When you go to the quintuplegic because you suffer from sleep snoring and sleep breath-holding, your doctor will usually ask for a PSG when he or she suspects that you have obstructive sleep apnea syndrome (OSAHS for short). So what is PSG?
PSG is an abbreviation for polysomnography, the full name in Chinese is polysomnography monitoring.
The usual methods include: overnight PSG monitoring
Nocturnal segmented PSG monitoring
or PSG monitoring with afternoon naps.
This article describes in detail the whole-night PSG monitoring. It is also a common technique used in mainstream sleep laboratories in China. This is the technique we use in our sleep research laboratory.
Overnight PSG monitoring: It is the “gold standard” for the diagnosis of Obstructive Sleep Apnea Syndrome (OSAHS) in China and abroad. It is called the gold standard because it includes electroencephalogram (EEG), electrooculogram (EOG), electromyogram (EMG), electrocardiogram (ECG), oral and nasal airflow, thoracoabdominal respiratory movements, oxygen saturation, body position, snoring, and EMG of the anterior tibial muscles. Having a complete and comprehensive record and analysis of your sleep throughout the night can accurately determine your sleep status and quality, which is of great value and significance for diagnosis. All other tests can only provide a certain aspect of diagnostic value. Therefore, we mostly call it the gold standard, especially in children with sleep snoring, when it is difficult to determine the diagnosis, the value and significance of PSG examination is even greater. The details are as follows.
(i) Sleep condition by recording EEG, EEG, EMG can accurately reflect the patient’s sleep condition and staging. (1) EEG: Distinguish between sleep and wakefulness, the various stages of sleep and the proportion of each stage.
(2) Electrooculogram (EEG): differentiate between REM and NREM according to whether the eyes are moving or not. (3) Electromyography: Record the electrical activity generated by the muscle activity in the jaw area to assist in differentiating REM and NREM.(ii) Respiration
(1) Oral and nasal airflow: A temperature-sensitive thermistor can be used to sense the temperature difference between exhaled and inhaled air to understand the presence or absence of airflow and to determine whether sleep apnea has occurred.
(2) Chest and abdominal movements: The presence or absence of chest and abdominal activities can be sensed by resistors or other conductive substances in the chest and abdominal bands to distinguish between central or obstructive sleep apnea.
(3) Oximetry: Continuous collection of blood oxygen saturation by a sensor clamped on the finger can give an idea of the duration and degree of hypoxia throughout sleep, which is useful for determining the severity of sleep apnea syndrome and estimating the effectiveness of treatment.
(iii) Cardiac condition
The ECG is used to understand the changes of heart rate and ECG waveform during the whole sleep process, to analyze the relationship between various arrhythmias and other abnormal waveforms and apnea, and to assess the treatment effect.
(iv) Other conditions
The above three aspects are sufficient to diagnose sleep apnea syndrome, in addition to polysomnography, which also records snoring to understand the nature of snoring, the relationship with sleep apnea and its frequency spectrum; the postural sensor, which can record the changes of the patient’s posture during sleep to understand the relationship between apnea and sleeping position, so as not to miss some apnea that only occurs in the supine position.
Nocturnal segmental PSG monitoring and PSG monitoring of afternoon naps are the monitoring methods used for special patients.
Formal monitoring generally requires no less than 7 hours of sleep overnight. The indications for its application are.
(i) Those with clinical suspicion of OSAHS.
② other clinical signs and symptoms supporting the presence of OSAHS, such as nocturnal asthma, pulmonary or neuromuscular disorders affecting sleep.
(iii) Unexplained daytime hypoxemia or erythrocytosis signs.
(iv) Unexplained nocturnal arrhythmias, nocturnal angina pectoris, and early morning hypertension.
⑤ monitoring the degree of hypoxia during the patient’s nighttime sleep to provide an objective basis for oxygen therapy.
⑥Diagnosis of other sleep disorder disorders.
⑦ Evaluate the therapeutic effect of various treatments on sleep apnea syndrome.