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 Table of Contents  
ORIGINAL ARTICLE
Year : 2021  |  Volume : 33  |  Issue : 3  |  Page : 294-300

Assessing the prevalence of velopharyngeal dysfunction and obstructive sleep apnea by correlating cone beam computed tomography parameters of soft palate with the stop bang questionnaire


Department of Oral Medicine and Radiology, Meenakshi Ammal Dental College, Chennai, Tamil Nadu, India

Date of Submission25-Mar-2021
Date of Decision25-May-2021
Date of Acceptance27-Jul-2021
Date of Web Publication28-Sep-2021

Correspondence Address:
Dr. V S Madhu Preetha
Department of Oral Medicine and Radiology, Meenakshi Ammal Dental College, Chennai, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jiaomr.jiaomr_81_21

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   Abstract 


Introduction: The relationship between soft palate length and nasopharyngeal depth can be used to determine the velopharyngeal dysfunction and is called Need's ratio. Need's ratio should be in a range of 0.6–0.7 in normal subjects. Any increase greater than 80% demonstrated a risk for developing velopharyngeal dysfunction. Aim: To assess the prevalence risk rate of obstructive sleep apnea using snoring, tiredness, observed apnea, blood pressure, body mass index, age, neck circumference, gender (STOP-BANG) questionnaire and to evaluate various parameters of the soft palate, pharyngeal depth, and determination of Need's ratio using CBCT. Materials and Method: In this prospective study, patients who reported for CBCT assessment in the age group ranging from 20 to 50 years were included. The sample size of the study was calculated to be 42. Furthermore, the patients were screened with the STOP- BANG questionnaire and shapes of the soft palate, velar length, width, and pharyngeal depth were obtained with the CBCT sections, and Need's ratio was calculated. Results: The collected data were analyzed with IBM. SPSS software 23.0. Based on the results of the STOP- BANG questionnaire, P value was found to be significant. Based on the CBCT parameters, the most common shape was the leaf-shaped soft palate. The velar length, width, and pharyngeal depth were found to be higher in males. Need's ratio was found to be increasing with an increase in age. A significant correlation of risk for OSA was established based on a comparison of questionnaire results with the results obtained from CBCT parameters with Need's ratio. Conclusion: CBCT is a static imaging technique, it can identify the anatomic risk factors for developing sleep apnea.

Keywords: CBCT, Need's ratio, obstructive sleep apnoea, questionnaire, velopharyngeal dysfunction


How to cite this article:
Madhu Preetha V S, Harsha Vardhan B G, Gopal K S, Lankupalli AS. Assessing the prevalence of velopharyngeal dysfunction and obstructive sleep apnea by correlating cone beam computed tomography parameters of soft palate with the stop bang questionnaire. J Indian Acad Oral Med Radiol 2021;33:294-300

How to cite this URL:
Madhu Preetha V S, Harsha Vardhan B G, Gopal K S, Lankupalli AS. Assessing the prevalence of velopharyngeal dysfunction and obstructive sleep apnea by correlating cone beam computed tomography parameters of soft palate with the stop bang questionnaire. J Indian Acad Oral Med Radiol [serial online] 2021 [cited 2021 Nov 29];33:294-300. Available from: https://www.jiaomr.in/text.asp?2021/33/3/294/326887




