Sleep Studies
Overview:
A sleep study is a recording of a subject’s sleep to gain an understanding of their sleep patterns and to investigate cardiorespiratory physiology during sleep. Sleep disorders can affect a person's physical health, daily activities, and mental health.
During a sleep study, the subject’s sleep routine should remain the same as usual; the only difference will be applying and wearing the monitoring devices. The various stages of sleep are identified by measuring eye movements (EOG), muscle movements (leg and jaw EMG), brain activity (EEG) and breathing.
During sleep, a person passes through 4 phases, or stages, of sleep - stages 1, 2, 3 and REM (rapid eye movement) sleep.
- Stage 1 sleep is light sleep, where we drift in and out of sleep and can be woken up easily. Eyes move very slowly and muscle activity slows down.
- A person spends almost half of their total sleep time in Stage 2 sleep. Eye movement stops and brain waves (or activity) become slower.
- During Stage 3 or Slow Wave Sleep, brain waves slow down even more and the EEG exhibits mostly delta waves (slow brain waves). There is no eye movement and minimal muscle activity.
- A person's breathing becomes more rapid, irregular, and shallow in REM sleep. The eyes jerk quickly in many directions, heart rate increases, and blood pressure rises. Most dreaming happens during REM sleep.
Sleep staging is physiologically different between species.
Method:
Polysomnography
Polysomnography is a multi-parametric recording of the biophysiological changes that occur during sleep and the recording is called a polysomnogram, or PSG. Polysomnography is used to diagnose many types of sleep disorders including narcolepsy, restless legs syndrome, REM behaviour disorder, parasomnias, and sleep apnea. Although it is not directly useful in diagnosing circadian rhythm sleep disorders, it often is used to rule out other sleep disorders. The PSG monitors many body functions including brain (EEG), eye movements (EOG), muscle activity or skeletal muscle activation (EMG), heart rhythm (ECG), and breathing function or respiratory effort during sleep:
- EEG/ECoG - It will usually consist of four "exploring" electrodes attached to the scalp near the central and occipital portions of the brain and two "reference" electrodes. The brain activity will be recorded, and the different stages of sleep will be identified.
- EOG - It is measured from two electrodes, one that is placed slightly out from and above the outer corner of the right eye and one that is placed slightly out and below the outer corner of the left eye. This will help determine when REM or NREM sleep occurs.
- EMG - It is used to monitor muscle tension in the body and any excessive amount of leg movements during sleep (which may be indicative of Periodic Limb Movement Disorder). It usually uses four electrodes, two leads are placed on the chin with one above the jaw line and one below (used to help determine when sleep occurs as well as REM sleep) and two more leads are placed on the shin muscle of each leg to measure leg movements (which may be indicative of Restless Legs Syndrome or RLS).
- ECG - Two or three electrodes are placed under the collar bone on each side of the chest, or one under the collar bone and the other six inches above the waist on either side of the body. Identification of ECG abnormalities may be used to indicate underlying heart problems.
- Pulse Oximetry and Respiratory Airflow & Effort – Pulse oximetry helps determine changes in blood oxygen levels that often occur with sleep apnea and other respiratory problems. In the study of sleep apnea, additional respiratory airflow and respiratory effort indicators maybe used. Nasal and oral airflow can be measured using pressure transducers, and/or a thermocouple. This allows the measurement of respiratory rate and helps to diagnose sleep apnea. In addition to nasal/oral airflow, respiratory belts that expand and contract upon breathing effort can be used together to measure respiratory effort.
- Additional parameters that may be measured include:
- Intravascular and Surface Blood Flow
- Invasive and Non-invasive Blood Pressure
- Skin and Rectal Temperature
Behavioural Observations
In some sleep studies, subjects are also monitored via a video camera to provide visual observation of their behaviour during sleep.
Software:
The LabChart Advantage:
(may require additional Modules and Extensions)
- Spectral frequency (FFT) analysis of EEG, EMG and snoring sounds using Spectrum
- A selection of digital filters including high, low and band-pass options
- Heart rate variability analysis using the HRV Module
- Circadian analysis of recordings over unlimited durations using the Circadian Analysis Module
- Synchronized video recording of the sleeping subject with the Video Capture Module
- Advanced, editable macro scripting for repetitive analyses
LabChart
LabChart software (for Windows and Macintosh) together with a PowerLab data acquisition system offers up to 32 channels of real-time data acquisition, data integrity, easy selection of hardware settings, powerful online and offline analysis, procedure automation, seamless extraction of experimental data and flexible display options. Additional acquisition and analysis functionality is provided with the use of specialized LabChart Extensions and LabChart Modules. Modules are available as part of LabChart Pro while Extensions are free for download from the website for existing LabChart users.
