Pharyngeal Cross-sectional Area Research Articles

Changes in Acoustic Pharyngometric Indices After Adenotonsillectomy in Children

Background and Objective This study aimed to assess the effectiveness of acoustic pharyngometry by examining the data before and after adenotonsillectomy in children with sleepdisordered breathing (SDB).Methods This prospective, observational study included 29 children (M/F = 17/12, age = 8.69 ± 2.52 years) with SDB who underwent acoustic pharyngometry before and after adenotonsillectomy. Pre- and postoperative acoustic pharyngometry data, such as the oropharyngeal junction area (OPJ), pharyngeal volume (Vp), glottic area (GL), maximal pharyngeal cross-sectional area (Apmax), minimal pharyngeal cross-sectional area (Apmin), and mean pharyngeal cross-sectional area (Apmean), were compared.Results Before surgery, Apmean was measured at 1.75 ± 0.81 cm<sup>2</sup> and increased to 2.24 ± 0.89 cm<sup>2</sup> after surgery (p < 0.001); this difference was statistically significant. Moreover, OPJ demonstrated statistically significant changes from 1.03 ± 0.62 cm<sup>2</sup> to 1.53 ± 0.77 cm<sup>2</sup> (p < 0.001); Apmin measured from 0.99 ± 0.51 cm<sup>2</sup> to 1.38 ± 0.69 cm<sup>2</sup> (p = 0.003); and Vp increased from 14.45 ± 7.05 cm<sup>3</sup> to 18.89 ± 7.72 cm<sup>3</sup> (p < 0.001) after surgical treatment.Conclusions Acoustic pharyngometry, a non-invasive and reproducible method, effectively reflects upper airway changes before and after adenotonsillectomy in children with SDB and ATH. This underscores its potential as a valuable tool for objectively evaluating upper airway obstruction caused by ATH in children.

Bariatric surgery reduces sleep apnea in obese patients with obstructive sleep apnea by increasing pharyngeal cross-sectional area during the early postoperative period

ObjectiveBariatric surgery (BS) is considered one of the most effective treatments for obese individuals with Obstructive Sleep Apnea (OSA). However, otolaryngologists have raised concerns about the structural alterations caused by BS on the upper respiratory tract, especially, on the pharyngeal cavity.MethodsIn this study, we recruited 42 individuals who underwent BS at our hospital. They were divided into two groups based on apnea–hypopnea index (AHI): mild group (5 ≤ AHI < 15) and moderate-severe group (AHI ≥ 15). The participants were followed up for 12 months and several indicators, including body mass index (BMI), polysomnography (PSG), and acoustic pharyngometry (APh), were assessed repeatedly before surgery and at 3, 6, and 12 months (m) after surgery.ResultsParticipants exhibited significant decreases in BMI (F = 128.1, P = 0.001) and total weight loss (F = 176.7, P < 0.001) after BS. The AHI value among obese patients with mild OSA decreased significantly within three months after surgery (0 day vs. 3 months, P < 0.01), and decreased significantly more than 12 months with moderate-to-severe patients (0 day vs. 3 months, 3 months vs. 6 months, 6 months vs. 12 months, P < 0.01). The therapeutic effect of OSA of the mild group was significantly better compared with that of the moderate-severe group at 6 months (mean rank = 28.13 vs. 14.21, P < 0.001) and 12 m (mean rank = 26.75 vs. 15.52, P = 0.001). The APh results revealed that the pharyngeal volume of the two groups increased significantly between 0 day and 6 months after surgery (P < 0.01). The oropharyngeal junction (OPJ) area and the glottal area were increased significantly between 0 day and 6 m after surgery (P < 0.01).ConclusionBS can relieve apnea and OSA symptoms among obese patients with OSA, especially in the early postoperative period. Moreover, OSA severity was closely associated with OPJ and glottal areas, rather than pharyngeal cavity volume.

Screening for Obstructive Sleep Apnea in an Atrial Fibrillation Population: What’s the Best Test?

