Acoustic pharyngometry measurement of minimal cross-sectional airway area is a significant independent predictor of moderate-to-severe obstructive sleep apnea

Obstructive sleep apnea detection during wakefulness: a comprehensive methodological review

Obstructive sleep apnea (OSA) is a chronic condition affecting up to 1 billion people, globally. Despite this spread, OSA is still thought to be underdiagnosed. Lack of diagnosis is largely attributed to the high cost, resource-intensive, and time-consuming nature of existing diagnostic technologies during sleep. As individuals with OSA do not show many symptoms other than daytime sleepiness, predicting OSA while the individual is awake (wakefulness) is quite challenging. However, research especially in the last decade has shown promising results for quick and accurate methodologies to predict OSA during wakefulness. Furthermore, advances in machine learning algorithms offer new ways to analyze the measured data with more precision. With a widening research outlook, the present review compares methodologies for OSA screening during wakefulness, and recommendations are made for avenues of future research and study designs.

Is There a Relationship between Voice Quality and Obstructive Sleep Apnea Severity and Cumulative Percentage of Time Spent at Saturations below Ninety Percent: Voice Analysis in Obstructive Sleep Apnea Patients

Background and Objectives: Apnea hypopnea index is the most important criterion in determining the severity of obstructive sleep apnea (OSA), while the percentage of the total number of times which oxygen saturation is measured below 90% during polysomnography (CT90%) is important in determining the severity of hypoxemia. As hypoxemia increases, inflammation will also increase in OSA. Inflammation in the respiratory tract may affect phonation. We aimed to determine the effects of the degree of OSA and CT90% on phonation. Materials and Methods: The patients were between the ages of 18−60 years and were divided into four groups: normal, mild, moderate, and severe OSA. Patients were asked to say the vowels /α:/ and /i:/ for 5 s for voice recording. Maximum phonation time (MPT) was recorded. Using the Praat voice analysis program, Jitter%, Shimmer%, harmonics-to-noise ratio (HNR), and f0 values were obtained. Results: Seventy-two patients were included. Vowel sound /α:/; there was a significant difference for Jitter%, Shimmer%, and HNR measurements between the 1st and the 4th group (p < 0.001, p < 0.001, and p < 0.001, respectively) and a correlation between CT90% and Shimmer% and HNR values (p < 0.001 and p < 0.021, respectively). Vowel sound /i:/; there was a significant difference in f0 values between the 1st group and 2nd and 4th groups (p < 0.028 and p < 0.015, respectively), and for Jitter%, Shimmer%, and HNR measurements between the 1st and 4th group (p < 0.04, p < 0.000, and p < 0.000, respectively), and a correlation between CT90% and Shimmer% and HNR values (p < 0.016 and p < 0.003, respectively). The difference was significant in MPT between the 1st group and 3rd and 4th groups (p < 0.03 and p < 0.003, respectively). Conclusions: Glottic phonation can be affected, especially in patients whose AHI scores are ≥15. Voice quality can decrease as the degree of OSA increases. The increase in CT90% can be associated with the worsening of voice and can be used as a predictor in the evaluation of voice disorders in the future.

Reliability of Acoustic Pharyngometry and Rhinometry Examination in Children and Adolescents

OBJECTIVES

The aim of this cross-sectional study was to examine the method error and reliability of acoustic pharyngometry and rhinometry in children and adolescents and to describe the feasibility of these methods in a young population.

MATERIAL AND METHODS

The study sample included 35 healthy subjects in the age of 9 to 14 years. The subjects were randomly recruited for the present project in the period from June 2021 to February 2022. Repeated measurements of the upper airway dimensions in standing mirror position were performed by the use of Acoustic Pharyngometer and Rhinometer. Volume (cm³), calculated resistance (cm H₂O/L/min), mean area (cm²), minimum cross-sectional area (MCA, cm²) and distance to MCA (cm) were examined. Method errors and reliability coefficients were evaluated using Dahlberg's formula and the Houston reliability coefficient. The feasibility of the methods were analysed using paired t-test and estimated by difference in drop-out rates.

RESULTS

No systematic error exhibited in the repeated measurements except volume in the left nostril (P = 0.017). The method errors of the acoustic pharyngometry and rhinometry were betweeen 0.0002 to 0.069 and 0.001 to 0.082 respectively. The Houston reliability coefficient for both methods were between 0.952 to 0.999. The acoustic pharyngometry was significantly more feasible compared to rhinometry (P < 0.001).

CONCLUSIONS

The study shows that acoustic pharyngometry and rhinometry in the standing mirror position are reliable methods, with acoustic pharyngometry being even more feasible than rhinometry, which is why it is recommended to practice the methods with children and ensure reliability of results before registering measurements.