   Introduction Top


The fibromuscular part of the palate, which is attached to the posterior edge of the hard palate is called the soft palate. The shape of the soft palate may play a role in upper airway obstruction in patients with obstructive sleep apnea syndrome.[1] The relationship of the length of velum and pharyngeal depth can be used to assess the velopharyngeal function. The ratio of pharyngeal depth to velar length is called Need's ratio.[2] According to previous studies, in normal individuals, Need's ratio is about 0.6–0.7. However, a greater ratio denotes velopharyngeal dysfunction.[3] Obstructive sleep apnea (OSA) is a common sleep disorder resulting from cessation or reduction of airflow during sleep because of repetitive total or partial collapse of the pharyngeal airway for at least 10 s with persistent respiratory effort.[4] The major risk factors of OSA are obesity, smoking habit, excessive alcohol intake, hyperlipidemia, and increasing age.[5] Various questionnaires are proposed to screen the patients for OSA and snoring, tiredness, observed apnea, blood pressure, body mass index, age, neck circumference, gender (STOP-BANG) questionnaire is the most widely accepted one in which history of snoring, tiredness during the daytime, choking or gasping during breathing, hypertension, BMI, age of the patient, neck size measurements, and gender are assessed, and scoring has been proposed for high, intermediate, and low risk of developing OSA.[6] With the widespread use of CBCT, dental patients at risk for OSA may be identified on CBCT examinations originally acquired for other diagnostic purposes.[7] The treatment of OSA includes lifestyle modifications, weight loss, avoidance of sedatives/alcohol, lateral body position during sleep, continuous positive airway pressure (CPAP), orthodontic devices, and finally surgical management.[8] Our study is the first study to mainly correlate both CBCT results with STOP- BANG questionnaire results thereby identifying the patients who are at higher risk of developing OSA, which is the main clinical significance of the study.

Aim

To assess the prevalence risk rate of obstructive sleep apnea using STOP-BANG questionnaire and to evaluate the shape of the soft palate, various dimensions of soft palate such as velar length, velar width, and pharyngeal depth and determination of Need's ratio using CBCT.

Objectives

To assess the prevalence risk rate of obstructive sleep apnea using STOP-BANG questionnaire. To compare the shape of the soft palate, velar length, velar width, and Need's ratio using CBCT among patients with various age groups and gender. To assess the prevalence risk rate of obstructive sleep apnea by estimation of Need's ratio using CBCT. To compare the STOP-BANG questionnaire results and CBCT values for all the patients.


   Materials and Method Top


This is a prospective institutional-based study conducted in the Department of Oral Medicine and Radiology from February 2019 to June 2019. The Ethical clearance was obtained from the Institutional Review Board for the study design on 12.3.2019, protocol number MADC/IRB-XXVIII/2019/435. Informed consent had been obtained from the patients in their respective vernacular languages. The consent form was designed based on the Helsinki declaration 1975. The study was performed on the patients who report for CBCT assessment of full skull for other dental diagnostic purposes with their age group ranging from 20 to 50 years. All the patients who were taking part in the study were given with STOP-BANG questionnaire [Annexure] for screening of obstructive sleep apnea. The height, weight, and neck measurements were measured, BMI was calculated and further based on the questionnaire scoring, the patients were categorized under high, intermediate, and low risk of OSA.

All scans were obtained from the planmeca ProMax CBCT machine using Romexis software. The imaging parameters were set at 120 kVp, 18.6 mAs, scan time 15 s, resolution 0.4 mm. All scans were taken with the patients standing upright in a natural head position, and molars in contact, and breathing through the nose.

Both the questionnaire and CBCT parameters were assessed by two Oral Medicine and Maxillofacial radiologists independently, and CBCT results were correlated with questionnaire results. In some patients, variations in parameters such as velar length, width, and pharyngeal depth were noted during assessment by the radiologists, and the mean value was taken in such cases.

The study group was divided into three categories based on their age as

Group-I: 20–30 years

Group-II: 31–40 years

Group-III: 41–50 years.

Statistical analysis

The collected data were analyzed with IBM. SPSS statistics software 23.0 Version. To describe the data descriptive statistics, frequency analysis was used, for categorical variables, percentage analysis for used, and for continuous variables, the mean and S. D were used. To find the significance in the multivariate analysis, the one-way analysis of variance (ANOVA) was used. To find the significance in categorical data, the Chi-Square test was used. In all the above statistical tools, the probability value. 05 was considered a significant level.

Sample size calculation

The sample size of the study was calculated to be 42 using Gpower software, with 14 patients in each group with an equal number of males and females in each group. The sample size was calculated based on the result of the pilot study performed on 12 patients with 4 patients in each group using MedCalc version 14.8.1 software and a single mean sampling method. The power of the sample size was found to be 0.8.

Inclusion criteria

  • Patients who reported for CBCT full skull assessment for dental diagnostic purposes.
  • Patients in the age group 20–50 years


Exclusion criteria

  • Patients who were below 20 years and above 50 years.
  • Cleft lip and palate patients.
  • Patients with craniofacial trauma, fracture, and previously surgically treated for head and neck trauma or lesion, and malignancy of palate, and pharynx.
  • Patients with craniofacial skeletal syndromes.


