Neuromechanical control of upper airway patency during sleep.

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 failure to lower their active critical pressures [-1.6 (SD 3.5) vs. -11.1 cmH2O (SD 5.3), P < 0.0001] in response to upper airway obstruction. Moreover, elevated mechanical loads placed some normal individuals at risk for sleep apnea. In this subset, dynamic responses to upper airway obstruction compensated for mechanical loads and maintained airway patency by lowering the active critical pressure. The present study suggests that increased mechanical loads and blunted neuromuscular responses are both required for the development of obstructive sleep apnea.     

Upper airway neuromuscular compensation during sleep is defective in obstructive sleep apnea

Obstructive sleep apnea is the result of repeated episodes of upper airway obstruction during sleep. Recent evidence indicates that alterations in upper airway anatomy and disturbances in neuromuscular control both play a role in the pathogenesis of obstructive sleep apnea. We hypothesized that subjects without sleep apnea are more capable of mounting vigorous neuromuscular responses to upper airway obstruction than subjects with sleep apnea. To address this hypothesis we lowered nasal pressure to induce upper airway obstruction to the verge of periodic obstructive hypopneas (cycling threshold). Ten patients with obstructive sleep apnea and nine weight-, age-, and sex-matched controls were studied during sleep. Responses in genioglossal electromyography (EMG(GG)) activity (tonic, peak phasic, and phasic EMG(GG)), maximal inspiratory airflow (V(I)max), and pharyngeal transmural pressure (P(TM)) were assessed during similar degrees of sustained conditions of upper airway obstruction and compared with those obtained at a similar nasal pressure under transient conditions. Control compared with sleep apnea subjects demonstrated greater EMG(GG), V(I)max, and P(TM) responses at comparable levels of mechanical and ventilatory stimuli at the cycling threshold, during sustained compared with transient periods of upper airway obstruction. Furthermore, the increases in EMG(GG) activity in control compared with sleep apnea subjects were observed in the tonic but not the phasic component of the EMG response. We conclude that sustained periods of upper airway obstruction induce greater increases in tonic EMG(GG), V(I)max, and P(TM) in control subjects. Our findings suggest that neuromuscular responses protect individuals without sleep apnea from developing upper airway obstruction during sleep.     

Variable site of airway narrowing among obstructive sleep apnea patients

The purpose of this was to determine whether the site of physiological narrowing within the upper airway was uniform or differed among patients with obstructive sleep apnea. Inspiratory pressures were measured with an esophageal balloon catheter and three catheters located at different sites along the upper airway: supralaryngeal airway, oropharynx, and nasopharynx. Peak inspiratory pressure differences between catheters allowed assessment of pressure gradients across three airway segments: lungs-larynx-retroepiglottal airway (esophageal-supralaryngeal pressure), hypopharynx (supralaryngeal-oropharynx pressure), and transpalatal airway (oropharynx-nasopharynx pressure). In five patients, hypopharyngeal obstruction was present, and in four patients no hypopharyngeal obstruction existed. In these four patients the site of obstruction was located at the level of the palate. In a given subject, the site of obstruction was the same during repeated measurements. The presence or absence of hypopharyngeal narrowing during sleep was not predictable from gradients measured across different segments of the upper airway during wakefulness. We conclude that the site of physiological upper airway obstruction varies among patients with obstructive sleep apnea and is not predictable from pressure measured during wakefulness. We speculate that uvulopalatopharyngoplasty may not relieve obstructive apneas in patients with hypopharyngeal obstruction.     

Assessment of pharyngeal airway stability in normal and micrognathic infants

A current hypothesis for obstructive sleep apnea states that 1) negative airway pressure during inspiration can collapse the pharyngeal airway, and 2) neural control of pharyngeal airway-dilating muscles is important in preventing this collapse. To test this hypothesis we performed nasal mask occlusions to increase negative pharyngeal airway pressures during inspiration in eight normal and five micrognathic infants. Both groups developed midinspiratory pharyngeal obstruction, but obstruction was more frequent in micrognathic infants and varied in some infants with sleep state. The airway usually reopened with the subsequent expiration. The occasional failure to reopen was presumably due to pharyngeal wall adhesion. If airway obstruction occurred in sequential breaths during multiple-breath nasal mask occlusions in normal infants, there was a breath-by-breath change in the airway pressure associated with airway closure (airway closing pressure); the airway closing pressure became progressively more negative. Micrognathic infants showed less ability to improve the airway closing pressure, but this ability increased with age. These findings suggest that nasal mask occlusion can test the competence of the neuromuscular mechanisms that maintain pharyngeal airway patency in infants. Micrognathic infants had spontaneous midinspiratory pharyngeal airway obstructions during snoring. Their episodes of obstructive apnea began with midinspiratory pharyngeal obstruction similar to that seen during snoring and nasal mask occlusions. These findings imply a similar pathophysiology for snoring, spontaneous airway obstruction, and obstruction during snoring.     