BackgroundAmong individuals with nonvalvular atrial fibrillation (AF), the prevalence of obstructive sleep apnea (OSA) can be as high as 85%. Continuous positive airway pressure treatment for moderate or severe OSA might improve AF outcomes and quality of life, so early identification of OSA might be of value. However, screening questionnaires for OSA are suboptimal because they are weighted toward tiredness and loud snoring, which might be absent in AF patients. NoSAS (Neck, Obesity, Snoring, Age, Sex) is a new OSA questionnaire that excludes these parameters. Acoustic pharyngometry (AP) is a potential novel screening technique that measures pharyngeal cross-sectional area, which is reduced in patients with OSA. MethodsWe prospectively compared the accuracy of the NoSAS, the STOP-BANG questionnaire (Snoring, Tiredness, Observed apnea, blood Pressure, Body mass index, Age, Neck circumference and Gender), and AP with home sleep apnea testing (HSAT) in consecutive patients with nonvalvular AF. ResultsOf 188 participants, 86% had OSA and 49% had moderate or severe OSA. Mean Epworth Sleepiness Scale scores were low; 5.9 (SD, 3.9), indicating that most participants were not sleepy. Receiver operating characteristic curves for comparisons of screening tests with HSAT showed suboptimal accuracy. For moderate plus severe and severe only groups respectively, the area under the curve was 0.50 (95% confidence interval [CI], 0.42-0.58) and 0.42 (95% CI, 0.34-0.52) for AP, 0.65 (95% CI, 0.58-0.73) and 0.63 (95% CI, 0.52-0.74) for the STOP-BANG questionnaire, and 0.68 (95% CI, 0.60-0.75) and 0.69 (95% CI, 0.59-0.80) for the NoSAS. ConclusionsAP and NoSAS are not sufficiently accurate for screening AF patients for OSA. Because of the high rates of OSA in this cohort, the potential benefits of OSA treatment, and the suboptimal accuracy of current screening questionnaires, cardiologists should consider HSAT for AF patients.

The Impact of Tonsillectomy on the Adult Singing Voice: Acoustic and Aerodynamic Measures

Singers undergoing tonsillectomy are understandably concerned about possible sequelae to their voice. The surgical risks of laryngeal damage from intubation and upper airway scarring are valid reasons for singers to carefully consider their options for treatment of tonsil-related symptoms. No prior studies have statistically assessed objective voice outcomes in a group of adult singers undergoing tonsillectomy. This study determined the impact of tonsillectomy on the adult singing voice by determining if there were statistically significant changes in preoperative versus postoperative acoustic, aerodynamic, and Voice-Related Quality of Life (VRQOL) measures. Prospective cohort study. Tertiary Referral Academic Hospital SUBJECTS: Thirty singers undergoing tonsillectomy from 2012 to 2019. Acoustic recordings were obtained with Computerized Speech Lab (CSL) (Pentax CSL 4500) and analyzed with the Multidimensional Voice Program (MDVP) (Pentax MDVP) and Pratt Acoustic Analysis Software. Estimates of aerodynamic vocal efficiency were obtained and analyzed using the Phonatory Aerodynamic System (Pentax PAS 6600). Preoperative VRQOL scores were recorded, and singers were instructed to refrain from singing for 3 weeks following tonsillectomy. Repeat acoustic and aerodynamic measures as well as VRQOL scores were obtained at the first postoperative visit. Average postoperative acoustic (jitter, shimmer, HNR) and aerodynamic (sound pressure level divided by subglottal pressure) parameters related to laryngeal phonatory function did not differ significantly from preoperative measures. The only statistically significant change in postoperative measures of resonance was a decrease in the 3rd formant (F3) for the /a/ vowel. Average postoperative VRQOL scores (79.8, SD18.7) improved significantly from preoperative VRQOL scores (89, SD12.2) (P=0.007). Tonsillectomy does not appear to alter laryngeal voice production in adult singers as measured by standard acoustic and aerodynamic parameters. The observed decrease in F3 for the /a/ vowel is hypothetically related to increasing the pharyngeal cross-sectional area by removing tonsillar tissue, but this would not be expected to appreciably impact the perceptual characteristics of the vowel. Singers' self-assessment (VRQOL) improved after tonsillectomy.

