Obstructive sleep apnoea (OSA) results from the recurrent collapse of the upper airway during sleep. Nasal abnormalities influence the stability of the pharynx. The aim of this study was to evaluate the volumetric and anatomical changes of the nasal cavity in patients with OSA. The Nasal Obstruction Symptom Evaluation (NOSE) scale was used to grade nasal obstruction. Sleep-related breathing disorders were evaluated by polysomnography. The nasal airway volume was obtained from computed tomography scans through volumetric reconstruction of the nasal airway. Alterations to the nasal anatomy were identified by nasal fibre-optic endoscopy. Ninety-four patient charts were analyzed. The final sample comprised 32 patients with severe OSA, 16 with moderate OSA, 23 with mild OSA, and 20 without OSA. Three groups were established based on nasal obstruction and OSA. The groups were compared for nasal airway volume ( P = 0.464) and body mass index ( P = 0.001). The presence of nasal septum deviation and inferior turbinate hypertrophy were related to the NOSE score ( P = 0.05 for both), apnoea–hypopnoea index ( P = 0.03 and P = 0.05, respectively), and nasal airway volume ( P = 0.71 and P = 0.78, respectively). In this nasal airway evaluation of OSA patients, the presence of sites of obstruction was correlated with the severity of OSA; this was not the case for the evaluation of the nasal airway volume dimensions.
Obstructive sleep apnoea (OSA) is a disease that has been increasingly recognized and diagnosed in recent years. Accurate diagnosis and appropriate treatment are key to the management of this illness, which has socioeconomic repercussions and complications, including an increased incidence of cardiovascular morbidity. The increasing prevalence of overweight in the Western population has been associated with a greater risk of developing OSA and snoring .
The American Academy of Sleep Medicine has defined OSA as a recurrent collapse of the upper airway during sleep, resulting in a total (apnoea) or partial (hypopnoea) reduction in airflow. Primary snoring is a low frequency snore caused by soft palate and uvula vibrations during sleep .
A large epidemiological study in the USA involving 5201 adult patients, showed that 19% of women and 33% of men over the age of 65 years snore . Another study demonstrated that approximately 18% of men and 7% of women have snoring problems . An epidemiological study conducted in Sao Paulo, Brazil reported a prevalence of OSA of 32.8% in the adult population .
Risk factors for OSA and snoring include age between 40 and 65 years, male sex, obesity, smoking, alcoholism, and a sedentary lifestyle . The main physical examination findings associated with OSA include increased neck circumference, oropharyngeal obstruction, web palate, nasal obstruction, turbinate hypertrophy, septal deformity, nasal cavity tumours, enlarged tonsils, macroglossia, and retrognathia. Anatomical findings such as vibration factors and a collapsed upper airway have been described in studies that have used cephalometry, computed tomography (CT), magnetic resonance imaging, and nasal fibre-optic endoscopy .
Symptoms may vary among patients, depending on the severity of disease. The most frequent are snoring and excessive daytime sleepiness. Witnessed nocturnal apnoea episodes, choking during sleep, non-restorative sleep, fragmented sleep, enuresis, morning headaches, cognitive decline, memory loss, reduced libido, and irritability are also observed with the development of OSA .
The role of the nose in the pathophysiology of OSA remains uncertain. This is an upper airway disease, in which the main site of obstruction is in the oropharynx. The nose itself may not collapse, but nasal abnormalities influence the stability of the pharynx. Increased nasal resistance limits the airflow, which can decrease intraluminal pressure in the cranial segments of the upper airway . Thus the upper airway may resemble a Starling resistor, wherein the upper airway is characterized as a hollow tube, with the nose representing partial obstruction at the inlet and the pharynx representing a collapsible downstream segment .
Most studies on nose function have been conducted by means of rhinomanometry and acoustic rhinometry evaluations and have shown a diminished nasal volume in OSA patients . A few studies have used CT, but no study has evaluated nasal airway volume by means of CT scans.
The aim of this study was to evaluate the volumetric changes of the nasal cavity in patients with OSA and nasal obstruction.
This study was conducted in compliance with the rules laid down by the Declaration of Helsinki and was approved by the Ethics in Research Committee of Araraquara Dental School – UNESP.
This article describes a cross-sectional study conducted by reviewing the medical records of adult patients attending the Oral and Maxillofacial Surgery Clinic, Dental School at Araraquara (UNESP) and the Otorhinolaryngology Clinic, Araraquara University (UNIARA). Patients were evaluated at a specific sleep outpatient clinic.
The following information was obtained from the medical records: dental physical examination, classification of facial morphology, otorhinolaryngology (ENT) examination, upper airway endoscopy, anthropometric variables, body mass index (BMI), baseline polysomnography, and CT scans to define the nasal cavity volume.