In search of the optimal surgical treatment for velopharyngeal dysfunction in 22q11.2 deletion syndrome: a systematic review

Background

Patients with the 22q11.2 deletion syndrome (22qDS) and velopharyngeal dysfunction (VPD) tend to have residual VPD following surgery. This systematic review seeks to determine whether a particular surgical procedure results in superior speech outcome or less morbidity.

Methodology/ Principal Findings

A combined computerized and hand-search yielded 70 studies, of which 27 were deemed relevant for this review, reporting on a total of 525 patients with 22qDS and VPD undergoing surgery for VPD. All studies were levels 2c or 4 evidence. The methodological quality of these studies was assessed using criteria based on the Cochrane Collaboration''s tool for assessing risk of bias. Heterogeneous groups of patients were reported on in the studies. The surgical procedure was often tailored to findings on preoperative imaging. Overall, 50% of patients attained normal resonance, 48% attained normal nasal emissions scores, and 83% had understandable speech postoperatively. However, 5% became hyponasal, 1% had obstructive sleep apnea (OSA), and 17% required further surgery. There were no significant differences in speech outcome between patients who underwent a fat injection, Furlow or intravelar veloplasty, pharyngeal flap pharyngoplasty, Honig pharyngoplasty, or sphincter pharyngoplasty or Hynes procedures. There was a trend that a lower percentage of patients attained normal resonance after a fat injection or palatoplasty than after the more obstructive pharyngoplasties (11–18% versus 44–62%, p = 0.08). Only patients who underwent pharyngeal flaps or sphincter pharyngoplasties incurred OSA, yet this was not statistically significantly more often than after other procedures (p = 0.25). More patients who underwent a palatoplasty needed further surgery than those who underwent a pharyngoplasty (50% versus 7–13%, p = 0.03).

Conclusions/ Significance

In the heterogeneous group of patients with 22qDS and VPD, a grade C recommendation can be made to minimize the morbidity of further surgery by choosing to perform a pharyngoplasty directly instead of only a palatoplasty.     

Early detection of upper airway obstructions by analysis of acoustical respiratory input impedance

Repetitive occurrence of partial or total upper airway obstruction characterizes several respiratory dysfunctions such as the obstructive sleep apnea syndrome (OSAS). In OSAS patients, pharyngeal collapses are linked to a decrease in upper airway muscle activity during sleep which causes decreased upper airway wall stiffness. Continuous positive airway pressure (CPAP) is recommended as the treatment of choice. Advancements in CPAP therapy require early detection of respiratory events in real time to adapt the level of the applied pressure to airway collapsibility. The forced oscillation technique (FOT) is a noninvasive method which reflects patients' airway patency by measuring respiratory impedance. The aim of this study was to evaluate by a mathematical model of the respiratory system if FOT can provide an early detection index of total or partial upper airway obstruction. Furthermore, the simulation should suggest which characteristic features are relevant for early apnea detection in measured clinical data. The respiratory system has been treated as a series of cylindrical segments. The oropharynx analog of the model allows simulation of upper airway collapse, mimicking the situation in patients with OSAS. We calculated the input impedance for different degrees of upper airway obstruction ranging from unobstructed airways to total occlusion. Furthermore, we simulated different upper airway wall compliances. We compared the simulation with real data. The results of the study suggest that FOT is a valuable tool for assessing the degree of upper airway obstruction in patients with OSAS. Especially, the phase angle of the impedance seems to be a potentially useful tool for early apnea detection by assessing the upper airway wall collapsibility. Received: 23 July 1998 / Accepted in revised form: 26 January 1999     