Reduced pharyngeal dimensions and obstructive sleep apnea in adults with cleft lip/palate and Class III malocclusion

ABSTRACT Objective: To three-dimensionally evaluate the upper airway of individuals with cleft lip and palate (CLP) and Class III malocclusion and the occurrence of obstructive sleep apnea (OSA). Methods: Twenty-one CLP individuals with Class III malocclusion, 20–29 years of age, who underwent computed tomography for orthognathic surgery planning, were prospectively evaluated. All participants underwent polysomnography, and the apnea-hypopnea index ≥ 5 events/hour was considered indicative of OSA. The total upper airway and its subdivisions volumes, as well as the minimum pharyngeal cross-sectional area (CSA), were assessed using Mimics software. Results: Among the 21 individuals analyzed, 6 (29%) presented with OSA. The total upper airway and the oropharynx mean volumes were significantly decreased in subjects with OSA when compared to individuals without OSA. Mean CSA was not statistically different between groups. Conclusion: CLP individuals with Class III malocclusion and OSA have an upper airway significantly smaller than individuals without OSA.

Pharyngeal distensibility during expiration is an independent predictor of the severity of obstructive sleep apnoea.

Pharyngeal distensibility and collapsibility reflect the passive properties of tissue in the airway, are an indicator of the ease with which an airway can be deformed and are related to the severity of obstructive sleep apnoea (OSA). During normal tidal respiration, the collapsibility of the pharynx during expiration is passive without confounding by neuromuscular activation that occurs during inspiration. We evaluated the distensibility and collapsibility of the upper airway in subjects with OSA during wakefulness using sophisticated dynamic computed tomography (CT) imaging. We hypothesized that the dynamic changes of the upper airway during expiration would be related to the severity of OSA. Twenty-three patients with OSA and eight normal subjects underwent simultaneous measurement of respiratory flow and airway calibre using ultrafast CT. The change in pharyngeal cross-sectional area divided by the change in concomitant flow (as distensibility or collapsibility) was measured and compared across different severities of OSA. The slope of this relationship between delta area and delta flow during expiration was significantly higher in severe OSA when compared with normal controls and mild-moderate OSA. Differences in airway distensibility or collapsibility between severity groups were significant in expiration but not in inspiration. Distensibility or collapsibility contributed most to the apnoea-hypopnoea index in regression modelling. Age, gender, and body mass index (BMI) were not significant independent predictors. Our study demonstrates that airway distensibility during the expiratory phase of awake respiration is correlated with the severity of OSA.

Predictive Value of the Combination of Body Weight and Minimal Pharyngeal Cross-sectional Area in Assessing Obstructive Sleep Apnea

Objectives: The study aims to evaluate the predictive value of a comprehensive index composed of simple biometric parameters in predicting apnea hypopnea index. Subjects and Methods: Ninety-four adult patients with obstructive sleep apnea-hypopnea syndrome were retrospectively reviewed. Pharyngeal axial-computed tomography and polysomnography were applied before surgery. Minimal pharyngeal cross-sectional area, sleep-associated monitoring indices including apnea hypopnea index, and biometric characteristics including body weight were all recorded. Correlations between these parameters were analyzed using correlation and multiple linear regression analyses. Results: Apnea hypopnea index was significantly correlated with minimal pharyngeal cross-sectional area (r=-0.390) and body weight (r=0.553). A notably higher correlation coefficient (r=0.681) was found between apnea hypopnea index and a new comprehensive index composed of minimal pharyngeal cross-sectional area and body weight data. Conclusion: Apnea hypopnea index might be largely influenced by a combined effect of minimal pharyngeal cross-sectional area and body weight. The new comprehensive parameter combining minimal pharyngeal crosssectional area and body weight is an effective indicator for the evaluation of obstructive sleep apnea.

