The Mechanics of Mouth-Breathing and Its Role in Nasal and Sleep Disorders (original) (raw)
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Sleep, 1993
Anatomical and/or neuromuscular abnormalities may cause obstructive sleep apnea (OSA), but the contribution of each to the obstructive process is unknown at this time. An anatomic hypothesis of pathogenesis of OS A states that apneics have a structurally narrowed pharynx. An alternative, but not mutually exclusive, neural hypothesis states that apneics have a subnormal activation of pharyngeal dilator muscles during sleep. In fact, apneics appear to have greater activity of the pharyngeal muscles than normals during wakefulness (1,2), suggesting that neuromuscular factors compensate for a structurally narrowed pharynx. In other words, neural factors and anatomic factors interact in a statedependent fashion. Undoubtedly, future research will show that neural and anatomic factors are tightly connected, interrelated and interacting. Because of the complexities posed by the interaction of neural and anatomic factors in the pathogenesis of OSA, we have chosen to separate the two in order to investigate the intrinsic mechanical properties of the pharynx. To this end, we depressed the pharyngeal muscle activity and have evaluated the mechanical properties of the hypotonic pharynx. The static mechanics of the pharyngeal airway is best expressed graphically by static pressure/area relationships, i.e. the "tube law" of the pharynx (Fig. 1). Cross-sectional area of the collapsible pharynx is determined by transmural pressure (Ptm), which is defined as the difference between luminal and tissue pressure (P tm = PI-ptJ This is an extension of the "balance of pressure" concept proposed by Remmers and coworkers (3) and Brouillette and Thach (4). When P trn increases, area increases in accordance with the "tube law" of the
Sleep Medicine, 2018
The recent and distant literature has extensive discussion of how sleep apnea, adeno-tonsillar growth, and facial structural deformity are related. Conventionally, the order of cause and effect are: Inflammatory/infectious process tonsillar/adenoid tissue growth 2) airway obstruction and mouth breathing/Obstructive Sleep Apnea (OSA) 3) altered facial structure (adenoid facies). Using this same reasoning, adenotonsillectomy is the first line of treatment in the prevention of structural abnormalities. However, Christian Guilleminault and his colleagues, through a lifetime of clinical research has challenged this paradigm. Through multiple articles and studies, Guilleminault et al teaches that even slight (subclinical) facial structure/muscle tone variations may be the inciting event triggering mouthbreathing and the eventual adenotonsillar growth in most patients. This is in essence, the reverse of the conventional paradigms. Initial treatments therefore shift from simplified removal of inflammatory tissue to limiting mouth-breathing via musculo-skeletal modification. The purpose of this paper is to synthesize and analyze the recent (and distant) relevant literature to provide support for, and provide a potential anatomic mechanism for Guilleminault et al's paradigm-questioning clinical observations.
The upper airway in sleep: physiology of the pharynx
Sleep Medicine Reviews, 2003
The upper airway is the primary conduit for passage of air into the lungs. Its physiology has been the subject of intensive study: both passive mechanical and active neural in¯uences contribute to its patency and collapsibility. Different models can be used to explain behavior of the upper airway, including the``balance of forces'' (airway suction pressure during inspiration versus upper airway dilator tone) and the Starling resistor mechanical model.
Biomechanics of the upper airway: Changing concepts in the pathogenesis of obstructive sleep apnea
2010
Obstructive sleep apnea (OSA) is a disorder characterized by repetitive, episodic collapse of the pharyngeal airway. Over the last two decades, understanding of the pathophysiology of sleep disordered breathing, which includes OSA, has improved. Once thought to be predominately related to anatomic constriction of the maxillomandibular complex, central nervous system regulation of breathing is now recognized as a significant contributor to the pathogenesis of OSA. Ventilator control, the central response to chemoreceptor phenomena, has important implications for oral and maxillofacial surgeons who treat OSA, particularly for patients who appear refractory to treatment with maxillomandibular advancement (MMA). The purpose of this article is to review the biomechanics of the upper airway as it relates to the pathophysiology of OSA, to discuss emerging concepts of ventilator control mechanisms in normal sleep versus sleep-disordered breathing and to discuss the concept of complex sleep apnea, a new category of sleep disordered breathing with both obstructive and central features.
