Journal of Indian Academy of Oral Medicine and Radiology

ORIGINAL ARTICLE
Year
: 2021  |  Volume : 33  |  Issue : 2  |  Page : 177--182

Obstructive sleep apnea: Dental perspective from upright to supine


Rupsa N Rout1, Sanat K Bhuyan2, Arpita Priyadarshini3, Damodhar Bhindhani4, Mamata Singh5, Satya Mohapatra6,  
1 Department of Oral Medicine and Radiology, SCB Dental College and Hospital, Cuttack, Odisha, India
2 Department of Oral Medicine and Radiology, Institute of Dental Sciences, Bhubaneswar, Odisha, India
3 Department of Physiology, Bolangir Medical College, Bolangir, Odisha, India
4 Department of Pulmonary Medicine, Aditya Care Hospitals, Bhubaneswar, Odisha, India
5 Department of Radiodiagnosis, Aswini Hospital, Cuttack, Odisha, India
6 Department of Radiodiagnosis, SUM Hospital, Bhubaneswar, Odisha, India

Correspondence Address:
Dr. Rupsa N Rout
SCB Dental College and Hospital, Cuttack, Odisha
India

Abstract

Aim: To evaluate diagnostic cephalometric parameters and their influence on skeletal and soft tissue components in obstructive sleep apnea (OSA). Materials and Methods: The study is a prospective case study of 40 diagnosed cases (as diagnosed by Type IV level study) of obstructive sleep apnea who were reported to the Department of Oral Medicine and Radiology with their age ranging from 28 to 75 years. Lateral cephalometric radiographs in upright and supine posture were taken, with teeth in centric relation, and the head aligned with Frankfort horizontal (FH) plane parallel to the floor. The focus-coronal plane distance was 5 feet, the film-coronal plane distance was 15 cm, and the magnification was 10%. Results: OSA patients experience an increase in values of sella nasion point A (SNA) and sella nasion point B (SNB) at the supine position with respect to the upright position and experience a decrease in values of nasion sella turcica odontoid process tangent (NSL-OPT) and nasion sella turcica- cervical vertebra tangent (NSL-CVT) at the supine position with respect to the upright position. The parameters of paramount importance in the pathogenesis of OSA are soft palate thickness, length, and tongue length. Conclusion: SNA, SNB and NSL-OPT, NSL-CVT are inversely related to each other and play a role in the consequence or pathogenesis of OSA. Tongue height is of the least significance in the pathogenesis of OSA. The cephalometric findings are of paramount importance to know the exact site of obstruction in the pathogenesis of OSA.



How to cite this article:
Rout RN, Bhuyan SK, Priyadarshini A, Bhindhani D, Singh M, Mohapatra S. Obstructive sleep apnea: Dental perspective from upright to supine.J Indian Acad Oral Med Radiol 2021;33:177-182


How to cite this URL:
Rout RN, Bhuyan SK, Priyadarshini A, Bhindhani D, Singh M, Mohapatra S. Obstructive sleep apnea: Dental perspective from upright to supine. J Indian Acad Oral Med Radiol [serial online] 2021 [cited 2021 Sep 26 ];33:177-182
Available from: https://www.jiaomr.in/text.asp?2021/33/2/177/319071


Full Text



 Introduction



Obstructive sleep apnea has been dated back to over 2000 years of its origin. During the 19th century, a new term was proposed by the name “PICKWICKIAN SYNDROME” and was targeted on obesity based on the novel “The Pickwick Papers” by Charles Dickens in which an overweight character named “Joe” exhibited symptoms of sleep apnea.[1] Polysomnography which is the gold standard or the diagnostic test of significance was first recorded in the year 1965 during sleep. During the 1960–1970s, tremendous research was carried on regarding the etiopathogenesis of OSA. Thereby foci of the interest shifted from obesity to other co-morbidities with sleep-disordered breathing.

