Diagnosis of Obstructive Sleep Apnea
Sleep apnea syndrome is a disorder that can be complex and that concerns many systems. Main methods of diagnosis that are referred to in diagnosing the patients are:
General physical examination
Ear, nose, throat examination
Examination that is performed through the nose with flexible fiber optic endoscope
Imaging methods (Tomography, MRI, measurement of the structures of the face and the dimensions of the air passages - Cephalometric analysis)
Polysomnography (Sleep test)
1. General physical examination: Sleep apnea syndrome is a complex disease and may occur due to many different reasons. Therefore, examination of only the upper respiratory tracts will not be sufficient in the diagnosis and treatment of the patients. Alcohol consumption of the patient, significant weight gain during the recent months and his/her metabolic condition (diabetes mellitus, thyroid diseases) should be examined and biochemical test should be made when necessary. Considering that the mood of the patient may increase the complaints, the patient’s condition of depression and sedative usage should be questioned.
The general condition of the patient (being overweight-obesity, position of the lower jaw, presence of malformations of the upper jaw) and determination of the region that is obstructed during respiration is important in the selection of the treatment and determination of its success.
Many studies showed that there was a relationship between blood pressure and sleep apnea syndrome. Due to the increase in the hormones that increase the blood pressure, blood pressure is high not only during the night, but during the day as well.
Height-weight and neck thickness: Measurement of the height, weight and circumference of the neck of the patients is important.
In adult men, neck circumference’s being over 43.18 cm is considered to be a risk factor. Sleep apnea syndrome was detected in 30% of the men in this group. The critical value in women is 38.10 cm dir.
The most practical measurement method of the height-weight ratio which is an important parameter in snoring and sleep apnea syndrome is the calculation of Body Mass Index – BMI which is specified as kg/m2. In adults over the age of 20, average BMI is around 25.5kg/m2. In men, BMI of over 27.8 and in women BMI over 27.3 is evaluated as overweight.
2. Ear, nose, throat examination: Upper respiratory tract consists of a hard bone-cartilage skeleton and soft tissues connected to them and starts at the nose and lips and ends in the larynx. In a patient applying with the suspicion of sleep apnea, a detailed examination of the upper respiratory tract is required. Since the examination cannot be performed while sleeping, determination of the possible regions of obstruction and collapse are targeted.
Skeletal structure of the face: In the first examination of the patient, the relationship of the structure of the upper and lower jaw and closing of the teeth are evaluated. For patients who are considered to have problem in the skeletal structure of the face, cephalometric studies should be performed.
Development retardation of the upper jaw and the placement of the lower jaw at the back (retrognatism) should be evaluated. In patients with retrognatism, since the tongue and soft tissues change places to the backwards, obstruction at the level of throat and tongue base develops.
Nose Examination: Intranasal obstructive pathologies increase the resistance of the nose and result in increase in negative pressure in upper airway which causes collapse and obstruction. In addition, in patients who will be using a device that provides continuous positive pressure during sleep (CPAP= Continuous Positive Air Pressure), nose anatomy should be evaluated and serious problems should be corrected. Otherwise, the device will not yield the expected result.
Mouth and Throat Examination: In patients with sleep apnea, the dimensions of the air passage and skeletal and soft tissue structure at the back of the palate and the tongue, where the majority of the problems are present, should be carefully observed and the extent of their responsibility in the problem should be evaluated during the examination.
The size of the tonsils is also important. Tonsils narrowing the throat and thus the respiratory tract are responsible for snoring and sleep apnea more or less.
3. Flexible fiber optic Nasopharyngolaryngoscopy: Consists of one of the most important stages of the examination. In this examination, when the mouth is slightly opened in its natural position, it is possible to evaluate the regions behind the palate and the tongue by entering from the nose.
4. Radiological imaging methods: Conventional graphies and cephalometric radiological imaging methods are used for the purpose of cephalometric analysis. CT and MRI that are indispensable in the diagnosis of many diseases have no role in sleep apnea syndrome except for scientific researches.
5. Sleep Analysis Test (Polysomnography): While the previously mentioned examination methods are useful in the determination of the location of obstruction, sleep analysis provides the actual diagnosis. It is not possible to diagnose sleep apnea syndrome without performing polysomnographic examination.
The complete sleep analysis considered to be the golden standard for diagnosis of sleep apnea syndrome. During the comprehensive sleep test regarded as Level 1 test, electroencephalography (EEG), electrooculography (EOG), electromyography (EMG), chest and abdomen movements, nasal and/or oral air flow, oxymetry, electrocardiography (ECG) and position are monitorized. The initiation and stages of sleep, extremity movements, cardiac arrhythmias, obstructive and central apnea attacks, desaturation amount are evaluated. The disadvantages of this polysomnography test are having to stay for a night in a hospital setting, the requirement for trained personnel and the presence of the physical setting. Analysis of the obtained data became very easy with the newly developed software.
Level 2 test covers the evaluation of all parameters outside the hospital. The advantages of the test are its performance in a more natural setting and cost effectiveness. In Level 2 polysomnography, the problem is not obtaining the data sufficiently and/or disappearance of the data. This results in the repetition of the test frequently.
In Level 3 polysomnography, the patient applies the test in his/her house again, however, limited number of parameters are examined (like obstructive-central apneas, O2 saturation, bradicardia-tachycardia and position changes). Since it gives no information related to sleep phases and arrhythmia, its value is limited.
In Level 4 polysomnography, only 1-2 parameters are reviewed (like pulse and O2 saturation). Though it is a very cheap technique, patients with mild-moderate sleep apnea syndrome may be missed.
A sleep analysis that contains REM (Rapid Eye Movement) and non REM sleeps that lasts for 3-4 hours is sufficient to diagnose sleep apnea syndrome. In REM sleep, pharyngeal airway stays still (atonic), in non REM sleep it is still present though tenseness decreases (hypotonic). Therefore, collapsing of the upper respiratory tract occurs more markedly in REM sleep. Tests that does not contain REM sleep should be repeated. Polysomnography is quiet a sensitive test, it was determined that the repetition of the test in consecutive nights does not change the diagnosis, it only results in slight shifts in RDI.
6. Sleep Endoscopy: In this evaluation patients are examined with flexible endoscopes after administration of sedation in operation room settings with monitorization of the depth of the sleep (Bispectral index -BIS) and locations, patterns and degree of airway collapse are evaluated. This subject is covered in detail under the topic of “sleep endoscopy”