The various shapes of the soft palate [Figure 1] were recorded in the CBCT images of the patients at rest. While interpreting, the scans in the sagittal sections were observed keeping the mid-sagittal plane in center.
Figure 1: CBCT –sagittal section showing various shapes of the soft palate at the level of the posterior nasal spine.a-Crooked shaped, b-Butt shaped, c- S shaped, d- Leaf shaped, e- Rat tail shaped

Click here to view


  • Velar length - Linear distance from the posterior nasal spine to the tip of the uvula. [Figure 2]
  • Velar width- Thickest section of the velum [Figure 3]
  • Pharyngeal depth - Linear distance from the posterior surface of the nasal spine to the posterior pharyngeal wall along the palatal plane. [Figure 4]
  • Need's ratio - Pharyngeal depth/Velar length.
Figure 2: CBCT-sagittal section showing velar length at the level of the posterior nasal spine

Click here to view
Figure 3: CBCT-sagittal section showing velar width at the level of posterior nasal spine

Click here to view
Figure 4: CBCT-sagittal section showing pharyngeal depth at the level of posterior nasal spine

Click here to view


Other than obtaining Need's ratio for evaluating the risk of OSA, the significance of measuring velar length, width, and pharyngeal depth at rest revealed the morphometric data of the soft palate based on gender and age in this population, which can be compared with other populations.


   Results Top


Based on gender and age

In our study, the total sample size was 42, with 14 patients in each group. Male and female patients were divided equally. The P value was found to be (P > 0.05) insignificant. The sample size was determined by conducting a pilot study among 12 patients using MedCalc version 14.8.1 software and a single mean sampling method. The mean age of the study group was 36.143, with a standard deviation of 9.52 and standard error of 1.47, with a minimum age of 20 years and maximum age of 50 years. Based on the ANOVA test, the P value was found to be highly significant based on gender and age.

Based on the stop bang questionnaire

About 40.5% of the patients said that they have the habit of snoring, and P value (0.047) was found to be < 0.05, which was significant. About 64.3% of the patients said that they felt tired, fatigued, or sleepy during the daytime, 35.7% of the study population said that they experienced choking/gasping in the middle of the sleep. A total of 11.9% gave a history of hypertension, about 4.8% of the patients had BMI greater than 35 kg/m2, with a mean value of 25.6, the standard deviation of about 5.09 and standard error of about 0.7, and the minimum value of 17.2 and maximum value of 40.1. In all these above categories, the P value was found to be insignificant. About 19% of the sample was equal to 50 years of age, and P value was found to be highly significant, P < 0.01. About 23.8% of the patients had neck circumference above 43 cm, P value (0.1) insignificant, and 50% of the patients belonged to the male gender, P- value (1.0) insignificant. According to the overall results of the STOP-BANG Questionnaire, about 16.7% of the patients came under high risk, 35.7% patients came under intermediate risk, and about 47.6% patients came under the low-risk category, respectively, and P value was found to be significant, P value-0.019. i.e. P < 0.05 [Graph 1], [Table 1].

Table 1: Chi-Square test for STOP BANG Questionnaire

Click here to view


Based on the shape of the soft palate

The shape of the soft palate was assessed based on the CBCT images. They were classified as a leaf, rat tail, S-shaped, crooked, and butt shaped. Leaf shape-45.2%, rattail shape-23.8%, butt shape-11.9%, crooked, and S-shape-9.5% each, respectively. The most common shape was a leaf-shaped soft palate. The P value was found to be 0.4, and insignificant [Graph 2].



Morphometric parameters of the soft palate

The parameters such as velar length, velar width, and pharyngeal depth were measured in sagittal sections of CBCT images. In velar length, the mean value was found to be 33.62, the standard deviation of 3.71 and standard error of 0.57, and the minimum value of about 24.52 mm, and the maximum value of 40.80 mm. The P value was found to be 0.49, which was insignificant. In velar width, the mean value was found to be 8.94, a standard deviation of 1.61, standard error of 0.24, and minimum value of about 6.51 mm, and a maximum value of about 14.14 mm. The P value >0.3, insignificant. In pharyngeal depth, the mean value was found to be 24.57, the standard deviation of 4.24 and standard error of 0.65, and the minimum value was found to be 6 mm and maximum 30.10 mm. The P value was 0.6, insignificant.

