Diagnosis

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The lack of diagnosis is the main problem facing both physicians as patients themselves. The lack of medical awareness about the mechanisms underlying the symptoms, is a recurring problem, that we face and that precludes the diagnosis. It is based on studies that only 5-9% of the population with obstructive sleep apnea, that requires treatment is relevant diagnosed. As a multifactorial pathophysiology, diagnosis of sleep apnea can often lead to misunderstandings and goes unnoticed as a state of chronic fatigue. It is necessary to establish a differential diagnosis against similar diseases and associated symptoms such as snoring and simple hypersomnia enrolled in daytime sleepiness, which are particular entities of OSA. Another problem facing patients and medical professionals is the lack of hospital coverage specializing in sleep breathing disorders. Although the sleep units have tripled in the last decade, they remain is insufficient to assume a high percentage of patients waiting for diagnosis. To bridge this gap, new diagnostic techniques are being developed by the new stand-alone devices such as Apnealink.

Medical History Anamnesis

The first step in the differential diagnosis of OSAHS is a detailed medical history including all personal details and any family history of OSAHS. The medical history, as reported by the patient, is extremely important but not definitive in the differential diagnosis of OSAHS due to the complicated pathophysiological mechanisms responsible for the condition. The anamnesis is very useful to rule out other pathologies connected with excessive daytime sleepiness generated by some bad sleeping habits or general lack of sleep.

In an OSAHS patient it is essential to extend the questionnaire to include information from spouses or relatives living with the patient due to the fact that the subjects are not aware of some of the specific night symptoms. The OSAHS patient suffers from sleep cycles where loud snoring culminates in respiratory efforts which cause micro-awakenings in the patient, irreparably fragmenting their sleep pattern. Bed partners are the ones who suffer snoring the most and can best give information about repeated episodes of asphyxia. This nocturnal activity goes unnoticed by the OSAHS patient who is unable to justify why they are experiencing excessive daytime sleepiness when they think they slept soundly.

OSAHS can provoke serious complications such as hypoxia (oxygen deficit), cardiovascular disease, disruption of the sleep pattern and cognitive dysfunction. It is important to gather detailed information about the profession of the patient in order to assess the significance of symptoms in daily life. Problems associated with shift work, especially night shifts are already documented as altering the normal sleep pattern and causing excessive daytime sleepiness. Certain types off work become a more severe problem for those with OSAHS, especially professional drivers or those handle dangerous goods. It is also important to take into consideration the existence of a genetic predisposition in patients with OSAHS, enquiring about other members of the family with Sleep Breathing Disorders.

Excessive Daytime Sleepiness (EDS) is a confusing symptom and is of little clinical value when determining an accurate OSAHS diagnosis. The presence of EDS is almost universal when it comes to sleep disorders. OSAHS can also be easily confused with chronic fatigue syndrome, and depressive conditions. It is because of these overlap in symptoms that OSAHS cannot be diagnosed on the basis of levels of drowsiness. Daytime sleepiness is a subjective symptom, difficult to quantify objectively. To address this problem, various tests have been developed which are easy to use and do not require special resources or expertise in order to approximately quantify sleepiness. These procedures include subjective measurements such as the Epworth Sleepiness Scale and control objectives such as the Multiple Sleep Latency Test (MSLT) and the Maintenance of Wakefulness Test (MWT).

Epworth Sleepiness Scale
The Epworth Sleepiness Scale is a simple questionnaire used by the patients themselves to evaluate their level of sleepiness. It consists of eight questions regarding everyday situations and the possibility of the patient falling asleep. The patient has to chose a number between 0 and 3 to evaluate the possibilities of falling asleep during the described activity. A score of 0 is assigned if the patient believes they could never fall asleep and 3 if they believe it very likely that they would fall asleep. The total score ranges from 0 to 24 and values above 10 are classified as Excessive Daytime Sleepiness (EDS). This is a subjective test and is used as a first approximation to the patient and must be validated by further medical investigation. The test does not determine the origin of the sleepiness. The most important objective techniques for quantifying the degree of sleepiness are the Multiple Sleep Latency Test (MSLT) and the Maintenance of Wakefulness Test (MWT).

Multiple Sleep Latency Test (MSLT)
This is the best tool when trying to objectively measure sleepiness. The time it takes for the patient to fall asleep is measured. The test is performed in a hospital sleep unit where the patient arrives first thing in the morning. The patient is asked to take four or five short naps of 20 minutes at two hour intervals. This is a test that takes place during the day. In order to obtain the most accurate results it is recommended that patient stays the previous night to perform a Polysomnography (PSG). This should register the Electroencephalogram (EEG), Electrooculogram (EOG), Electromyogram (EMG) and the Electrocardiogram (ECG or EKG). The daytime test should take place as follows. The patient should lie down in a dark room with favourable resting conditions. The first nap should attempted 1.5 -2 hours after waking up from the previous nights sleep. Subsequently they should take four or five more naps at 2 hour intervals.

The following guidelines should be employed prior to each nap: no smoking for 30 minutes beforehand, no physical activity for 15 minutes beforehand, the patient should get comfortable in the room 10 minutes beforehand, the electrodes should be placed on the patient who is already lying down 5 minutes beforehand. Lastly the patient should be asked to close their eyes and try to sleep. The time it takes from lights-out until the patient falls asleep is known as "latency". The latency period can be calculated using this test. A normal latency period is >10 minutes. By contrast, a latency period of < 5 minutes indicates hypersomnia. A latency of between 5 and 10 minutes is recorded as moderate hypersomnia.

Maintenance of Wakefulness Test (MWT)
This is an optional test using a similar methodology to the Multiple Sleep Latency Test (MSLT). The neurophysiological variables recorded are the same as those used in MSLT and PSG, however the procedure is reversed. The test consists of resisting four morning naps for 20 -40 minutes repeated at intervals of 2 hours. The patient is asked to sit comfortably in a dark room without stimulation and try to stay awake (without going to extreme measures). This test is very useful because it replicates the monotonous sleep-inducing conditions which a patient is exposed to on a daily basis and which can lead to work and traffic accidents. The individual sleep tests end when the patient reaches a certain stage of sleep or, if the patient didn't fall asleep, 20 minutes after the test began. The result is considered abnormal if the patient manages to stay awake for less than 11 minutes (on average).

Oxford Sleep Resistance Test (OSLER Test)
This is the most simple and cost effective test not requiring neurophysiological monitoring nor specialised staff. The test involves sitting a patient in a dark isolated room where the light flicks on automatically on every 3 seconds. The patient has to press a button to register when they see the light. The reaction time taken to press the button is not registered, just whether or not the button is or is not pressed. If the button is not pressed during the course of 7 flashes (21 seconds) the patient is deemed to be asleep. The series of light flashes are repeated four times at 2 hour intervals from when the patient is deemed to be asleep in the previous light flash series. If however, the patient does not fall asleep during the light flash series the following series commence 40 minutes after the start of the last light flash series. This is an economic alternative to the MWT in order to assess the ability of the patient to stay awake in low stimulus situations.

Psychomotor Vigilance Test (PVT)
This test measures the reaction time to a visual stimulus. It is used to evaluated a subject's attention span capacity. The test is performed as follows: The subject has to push a button each time they see a light flash. The light flashes at intervals of between 2 and 10 seconds. This test differs from the OSLER Test because it registers the amount of time taken for the button to be pressed. The following parameters can be calculated: How many times the reaction time is over 500th millisecond, the median reaction time and the fastest and slowest reaction times. Sleep deprived subjects show slower than the average reaction times in all parameters.