Acoustic pharyngometry - A new method to facilitate oral appliance therapy

Background

There is lack of reliable and accurate methods to predict treatment outcomes of oral appliance (OA) treatment. Acoustic pharyngometry (AP) is a non‐invasive technique to evaluate the volume and minimal cross‐sectional area of the upper airway, which may prove useful to locate the optimal position of OAs.

Objective

This retrospective study aimed to evaluate the effect of applying AP to OA treatment of patients with obstructive sleep apnoea (OSA).

Methods

All patients (n = 244) treated with OAs following an AP protocol at two dental clinics between 2013 and 2018 were invited to participate. A total of 129 patients accepted the invitation, and 120 patients (75 men, 45 women) were included in the analyses. Mean baseline age, BMI and apnoea hypopnea index (AHI) were 59.1 ± 0.9 years, 27.8 ± 0.4 and 21.9 ± 1.1, respectively. Mean follow‐up time was 318 ± 24 days.

Results

AHI at follow‐up was 6.4 ± 0.7, resulting in a treatment success rate of 86.7% (≥50% reduction of baseline AHI). The number of failures (<50% reduction of baseline AHI) did not differ significantly among patients with mild, moderate and severe OSA. 87.6% of the patients reported OA usage every night, and 95.5% reported > 5 hours usage per night, when worn.

Conclusion

The AP protocol applied seems to contribute to the excellent effect of OA treatment in this study. Further research on the application of AP in OA treatment is necessary in order to clarify its possible beneficial contribution to improving OA therapy.

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

Background

Among 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.

Methods

We 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.

Results

Of 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.

Conclusions

AP 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 Reliability and Influence of Body Position on Acoustic Pharyngometry and Rhinometry Outcomes

OBJECTIVES

The aim of this cross sectional study was to analyze the method error and reliability in acoustic pharyngometry and rhinometry and to analyze the difference between standing and sitting position in acoustic pharyngometry and rhinometry.

MATERIAL AND METHODS

The sample comprised 38 healthy subjects (11 men and 27 women) as part of a control group in another study. The subjects underwent repeated measures of acoustic pharyngometry and rhinometry in standing and sitting position. Upper airway dimensions in terms of volume, minimum cross-sectional areas (MCA) and distances were evaluated using the Eccovision® Acoustic Pharyngometer and Rhinometer. Method error and reliability were analyzed using paired t-test, Dahlberg's formula and the Houston reliability coefficient, and differences between body positions were analyzed using paired t-test.

RESULTS

There was no systematic error in the repeated measures except for the distance to MCA in the left nostril in sitting position (P = 0.041). The method error for the pharyngometry ranged between 0.001 to 0.164 cm/cm2/cm3 and the reliabity was 0.99. The method error for rhinometry ranged between 0.001 to 0.37 cm/cm2/cm3 and the reliability between 0.99 to 1. Difference between standing and sitting position was found only in the pharyngeal airway in terms of volume (P = 0.025) and mean area (P = 0.009) with smaller airway in sitting position.

CONCLUSIONS

The results indicate that acoustic pharyngometry and rhinometry are reliable methods to perform repeated measures of the upper airway dimensions especially in the standing mirror position. It may be essential to perform the measures with the patient positioned in the same body position each time.

Evaluation of Airway Dimensions Following Mandibular Setback with Surgery-First Orthognathic Versus Conventional Orthognathic Approach

Background

To evaluate changes in airway dimensions following mandibular setback with conventional orthognathic approach (COA) and surgery-first orthognathic approach (SFOA).

Materials and Methods

Treatment records of 20 patients who underwent mandibular setback with SFOA/COA were divided into two groups (COA and SFOA, ten patients in each group). Acoustic pharyngometry values were obtained at T0 (01 week prior to surgery), T1 (01-month post-surgery) and T2 (01-year post-surgery). Percentage change in mean volume and area was obtained at T1 (T1-T0) to evaluate airway changes and at T2 (T2-T1) to compare relapse of airway changes in both groups. Changes in airway per mm setback at T1 (T1-T0) and T2 (T2-T1) were also obtained in both groups.

Results

For both parameters, SFOA showed greater reduction at T1 and greater relapse at T2 as compared to COA. The reduction in airway volume at T1 was 0.56 mm/mm setback in COA compared to 1.06 mm/mm setback in SFOA (P-value > 0.05). The relapse in airway volume at T2 was 0.15 mm/mm setback in COA compared to 0.25 mm/mm setback in SFOA (P-value > 0.05). The reduction in area at T1 was 0.062 mm/mm setback in COA compared to 0.110 mm/mm setback in SFOA (P-value > 0.05). The relapse in area at T2 was 0.016 mm/mm setback in COA compared to 0.034/mm setback in SFOA (P-value < 0.05).