Need's ratio

Need's ratio is calculated by dividing the pharyngeal depth by velar length. The mean value was found to be 0.7, the standard deviation to be 0.08 and standard error to be 0.01, and the minimum value was 0.6, and the maximum value was 0.8. About 52.4% came under the risk category, and 47.6% of patients came under the normal category in screening for OSA. The P value was found to be 0.3, insignificant [Graph 3].



Correlation of stop bang questionnaire and Need's ratio results

Correlation of risk of OSA based on the questionnaire with the results obtained from CBCT with Need's ratio. The P value was found to be highly significant (P value < 0.01) [Graph 4]. Based on the STOP-BANG questionnaire, among 42 patients, 20 patients came under low risk, 15 patients under intermediate risk, and 7 patients under high risk. Based on Need's ratio, 22 patients came under the risk category, and 20 patients had a normal Need's ratio. On comparing both the results, four patients who came under intermediate risk based on the questionnaire had normal Need's ratio value. Whereas five patients who came under low risk based on the questionnaire came under the risk category based on Need's ratio, which indicates that, despite the low risk, even the morphology of the soft palate can be a causative factor in the risk for developing OSA. The patients with intermediate-risk in the questionnaire, but normal Need's ratio are highly prone to fall under the high-risk category and have higher chances of developing OSA. Comparing the overall results based on the questionnaire and Need's ratio, there was a highly significant correlation between these both. The risk of developing OSA increases with age with the least risk rate among 20–30 years, followed by 31–40 years, and the highest risk rate among patients aged 41-–50 years.




   Discussion Top


The human soft palate plays a critical role in breathing, swallowing, and speech.[9] Soft palate collapse during sleep is commonly seen in patients with obstructive sleep apnea (OSA), a potentially life-threatening disorder.[10],[11] Detection of the sites of obstruction and narrowing of the upper airway is of clinical importance in the pathophysiology of OSAS as well as in the planning of treatment.[12] The gold standard investigating modality in OSA is polysomnography (PSG). PSG includes electroencephalography along with electromyography, electrooculogram, airflow, pulse oximetry, respiratory effort, electrocardiographic tracings, body position, and apnoea-hypopnoea index.[13]

A newer modality in dental setup for evaluating pharyngeal and velar morphology is 3D cone-beam computed tomography. Various morphometric measurements of soft palate were obtained in the median sagittal plane using CBCT.[14],[15]

Based on age groups, it was found that 41–-50 years of age group have increasing velopharyngeal parameters such as the length, width, pharyngeal depth, and Need's ratio, followed by 31–40 years of age group and 21–30 years, which is following the study done by Verma et al., 2014 and Priyal et al., 2016.[16],[17]

Based on gender, Kollias and Krogstad et al., 1999[18] showed that the increase in the velar length, width was equal among males and females, however in our study, it was noted to be significantly greater in males than in females, which was following the study done by Verma et al., 2014 and Agarwal et al., 2016. Where as the pharyngeal depth and Need's ratio were found to be higher in males in our study, which contradicts the study done by Verma et al., 2014 and Priyal Agarwal et al., 2016.

Based on shapes of the soft palate, Pepin et al., 2000,[19] found that a “hooked” morphology of the velum, indicated a high risk for obstructive sleep apnea in awake patients. An angulation of 300 between the distal part of the uvula and the longitudinal axis of the velum is considered as hooking of the soft palate. In our study, the hooked shape was indicated as a crooked shape, which was in about 9.5% of the total study population. Studies done by Niu et al.,[20] Kumar and Gopal et al., 2011[21] and Chalkoo AH et al., 2015[22] showed that the most common shape of the soft palate was leaf shape, which is following our study, about 45.7% of patients had leaf-shaped soft palate. The literature described that this type is the classic velar morphology. Whereas in studies conducted by Agarwal et al., 2016 and Shaliputra Magar et al., 2018[23] the rat tail shape was the most common shape (46.25%), which contradicts our study, where the rat tail shape was the second most common type (23.8%). The S-shaped soft palate was seen in 1.5% of the cases in Deepa et al., 2013[24]. study, and about 4.7% of the cases in a study conducted by Verma et al., 2014 and about 9.9% of cases in a study conducted by Agarwal et al., 2016, which is following our study (9.5%). About 3.5% of the cases had an S-shaped soft palate in the study done by Chalkoo AH et al., 2015, which contradicts the results of our study.

