*2.3.1 Radiological diagnosis*

*Cephalometry*: It is the standardized lateral radiographic imaging of the head and neck with which bone and soft tissue boundaries are evaluated in individuals with OSA. It is useful in diagnosing frequently encountered craniofacial and upper airway soft tissue anatomy-related anomalies like the hyoid, mandibular, tongue, soft palate, and facial anomalies. Maxillo-mandibular retrognathism has in patients with OSA and it has been accepted as an indicator of maxillary prognathism. Horizontal and vertical length of the mandibula affects the oral floor and the position of the tongue. The length of the horizontal ramus of the mandibula shortens in individuals with snoring and apnea, whereas vertical ramus only shortens in people who snore. Total facial height is found to have increased in OSA patients compared

to the normal population. Hyoid bone is the point where the dilator muscles of the upper airways attach; it is shown to have a lower location in OSA patients [26–28]. The distance between the root of the tongue and posterior pharyngeal wall (posterior airway space, PAS) is shortened in OSA patients. When PAS is measured by cephalometry in OSA patients, it is shown to have significantly narrowed in nasopharyngeal and oropharyngeal regions, gets larger towards the hypopharyngeal region, and gets within normal limits at the level of epiglottis. Computerized tomography (CT) is an imaging technique that provides detailed information about the size, cross-sectional area, and neighboring tissues of the upper respiratory system thanks to its superior bone and soft tissue resolution. It is not routinely used. Magnetic resonance (MR) is a noninvasive technique providing excellent views of all soft tissues of the upper respiratory system including the adipose tissues, and the images are obtained in the supine position by covering axial, sagittal, and coronal planes. It is superior to CT when evaluating PAS which is important for surgical treatment. Its biggest advantage is not having radiological exposure. MRI examinations of upper respiratory systems of individuals with OSA have been compared and significant increased have been shown in the adipose tissues of the supportive wall structures of soft palate, tongue and the pharynx. In another study, the narrowing of the upper airways was not due to adipose pads; it was reported to take place due to significant thickening of the lateral pharyngeal wall. Fluoroscopy is an imaging technique allowing for a dynamic evaluation of the upper airways when the patient is awake of sleeping. Tongue and pharyngeal regions are covered with barium, and for better visualization of the hypopharynx, the head is kept at an angle of 30 degrees. Its disadvantages are radiation exposure, not being able to obtain crosssectional images, and not being able to perform bone structure measurements [28–30]. Acoustic reflection relies on the reflection of sound waves sent onto the upper respiratory tract, it does not utilize radiation, and it is a noninvasive imaging technique. In a study employing this technique, cross-sectional areas of the pharynx and glottis were found to have significantly reduced demonstrating a correlation between the degree of OSA and the horizontal cross-sectional area of the pharynx.

#### *2.3.2 Endoscopic diagnosis*

Nasopharyngolaryngoscopy is a diagnostic technique spanning the upper airways from the nose to the glottis to analyze the dynamic changes of the airways and to identify the level at which airways collapse. Fiberoptic nasopharyngoscopy only shows the open-closed status of the airways; it cannot measure and interpret the surrounding soft tissue areas. By having the patient perform Müller maneuver, the degree and the level of the collapse is diagnosed [29, 30].

#### *2.3.3 Polysomnography (PSG)*

The process of recording sleep with electrophysiological signals is called "polysomnography," ("PSG"). Sleep recordings that appear on computer screen or paper are called "polysomnogram." Electrophysiological signals recorded throughout one night during sleep and wakefulness are as follows: "Electroencephalogram (EEG), electromyogram (EMG; chin, arms and legs), electrooculogram (EOG), electrocardiogram (ECG), snoring, and oronasal air flow (L/s), chest and abdomen movements (respiratory effort recordings), oxygen saturation, and body position and real time-video-image recordings" [31].

PSG is a gold standard technique for OSA diagnosis. For this test, patients are prepared by sleep technicians (**Figure 2**).

**135**

*Diagnosis*

**Figure 2.**

*for the diagnosis of OSA.*

*DOI: http://dx.doi.org/10.5772/intechopen.91368*

and scoring of respiratory events."

the identification of respiratory effort [31].

apneas are scored as obstructive apnea.

scoring based on [31, 32].

arousal (**Figure 6**).

When defining respiratory events in PSG, we need to perform "scoring of sleep

*Patient is prepared for PSG by the sleep technician. She is wearing an airflow cannula which is very important* 

Scoring of sleep is done through staging of sleep. For staging sleep, polysomnography recordings are separated into 30 s intervals (epoch); each epoch is scored with a sleep stage. Sleep stages are as follows: "Stage N1, Stage N2, Stage N3, Stage R, and Stage W (wakefulness)." Every 30 s interval needs to be staged with one of these stages. Three main physiological signals are used when staging sleep: "EEG, EMG, and EOG." For each epoch, these three parameters are assessed, and a sleep stage name is assigned to each 30 s interval. Sleep staging is based on certain principles [31].