Pharyngeal resistance in normal humans: influence of gender, age, and obesity

Investigation into the etiology of obstructive sleep apnea is beginning to focus increasing attention on upper airway anatomy and physiology (patency and resistance). Before conclusions concerning upper airway resistance in these patients can be made, the normal range of supraglottic and, more specifically, pharyngeal resistance needs to be better defined. We measured supraglottic and pharyngeal resistances during nasal breathing in a normal population of 35 men and women. Our technique measured epiglottic pressure with a balloon-tipped catheter, choanal pressure using anterior rhinometry, and flow with a sealed face mask and pneumotachograph. Resistance was measured at a flow rate of 300 ml/s during inspiration. Men had a mean pharyngeal resistance (choanae to epiglottis) of 4.6 +/- 0.8 (SE) cmH2O X l-1 X s, whereas women demonstrated a significantly (P less than 0.01) lower value, 2.3 +/- 0.3 cmH2O X l-1 X s. Supraglottic resistance was also higher in men (P = 0.01). Age (r = 0.73, P less than 0.01) correlated closely with pharyngeal resistance in men, but no such correlations could be found in women. These results may have implications in the epidemiology of obstructive sleep apnea.     

Tracheal hysteresis in sleep apnea

The collapsibility of pharyngeal walls, characteristic of patients with obstructive sleep apnea, likely results from reduced tone of the pharyngeal muscles. This reduction in the upper airway muscle tone may not end at the pharynx but may extend further distally, e.g., into the trachea. Because tracheal tone cannot be measured directly in conscious humans, we inferred the tone from the relative hysteresis of the tracheal area compared with the lung. Relative hysteresis was measured by plotting the cross-sectional area of a tracheal segment obtained by the acoustic reflection technique vs. lung volume. All measurements were performed during wakefulness. We found that in 42 patients with obstructive sleep apnea (apnea/hypopnea index greater than 10), relative hysteresis of the proximal trachea was predominantly clockwise, i.e., smaller than that of the lung parenchyma; in the 33 nonapneic patients (apnea/hypopnea index less than or equal to 10), it was predominantly counter-clockwise, i.e., larger than that of the lung parenchyma. For the distal trachea all patients, apneic and nonapneic, had similar, clockwise, relative hysteresis. We conclude that reduction in the upper airway muscle tone in patients with obstructive sleep apnea extends into the trachea.     

Compensatory responses to upper airway obstruction in obese apneic men and women

Defective structural and neural upper airway properties both play a pivotal role in the pathogenesis of obstructive sleep apnea. A more favorable structural upper airway property [pharyngeal critical pressure under hypotonic conditions (passive Pcrit)] has been documented for women. However, the role of sex-related modulation in compensatory responses to upper airway obstruction (UAO), independent of the passive Pcrit, remains unclear. Obese apneic men and women underwent a standard polysomnography and physiological sleep studies to determine sleep apnea severity, passive Pcrit, and compensatory airflow and respiratory timing responses to prolonged periods of UAO. Sixty-two apneic men and women, pairwise matched by passive Pcrit, exhibited similar sleep apnea disease severity during rapid eye movement (REM) sleep, but women had markedly less severe disease during non-REM (NREM) sleep. By further matching men and women by body mass index and age (n = 24), we found that the lower NREM disease susceptibility in women was associated with an approximately twofold increase in peak inspiratory airflow (P = 0.003) and inspiratory duty cycle (P = 0.017) in response to prolonged periods of UAO and an ～20% lower minute ventilation during baseline unobstructed breathing (ventilatory demand) (P = 0.027). Thus, during UAO, women compared with men had greater upper airway and respiratory timing responses and a lower ventilatory demand that may account for sex differences in sleep-disordered breathing severity during NREM sleep, independent of upper airway structural properties and sleep apnea severity during REM sleep.     

Control of respiratory activity of the genioglossus muscle in micrognathic infants

The genioglossus (GG) muscle activity of four infants with micrognathia and obstructive sleep apnea was recorded to assess the role of this tongue muscle in upper airway maintenance. Respiratory air flow, esophageal pressure, and intramuscular GG electromyograms (EMG) were recorded during wakefulness and sleep. Both tonic and phasic inspiratory GG-EMG activity was recorded in each of the infants. On occasion, no phasic GG activity could be recorded; these silent periods were unassociated with respiratory embarrassment. GG activity increased during sigh breaths. GG activity also increased when the infants spontaneously changed from oral to nasal breathing and, in two infants, with neck flexion associated with complete upper airway obstruction, suggesting that GG-EMG activity is influenced by sudden changes in upper airway resistance. During sleep, the GG-EMG activity significantly increased with 5% CO2 breathing (P less than or equal to 0.001). With nasal airway occlusion during sleep, the GG-EMG activity increased with the first occluded breath and progressively increased during the subsequent occluded breaths, indicating mechanoreceptor and suggesting chemoreceptor modulation. During nasal occlusion trials, there was a progressive increase in phasic inspiratory activity of the GG-EMG that was greater than that of the diaphragm activity (as reflected by esophageal pressure excursions). When pharyngeal airway closure occurred during a nasal occlusion trial, the negative pressure at which the pharyngeal airway closed (upper airway closing pressure) correlated with the GG-EMG activity at the time of closure, suggesting that the GG muscle contributes to maintaining pharyngeal airway patency in the micrognathic infant.     