In a study conducted by Johnston and Richardson et al., 1999[25] and Taylor et al., 2003, a significant increase in velar length and width was noted with an increase in age. This was in accordance with the findings of Verma et al., 2014 and Agarwal et al., 2016 and our study.

According to the results of studies done by Subtelny et al., 1957,[26] Hoopes et al., 1970[27] and Simpson and Colton et al.,[28] 1972, Need's ratio was found to be higher in males than females, which is in accordance with our study, where the overall mean Need's ratio was 0.74. Nakamura et al.,[29] 2003 reported that patients with persistent VPI had a shorter VL and greater PD, resulting in a lower value of Need's ratio (PD/VL). The results were contradicting with those of Deepa et al., 2013 and Verma et al., 2014 and Aggarwal et al., 2016. Thus, in our study, males were more prone to VPI than females.

Need's ratio varies with various shapes of soft palate i.e. in the study done by Agarwal et al., 2016 Need's ratio was maximum in crook shape (0.81) as compared to other previous studies in which S-shaped soft palate accounted for maximum Need's ratio. In our study, Need's ratio was found to be maximum in the butt-shaped soft palate and S-shaped followed by the crooked-shaped soft palate. Our study is the first one to compare the risk of OSA based on Need's ratio values using CBCT and clinical STOP-BANG questionnaire risk value criteria, which showed a highly significant correlation between the two parameters.

Limitations

The movement of the velopharynx during sleep is recorded well by functional MRI or with an oropharyngeal endoscopic procedure.[30] As CBCT was taken with patients in a static position in our study, the accuracy rate was slightly compromised, and the area of constriction varied which is the main limitation of this study.

Future prospects

With the aid of CBCT, the study can be further extended to a larger population which will add significance to the power of the study. Furthermore, the area and volumetric analysis of the upper airway, can also be obtained with the help of CBCT giving accurate region of obstruction, which will assist in the surgical management of patients with obstructive sleep apnea.[31]


   Conclusion Top


Thus the morphometric evaluation of soft palate including its shape, velar length, width, pharyngeal depth are analyzed and further, prevalence risk rate of OSA using STOP BANG questionnaire and need's ratio was estimated in our study population.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.


   Annexure Top


STOP BANG QUESTIONNAIRE

NAME:

AGE:

HEIGHT:

WEIGHT:

STOP BANG QUESTIONNAIRE

  • SNORING? Do you Snore Loudly (loud enough to be heard through closed doors or your bed-partner elbows you for snoring at night)?
  • Yes No
  • TIRED? Do you often feel Tired, Fatigued, or Sleepy during the daytime (such as falling asleep during driving or talking to someone)?
  • Yes No
  • OBSERVED? Has anyone Observed you Stop Breathing or Choking/Gasping during your sleep?
  • Yes No
  • PRESSURE? Do you have or are being treated for High Blood Pressure?
  • Yes No
  • BODY MASS INDEX more than 35 kg/m2?
  • Yes No
  • AGE older than 50 year old?
  • Yes No
  • NECK SIZE large? (Measured around Adams apple) For male, is your shirt collar 17 inches/43 cm or larger? For female, is your shirt collar 16 inches/41 cm or larger?
  • Yes No
  • GENDER = Male?
  • Scoring Criteria:
  • For general population
  • Low risk of OSA: Yes to 0-2 questions
  • Intermediate risk of OSA: Yes to 3-4 questions
  • High risk of OSA:
  • Yes to 5-8 questions
  • Or Yes to 2
  • Or more of 4 STOP questions + male gender
  • Or Yes to 2 or more of 4 STOP questions + BMI > 35 kg/m2
  • Or Yes to 2 or more of 4 STOP questions + neck circumference (17”/43 cm in male, 16”/41 cm in female.




 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1]



 

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