Evaluation of nasal obstruction
The Nasal Obstruction Symptom Evaluation (NOSE) scale was used to grade nasal obstruction. The scale consists of five questions, each with a score range of 0 to 4. The scores are added together and multiplied by 5. Thus, the NOSE scale score ranges from 0 to 100. In this study, individuals whose NOSE scale score exceeded 60 points were considered to have nasal obstruction ( Fig. 1 ).
Evaluation of sleep-related breathing disorders
Polysomnography examinations were performed at the Araraquara Sleep Institute. Sleep was assessed during an average period of 6 h. The parameters evaluated during sleep were electroencephalography (EEC), electrooculography (EOG), electromyography (EMG), electrocardiography (ECG), airflow (nasal and oral), respiratory effort (thoracic and abdominal), other body movements (by means of EMG), blood gases (oxygen saturation, carbon dioxide concentration), and body temperature. The technique used was that defined by the Rules for Scoring Respiratory Events in Sleep of the American Academy of Sleep Medicine (2012 manual).
A medical specialist in sleep calculated each patient’s apnoea–hypopnoea index (AHI), which was the sum of the apnoea and hypopnoea events divided by the number of hours of sleep. This index was used to classify the severity of OSA as follows: no OSA (AHI <5 events/h), mild OSA (AHI 5–15 events/h), moderate OSA (AHI 15–30 events/h), and severe OSA (AHI >30 events/h).
Evaluation of nasal airway volume
CT images were obtained with the patient placed in the supine position, with the head fixed so that the Frankfort plane was perpendicular to the floor. All subjects were instructed to inhale and to hold their breath during image acquisition, exhaling immediately afterwards.
The sections were obtained in the coronal plane, from the anterior nasal spine to the posterior limit of the nasopharynx. All images were stored on a DVD for later analysis using specific software. The three-dimensional images of the CT scans were imported and reconstructed using OsiriX v.7.0 32-bit software (OsiriX Foundation, Geneva, Switzerland) to define the nasal volume . Thus, images were generated corresponding to consecutive coronal sections of the region of interest, with spacing of 4 mm.
A trained and blinded observer conducted the evaluation process. The evaluation was repeated for 30% of the sample, by the same evaluator, after a minimum period of 30 days, in order to establish the method error. The values obtained in the re-evaluation were similar to those initially measured.
All measurements were performed on coronal CT slices with a thickness of 0.25 mm and 4 mm distance between slices. To determine the volume of the nasal airway, the area was measured in all CT slices. The outline of the nasal airway was manually traced in each slice by means of the computer trackpad, considering only the free space of the nasal cavity, i.e. turbinate and septum deviation were not included in the area calculation ( Fig. 2 ). The software tool OsiriX calculated the area automatically. A TIFF image was then generated for each section of the CT for which the area was calculated.
The nasal airway volume for each CT slice was calculated by multiplying the area and height, which was equivalent to the distance between the coronal slices ( Fig. 3 ). The OsiriX software tool calculated the area of the missed slices spaced by 4 mm. The volume of the entire free airway of the nose was the sum of all volumes measured in each slice. The nasal airway volume obtained was similar to a pyramid composed of the free airway space of the nose.
Grading of endoscopic findings
Nasal endoscopy was performed for all subjects included in the study. This was done with a flexible fiberscope without the use of vasoconstrictor medication. Nasal septum deviation (NSD) was identified when the septum blocked the fiberscope path and/or there was a contact with the lateral wall of the nose. Inferior turbinate hypertrophy (ITH) was identified when the turbinate blocked the fiberscope path.
Patients of both sexes, aged between 18 and 70 years, and evaluated between December 2014 and December 2015, were included. Patients with the following conditions were excluded: morbid obesity (BMI >40 kg/m 2 ), craniofacial abnormalities (craniodysostosis, craniostenosis, and meningomyelocele), nasal obstruction due to nasal polyps, presence of any craniofacial or airway tumour, laryngeal and pharyngeal paralysis, and previous surgery to the upper airway.
In an attempt to evaluate the effect of OSA and nasal obstruction on nasal airway volume, the individuals in this sample were divided into three groups: (1) group I (control) comprised subjects without OSA (AHI <5 events/h) and without nasal obstruction (NOSE <60 points); (2) group II comprised subjects with OSA (AHI ≥5 events/h) and without nasal obstruction (NOSE <60 points); (3) group III comprised subjects with OSA (AHI ≥5 events/h) and with nasal obstruction (NOSE ≥60 points). These are the three possibilities in the evaluation of the nasal function of subjects with OSA and nasal obstruction symptoms for comparison with a control group.