Induction of airway collapse with subatmospheric pressure in awake patients with sleep apnea

To determine whether the pharyngeal airway is abnormal in awake patients with obstructive sleep apnea (OSA), we measured the ability of the pharyngeal airway to resist collapse from subatmospheric pressure applied to the nose in awake subjects, 12 with OSA and 12 controls. Subatmospheric pressure was applied to subjects placed in the supine position through a tightly fitting face mask. We measured airflow at the mask as well as mask, pharyngeal, and esophageal pressures. Ten patients developed airway obstruction when subatmospheric pressures between 17 and 40 cmH2O were applied. Obstruction did not occur in two patients with the least OSA. Obstruction did not occur in 10 controls; one obese control subject developed partial airway obstruction when -52 cmH2O was applied as did another with -41 cmH2O. We conclude that patients with significant OSA have an abnormal airway while they are awake and that application of subatmospheric pressure may be a useful screening test to detect OSA.     

Distraction osteogenesis for obstructive apneas in patients with congenital craniofacial malformations

Infants with congenital craniofacial malformations often have associated severe mandibular hypoplasia causing obstruction of the hypopharynx by retroposition of the base of the tongue into the posterior pharyngeal airway. Management depends on the severity of the airway obstruction. Most cases can be managed by prone positioning until the infant outgrows the problem at 3 to 6 months of age. In more critical cases, monitoring of oxygen saturation, temporary placement of a nasopharyngeal tube, and placement of an endotracheal tube will be useful procedures. Tracheotomy is an effective method for more severe cases, but longstanding tracheotomies result in high morbidity and occasional mortality. Mandibular distraction was performed in seven patients, ranging in age from 1 to 18 months, with critical obstructive apnea secondary to mandibular hypoplasia characterized by an apnea/hypopnea index greater than 20 apneas per hour and oxygen saturation below 80 percent. Two patients were tracheotomized previously. Mandibular lengthening, from 16 to 25 mm on the left side and from 10 to 22 mm on the right, was achieved in 21 to 25 days. Improvement of airway obstruction parameters was measured on polysomnograms and lateral cephalograms. Mandibular lengthening by gradual distraction is a successful method for young patients with severe mandibular hypoplasia causing critical obstructive apneas. Avoidance of tracheotomy or early decannulation in previously tracheotomized patients is a great advantage for patients with congenital craniofacial malformation.     

Effect of age and weight on upper airway function in a mouse model

Defects in pharyngeal mechanical and neuromuscular control are required for the development of obstructive sleep apnea. Obesity and age are known sleep apnea risk factors, leading us to hypothesize that specific defects in upper airway neuromechanical control are associated with weight and age in a mouse model. In anesthetized, spontaneously breathing young and old wild-type C57BL/6J mice, genioglossus electromyographic activity (EMG(GG)) was monitored and upper airway pressure-flow dynamics were characterized during ramp decreases in nasal pressure (Pn, cmH?O). Specific body weights were targeted by controlling caloric intake. The passive critical pressure (Pcrit) was derived from pressure-flow relationships during expiration. The Pn threshold at which inspiratory flow limitation (IFL) developed and tonic and phasic EMG(GG) activity during IFL were quantified to assess the phasic modulation of pharyngeal patency. The passive Pcrit increased progressively with increasing body weight and increased more in the old than young mice. Tonic EMG(GG) decreased and phasic EMG(GG) increased significantly with obesity. During ramp decreases in Pn, IFL developed at a higher (less negative) Pn threshold in the obese than lean mice, although the frequency of IFL decreased with age and weight. The findings suggest that weight imposes mechanical loads on the upper airway that are greater in the old than young mice. The susceptibility to upper airway obstruction increases with age and weight as tonic neuromuscular activity falls. IFL can elicit phasic responses in normal mice that mitigate or eliminate the obstruction altogether.     

