My name is Bharat Singh. I am Certified sleep study technician from World Sleep Federation. I started my carrier in sleep field in 2009 from AIIMS Hospital Delhi under Dr. Garima Shukla (Professor of Neurology, AIIMS, New Delhi).
I am doing sleep studies (diagnostic, split night studies, Titration studies, MSLT and actigraphy studies) manual sleep scoring, EEG (Routine & Video EEG).
Ph.No: (+91) 9873975578
Following Respiratory parameters are recorded during sleep studyAirflow, Respiratory effort, Oxygen saturation, snoring and CO2 levels in children and suspected Hypoventilating patients.
5 sensors that can be used to record airflow during diagnostic study areThermistor, Thermocouple, Pressure Transducer, expired CO2 sensors and Pneumotachography.
AASM recommends Thermistor and pressure transducer.
We should measure airflow by pap device flow signal during titration study and should not place thermistor or pressure transducer under the mask.
During level 1 diagnostic sleep study airflow is recorded using both thermistor and pressure transducer. In Home Sleep Testing (HST) airflow can be recorded using either thermistor or pressure transducer.
A Thermistor has a series of resistors whose values are changed by the temperature changes around them. These value changes affect a current that is generated either by the recording system into which they are plugged or by inline batteries.
A thermocouple comprises two wires made from dissimilar metals. A temperature change at the junction of these two metals will generate an electrical signal because of their metallurgical properties. This is accomplished using specific metals. Different metals are used to measure different temperature ranges resulting in different Types of thermocouples.
It measures pressure fluctuations at the nares as a surrogate of airflow. The square root of pressure curves is directly proportional to flow.
The oronasal thermal sensor is the recommended sensor for the identification of apneas and the nasal pressure transducer is the recommended sensor for the identification of Hypopnea during diagnostic sleep study.
Pap device flow signal sensors are recommended in titration sleep study to define Apnea and Hypopnea.
| Respiratory event | Alternate sensor |
| Apnea | Nasal pressure transducer RIP Sum RIP Flow PVDF Sum |
| Hypopnea | End Tidal CO2 in children Oronasal thermal sensor RIP Sum RIP Flow PVDF Sum |
Pneumotachographs measure the flow according to the Venturi effect. The Venturi effect is the phenomenon that occurs when a flowing fluid is forced through a narrow section, resulting in a pressure decrease and a velocity increase.
There are 2 types of pneumotachographs: Fleish and Lilly.
The Lilly type measures the difference in pressure over before and after a membrane with known resistance.
Fleisch types use a series of parallel capillaries. It includes a tube for connection on CPAP/BiPAP devices to analyse the quantitative breathing and leakage flow.
4 types of sensors that can be used to measure respiratory effort are Eophageal pressure transducer, Respiratory inductance plethysmography (RIP) belts, Polyvinylidene fluoride (PVDF) belts and Intercostal/Diaphragm EMG.
We can use piezoelectric belts as well to measure respiratory effort but AASM neither recommends it nor contradicts its usage. Esophageal pressure transducer is the gold standard for measuring respiratory effort.
During level 1 diagnostic sleep study respiratory effort is recorded using both abdominal and chest belts. In HST one belt either chest or abdominal can be used.
Piezoelectric belts- Piezoelectric belts contains a piezo-electric device that responds linearly to changes in length. It measures changes in thoracic or abdominal circumference during respiration. These measurements can indicate inhalation, expiration and breathing strength and can be used to derive breathing rate. The transducer may be used to characterize breathing patterns. The transducer is a solidstate device that requires no excitation. It is comfortable to wear, rugged, reliable and washable.
RIP belts- RIP belts have a wire running through the length of belts in a zigzag fashion. When chest and abdomen expand the inductance of the wire changes which is proportional to the cross sectional area belt encloses. This change in inductance is recorded as signal. To ensure quality signals, RIP belts should be placed at the standard locations: near the nipple line (or mid-chest) and just above the belly button.
To record the activity of the diaphragm, Surface electrodes are placed in the seventh or eighth intercostals space on the right side of the body at the midclavicular line, and for the external intercostals muscles, electrodes were placed in the 2nd or 3rd intercostal space at the midclavicular line.
Piezo sensor and microphone.
660 nm (red) and 940 nm (infrared) wavelengths are used to measure SpO2 by pulse oximeter.
Maximum averaging time should be 3 sec at a heart rate of 80bpm.
Arterial blood gases (ABG), Transcutaneous CO2 (TcCO2) monitoring and End tidal CO2 (EtCO2) monitoring can be used to measure CO2 levels during diagnostic sleep study. during titration sleep study we can use ABG or TcCO2 for monitoring CO2 levels.