A Home Sleep Test (HST) is a convenient, at-home method for gathering information about sleep patterns, serving as an alternative to facility-based studies. This portable, unattended testing process helps physicians determine if a sleep disorder is present.
Defining the Home Sleep Test and Its Purpose
A Home Sleep Test is a simplified, overnight breathing monitor used by a patient in their own bed to gather diagnostic data. These devices measure fewer parameters than an in-lab study, making them less intrusive and easier to use. They primarily focus on detecting breathing irregularities during sleep, which can indicate Obstructive Sleep Apnea (OSA).
The purpose of the HST is to diagnose OSA in patients who have a high probability of the condition and no other complex medical issues. Devices are classified as Type III or Type IV, based on the number of channels they measure. Type III tests record a minimum of four parameters, including airflow, respiratory effort, heart rate, and blood oxygen saturation. Type IV devices are the most simplified, often monitoring only oxygen saturation and heart rate.
The Mechanics of Taking a Home Sleep Test
The process begins after a medical evaluation determines the HST is the appropriate diagnostic tool. The patient receives the testing kit, often delivered or picked up at a clinic, along with detailed instructions. Preparation usually includes avoiding caffeine and alcohol before bed and maintaining a normal sleep schedule for the night of the test.
To begin the study, the patient attaches the provided sensors just before going to sleep. Common equipment includes a nasal cannula, a thin tube that sits inside the nostrils to measure airflow and breathing pressure. A pulse oximeter, typically a small clip placed on a finger, measures the blood oxygen level and heart rate throughout the night.
Many devices also require a flexible belt placed around the chest or abdomen to measure respiratory effort, recording the movement of the chest wall. Once the sensors are secured and the device is activated, the patient sleeps as normally as possible. In the morning, the equipment is removed and returned to the provider for data download and analysis.
Comparing Home Tests to In-Lab Sleep Studies
The difference between an HST and a full, in-lab sleep study, known as Polysomnography (PSG), lies in the amount and type of data collected. PSG is conducted in a sleep center under technician supervision and is considered the gold standard for comprehensive sleep evaluation. The HST is performed unsupervised at home, which can lead to a more typical night of sleep.
PSG monitors a wider range of physiological signals, including brain waves (EEG), eye movements, and leg movements, in addition to respiratory data. Since HSTs do not include EEG sensors, they cannot precisely measure sleep stages or total sleep time. This makes HSTs less suitable for diagnosing complex sleep disorders like narcolepsy.
A physician prescribes an HST when there is a strong suspicion of moderate to severe OSA in a healthy patient. If the HST result is negative despite persistent symptoms, or if the patient has other medical conditions, a full PSG is usually ordered. While the HST is more convenient and cost-effective, the PSG provides a more holistic view of sleep architecture and non-respiratory issues.
Interpreting the Results and Next Steps
Once the device is returned, the recorded data is downloaded and analyzed by a sleep technician or physician. The most important metric derived from the HST is the Apnea-Hypopnea Index (AHI), or sometimes the Respiratory Event Index (REI). This index represents the average count of apneas (complete pauses in breathing) and hypopneas (partial reductions in airflow) that occur per hour of recording time.
The AHI score determines the severity of Obstructive Sleep Apnea. An AHI of 5 to 15 events per hour is classified as mild, 15 to 30 as moderate, and greater than 30 indicates severe sleep apnea. The report also details the lowest blood oxygen saturation level recorded, since repeated drops in oxygen are an indicator of the disorder’s impact.
Following the diagnosis, the healthcare provider discusses treatment options based on the severity score. For most cases of OSA, the recommendation is Continuous Positive Airway Pressure (CPAP) therapy, which uses a machine to keep the airway open during sleep. Other options, such as oral appliances or lifestyle changes, may be considered based on the individual’s specific needs.