Conclusion

In setback cases, SFOA has greater airway reduction immediate post-surgically and greater relapse at 01-year follow-up. Predicting these changes at diagnostic and treatment planning stage may prevent potential adverse events on airway.

Utility of acoustic pharyngometry for screening of obstructive sleep apnea

OBJECTIVE

To determine whether combining acoustic pharyngometric parameters with cephalometric and clinical parameters could improve the predictive power for significant obstructive sleep apnea (OSA) in a Korean population.

METHODS

A total of 229 consecutive adult patients with suspected OSA were enrolled. The predictability for significant OSA using acoustic pharyngometric or cephalometric parameters or combining these parameters and clinical factors was calculated and compared using multivariate logistic regression and receiver operating characteristic (ROC) curves.

RESULTS

In multivariate logistic regression, age, sex, minimum upper airway cross-sectional area (UA-CSA), and mandibular plane to hyoid distance (MPH) were all significant independent predictors of significant OSA. The minimum UA-CSA of 0.85 cm² provided fair discrimination for OSA [area under the curve (AUC): 0.60, 95% confidence interval (CI): 0.52-0.67]. The MPH of 18.75 mm provided fair discrimination for OSA (AUC; 0.65, 95% CI: 0.58-0.72). The discriminative ability of the final model of multivariate ROC curve analyses that included the minimum UA-CSA, age, sex, body mass index (BMI), and MPH was better than the minimum UA-CSA alone (AUCs: 0.77 vs. 0.60). Optimal cut-off values of predictors for discriminating significant OSA were as follows: male for sex, 40 years for age, 25.5 kg/m² for BMI, 1.06 cm² for minimum UA-CSA, and 18 mm for MPH.

CONCLUSION

Minimum UA-CSA measured using acoustic pharyngometry while sitting might be a useful method to predict OSA. Combining minimum UA-CSA with age, sex, BMI and MPH improved the predictive value for significant OSA.

The effect of body position on airway patency in obstructive sleep apnea: CT imaging analysis

PURPOSE

Positional change during sleep influences upper airway patency. However, few studies have used imaging techniques to demonstrate the change. This study aims to determine the effect of positional change on the upper airway space.

METHODS

A total of 118 subjects with sleep breathing disorders were analyzed. Participants underwent upper airway CT scans in the supine and lateral decubitus positions (right and left). They were divided into non-obstructive sleep apnea (n = 28) and obstructive sleep apnea (n = 90) groups. We measured the minimal cross-sectional area of the retropalatal/retroglossal spaces and compared the differences of those two spaces in the supine and lateral positions. CT was performed while patients were awake.

RESULTS

The minimal cross-sectional area in the OSA group was significantly smaller than non-OSA group in both supine (median[interquartile range], 8.3[0.0-25.1] vs 22.2[1.0-39.6]; P = 0.018) and lateral decubitus positions (5.2[0.0-16.9] vs 21.3[6.1-38.4]; P = 0.002). As the body position of OSA patients shifted from supine to lateral, the retroglossal space increased significantly (67.3[25.1-116.3] vs 93.3[43.4-160.1]; P < 0.001). However, there was no significant difference in the retropalatal space between the supine and lateral decubitus positions.

CONCLUSIONS

Positional change from the supine to lateral decubitus position expands the upper airway lumen, especially the retroglossal space. Positional OSA may be related to anatomical change of the upper airway lumen based on body position.

Utility of Acoustic Pharyngometry for the Diagnosis of Obstructive Sleep Apnea

RATIONALE

Owing to resource limitations, the testing of patients for obstructive sleep apnea (OSA) is often delayed. There is a need to accurately triage and expedite testing in those with a high pretest probability of OSA. Acoustic pharyngometry is a simple, noninvasive technique used to assess the upper airway cross-sectional area (UA-XSA), which is known to be reduced in those with OSA.

OBJECTIVES

To determine the discriminative ability and predictive value of UA-XSA measurements by acoustic pharyngometry for OSA.

METHODS

We conducted a cross-sectional study with a clinical cohort of consecutive adults with suspected OSA who had undergone both polysomnography and acoustic pharyngometry. OSA was defined as an apnea-hypopnea index greater than or equal to 5. Multivariable logistic regression analyses and receiver operating characteristic curves were used.