Predictive Value of the Combination of Body Weight and Minimal Pharyngeal Cross-sectional Area in Assessing Obstructive Sleep Apnea

Predictive Value of the Combination of Body Weight and Minimal Pharyngeal Cross-sectional Area in Assessing Obstructive Sleep Apnea

Pregnancy is associated with a decrease in pharyngeal but not tracheal or laryngeal cross-sectional area: a pilot study using the acoustic reflection method

BackgroundThe risk of difficult upper airway access is increased during pregnancy, especially in labor. Changes in upper airway calibre have been poorly studied during pregnancy. The acoustic reflection method is a non-invasive technique that allows a longitudinal assessment of the cross-sectional area of the upper airway from the mouth to carina. We used this technique to evaluate upper airway calibre during normal pregnancy. MethodsWe conducted a prospective, single centre, observational study with a clinical and upper airway acoustic reflection method evaluation of healthy women during the first, second and third trimesters of pregnancy, and up to two days and one month after delivery. ResultsFifty women participated to the study. The mean pharyngeal cross-sectional area decreased between the first and third trimesters (P<0.001) with no significant change of the minimal and mean tracheal cross-sectional areas. The Mallampati score increased during pregnancy between the first and third trimesters (P<0.001). ConclusionUsing measurements with the acoustic reflection method, normal pregnancy is associated with a significant reduction in the cross-sectional area of the pharynx and a concomitant increase in the Mallampati score. No change was observed in the minimal and mean tracheal cross-sectional areas.

A three-microphone acoustic reflection technique using transmitted acoustic waves in the airway

The acoustic reflection technique noninvasively measures airway cross-sectional area vs. distance functions and uses a wave tube with a constant cross-sectional area to separate incidental and reflected waves introduced into the mouth or nostril. The accuracy of estimated cross-sectional areas gets worse in the deeper distances due to the nature of marching algorithms, i.e., errors of the estimated areas in the closer distances accumulate to those in the further distances. Here we present a new technique of acoustic reflection from measuring transmitted acoustic waves in the airway with three microphones and without employing a wave tube. Using miniaturized microphones mounted on a catheter, we estimated reflection coefficients among the microphones and separated incidental and reflected waves. A model study showed that the estimated cross-sectional area vs. distance function was coincident with the conventional two-microphone method, and it did not change with altered cross-sectional areas at the microphone position, although the estimated cross-sectional areas are relative values to that at the microphone position. The pharyngeal cross-sectional areas including retropalatal and retroglossal regions and the closing site during sleep was visualized in patients with obstructive sleep apnea. The method can be applicable to larger or smaller bronchi to evaluate the airspace and function in these localized airways.

Influence of upper airway size on volume exhaled under negative pressure during evaluation of upper airway collapsibility

