Technical Specifications and Sensor Configurations Utilized in Modern Type 3 Home Sleep Apnea Diagnostic Devices
The accuracy of a Home Sleep Apnea Test is fundamentally tied to the quality of its sensors. A standard Type 3 HSAT device integrates several key components to capture the respiratory profile of the patient.
The first is the Nasal Pressure Transducer. This sensor, usually a soft plastic cannula, measures the pressure of airflow entering and exiting the nostrils. It is highly sensitive to "hypopneas"—partial reductions in breathing—that might be missed by less sensitive thermal sensors.
The second core component is the Pulse Oximeter. Usually worn on the fingertip, this sensor uses light absorption to monitor the percentage of oxygen in the blood ($SpO_{2}$). In a typical apnea event, the cessation of breathing leads to a "desaturation," or a drop in blood oxygen. A drop of 3% or 4% is a critical marker used in scoring sleep apnea. Alongside oxygen levels, the oximeter also tracks the heart rate, providing data on "tachycardia" or "bradycardia" (fast or slow heart rates) that often accompany respiratory distress.
Thirdly, Respiratory Inductance Plethysmography (RIP) Belts are used. These elastic bands are placed around the chest and sometimes the abdomen. They contain small wires that measure the expansion and contraction of the torso. This is vital for distinguishing between Obstructive Sleep Apnea (where the chest still tries to move but the airway is blocked) and Central Sleep Apnea (where the brain stops sending signals to the chest to breathe). By analyzing the relationship between airflow and chest movement, the diagnostic software can determine the specific nature of the breathing disorder.