform, and that there is likely a small, highly compliant region that is vulnerable to collapsing pressure, but also amenable to expansion and/or stiffening with contraction of the tongue muscles.…”

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confidence: 99%

Influence of tongue muscle contraction and dynamic airway pressure on velopharyngeal volume in the rat

Fregosi¹

2008

Journal of Applied Physiology

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Fregosi RF. Influence of tongue muscle contraction and dynamic airway pressure on velopharyngeal volume in the rat. J Appl Physiol 104: 682-693, 2008. First published December 13, 2007 doi:10.1152/japplphysiol.01043.2007.-The mammalian pharynx is a collapsible tube that narrows during inspiration as transmural pressure becomes negative. The velopharynx (VP), which lies posterior to the soft palate, is considered to be one of the most collapsible pharyngeal regions. I tested the hypothesis that negative transmural pressure would narrow the VP, and that electrical stimulation of extrinsic tongue muscles would reverse this effect. Pressure (Ϫ6, Ϫ3, 3, and 6 cmH 2O) was applied to the isolated pharyngeal airway of anesthetized rats that were positioned in a 4.7-T MRI scanner. The volume of eight axial slices encompassing the length of the VP was computed at each level of pressure, with and without bilateral hypoglossal nerve stimulation (0.1-ms pulse, one-third maximum force, 80 Hz). Negative pressure narrowed the VP, and either whole hypoglossal nerve stimulation (coactivation of protrudor and retractor muscles) or medial nerve branch stimulation (independent activation of tongue protrudor muscles) reversed this effect, with the greatest impact in the caudal one-third of the VP. The dilating effects of medial branch stimulation were slightly larger than whole nerve stimulation. Positive pressure dilated the VP, but tongue muscle contraction did not cause further dilation under these conditions. I conclude that the narrowest and most collapsible segment of the rat pharynx is in the caudal VP, posterior to the tip of the soft palate. Either coactivation of protrudor and retractor muscles or independent contraction of protrudor muscles caused dilation of this region, but the latter was slightly more effective. apnea; functional electrical stimulation; hypoglossal nerve; magnetic resonance imaging; pharynx; upper airway THE PHARYNX IS A MUSCULAR tube with little skeletal support and is thus subject to collapse as its transmural pressure becomes negative during inspiratory contractions of the diaphragm and accessory inspiratory muscles. Various skeletal muscles residing within the pharyngeal walls (e.g., pharyngeal constrictor muscles), or lying within and adjacent to the pharynx (e.g., tongue and palatal muscles), are capable of dilating and/or stiffening it. Indeed, the posterior segment of the tongue comprises a large portion of the anterior pharyngeal wall, so movement and/or stiffening of the tongue can have a marked impact on the dimensions and compliance of the oropharynx and velopharynx (VP). For both anatomic and physiological reasons, neuromuscular activation is inadequate in at least some patients with primary snoring, upper airway resistance syndrome, or obstructive sleep apnea (41, 54). These patients cannot maintain a positive pharyngeal transmural pressure during sleep, leading to periodic pharyngeal collapse with associated hypoventilation and hypoxia throughout the night.At present, the favored treatme...

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Regional velopharyngeal compliance in the rat: influence of tongue muscle contraction

Cited by 14 publications

References 46 publications

Parameters affecting pharyngeal response to genioglossus stimulation in sleep apnoea

Parameters affecting pharyngeal response to genioglossus stimulation in sleep apnoea

Upper airway collapse and reopening induce inflammation in a sleep apnoea model

Influence of tongue muscle contraction and dynamic airway pressure on velopharyngeal volume in the rat

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