A Home Sleep Test (HST) is a portable diagnostic procedure that measures physiological parameters related to breathing disorders during sleep in a person’s natural environment. It is primarily used to confirm a diagnosis of Obstructive Sleep Apnea (OSA). Unlike a comprehensive in-lab polysomnography study, the HST is a more cost-effective and convenient alternative, requiring fewer sensors and eliminating the need for an overnight stay in a clinic. The test provides sufficient data to assess the severity of sleep-disordered breathing for patients highly suspected of having OSA.
Initiating the Study
The process begins with a consultation with a physician, as a prescription is mandatory to obtain the testing device. During this initial visit, the medical provider assesses the patient’s symptoms and health history to determine if a home study is appropriate. An HST is generally recommended for individuals with a high probability of having moderate to severe OSA, who do not have complex medical conditions like severe pulmonary disease or congestive heart failure that could skew the results.
If the home test is deemed suitable, the official order is placed with a sleep center or diagnostic service. The patient then coordinates the logistics of receiving the device, which is typically shipped directly to their home or picked up from a local clinic. Before using the device, the patient may complete a sleep questionnaire to provide the specialist with context about their sleeping patterns and daytime symptoms.
Understanding the Monitoring Equipment
The device utilized for an HST is commonly classified as a Type III portable monitor, which records a minimum of four distinct physiological channels of data. These channels capture cardiopulmonary metrics related to breathing, effort, heart rate, and blood oxygen levels.
A nasal cannula is placed at the nostrils to measure airflow by sensing pressure changes during inhalation and exhalation. One or two effort belts wrap around the chest and/or abdomen to measure the mechanical movement associated with breathing effort. This respiratory effort data is helpful in differentiating between Obstructive and Central sleep apnea events.
A pulse oximeter is a core component that usually clips onto a fingertip to track heart rate and arterial oxygen saturation. Drops in oxygen saturation, which reflects the amount of oxygen carried by the red blood cells, are an indicator of impaired breathing during sleep. All sensors connect to a small, portable data collection unit, which records the information for analysis.
Step-by-Step Guide to Conducting the Test
Preparation for the home study should begin several hours before bedtime. On the day of the test, it is recommended to avoid consuming caffeine or alcoholic beverages, as these substances can interfere with normal sleep and respiratory events. Avoiding daytime naps and the application of heavy lotions or body creams is also advised, as oils can prevent sensors from adhering properly.
To set up the equipment, the user should first review the provided instructions and identify all the components. The physical setup involves attaching the sensors to the body:
- The effort belt is positioned around the torso, often over a thin layer of clothing, and secured to be snug yet comfortable.
- The finger probe is placed on the index or ring finger, with the sensor positioned over the nail bed. The wire may be taped down to the wrist for security.
- The nasal cannula must be carefully inserted so the two small prongs sit inside the nostrils, with the tubing looped over the ears and secured under the chin.
Once all sensors are connected to the main recording unit, the device is powered on according to the specific model’s instructions, often by pressing and holding a central button. It is important to confirm that all accessory lights are lit, indicating a successful connection before attempting to sleep.
The individual should attempt to sleep as they normally would, remaining connected to the device for the entire night. If the user wakes briefly, they should not remove the sensors or turn the device off, as this could interrupt the data recording. In the morning, the user follows the instructions to shut down the recording unit, which typically involves holding the power button until the device confirms it is off.
Data Return and Analysis
The final step is the careful disassembly and return of the equipment. Once the device is powered down and all sensors are removed, every component is placed back into the original packaging. The kit is then returned to the provider, either by shipping it back in a pre-paid box or by dropping it off at the facility.
The recorded data is downloaded by a technician and sent to a board-certified sleep medicine physician for scoring and interpretation. The physician’s analysis focuses on the Apnea-Hypopnea Index (AHI). This index represents the average number of apneas (complete airflow cessation) and hypopneas (partial airflow reduction) that occur per hour of recording time.
Severity is classified based on the calculated AHI: an AHI between 5 and 14 events per hour indicates mild OSA, 15 to 29 is moderate, and 30 or more events per hour signifies severe OSA. The physician also examines other metrics, such as the oxygen desaturation index and heart rate variability. The process concludes with a follow-up consultation where the specialist reviews the diagnostic report, discusses the findings, and outlines a treatment plan.