The first scientist to have put a sleep clinic was Dr. William Dement of the USA in 1970 at Stanford University, California and later after 2 years, he was joined by Christian Gullieminault.[2] During this period, the oropharynx was diagnosed to be the locus of airway closure, and not the larynx as was thought to be. The first research was conducted by Eliot Philipsen at Toronto, Canada in the year 1970 on dogs. Six years later, he was joined by Colin Sullivan wherein they worked on hypopnea and control mechanisms during sleep cycle rhythm, and has designed a mask in 1979 for dogs that could deliver air. Experimentation was conducted on dogs, and tracheostomy was done which was later used for severely affected OSA patients.[3]

Experimentation on dogs was later applied on human beings, and the first continuous positive airway pressure was built on patients by Sullivan. The first major epidemiological study was done by Young et al.[4] in the year 1997 and in 2000, four papers were published. Here, OSA was found in association with hypertension. By 2001, other comorbidities were found to be associated with OSA such as coronary heart disease, heart failure, stroke, etc.[2] Hence, the aim of the study was to evaluate the diagnostic cephalometric parameters in obstructive sleep apnea patients. The parameters were further studied to find the influence on skeletal and soft tissue components in both upright and supine posture.

 Materials and Methods



The study was a prospective case observational type and performed in a period of 2016–2017 in the Department of Oral Medicine and Radiology and Department of Radiodiagnosis, of a Dental and Medical college in Bhubaneswar, Odisha, India. The sample size was calculated for paired t-tests as the basic purpose is to compare mean parameters between the up-right and supine position. The input parameters had been taken as Effect size = 0.5, α error probability = 0.05, and power (1-β error probability) =0.90. The minimum required sample size comes out to be 36. However, we had a sample size of 40. The computation has been made using G* Power 3.1.9.4 software.[5] The present study included 40 diagnosed cases (as diagnosed by Type IV level study) of obstructive sleep apnea who reported to the Department of Oral Medicine and Radiology with their age ranging from 28 to 75 years for screening and evaluation to be done for the present study. Out of these patients, 6 are females and 34 are males. The study was given ethical clearance with reference number DMR/IMS-SM/SOA/16032 dated 27th May 2016 from Institute of Medical Sciences and Sum Hospital. Informed consent was obtained from all participants of the study. The Helsinki declaration was also duly signed by them.

The 1994 review divided portable monitoring (PM) into 4 types:

TYPE I: Full attended polysomnography (≥7 channels) in a laboratory setting.

TYPE II: Full unattended polysomnography (≥7 channels)

TYPE III: Limited channel devices (usually using 4–7 channels)

TYPE IV: 1 or 2 channels usually using oximetry as one of the parameters.

Samples were chosen on the basis of the following criteria:

Age over 25 yearsApnea Hypopnea Index (AHI) >10 events/hour during an overnight Type IV level study.Body Mass Index (BMI) >25,Who complained of habitual snoring and daytime sleepinessPatients satisfying Berlin's Questionnaire and STOP BANG Questionnaire.Individuals who were willing to undergo this investigation.

The samples were excluded on the criteria that

No other race people are considered other than the Asian population.Children under <18 years are excluded.Any pathology-related factors affecting the criteria of measurements should be avoided i.e. central causes are avoided.

Each patient's body mass index (BMI) and apnea-hypopnea index (AHI) was recorded. The neck circumference was measured using a measuring tape at the level of the cricoid cartilage. While measuring the neck circumference, the patients were in erect posture and the neck musculature must be relaxed. The measurement >40 cm was more prone for OSA and was positively recorded in the case history proforma. The present study included BERLIN's Questionnaire and snoring, tiredness, observed apnea, high blood Pressure (STOP) Body mass index (BMI), Age, Neck circumference, and Gender (BANG) Questionnaire (developed by Anesthetist Francis Chung et al. 2008) for evaluation of OSA severity. The severity or the likelihood for the development of OSA is established. The questionnaire served as a screening tool for the OSA, which was later to be confirmed with TYPE IV level study.

The present study is based on landmark-based geometric morphometric evaluation using cephalometry. The cephalometric machine used was TEJAS 6000 with a manual collimator working under a specification of 150 KVp and 1.5 mm Al (total filtration) 24 V with a maximum exposure of 15 s at 6 mA. Standardized lateral cephalograms were taken with an X-ray device for the evaluation of the patients.