Contribution of male sex, age, and obesity to mechanical instability of the upper airway during sleep.

Male sex, obesity, and age are risk factors for obstructive sleep apnea, although the mechanisms by which these factors increase sleep apnea susceptibility are not entirely understood. This study examined the interrelationships between sleep apnea risk factors, upper airway mechanics, and sleep apnea susceptibility. In 164 (86 men, 78 women) participants with and without sleep apnea, upper airway pressure-flow relationships were characterized to determine their mechanical properties [pharyngeal critical pressure under hypotonic conditions (passive Pcrit)] during non-rapid eye movement sleep. In multiple linear regression analyses, the effects of body mass index and age on passive Pcrit were determined in each sex. A subset of men and women matched by body mass index, age, and disease severity was used to determine the sex effect on passive Pcrit. The passive Pcrit was 1.9 cmH(2)O [95% confidence interval (CI): 0.1-3.6 cmH(2)O] lower in women than men after matching for body mass index, age, and disease severity. The relationship between passive Pcrit and sleep apnea status and severity was examined. Sleep apnea was largely absent in those individuals with a passive Pcrit less than -5 cmH(2)O and increased markedly in severity when passive Pcrit rose above -5 cmH(2)O. Passive Pcrit had a predictive power of 0.73 (95% CI: 0.65-0.82) in predicting sleep apnea status. Upper airway mechanics are differentially controlled by sex, obesity, and age, and partly mediate the relationship between these sleep apnea risk factors and obstructive sleep apnea.     

Respiratory motor activity: influence of neuromodulators and implications for sleep disordered breathing

Sleep, especially rapid-eye-movement sleep, causes fundamental modifications of respiratory muscle activity and control mechanisms, modifications that can predispose individuals to sleep-related breathing disorders. One of the most common of these disorders is obstructive sleep apnea (OSA) that affects approximately 4% of adults. OSA is caused by repeated episodes of pharyngeal airway obstruction that can occur hundreds of times per night, leading to recurrent asphyxia, arousals from sleep, daytime sleepiness, and adverse cardiovascular and cerebrovascular consequences. OSA is caused by the effects of sleep on pharyngeal muscle tone in individuals with already narrow upper airways. Moreover, since OSA occurs only in sleep, this disorder by definition is a state-dependent process ultimately caused by the influence of sleep neural mechanisms on the activity of pharyngeal motoneurons. This review synthesizes recent findings relating to control of pharyngeal muscle activity across sleep-wake states, with special emphasis on the influence of neuromodulators acting at the hypoglossal motor nucleus that inervates the genioglossus muscle of the tongue. The results of such basic physiological studies may be relevant to identifying and developing new pharmacological strategies to augment pharyngeal muscle activity in sleep, especially rapid-eye-movement sleep, as potential treatments for OSA.     

Mandible position and activation of submental and masseter muscles during sleep.

Movement of the mandible could influence pharyngeal airway caliber because the mandible is attached to the tongue and to muscles that insert on the hyoid bone. In normal subjects and patients with obstructive sleep apnea (OSA) we measured jaw position during sleep with strain gauges, as well as masseter and submental electromyograms, airflow, esophageal pressure, oximetry, electroencephalograms, and electrooculograms. Jaws of patients with OSA were open more than those of normal subjects at end expiration and opened further at end inspiration, particularly at the termination of apneas when the masseter and submental muscles contracted. Masseter activation occurred only in patients with OSA and in a pattern similar to that of submental muscles. Jaw opening at end expiration could narrow the upper airway, whereas opening at end inspiration could reflect efforts to expand the airway with tracheal tug and with submental muscle activation and efforts to open the mouth to allow mouth breathing. Masseter contraction does not close the jaw but may serve to stabilize it.     

Developmental changes in upper airway dynamics.

