Apnea is a medical condition where there is a 10 seconds or longer pause in breathing. This usually occurs during sleep (Sleep Apnea) or under tranquilizers or any anesthetics.
An apnea monitor can have all or some of the following components:
1. Apnea Detecting System: A monitoring device may detect apnea one or more of the following mechanisms:
a. Transthoracic Impedance Pneumography: This mechanism operates on the fact that when a patient breathes in, the electrical impedance across his thorax varies. The impedance increases during inhalation and decreases during exhalation. These impedance changes can be measured and used to determine respiration rate by the use of surface electrodes.
b. Electrocardiography (ECG): This monitors the rate and rhythm of heart. It helps diagnose the obstructive sleep apnea based on detection of the periodic cardiac oscillations and the inter-beat intervals that are often caused by sleep apnea.
c. Electro-encephalography (EEG): This measures the brain waves and helps diagnose a rare type of sleep apnea that involves the central nervous system. It occurs when the brain fails to signal the muscles that control breathing.
d. Electromyography: It diagnoses apnea by monitoring muscle activities and signals across upper respiratory tract muscles or diaphragm.
e. Airflow sensors: Airflow can be monitored in several ways such as monitoring airflow in and out of the lungs using thermistors, proximal airway pressure sensors or carbon dioxide (CO2) sensors and be utilized to detect apnea.
f. Pulse Oximetry: This is another technique to measure heart rates and blood oxygen levels in detecting the occurrence of apnea.
g. Mattress-type motion sensors: In this technique, motion sensors are placed between bed sheet and mattress which monitor the breathing movements during sleep by measuring the changes in the capacitance or resistance of the transducer.
2. Accessories: Apnea detectors may also include the following features:
a. Uninterruptible power source: It can be AC or a DC source.
b. Battery backup: A battery backup with appropriate life is essential for any portable (or non-portable) apnea detector.
c. Low battery alarm: An alarm that would sound if the battery level reaches a certain point (e.g.20%).
d. Optical Coupling: It is beneficial to isolate the patient from direct power supply.
e. Sound and Video Recording: It can record the breathing, snoring and other movements during the sleep.
f. Sound Alarm: An alarm of appropriate loudness that goes off if the breathing stops for certain time (e.g. 10 seconds). This includes a distant alarm at the monitoring room (or a care-taker’s room) that would notify an easily available person about the emergency.
g. Vibrating Motor Strap: A vibrating strap that can wake a person up so that he starts breathing again can come in handy.
h. Body Position sensor: It helps determine whether the patient sleeps on his back (supine), front (prone) or side, and how it influences his apnea.
i. Snoring Intensity index (dB): It measures the intensity of snoring as loud snoring is a major indicator of sleep apnea.