MEASUREMENTS AND MAIN RESULTS

The cohort included 576 subjects, 87% of whom had OSA and 64% of whom were men. The subjects' median body mass index (BMI) was 30.3 kg/m², and their median age was 57 years. The median UA-XSA at FRC when sitting was significantly smaller in those with OSA compared with those without OSA (3.3 cm² [interquartile range, 2.7-3.8] vs. 3.7 cm² [interquartile range, of 2.9-4.2]). When the analysis was controlled for age, sex, BMI, and comorbidities, the odds of OSA increased for every 1-cm² decrease in the mean UA-XSA FRC when sitting (odds ratio, 1.62; 95% confidence interval, 1.23-2.13). The mean UA-XSA provided fair discrimination for OSA (area under the curve, 0.60). A cutoff value of 3.75 cm², the point with the best sum of sensitivity and specificity, had sensitivity of 73% and specificity of 46%. The magnitude of the incremental discriminative value of UA-XSA over clinical variables (age, sex, BMI, and comorbidities) was small and nonsignificant (P = 0.5).

CONCLUSIONS

The mean UA-XSA at FRC when sitting or supine provided no further significant advantage over clinical variables for the discernment of OSA.

New Approaches to Diagnosing Sleep-Disordered Breathing

Novel concepts and technological advances have the potential to change the landscape on which clinical sleep medicine is practiced. Screening for sleep apnea will take advantage of readily available mobile telephone technology (sound, accelerometers) to enable widespread recognition of sleep-disordered breathing. Advanced computer-assisted scoring algorithms will improve efficiency and reliability of sleep apnea diagnoses. As the field adopts a personalized approach to therapies, methods to determine the mechanisms of sleep apnea in individuals will be developed-utilizing simplified tests and available recordings-with the promise of predicting outcomes of novel therapies.

Elevated upper body position improves pregnancy-related OSA without impairing sleep quality or sleep architecture early after delivery

BACKGROUND

During pregnancy, upper airway resistance is increased, predisposing vulnerable women to pregnancy-related OSA. Elevation of the upper body increases upper airway cross-sectional area (CSA) and improves severity of OSA in a subgroup of nonpregnant patients (positional-dependent sleep apnea). We tested the hypothesis that elevated position of the upper body improves OSA early after delivery.

METHODS

Following institutional review board approval, we conducted a randomized, crossover study on two postpartum units of Massachusetts General Hospital. Women during the first 48 h after delivery were included. Polysomnography was performed in nonelevated and 45° elevated upper body position. Upper airway CSA was measured by acoustic pharyngometry in nonelevated, 45° elevated, and sitting body position.

RESULTS

Fifty-five patients were enrolled, and measurements of airway CSA obtained. Thirty patients completed polysomnography in both body positions. Elevation of the upper body significantly reduced apnea-hypopnea index (AHI) from 7.7 ± 2.2/h in nonelevated to 4.5 ± 1.4/h in 45° elevated upper body position (P = .031) during sleep. Moderate to severe OSA (AHI > 15/h) was diagnosed in 20% of postpartum patients and successfully treated by elevated body position in one-half of them. Total sleep time and sleep architecture were not affected by upper body elevation. Change from nonelevated to sitting position increased inspiratory upper airway CSA from 1.35 ± 0.1 cm2 to 1.54 ± 0.1 cm2 during wakefulness. Position-dependent increase in CSA and decrease in AHI were correlated (r = 0.42, P = .022).

CONCLUSIONS

Among early postpartum women, 45° upper body elevation increased upper airway CSA and mitigated sleep apnea. Elevated body position might improve respiratory safety in women early after delivery.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT01719224; URL: www.clinicaltrials.gov.

Quantifying the ventilatory control contribution to sleep apnoea using polysomnography

Elevated loop gain, consequent to hypersensitive ventilatory control, is a primary nonanatomical cause of obstructive sleep apnoea (OSA) but it is not possible to quantify this in the clinic. Here we provide a novel method to estimate loop gain in OSA patients using routine clinical polysomnography alone. We use the concept that spontaneous ventilatory fluctuations due to apnoeas/hypopnoeas (disturbance) result in opposing changes in ventilatory drive (response) as determined by loop gain (response/disturbance). Fitting a simple ventilatory control model (including chemical and arousal contributions to ventilatory drive) to the ventilatory pattern of OSA reveals the underlying loop gain. Following mathematical-model validation, we critically tested our method in patients with OSA by comparison with a standard (continuous positive airway pressure (CPAP) drop method), and by assessing its ability to detect the known reduction in loop gain with oxygen and acetazolamide. Our method quantified loop gain from baseline polysomnography (correlation versus CPAP-estimated loop gain: n=28; r=0.63, p<0.001), detected the known reduction in loop gain with oxygen (n=11; mean±sem change in loop gain (ΔLG) -0.23±0.08, p=0.02) and acetazolamide (n=11; ΔLG -0.20±0.06, p=0.005), and predicted the OSA response to loop gain-lowering therapy. We validated a means to quantify the ventilatory control contribution to OSA pathogenesis using clinical polysomnography, enabling identification of likely responders to therapies targeting ventilatory control.