Neuromechanical control of upper airway patency during sleep
Journal of Applied Physiology, 2006
Obstructive sleep apnea is caused by pharyngeal occlusion due to alterations in upper airway mechanical properties and/or disturbances in neuromuscular control. The objective of the study was to determine the relative contribution of mechanical loads and dynamic neuromuscular responses to pharyngeal collapse during sleep. Sixteen obstructive sleep apnea patients and sixteen normal subjects were matched on age, sex, and body mass index. Pharyngeal collapsibility, defined by the critical pressure, was measured during sleep. The critical pressure was partitioned between its passive mechanical properties (passive critical pressure) and active dynamic responses to upper airway obstruction (active critical pressure). Compared with normal subjects, sleep apnea patients demonstrated elevated mechanical loads as demonstrated by higher passive critical pressures [−0.05 (SD 2.4) vs. −4.5 cmH2O (SD 3.0), P = 0.0003]. Dynamic responses were depressed in sleep apnea patients, as suggested by fail...
Nature and Science of Sleep
Identification of upper airway (UA) obstruction based on pharyngeal factors is important for obstructive sleep apnea (OSA) evaluation. This study is to assess the association between UA collapse characteristics and Friedman tongue position (FTP) in patients with OSA through drug-induced sleep endoscopy (DISE). Patients and Methods: Retrospective study in individuals with OSA who were intolerant to continuous positive airway pressure (CPAP) treatment, submitted to DISE between June 1, 2013, and July 31, 2017. All subjects were classified as having an FTP grade of I to IV, and the velum, oropharynx, tongue base, epiglottis (VOTE) classification was used to analyze the DISE findings. UA collapse characteristics by DISE and FTP grading were compared between groups. The associations between specific DISE findings and FTP were analyzed. Results: In total, 205 patients were assessed. A positive and significant correlation was identified between the presence of retropalatal complete concentric collapse (CCC) and FTP grade, according to the following distributions: I, 17.4%; II, 22.9%; III, 33.7%; and IV, 48.7% (P = 0.014). A logistic regression model revealed that CCC was associated with FTP grade IV. After adjusting for age, sex, body mass index (BMI), and tonsil size (TS), the grade IV individuals had a 4.4-fold higher risk of having CCC than grade I individuals (P = 0.026). Multiple collapse sites and palatopharyngeal or combined (palatopharyngeal and hypopharyngeal) collapse were more prevalent in grade IV individuals. Conclusion: OSA patients intolerant to CPAP have a strong positive correlation between the FTP grade and presence of retropalatal CCC. FTP grade IV is an independent risk factor for velum-CCC, controlling for sex, age, BMI, and TS grade.