It has been shown that volume exhaled in the first 0.5s after application at the mouth of 5cmH(2)O negative pressure (V,NEP(0.5)) during wakefulness strongly reflects critical pressure (Pcrit) during sleep but only in males with neck circumference (NC) >37cm. The aim of this study was to establish the relationship between upper airway (UA) size and V,NEP(0.5), to obtain V,NEP(0.5) values as percent predicted and then correlate them with Pcrit obtained in the same subjects. In 20 (8 women) normal subjects (age, 39 ± 16years; BMI, 22.5 ± 3.0kg/m(2); AHI, 0.8 ± 1.0), NC, mean pharyngeal cross-sectional area (APmean) by acoustic pharyngometry and V,NEP(0.5) in the supine position were measured. Correlations between APmean, NC and V,NEP(0.5) were performed. A strong relationship was found between APmean and NC, and the predicted V,NEP(0.5) values were obtained using the equation derived from the relationship between V,NEP0.5 and NC. Subsequently, nine normal subjects (age, 26.3 ± 2.5yrs, BMI 23.9 ± 3.2kg/m(2), AHI 2.3 ± 0.5), ten snorers (age, 68 ± 11years; BMI, 26.6 ± 4.6kg/m(2); AHI, 3.5 ± 0.8) and ten OSAH patients (age, 64 ± 9years; BMI, 32 ± 4.9kg/m(2); AHI, 43.8 ± 24.4) underwent measurement of V,NEP(0.5) in the supine position while awake and Pcrit during sleep. Correlations between Pcrit and both V,NEP(0.5) and V,NEP(0.5) expressed as percent predicted were performed in all subjects. Controls had V,NEP(0.5) of 387 ± 103mL (100.1 ± 13% predicted) and Pcrit of -3.7 ± 2.0cmH(2)O, snorers had V,NEP(0.5) of 320 ± 33mL (62 ± 12% predicted) and Pcrit of -0.6 ± 0.3cmH(2)O while OSAH patients had V,NEP(0.5) of 295 ± 67mL (48 ± 12% predicted) and Pcrit of 1.0 ± 1.0cmH(2)O. The linear regression analysis showed a close and highly significant correlation between V,NEP(0.5) percent predicted and Pcrit (r (2) = 0.79, p < 0.001). V,NEP(0.5) expressed as percent predicted according to NC strongly reflects Pcrit in a wide range of values and can be used as a surrogate of Pcrit to assess UA collapsibility independently from UA size and sex.

Lung volume and pharyngeal stability in sleeping humans: the knee bone is connected to the thigh bone

in 1988 the Journal of Applied Physiology published a seminal article by William Van de Graaff ([13][1]) demonstrating that inflation of the thorax in anesthetized dogs decreased upper airway resistance independently of upper airway muscle activity. The mechanism underlying this effect was shown to

Pharyngeal cross-sectional area and pharyngeal compliance in normal Japanese males and females

It is reported that obstructive sleep apnea syndrome (OSAS) has a marked elderly male predominance and that patients with OSAS have reduced pharyngeal cross-sectional area and increased pharyngeal collapsibility. These reports suggest that the size and mechanical properties of the pharynx have sex- and age-related differences even in normal subjects. However, there are only a few reports on normal values of pharyngeal cross-sectional area and compliance. The purpose of this study was to determine the normal values of the pharyngeal cross-sectional area and compliance in Japanese healthy subjects and to determine sex-related differences and the effect of age, body size, and body posture on these parameters. We examined 181 subjects with an age range spanning 21-69 years, with normal range of body mass index and without enlarged tonsils or jaw retrusion. No subject complained of symptoms suggestive of OSAS. We measured the pharyngeal cross-sectional area in three body positions (sitting, lateral and supine) using the acoustic reflection technique (AAAR). Fifty airway area versus distance functions with a rate of 3 times per second were measured and averaged in each body position during normal breathing of room air. After identifying the fauces and the glottis on the averaged area versus distance function, we defined a region between 2 cm distal to the fauces and 2 cm proximal to the glottis as a pharyngeal segment and computed the mean area of that segment (mean pharyngeal cross-sectional area).(ABSTRACT TRUNCATED AT 250 WORDS)

Interacting effects of genioglossus stimulation and mandibular advancement in sleep apnea