ECG Analysis Module
The ECG Analysis Module (Windows) provides quick and easy automatic detection and analysis of ECG signals recorded in LabChart. As the raw data is unaltered by calculations, the ECG can be re-analyzed at any time. The module is suited for analysis of ECG from humans, pigs, dogs, rabbits, guinea pigs, rats and mice.
It provides:
- Real-time analysis and data extraction of ECG parameters
- PQRST amplitudes
- Time intervals such as RR, PR, JT, QT and QTc
- Analysis of ECG parameters in real-time or offline
- Automated detection and averaging of ECG cycles
- Automated tabulation and data extraction of ECG parameters
- Automated real-time or offline ECG Plots
- QT vs RR, QT vs Time & RR vs Time plots
- Waterfall plot
Heart Rate Variability (HRV) Module
The HRV Module (Windows and Macintosh) provides a comprehensive set of tools for the analysis and display of variation in the interval between heartbeats in human and animal electrocardiogram recordings.
The HRV Module:
- Detects and analyzes R waves & RR interval variation in ECG real-time or offline recordings
- Includes or excludes ectopic beats from analysis
- Adds R waves or removes short artifacts from analysis
- Exports data analysis
- NN Intervals, RR Intervals, Spectrum NN Intervals & Report
- Automated HRV Analysis Windows
- Poincaré Plot, Tachogram & Spectrum
- Period Histogram & Delta NN Histogram
Circadian Analysis Module
The Circadian Analysis Module (Windows) analyzes data with a daily pattern and generates graphical and tabular views of the daily and averaged circadian data. The Circadian Analysis Module features:
- Circadian Analysis Settings dialog which allows;
- Selection of channels to be included for analysis
- Customizable time settings including day length, start time and averaging interval
- A data exclusion filter which ignores data that falls outside preset upper and lower limits
- Light on/off shading to demonstrate night and day in the Averaging View
- Analysis Averaging View plots average interval data for single or multiple channels. You can choose to view the Average day, or show all days overlayed on top of the Average day.
- Circadian Analysis Table View automatically displays calculated parameters for each single day, as well as determining an average day. Users can tab through the Table View for different channels. Parameters calculated and displayed include:
- Maximum
- Minimum
- Maximum-Minimum
- Time at Maximum
- Time at Minimum
- Mean
- Exportable Analysis Averaging View plot and Table View as text or image formats
Video Capture Module
The Video Capture Module (Windows and Macintosh) allows simultaneous recording of a QuickTime movie and a LabChart data file to permit supplementary behavioural observations of a sleeping subject. The Video Capture Module supports most video cameras with USB or FireWire connections or input from any frame capture cards supported by QuickTime. The Video Capture Module:
- Synchronizes simultaneous recording and playback of LabChart data and a QuickTime movie
- Provides various movie capture options
- Two standard QuickTime settings
- Video and/or audio
- Movie size
- Hard disk space allocation
- Provides a preview window for the initial setting of image quality
- Provides easy navigation data or movie frames
- Movie Marker feature
- Set Movie Position
Scope View
Scope View provides the display and analysis capabilities of a digital storage oscilloscope to facilitate recording and viewing consecutive sweeps of data in LabChart. These sweeps, or pages, can be overlayed and averaged. Additionally, Scope View:
- Provides the ability to record, display and analyse any high frequency signal that is time-locked to a stimulus (e.g. auditory evoked potentials)
- Features a new 3D Depth and Saturation Overlay option in the Scope Overlay Options to help distinguish overlaid traces.
- Is recommended because it provides signal averaging functions that are necessary to extract the evoked response from background noise.
GLP and 21 CFR Part 11
For those researchers working within a laboratory requiring GLP and 21 CFR Part 11 compliance the GLP Client and GLP Server are available for use with LabChart (Windows only) and PowerLab data acquisition systems. For more information, visit the Good Laboratory Practice application page or contact your nearest ADInstruments representative.
