Having a Sleep Study?
Below is a description of what a Sleep Study is, and the equipment that may be used during your study.
Polysomnogram
A Polysomnogram is a continuous and simultaneous recording of multiple physiologic variables during sleep. The most common variables are: electroencephalogram, electro-oculogram, electromyogram, electrocardiogram, respiratrory movements, and leg movements.
Polysomnography (PSG)
Polysomnography is another name for "Sleep Study". It is the study of the continous and simultaneous recording of multiple physiologic variables during sleep. The most common variables are: electroencephalogram, electro-oculogram, electromyogram, electrocardiogram, respiratrory movements, and leg movements. Polysomnography is used in the study of sleep and sleep disorders. A PSG is usually performed in the sleep laboratory, but some sleep diagnostic equipment is ambulatory and allows the subject to be tested in his/her own home. In the process of diagnosing sleep disorders, methods in addition to PSG are used. These are for example, physical examinations, medical histories and questionnaires. Whether the study is performed at the sleep laboratory or in the patient's home, the same initial steps described below are taken to prepare the study.
In The Sleep Lab
Typically, the subject arrives at the clinic in the afternoon or early evening. Depending on the scope of the study, it takes about 1 - 1 ½ hours to complete the sensor assembly. A complete sleep study requires that electrodes be placed on the head, around the eyes, behind the ears, under the chin, on the torso and sometimes on the legs. Other sensors are also placed on their person. A cannula is placed in the nostrils, a thermistor is placed above the upper lip, a vibration sensor is placed on the neck and straps are wrapped around the chest and belly. A small body position sensor is placed on one of the straps and a sensor is placed on one of the fingers.
Sleep Parameters
The electrodes that are placed on the head record the Electroencephalogram (EEG). The EEG is a recording of the brain wave activity. The electrodes around the eyes record the Electro-oculogram (EOG). The EOG records the eye movements that define REM sleep or dream sleep. The electrodes around the chin record the Electromyogram (EMG) or the muscle activity. Muscle tone, a term for resting muscle potential, is an important parameter in the sleep pattern. Finally, the electrodes on the torso record the heart rate or Electrocardiogram (EKG). Together, these parameters allow the clinician to assess the sleep architecture, or how the sleep is composed. Sleep disorders related to respiratory difficulties are assessed with additional sensors placed on the patient.
Respiratory Parameters
To record the breathing pattern, either thermistors or nasal pressure transducers are used to measure the breathing, or airflow, through the nose and/or mouth. Straps are placed around the chest and abdomen to record the respiratory movements, a vibration sensor is placed on the neck to detect snoring and a position sensor is also used to signify the major sleeping positions of the person, because people may breathe differently in different body positions. Saturation levels are also recorded to detect the level of oxygen in the blood. When apneas (airflow cessation) take place, the levels of oxygen in the blood decrease. The decrease is called desaturation. An infrared sensor, usually placed on the finger, detects the color of the blood through the fingernail.
Additional Parameters
Sensors or electrodes are often placed on the legs to detect leg movements. Leg movements during sleep may be common for some people and can disrupt their sleep. Temperature sensors may occasionally be used during a PSG, but these are not used in standard practice. Also, nocturnal penile tumescence is recorded during sleep to assess penile dysfunction. Again, this parameter is not used in standard PSG.
The Night of Your Sleep Study
Once the electrode attachment and hookup is complete, the person goes to sleep. If the PSG is performed in a sleep laboratory, a technician sits in a control room and watches over the data being recorded. The technician makes sure that all the electrodes and sensors stay in place and that the recording equipment works properly during the PSG. Sometimes the bedroom is monitored with a closed circuit television, and the person being recorded can contact the technician if required. If the study is performed at home, the data is recorded onto a memory card and the person can move about quite freely. The downside to recording at home is that there is no control over the data being acquired. If something goes wrong, such as a sensor falling off, then there is no one to fix the problem. The positive side to recording at home is that people usually sleep better in familiar surroundings.
The Morning After Your Sleep Study
Once the study is complete, the technician removes all the sensors and electrodes and the person is free to go home after a short interview with the clinician. If the PSG was performed at home, the patient often removes the sensors himself and must return the equipment to the sleep laboratory. Regardless of the type of study, the data is stored on a computer and the clinician may use diagnostic software to analyze the signals and print out a report with the results of the study. Based on the analysis and reports, the clinician determines the diagnosis and recommends treatment solutions, if necessary.