Both mandibular advancement (MA) and stimulation of the genioglossus (GG) have been shown to improve upper airway patency, but neither one achieves the effect of continuous positive airway pressure (CPAP) treatment. In the present study we assessed the combined effect of MA and GG stimulation on the relaxed pharynx in patients with obstructive sleep apnea (OSA). We evaluated responses of upper airway pressure-flow relationships and endoscopically determined pharyngeal cross-sectional area to MA and electrical stimulation of the GG in 14 propofol-anesthetized OSA patients. Measurements were undertaken at multiple levels of CPAP, enabling calculation of the critical closing pressure (Pcrit), upstream resistance (Rus), and pharyngeal compliance. GG stimulation, MA, and the combination of both shifted the pressure:flow relationships toward higher flow levels, resulting in progressively lower Pcrit (from baseline of 2.9 +/- 2.2 to 0.9 +/- 2.5, -1.4 +/- 2.9, and -4.2 +/- 3.3 cmH(2)O, respectively), without significant change in Rus. DeltaPcrit during GG stimulation was significantly larger during MA than under baseline conditions (-2.8 +/- 1.4 vs. -2.0 +/- 1.4 cmH(2)O, P = 0.011). Combining the effect of GG stimulation with MA lowered Pcrit below 0 in all patients and restored pharyngeal patency to a level that enabled flow above the hypopnea level in 10/14 of the patients. Velopharyngeal compliance was not affected by either manipulation. We conclude that the combined effect of MA and GG stimulation is additive and may act in synergy, preventing substantial flow limitation of the relaxed pharynx in most OSA patients.

Obstructive Sleep Apnea Syndrome and Asthma: What Are the Links?

Recent data suggest that obstructive sleep apnea syndrome (OSAS) is an independent risk factor for asthma exacerbations. Neuromechanical reflex bronchoconstriction, gastroesophageal reflux, inflammation (local and systemic), and the indirect effect on dyspnea of OSAS-induced cardiac dysfunction have been suggested as mechanisms that lead to worsening asthma control in patients with concomitant OSAS. Vascular endothelial growth factor-induced airway angiogenesis, leptin-related airway changes, and OSAS-induced weight gain also may play a common mechanistic role linking both disorders. Several studies have confirmed that asthmatic patients are more prone to develop OSAS symptoms than are members of the general population. The common asthmatic features that promote OSAS symptoms are nasal obstruction, a decrease in pharyngeal cross sectional area, and an increase in upper airway collapsibility. Clarifying the nature of the relationship between OSAS and asthma is a critical area with important therapeutic implications.

Evaluation of pharyngeal shape and size using anatomical optical coherence tomography in individuals with and without obstructive sleep apnoea

This study compared shape, size and length of the pharyngeal airway in individuals with and without obstructive sleep apnoea (OSA) using a novel endoscopic imaging technique, anatomical optical coherence tomography (aOCT). The study population comprised a preliminary study group of 20 OSA patients and a subsequent controlled study group of 10 OSA patients and 10 body mass index (BMI)-, gender- and age-matched control subjects without OSA. All subjects were scanned using aOCT while awake, supine and breathing quietly. Measurements of airway cross-sectional area (CSA) and anteroposterior (A-P) and lateral diameters were obtained from the hypo-, oro- and velopharyngeal regions. A-P : lateral diameter ratios were calculated to provide an index of regional airway shape. In all subjects, pharyngeal CSA was lowest in the velopharynx. Patients with OSA had a smaller velopharyngeal CSA than controls (maximum CSA 91 +/- 40 versus 153 +/- 84 mm(2); P < 0.05) but comparable oro- (318 +/- 80 versus 279 +/- 129 mm(2); P = 0.48) and hypopharyngeal CSA (250 +/- 105 versus 303 +/- 112 mm(2); P = 0.36). In each pharyngeal region, the long axis of the airway was oriented in the lateral diameter. Airway shape was not different between the groups. Pharyngeal airway length was similar in both groups, although the OSA group had longer uvulae than the control group (16.8 +/- 6.2 versus 11.2 +/- 5.2 mm; P < 0.05). This study has shown that individuals with OSA have a smaller velopharyngeal CSA than BMI-, gender- and age-matched control volunteers, but comparable shape: a laterally oriented ellipse. These findings suggest that it is an abnormality in size rather than shape that is the more important anatomical predictor of OSA.

