Thermistor/ thermocouple: records upper airway flow rate.
Thermistor resistance fluctuations are induced by temperature changes of air passing in and out through the mouth and nostrils- generates a potential.
Two thermocouples are attached at the nostrils and a third is placed in front of the mouth.
A small plastic mask funneling upper airway air movement to a single sensor can be substituted, but may be less comfortable for the patient.
Common method of monitoring respiratory movement.
Improved method of spirometry.
Separates chest and abdominal movement and then adds them together, mimicking total spirometric volume.
Sensors are two wire coils, one placed around the chest and the other around the abdomen.
A change in mean cross-sectional coil area produces a proportional variation in coil inductance, which is converted into a voltage change by a variable frequency oscillator.
Sensors for plethysmography
Sensors for respiratory effort
Transducer for thoracoabdominal movement
Transducer for thoracoabdominal movement
Measures transthoracic and transabdominal impedance changes with respiration.
Measures the magnetic field generated between two sides of a body by chest and abdominal movement.
Apparatus : ferrite wire coils held in rubber sleeves and attached to aluminum plates.
Apnea and hypopnea
Absence of or > 90% decrease in airflow compared to baseline lasting ≥ 10 sec.
Classified as central, obstructive or mixed.
Any of the following respiratory events lasting ≥ 10 sec:
1. ≥ 50% reduction of airflow (<90%).
2. ≥ 30% reduction of airflow (but <50%) but associated with ≥ 4% oxygen desaturation.
Snoring detected by:
Room microphone and recorded directly on the polysomnogram tracing.
Vibration sensor - a small rubber disk containing a piezocrystal that is taped to the patient's throat area
Signal is appropriately filtered, rectified, and integrated before display.
May pick up snoring of patient’s attender.
Chin EMG, airflow and snoring sensors
Intrathoracic Pressure Monitoring
Endoesophageal pressure probe: most sensitive detection of heightened respiratory effort.
An endoesophageal tube is passed nasally till the probe is about 5 cm above the esophageal-gastric junction.
Measures increases in intrathoracic negative pressure to overcome increased upper airway resistance.
Indirect Arterial Blood Gas Monitoring
Severity of the various sleep-related breathing impairment can be assessed by:
1. O 2 saturation (%)
2. O 2 tension (mm Hg, torr)
3. Transcutaneous TcCO 2
Useful in pulmonary or muscular diseases (e.g., COPD, myotonic dystrophy).
Continuous oxygen saturation monitoring is routine.
Finger or ear probe:
1. Contains two fiberoptic bundles enclosed in Teflon or light-emitting diodes and a light sensing apparatus.
2. Based on the absorption of certain wavelengths of light.
Change in SaO2 associated with a respiratory event appears 20-40 sec after the actual event.
The skin is cleaned with 70% isopropyl alcohol and may be arterialized by brisk rubbing.
Transcutaneous oxygen tension is measured.
Detects arterial oxygen tension in mmHg of mercury or torr.
Skin over chest wall is the most often used site.
The electrode contains a thermistor-regulated heating resistor to ensure necessary skin arterialization.
Electrode site may have to be altered during the night to avoid heat blistering.
It is accurate, but cumbersome and uncomfortable.
Not used commonly.
Transcutaneous CO 2 measures may be monitored.
pO 2 and CO 2 detections are performed by two parts of the same probe.
May rarely be used to determine respiratory rate.
To document CO 2 retention in various sleep-related respiratory disorders.
2. Hypoventilation syndromes.
ECG abnormalities in sleep apnea patients:
1. Marked sinus arrhythmia.
2. Extra systoles.
3. Prolonged asystolic episodes.
4. Atrial or ventricular fibrillation.
5. Nocturnal angina may show ST segment deviation.
Also in sleep terrors, idiopathic CNS hypersomnia, or psychophysiological (stress-related) insomnia.
Gastro-esophageal reflux of acidic stomach contents into the lower esophagus may cause insomnia.
pH probe is introduced nasally and swallowed to about 5 cm above the esophageal sphincter.
Psychogenic Vs organic causes of impotence.
Psychogenic cases: Normal REM sleep-related erections.
Strain gauge technique: to calibrate, record, score NPT.
Supplemented by bulbocavernosus EMG activity.
Core Body Temperature
Rectal body temperature approximates core body temperature.
Define several disorders of the circadian sleep-wake cycle.
May be abnormal in various neurological lesions: - damage to the suprachiasmatic nuclei.
A number of commercially available recording devices exist, usually as part of an ambulant monitoring system.
Sleep staging NREM REM Stage 1 Stage 2 Stage 3 Stage 4 CAP Non-CAP Phase B Phase A
Proportion of sleep stages
Stage 1: 10-12%
Stage 2: 45-55%
Stage 3 and 4: 15-20%
Sleep is entered through NREM.
NREM-REM cycle every 90 minutes.
4-6 cycles per major sleep episode.