Five skeletal characteristics were evaluated in this study namely: [Figure 1]{Figure 1}

Sella Nasion Point A (SNA),Sella Nasion Point B (SNB),Difference between SNA and SNB (ANB)Nasion Sella turcica- Odontoid process tangent (NSL-OPT),Nasion Sella turcica- Cervical vertebra tangent (NSL-CVT) [Figure 2].{Figure 2}

Abbreviations used:

SP - T - Soft palate thickness: The linear distance between SSP and ISP.SP - L - Soft palate length: The linear distance between PNS and U.T - L - Tongue length: The linear distance from pointE (epiglottis) and tongue tip (TT).T - H - Tongue height: The linear distance between the midpoint of E-TT (tongue length) and the most prominent point on the dorsum of the tongue.SPAS - Superior posterior airway space: The minimum distance between the posterior part of the soft palate and posterior pharyngeal wall.MPAS - Middle posterior airway space: The minimum distance between the posterior pharyngeal wall and the tip of the soft palate.IPAS - Inferior posterior airway space: The minimum distance of the posterior airway space at the angle of mandible measured along line Go-Pt. B.NSL - OPT-Cranio-cervical angulation: The angle formed by the line sella nasion and odontoid process tangent.NSL - CVT-Cranio-cervical angulation: The angle formed by the line sella nasion and cervical vertebra tangent.

All the images were taken during the holding of breath after deep inspiration with the head of the patients fixed by ear rods using the lateral cephalometric projections. All the images were digital on Image Works CR 13.01 taken in a standardized position i.e. the teeth in centric relation, and the head aligned with the Frankfort horizontal (FH) plane (defined by a line extending from the tragus of the ear to the inferior edge of the ipsilateral orbit) parallel to the floor. This position was stabilized with ear rods and nasal support to prevent the head from rotating during exposure. The focus-coronal plane distance was 5 feet, film-coronal plane distance was 15 cm, and the magnification was 10%.

During the morphometric evaluation, the upper airway soft tissue structures were evaluated in the supine position, whereas in the erect or upright position the craniofacial characteristics were evaluated [Figure 1] and [Figure 2]. All the 24 variables i.e. 12 each in erect and supine cephalometry were compared. The patient's head was fixed with ear rods and two pointers were placed at nasion and orbitale, respectively, for proper orientation of the head. The dorsum of the tongue was coated with barium sulfate contrast to enhance the outline of the tongue and pharyngeal soft tissues. While taking the cephalograms, the distance between the midsagittal plane of the subject and the X-ray source was fixed at 5 feet, and the median plane to film distance was 15 cm; thus, the constant enlargement was 10%.

 Results



Observations on 40 cases of OSA were recorded as per the protocol of the study. The data collected in the process were codified and entered into Statistical Package for the Social Sciences (SPSS) SPSS 16.0 software for statistical analysis.

[Table 1] presented mean values of the characteristics along with the differences of characteristics in upright and supine positions and the results of paired t-test.{Table 1}

The present study, 12 cephalometric characteristics have been observed. These are divided into three groups,

Skeletal characteristics,Soft tissue characteristics,Soft tissue airway space.

All the characteristics were measured both in the upright and supine position [Figure 3].{Figure 3}

The mean difference of SNA in the upright and supine position is -4.4 ± 3.9° (P = 0.001). The mean difference of SNB in the upright and supine position is -4.3 ± 3.7° (P = 0.001). This indicated there is an increase of 4.4 and 4.3° in the SNA and SNB in the supine position with respect to the upright position, respectively, and these differences are statistically significant which suggests that the angle with respect to point A and point B formed by sella turcica increases significantly which further implies that these parameters have a significant role to play as a consequence of OSA rather than in the development of OSA. The mean difference of ANB in the upright and supine position is -0.100 ± 2.5° (P = 0.802), this is quite insignificant. The difference of the parameters is not so significant which stresses the fact that there are other compensatory mechanisms to prevent the development of OSA or rather the neutralizing factors which try to prevent the development of the obstruction have a significant role to play such as retrognathism of the jaw.

NSL-OPT and NSL-CVT decrease in the supine position with respect to the upright position. The mean decreases are 2.7 ± 5.5° (P = 0.003) and 2.1 ± 4.7° (P = 0.008) of NSL-OPT and NSL-CVT, respectively. These figures of change in supine with respect to upright are suggestive that the decrease in angulation of NSL with odontoid process tangent and cervical vertebra tangent may be a deterministic parameter in the pathogenesis of OSA but limit the extent in the consequence of OSA as the change in values obtained are very minimal, so there are other factors to be considered for the condition to develop into OSA.