Electrophysiological signal recordings that are required for the interpretation of respiratory events in PSG are as follows: "oxygen saturation, nasal/oronasal air flow (nasal cannula, thermistor), thoracic respiratory effort, abdominal respiratory effort, EEG recordings (absolutely needed to identify arousal), body position, tracheal microphone, ECG, and leg EMG recordings." Measurement of thoracic and abdominal movements is the most frequently used technique in sleep laboratories in

The American Academy of Sleep Medicine (AASM) has published the rules to be used when reporting sleep and sleep-associated events as well as respiratory event

Apnea is the cessation of air flow in the mouth and nose for l0 seconds of longer. There are three types of apnea. (i) Obstructive apnea consists of the absence of air flow despite respiratory effort (**Figure 3**). (ii) Central apnea consists of the absence of airflow in the absence of respiratory effort (**Figure 4**). (iii) Mixed apnea consists of the absence of airflow in the absence of respiratory effort, followed by increase in respiratory effort despite the absence of airflow (**Figure 5**). Nowadays, mixed

Hypopnea is a 50% reduction in air flow (currently this value is reduced down to 30%) for 10 s or longer together with a 3% decrease in oxygen saturation and

#### **Figure 2.**

*Updates in Sleep Neurology and Obstructive Sleep Apnea*

to the normal population. Hyoid bone is the point where the dilator muscles of the upper airways attach; it is shown to have a lower location in OSA patients [26–28]. The distance between the root of the tongue and posterior pharyngeal wall (posterior airway space, PAS) is shortened in OSA patients. When PAS is measured by cephalometry in OSA patients, it is shown to have significantly narrowed in nasopharyngeal and oropharyngeal regions, gets larger towards the hypopharyngeal region, and gets within normal limits at the level of epiglottis. Computerized tomography (CT) is an imaging technique that provides detailed information about the size, cross-sectional area, and neighboring tissues of the upper respiratory system thanks to its superior bone and soft tissue resolution. It is not routinely used. Magnetic resonance (MR) is a noninvasive technique providing excellent views of all soft tissues of the upper respiratory system including the adipose tissues, and the images are obtained in the supine position by covering axial, sagittal, and coronal planes. It is superior to CT when evaluating PAS which is important for surgical treatment. Its biggest advantage is not having radiological exposure. MRI examinations of upper respiratory systems of individuals with OSA have been compared and significant increased have been shown in the adipose tissues of the supportive wall structures of soft palate, tongue and the pharynx. In another study, the narrowing of the upper airways was not due to adipose pads; it was reported to take place due to significant thickening of the lateral pharyngeal wall. Fluoroscopy is an imaging technique allowing for a dynamic evaluation of the upper airways when the patient is awake of sleeping. Tongue and pharyngeal regions are covered with barium, and for better visualization of the hypopharynx, the head is kept at an angle of 30 degrees. Its disadvantages are radiation exposure, not being able to obtain crosssectional images, and not being able to perform bone structure measurements [28–30]. Acoustic reflection relies on the reflection of sound waves sent onto the upper respiratory tract, it does not utilize radiation, and it is a noninvasive imaging technique. In a study employing this technique, cross-sectional areas of the pharynx and glottis were found to have significantly reduced demonstrating a correlation between the degree of OSA and the horizontal cross-sectional area of the pharynx.

Nasopharyngolaryngoscopy is a diagnostic technique spanning the upper airways from the nose to the glottis to analyze the dynamic changes of the airways and to identify the level at which airways collapse. Fiberoptic nasopharyngoscopy only shows the open-closed status of the airways; it cannot measure and interpret the surrounding soft tissue areas. By having the patient perform Müller maneuver,

The process of recording sleep with electrophysiological signals is called "polysomnography," ("PSG"). Sleep recordings that appear on computer screen or paper are called "polysomnogram." Electrophysiological signals recorded throughout one night during sleep and wakefulness are as follows: "Electroencephalogram (EEG), electromyogram (EMG; chin, arms and legs), electrooculogram (EOG), electrocardiogram (ECG), snoring, and oronasal air flow (L/s), chest and abdomen movements (respiratory effort recordings), oxygen saturation, and body position

PSG is a gold standard technique for OSA diagnosis. For this test, patients are

the degree and the level of the collapse is diagnosed [29, 30].

**134**

*2.3.2 Endoscopic diagnosis*

*2.3.3 Polysomnography (PSG)*

and real time-video-image recordings" [31].

prepared by sleep technicians (**Figure 2**).

*Patient is prepared for PSG by the sleep technician. She is wearing an airflow cannula which is very important for the diagnosis of OSA.*

When defining respiratory events in PSG, we need to perform "scoring of sleep and scoring of respiratory events."