Nocturnal haemodialysis increases pharyngeal size in patients with sleep apnoea and end-stage renal disease

Sleep apnoea is common in patients with end-stage renal disease (ESRD) and is improved by nocturnal haemodialysis (NHD). Recent findings from our laboratory indicate the development of ESRD is associated with pharyngeal narrowing. We hypothesized that NHD increases pharyngeal cross-sectional area and that this is associated with an improvement in sleep apnoea. Twenty-four patients (aged 32-68 years), receiving conventional haemodialysis (CHD) (4 h/day, 3 days/week), were recruited for overnight polysomnography and estimation of pharyngeal cross-sectional area at functional residual capacity (FRC) and residual volume (RV). Patients were divided into apnoeic and non-apnoeic groups based on an apnoea-hypopnoea index (AHI) > or = 15/h. Following conversion from CHD to NHD (8 h/night, 3-6 nights/week) all measurements were repeated and apnoeic patients were classified as 'responders' if AHI fell to < 15 events/h. Conversion from CHD to NHD was associated with an increase in pharyngeal cross-sectional area (FRC: 3.29 +/- 0.67 vs 3.39 +/- 0.75 cm(2); RV: 1.91 +/- 0.51 vs 2.13 +/- 0.48 cm(2), P < 0.05), which was not significantly different between groups. Sleep apnoea improved in three patients. Conversion from CHD to NHD is associated with an increase in pharyngeal cross-sectional area. This may play a role in some patients whose sleep apnoea improves on NHD.

Pharyngeal narrowing in end-stage renal disease: implications for obstructive sleep apnoea

Sleep apnoea is common in patients with end-stage renal disease (ESRD). It was hypothesised that this is related to a narrower upper airway. Upper airway dimensions in patients with and without ESRD and sleep apnoea were compared, in order to determine whether upper airway changes associated with ESRD could contribute to the development of sleep apnoea. An acoustic reflection technique was used to estimate pharyngeal cross-sectional area. Sleep apnoea was assessed by overnight polysomnography. A total of 44 patients with ESRD receiving conventional haemodialysis and 41 subjects with normal renal function were studied. ESRD and control groups were further categorised by the presence or absence of sleep apnoea (apnoea/hypopnoea index > or =10 events.h(-1)). The pharyngeal area was smaller in patients with ESRD compared with subjects with normal renal function: 3.04 +/- 0.84 versus 3.46 +/- 0.80 cm(2) for the functional residual capacity and 1.99 +/- 0.51 versus 2.14 +/- 0.58 cm(2) for the residual volume. The pharynx is narrower in patients with ESRD than in subjects with normal renal function. In conclusion, since a narrower upper airway predisposes to upper airway occlusion during sleep, it is suggested that this factor contributes to the pathogenesis of sleep apnoea in dialysis-dependent patients.

Effect of genioglossus contraction on pharyngeal lumen and airflow in sleep apnoea patients

The purpose of the present study was to quantify the mechanical effect of genioglossus stimulation on flow mechanics and pharyngeal cross-sectional area in patients with obstructive sleep apnoea, and to identify variables that determine the magnitude of the respiratory effect of tongue protrusion. The pressure/flow and pressure/cross-sectional area relationships of the velo- and oropharynx were assessed in spontaneously breathing propofol-anaesthetised subjects before and during genioglossus stimulation. Genioglossus contraction decreased the critical pressure significantly from 1.2+/-3.3 to -0.7+/-3.8 cmH(2)O, with individual decreases ranging -0.6-5.9 cmH(2)O. Pharyngeal compliance was not affected by genioglossus contraction. The pharyngeal response to genioglossus stimulation was related to the magnitude of advancement of the posterior side of the tongue, but not to the severity of sleep apnoea, critical pressure, compliance or the shape and other characteristics of the velopharynx. Genioglossus contraction enlarges both the velo- and the oropharynx and lowers the critical pressure without affecting pharyngeal stiffness. The response to genioglossus stimulation depends upon the magnitude of tongue protrusion achieved rather than on inherent characteristics of the patient and their airway.

This Month in Anesthesiology

This Month in Anesthesiology