Sleep Science, 2022
Objectives: To organize an assessment instrument with questionnaires and myofunctional orofacial/ oropharyngeal assessment for OSA patients and correlate it with the upper airway obstructive site detected during drug-induced sleep endoscopy (DISE). Material and Methods: 29 OSA patients aged 22-65 years with an indication to undergo DISE to evaluate an alternative treatment to PAP and signed the consent form. Patients over 65 years old with maxillofacial deficiency and BMI>30 were excluded. The subjects answered the Pittsburgh, Berlin (snore), and Epworth questionnaires. The myofunctional orofacial/oropharyngeal assessment comprised soft palate, palatine pillars, and uvula (structure and mobility), tonsils (size), mandible (bony bases), hard palate (depth and width), tongue (posture, volume, width, and height), floor of mouth (mylohyoid), tongue suction and sustaining (mobility), "lowering of the back of the tongue" (stimulus), which were scored by three speech-language pathologists with expertise. DISE was scored according to VOTE classification. The statistical analysis (t-test) compared groups without and with obstruction in VOTE with questionnaires and myofunctional orofacial/oropharyngeal assessment. Results: The following were significantly different: snoring frequency (p=0.03) with VOTE/velopharynx; intensity (p=0.02) and frequency of snoring (p=0.03) with VOTE/lateral wall of oropharynx; suction the tongue and sustain (p=0.02) with VOTE/velopharynx; hard palate depth (p=0.02) and width (p=0.05) with obstruction VOTE/epiglottis; tonsils volume (p=0.05) with VOTE/epiglottis; tongue posture (p=0.00) with obstruction VOTE/epiglottis; floor of the mouth (p=0.02) with VOTE/epiglottis. Conclusion: Higher snoring frequency and intensity was observed in patients with obstruction at the velopharynx and oropharyngeal lateral wall. Obstruction at the velopharynx was associated with poor tongue ability to suck the tongue against the hard palate. Obstruction at the epiglottis had structural and functional associations, including the oropharyngeal lateral wall, affected by the palatine tonsils size, depth and width of the hard palate, tongue position, and flaccidity of the floor of mouth. Considering that this is a preliminary study, the data should be carefully verified and not generalized.
Journal of Sleep Research, 2011
The critical pressure at which the pharynx collapses (Pcrit) is an objective measurement of upper airway collapsibility, an important pathogenetic factor in obstructive sleep apnoea. This study examined the inherent variability of passive Pcrit measurement during sleep and evaluated the effects of sleep stage and body posture on Pcrit. Repeated measurements of Pcrit were assessed in 23 individuals (15 male) with diagnosed obstructive sleep apnoea throughout a single overnight sleep study. Body posture and sleep stage were unrestricted. Applied upper airway pressure was repetitively reduced to obtain multiple measurements of Pcrit. In 20 subjects multiple measurements of Pcrit were obtained. The overall coefficient of repeatability for Pcrit measurement was 4.1 cm H 2 O. Considering only the lateral posture, the coefficient was 4.8 cm H 2 O. It was 3.3 cm H 2 O in the supine posture. Pcrit decreased from the supine to lateral posture [supine mean 2.5 cm H 2 O, 95% confidence interval (CI) 1.4-3.6; lateral mean 0.3 cm H 2 O, 95% CI)0.8-1.4, P = 0.007] but did not vary with sleep stage (P = 0.91). This study has shown that the overall coefficient of repeatability was 4.1 cm H 2 O, implying that the minimum detectable difference, with 95% probability, between two repeated Pcrit measurements in an individual is 4.1 cm H 2 O. Such variability in overnight measures of Pcrit indicates that a single unqualified value of Pcrit cannot be used to characterize an individualÕs overall collapsibility during sleep. When within-subject variability is accounted for, change in body posture from supine to lateral significantly decreases passive pharyngeal collapsibility.
Nasal obstruction and palate-tongue position on sleep-disordered breathing
Clinical and experimental otorhinolaryngology, 2013
We wanted to evaluate whether the presence of nasal obstruction makes a change on the association between the modified Mallampati score and the severity of sleep-disordered breathing (SDB) and the sleep quality. Polysomnography (PSG), the modified Mallampati score (MMS), the body-mass index, and a questionnaire about nasal obstruction were acquired from 275 suspected SDB patients. The subjects were divided into two groups according to the presence of nasal obstruction. The clinical differences between the two groups were evaluated and the associations between the MMS and PSG variables in each group were also assessed. Significant correlations were found between the MMS and many PSG variables, including the apnea-hypopnea index, the arousal index and the proportion of deep sleep, for the patients with nasal obstruction, although this was not valid for the total patients or the patients without nasal obstruction. The severity of SDB and the quality of sleep are well correlated with th...