REM duration progressively lengthens.
Early cycles dominated by slow wave sleep.
Stage W: Awake state Eyes open: slow eye movements when drowsy. Eyes closed: REMs or none. Relatively high tonic activity. Voluntary control. Voluntary control Eyes closed: rhythmic α , occipital dominant; disappears on eye opening. Eyes open: low voltage mixed frequency. EMG EOG EEG
Stage 1 Vertex sharp waves: biphasic sharp transients, maximal centrally. Tonic activity is less compared to awake state. Decreased blinking rate. SEMs ( 0.25-0.5Hz) lasting several seconds.
Attenuation of α .
Relatively low voltage, mixed frequency (2- 7/s).
Vertex sharp waves in late stage.
Synchronous high voltage theta waves in children.
EMG EOG EEG
Stage 2 Tonic activity low No eye movements, or occasional SEMs. Background: Relatively low voltage, mixed frequency(3-7/sec). Sleep spindles: K complex: Biphasic; maximum at vertex. Delta activity <20% EMG EOG EEG
Waxing and waning pattern.
12- 14 Hz central bursts.
Should last > 0.5 sec to be scored.
Amplitude criteria: 15 µV.
Voltage tends to become smaller with age.
K complexes consist of all or any 2 of 3 main components
Negative vertex sharp-wave.
Following positive slow-wave maximal frontally
Sleep spindle maximal in the central regions.
Should last > 0.5-sec to be scored.
Sleep spindle and K complex
Three Minute Rule
In Stage 2 if six successive epochs (or 3 minutes) look like Stage 1, these have to be coded as Stage 2 as long as a sleep spindle or K-complex is seen during this time-frame.
If, after the three minutes (6 epochs), no sleep spindles or K-complex are seen, then retrace to the last epoch of Stage 2 and code the six epochs as Stage 1.
Stage 4 Stage 3 Low level tonic activity. None. Delta activity (2/sec or less), high amplitude(> 75 µV). 20%-50% of epoch. Maximum in central. Sleep spindles may be seen. Low level tonic activity. None. Delta activity with high amplitude(> 75 µV) comprising >50% of epoch. Sleep spindles and K complex occur rarely. EMG EOG EEG
Stage REM Tonic: suppression. Phasic: twitches. Phasic: intense REM. Tonic: none or few. Relatively low voltage, mixed frequency saw tooth waves; theta activity; slow alpha. Initial REM period at times contains some low-voltage spindles. EMG EOG EEG
Stages of sleep
Proportion of sleep stages
Sleep stages and age
Sleep terminology Time spent in sleep/ time in bed (Normal >85%) Sleep efficiency (REM+ NREM)- awake time Total sleep time Light off to sleep onset. Latency of sleep onset 3 consecutive epochs of Stage 1 NREM, or first epoch of any other Stage. Sleep onset Total minutes spent in bed. Time in bed End of recording. Light on Start of recording. Lights out Fixed time domain of 30 sec. Epoch
Movement time (MT): is scored for each epoch in which more than 50% of the epoch is obscured by movement artifacts that make staging impossible.
1. Must be preceded and followed by epochs of definite EEG sleep.
2. Distinguish from movement during arousals and during wakefulness.
Wake percentage: is the percentage of wake period from lights out to lights on.
REM latency: time from sleep onset to first appearance of REM sleep.
Differs from awakening.
EEG frequency shift lasting >3 sec (alpha,theta or beta) preceded by > 10 sec of continuous sleep.
REM sleep: arousal requires increased chin EMG activity.
May or may not be associated with body movements or respiratory events.
More than 10-15/hr is abnormal.
Consist of brief arousals typically lasting 5 to 10 seconds.
No change of sleep stage.
Increased day time somnolence.
Periodic limb movements are scored in sleep only when there are ≥ 4 limb movements in sequence occuring > 5 sec but < 90 sec apart.
A limb movements is an increase in the limb activity lasting 0.5 to 5 sec with an amplitude of > 25% of the burst of EMG activity recorded during biocalibration.
Generating a report
Summary of the entire night’s PSG data in a graphic form.
Helpful to open a window for the hypnogram simultaneously while reviewing PSG.
Allows to easily select the part of the study one wishes to see.
Switch the epochs rapidly for comparison of sleep stages.
Test Date: 8/28/2009
Age/Sex: Pt ID no:
Height: Weight: EEG# PSG
Technician: Referring Doctor:
Summary Of Sleep Parameters
Study Start Time: 9:49:57 PM Lights Off Time: 9:49:57 PM
Study End Time: 5:35:07 AM Lights On Time: 5:35:07 AM
Total Study Time (TIB): 465.2 Minutes 7.8 Hours 930.3 Epochs
Sleep Period Time (SPT): 383.5 Minutes 6.4 Hours 767.0 Epochs
Total Sleep Time (TST): 290.5 Minutes 4.8 Hours 581.0 Epochs