Normal children have a less collapsible upper airway in response to subatmospheric pressure administration (P(NEG)) during sleep than normal adults do, and this upper airway response appears to be modulated by the central ventilatory drive. Children have a greater ventilatory drive than adults. We, therefore, hypothesized that children have increased neuromotor activation of their pharyngeal airway during sleep compared with adults. As infants have few obstructive apneas during sleep, we hypothesized that infants would have an upper airway that was resistant to collapse. We, therefore, compared the upper airway pressure-flow (V) relationship during sleep between normal infants, prepubertal children, and adults. We evaluated the upper airway response to 1). intermittent, acute P(NEG) (infants, children, and adults), and 2). hypercapnia (children and adults). We found that adults had a more collapsible upper airway during sleep than either infants or children. The children exhibited a vigorous response to both P(NEG) and hypercapnia during sleep (P < 0.01), whereas adults had no significant change. Infants had an airway that was resistant to collapse and showed a very rapid response to P(NEG). We conclude that the upper airway is resistant to collapse during sleep in infants and children. Normal children have preservation of upper airway responses to P(NEG) and hypercapnia during sleep, whereas responses are diminished in adults. Infants appear to have a different pattern of upper airway activation than older children. We speculate that the pharyngeal airway responses present in normal children are a compensatory response for a relatively narrow upper airway.     

Glottic and cervical tracheal narrowing in patients with obstructive sleep apnea

There are several studies showing that patients with idiopathic obstructive sleep apnea (OSA) have a narrow and collapsible pharynx that may predispose them to repeated upper airway occlusions during sleep. We hypothesized that this structural abnormality may also extend to the glottic and tracheal region. Consequently, we measured pharyngeal (Aph), glottic (Agl), cervical tracheal (Atr1), midtracheal (Atr2), and distal (Atr3) tracheal areas during tidal breathing in 66 patients with OSA (16 nonobese and 50 obese) and 8 nonapneic controls. We found that Aph, Agl, and Atr1, but not Atr2 or Atr3, were significantly smaller in the OSA group than in the control group. Obese patients with OSA had the smallest upper airway area, although the nonapneic controls had the largest areas. Multiple linear regression analysis revealed that the pharyngeal area, cervical tracheal area, and body mass index were all independent determinants of the apnea-hypopnea index, accounting for 31% of the variability in apnea-hypopnea index. Aph, Agl, and Atr showed significant correlation with the body mass index. We conclude that sleep-disordered breathing is associated with diffuse upper airway narrowing and that obesity contributes to this narrowing. Furthermore, we speculate that a common pathophysiological mechanism may be responsible for this reduction in upper airway area extending from the pharynx to the proximal trachea.     

MRI study of regional variations of pharyngeal wall compliance in cats

Upper airway compliance indicates the potentialof the airway to collapse and is relevant to the pathogenesis ofobstructive sleep apnea. We hypothesized that compliance would varyover the rostral-to-caudal extent of the pharyngeal airway. In aparalyzed isolated upper airway preparation in cats, we controlledstatic upper airway pressure during magnetic resonance imaging (MRI, 0.391-mm resolution). We measured cross-sectional area andanteroposterior and lateral dimensions from three-dimensionalreconstructed MRIs in axial slices orthogonal to the airway centerline.High-retropalatal (HRP), midretropalatal (MRP), and hypopharyngeal(HYP) regions were defined. Regional compliance was significantlyincreased from rostral to caudal regions as follows: HRP < MRP < HYP (P < 0.0001), and compliancedifferences among regions were directly related to collapsibility. Thusour findings in the isolated upper airway of the cat support thehypothesis that regional differences in pharyngeal compliance exist andsuggest that baseline regional variations in compliance andcollapsibility may be an important factor in the pathogenesis andtreatment of obstructive sleep apnea.

     

骨性Ⅲ类错合畸形患者正颌术后呼吸道情况随访调查

目的：通过评估骨性Ⅲ错合畸形患者正颌手术后睡眠时期的呼吸功能情况,研究该类患者正颌手术后存在呼吸道梗阻的可能性。为临床治疗提供依据。方法：分析56例接受正颌手术的骨性Ⅲ类错合畸形患者的术前及术后1周、1月、3月和术后6月的多导睡眠图报告。设计问卷调查表评估手术影响日间嗜睡度的变化。从PSG报告上获得的术前术后有代表性的2项参数睡眠呼吸暂停低通气指数与最低氧饱和度分别进行比较。结果：数据显示术前和术后AHI指数及SpO2无显著性差异（统计学上无差异）。54例病人术后均未出现睡眠呼吸障碍症状。2例病人术后出现睡眠时期打鼾,但术后随访6月后打鼾逐渐消失。结论：骨性Ⅲ类错合畸形患者正颌术后无明显呼吸道梗阻症状。但若患者同时具有超重、短颈、舌体大等其他危险因素及仅行下颌骨后退手术可能导致睡眠呼吸暂停低通气综合症的发生。