Scoring of sleep is done through staging of sleep. For staging sleep, polysomnography recordings are separated into 30 s intervals (epoch); each epoch is scored with a sleep stage. Sleep stages are as follows: "Stage N1, Stage N2, Stage N3, Stage R, and Stage W (wakefulness)." Every 30 s interval needs to be staged with one of these stages. Three main physiological signals are used when staging sleep: "EEG, EMG, and EOG." For each epoch, these three parameters are assessed, and a sleep stage name is assigned to each 30 s interval. Sleep staging is based on certain principles [31].

Electrophysiological signal recordings that are required for the interpretation of respiratory events in PSG are as follows: "oxygen saturation, nasal/oronasal air flow (nasal cannula, thermistor), thoracic respiratory effort, abdominal respiratory effort, EEG recordings (absolutely needed to identify arousal), body position, tracheal microphone, ECG, and leg EMG recordings." Measurement of thoracic and abdominal movements is the most frequently used technique in sleep laboratories in the identification of respiratory effort [31].

The American Academy of Sleep Medicine (AASM) has published the rules to be used when reporting sleep and sleep-associated events as well as respiratory event scoring based on [31, 32].

Apnea is the cessation of air flow in the mouth and nose for l0 seconds of longer. There are three types of apnea. (i) Obstructive apnea consists of the absence of air flow despite respiratory effort (**Figure 3**). (ii) Central apnea consists of the absence of airflow in the absence of respiratory effort (**Figure 4**). (iii) Mixed apnea consists of the absence of airflow in the absence of respiratory effort, followed by increase in respiratory effort despite the absence of airflow (**Figure 5**). Nowadays, mixed apneas are scored as obstructive apnea.

Hypopnea is a 50% reduction in air flow (currently this value is reduced down to 30%) for 10 s or longer together with a 3% decrease in oxygen saturation and arousal (**Figure 6**).

#### *Updates in Sleep Neurology and Obstructive Sleep Apnea*

#### **Figure 3.**

*Polysomnographic record image of obstructive apnea.*

#### **Figure 4.**

Arousal is shifting to a more superficial level of sleep and wakefulness for short periods of time.

Respiratory effort-related arousals (RERA) are seen in the absence of cessation or reduction of air flow during the respiratory effort.

Apnea index (AI) defines the number of apneas that are seen during 1 h when sleeping.

**137**

**Figure 6.**

*Polysomnographic record image of hypopnea.*

Apnea-hypopnea index (AHI) is calculated by the total number of apnea and hypopneas divided by the time spent while sleeping. When RERA is added to this

Characteristic PSG findings for OSA are as follows: (i) Increases in the duration of superficial sleep and decreases in the duration of deep sleep and REM. (ii) Apneas and hypopneas repeat frequently. (iii) Oxygen desaturation repeats frequently. (iv)

number, the name of the index is respiratory disturbance index (RDI).

*Diagnosis*

**Figure 5.**

*Polysomnographic record image of mixed apnea.*

*DOI: http://dx.doi.org/10.5772/intechopen.91368*

## *Diagnosis DOI: http://dx.doi.org/10.5772/intechopen.91368*

#### **Figure 5.**

*Updates in Sleep Neurology and Obstructive Sleep Apnea*

**136**

sleeping.

**Figure 4.**

**Figure 3.**

*Polysomnographic record image of obstructive apnea.*

periods of time.

Arousal is shifting to a more superficial level of sleep and wakefulness for short

Respiratory effort-related arousals (RERA) are seen in the absence of cessation

Apnea index (AI) defines the number of apneas that are seen during 1 h when

or reduction of air flow during the respiratory effort.

*Polysomnographic record image of central apnea.*

*Polysomnographic record image of mixed apnea.*

#### **Figure 6.**

Apnea-hypopnea index (AHI) is calculated by the total number of apnea and hypopneas divided by the time spent while sleeping. When RERA is added to this number, the name of the index is respiratory disturbance index (RDI).

Characteristic PSG findings for OSA are as follows: (i) Increases in the duration of superficial sleep and decreases in the duration of deep sleep and REM. (ii) Apneas and hypopneas repeat frequently. (iii) Oxygen desaturation repeats frequently. (iv)

REM sleep can increase the frequency and duration of apneas and the degree and the duration of oxygen desaturation. Sleeping in supine position contributes to this increase. (v) It is typical to see paradoxical thoracic and abdominal movements during apnea. (vi) During apnea, the heart rate possibly slows down, and it increases in the period following the apnea; arrhythmias can be observed. (vii) In respiratory sound recordings, an irregular loud snoring that is interrupted by apneas is heard.

The degree of the disease is identified by AHI value calculated on the basis of PSG assessment: "AHI < 5, normal; AHI = 5–15, mild OSA; AHI = 16–30, moderate OSA; AHI > 30, severe OSA" [33].