Both NSL-OPT and NSL-CVT have got a change in values of 2°, i.e. both are mutually interlinked in the pathogenesis of OSA and the change in the value of minimal in supine with respect to upright. The OSA patient experiences an increase in values of SNA and SNB at supine with respect to upright and experienced a decrease in values of NSL-OPT and NSL-CVT at the supine position with respect to the upright position. So SNA, SNB and NSL-OPT, NSL-CVT are inversely related to each other.

Four soft tissue parameters were evaluated in the study namely,

Soft-palate thickness (SP-T),Soft-palate length (SP-L),Tongue length (T-L),Tongue height (T-H). [Table 2] and [Figure 4],{Table 2}{Figure 4}

[Table 2] presented mean values of the above characteristics along with the difference of characteristics in upright and supine positions and the results of paired t-test.

Soft palate thickness increases at the supine position, soft palate length and tongue length decrease at the supine position significantly, and tongue height did not change much significantly at the supine position. Though the decrease is evident, the proportion of decrease is very minimal which is present in tongue and soft palate length, and the thickness of the soft palate is increased to a less extent. The parameters of paramount importance in the pathogenesis of OSA are soft palate thickness and length and tongue length.

 Evaluation of Soft Tissue Airway



Three characteristics were evaluated at the upright and supine positions. These were:

Superior posterior airway space (SPAS)Middle posterior airway space (MPAS)Inferior posterior airway space (IPAS) [Table 3] and [Figure 5]{Table 3}{Figure 5}

The mean difference of SPAS (U)-SPAS (S) was 0.43 ± 0.35 (P = 0.001). The mean difference of MPAS and IPAS at the upright and supine position were 0.35 ± 0.25 and 0.33 ± 0.26, respectively, with a P value of 0.000 in both cases. This implies a significant decrease in three characteristics at the supine position with respect to upright position i.e. the airway space is considerably reduced in the supine position in obstructive sleep apnea patients which may be one of the contributing factors for OSA.

All the three characteristics i.e. SPAS, MPAS, and IPAS were significantly decreased across the cases at the supine position with respect to upright, and the equal proportion of decrease in the three locations of airway space suggests that the anatomy of the person's airway space quite significantly and logically decreased which may lead to the pathogenesis of OSA.

 Discussion



Lateral cephalometry is a 2D representation of a 3D anatomical structure. Lateral cephalometry has been used since time immemorial for the evaluation of airway structures for OSA. The present study has shown an increase of 4.4° and 4.3° in SNA and SNB angle when the patients were subjected to supine cephalometry and with a statistically significant value. But the study by Bhardwaj et al.[6] has shown an increase of 3.3° and 4.0°, respectively for SNA and SNB with statistically significant values for SNB but not for SNA. The difference in angulation i.e. ANB is not quite significant i.e. 0.1° of change from the standard protocol of 2° for a normal subject. But the ANB angulation has come out to be significant in the study by Bhardwaj et al.[6] with a change of angulation of 2° with respect to supine position when compared to erect posture. Similarly, studies by Ahmet Yalcin Gugnor et al.[7] have shown the SNA and SNB angles to increase by 3.84° and 4.59°, respectively but statistically insignificant value. The ANB angle has shown to be a change of 3° but with an insignificant value.

A study by Borges et al.[8] found an insignificant value for SNA, SNB as well as for ANB with the change of degree of 3.38°, 4.2° and 2°, respectively. Similarly, statistically insignificant values were obtained in the studies by J.M. Battagel et al.[9] 3.9°, 4.2°, and 2.7° for the SNA, SNB, and ANB angles, respectively. A study by Gokmet Kurt et al. on 20 patients diagnosed with OSA found mean ± SD for SNA, SNB, and ANB to be 80.48 ± 3.98, 78.49 ± 4.4, and 1.99 ± 2.86, respectively which is inconsistent with the present study. The mean ± SD of SNA, SNB, and ANB in the control group was found to be 78.6 ± 3.9, 76.6 ± 4, and 1.7 ± 2.7, respectively.