Hardware:
PowerLab Data Acquisition Systems
The PowerLab is a high-performance data acquisition unit capable of recording at speeds of up to 400,000 samples per second continuously to disk (aggregate). PowerLab units are compatible with instruments, signal conditioners and transducers supplied by ADInstruments, as well as many other third-party companies. In addition to standard single-ended BNC inputs, 4 differential Pod ports are also available for direct connection of Pod signal conditioners and appropriate transducers. Research PowerLab units include:
- PL3508 PowerLab 8/35 – 8 Channels
- PL3516 PowerLab 16/35 – 16 Channels
Signal Conditioners
EEG, EMG, ECG, EOG (AC coupled only) Measurements
The following ADInstruments' biological amplifiers are fully isolated for connection to human or animal subjects:
- A differential amplifier that consists of eight electrically isolated differential input AC amplifiers
- A shared ground connection across all eight inputs
- Supplied with two packets of MLA0310 Lead Wires (1.8 m, 10 snap on)
- A fully isolated, 16 channel stand-alone biological amplifier that consists of 8 modules, with each module containing two channel amplifiers that share a common ground input
- Electrodes are NOT supplied and must be ordered separately
Blood Oxygen Saturation
The Oximeter Pod is used for the non-invasive measurement of blood oxygen saturation (SpO2).
Temperature
- For biological measurements such as skin and nasal temperature and respiratory detection in the range 5°C to 45°C
- Supports both absolute and relative temperature measurements
- Temperature probe NOT included and must be ordered separately
Instruments
Blood Flow
- Single-channel laser Doppler flow meter for use with a specialized fibre optic probe to measure blood cell perfusion in the microvasculature of tissues and organs
- Features two analog outputs, one provides a Laser Doppler Flowmetry (LDF) signal and the other provides a signal proportional to percentage backscatter (BSC) from the tissue.
- It can be used for:
- Evaluation of vasoactive drugs on microcirculation
- Monitoring of peripheral circulation
- Monitoring of exposed animal tissue microcirculation
- Laser Doppler probes NOT included and must be ordered separately
Transducers and Accessories
Respiration
MLT1132 Piezo Respiratory Belt Transducer
MLT1132/D Piezo Respiratory Belt Transducer (DIN)
- Contains a piezo-electric device that responds linearly to changes in length
- Measures changes in thoracic or abdominal circumference during respiration
- Measurements can indicate inhalation, expiration and breathing strength and can be used to derive breathing rate and characterize breathing patterns
Biopotentials
Suitable electrodes and accessories:
MLAWBT9 Flat EEG Electrodes for recording ECG, EEG, EOG and EMG
MLA0315 Lead Wires (unshielded, 5 snap on)
MLA1010B Disposable ECG Electrodes (1000)
MLA1010 Disposable ECG Electrodes (100)
MLA700 Reusable ECG Electrodes
MLA710 Chest ECG Electrodes (suction)
MLA1093B Abrasive Gel
MLA1090 Alcohol Swabs (1000)
MLA1095B Electrode Paste
MLA1090B Electrode Cream
MLAEC1 EEG Electro-cap System 1 (medium cap)
MLAEC2 EEG Electro-cap System 2 (large & medium cap)
Electro-cap System:
- Includes a cap for EEG, electrode adapter (suits the MLA2540 5-Lead Shielded Bio Amp Cable), body harness, quick insert electrode, ear electrodes (one pair), disposable sponge disks (100), needle/syringe kit, electro-gel (16 oz), head measuring tape, ivory cleaning liquid and a manual
- Suitable for use with the ADInstruments ML138 Octal Bio Amp or the GT201 16 Channel Bio Amp
- Replacement Accessories incude:
Temperature
Compatible transducers for the ML309 Thermistor Pod include:
- MLT422/A Skin Temperature Probe (2 m) for measurement of skin temperature
- MLT415/A Temperature Nasal Probe for measurement of nasal air temperature
Blood Flow
There are several ML191 Blood FlowMeter surface probes available including:
Cerebral sympathetic nerve activity has a major regulatory role in the cerebral circulation in REM sleep
Cassaglia PA, Griffiths RI, Walker AM, Journal of Applied Physiology, 1050-1056, 2009
Maturation of the initial ventilatory response to hypoxia in sleeping infants
Richardson H.L, Parslow P.M, Walker A.M, Harding R and Horne R.S.C., Journal of Sleep Research, 117-127, 2007
Ventilatory long-term facilitation in mice can be observed during both sleep and wake periods and depends on orexin
Terada J, Nakamura A, Zhang W, Yanagisawa M, Kuriyama T, Fukuda Y, Kuwaki T, Journal of Applied Physiology, 499-507 , 2008
Evaluation of pharyngeal shape and size using anatomical optical coherence tomography in individuals with and without obstructive sleep apnoea
Walsh J H, Leigh M S, Paduch A, Maddison K J, Philippe D L, Armstrong J J, Sampson D D, Hillman D R, Eastwood P R
, Journal of Sleep Research, 230–238, 2008
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