The decrease in supine posture was found to be 2.7 ± 5.5° and 2.1 ± 4.7° for NSL-OPT and NSL-CVT, respectively, in the present study. Both have been found to be of statistically significant value and as the modal values of 2° have been found in both angulations, the change is minimal so these parameters have been found to be of least significance in determining OSA. Similar results coinciding with the present study were obtained from Bhardwaj et al.[6]

There is an increase of 0.68 mm in soft palatal thickness but a decrease of 1.12 mm in soft palatal length. Similarly, tongue length has decreased by 1.57 mm and height of tongue by 0.14 mm. A statistically significant value has been obtained for all the soft tissue characteristics except for tongue height. In comparison to the present study, similar values have been obtained by Bhardwaj et al.[6] wherein the study group has shown that with a change in posture, soft palatal length decreased and thickness increased and tongue length decreased but with no significant change in tongue height. The correlation coefficient has shown a significant positive correlation coefficient for soft palatal length and thickness as well as in tongue length but no significant change in tongue height.

Another study by Aylin Yucel et al.[10] soft palatal thickness maximum distance perpendicular toposterior nasal spine (PNS) was found to be of a significant value. The study establishes that soft palate thickness increases to a significant extent in OSA patients in supine posture which is in accordance with the present study. Tongue obstruction along with soft palatal changes takes place in OSAS patients as in tsupine posture the tongue length, soft palatal length, and thickness increases and falls back in the oral cavity causing reduced retropalatal measurement and thus finally causing an obstruction.[11],[12]

There is a significant decrease in airway patency at the nasopharynx, oropharynx, and hypopharynx. At all three levels, the decrease has been found to be approx. 0.20–0.23 mm. In contrast to the present study, superior posterior airway space shows a significant reduction of the airway in both the control and study group according to Bhardwaj et al.[6]. The mean ± SD in case of study group SPAS has been found to be 3.30 ± 1.95 mm and with a significant P value (0.001) Similarly, MPAS and IPAS have, 4.40 ± 2.17 and 7.90 ± 3.21 mm, respectively and with a P value of 0.001 and 0.01 (significant). But the correlation coefficient has been found to be insignificant at all three levels. In another study by Gokmet Kurt et al.[13] the SPAS, MPAS, and IPAS were found to be 25.77 ± 3.53, 9.83 ± 4.21, and 11.28 ± 2.7, respectively which is consistent with the present study, and among all the parameters only MPAS was found with significant P value i.e. middle airway space can be an important parameter determining the obstruction site among OSA cases. A study by Borges et al.,[8],[14] when space between the base of the tongue and posterior pharyngeal wall was evaluated in a sample size of 54 males, the Pearson correlation coefficient was found with a two-tailed P value of 0.124 and in a sample size of 39 females 0.951. But when the posterior airway space was compared among males and females, the value was statistically insignificant.

Limitations and future prospects

Cephalometry is a two-dimensional representation of a three-dimensional anatomical structure. So MRI serves as the gold standard for the measurement of parameters in airway obstruction. The study expands the future prospect of including the MRI findings and comparing them with cephalometric findings that are to be in the next part of the study.[14],[15]

 Conclusion



There is an increase of 4.4° and 4.3° for SNA and SNB, respectively, with a change in posture. So one may expect a change of 4 ± 1° change with respect to supine posture wherein the susceptibility to OSA increases. SNA, SNB and NSL-OPT, NSL-CVT are inversely related to each other and play a role in the consequence or pathogenesis of OSA. The physician needs to check for soft palate thickness, length, and tongue length while diagnosing cases of OSA. SPAS, MPAS, and IPAS were significantly and equally decreased across the cases at the supine position with respect to the upright in the three locations of airway space suggesting that the anatomy of the person's airway space quite significantly and logically decreased which may lead to the pathogenesis of OSA.[13]

Acknowledgement

The author sincerely acknowledges the contributions of Dr. Ranjan Sahoo, Dr. Samir Sahoo, and Dr. Rajat Panigrahi for bringing in the quality of the manuscript, extending their academic excellence, and helping in the completion of the research.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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