What is the role of ambulatory monitors in the workup of sleep-disordered breathing (SDB)?

Updated: Feb 13, 2020
  • Author: Vittorio Rinaldi, MD; Chief Editor: Zab Mosenifar, MD, FACP, FCCP  more...
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Home sleep testing pursues the goal of simplify the diagnosis of sleep apnea while retaining the essential recording features of PSG. There is some evidence to suggest that home sleep studies have benefits in terms of time and cost, but for diagnostic reliability, an in-laboratory sleep study may be required in more than half of the cases.

Various types of ambulatory (to be used at home) monitors can measure parameters such as airflow, chest, and abdomen movements (as indicators of respiratory effort); oxygen desaturations; snoring; pulse; and body position. [52, 53]

Although the data from such studies are not as detailed or accurate as those obtained from an overnight PSG, these studies can often be used to differentiate primary snoring from snoring with apneas and can usually provide an indication of the frequency with which apneas are occurring. In contrast, techniques that measure only one parameter (eg, home oximetry alone) seem to be less accurate than those that track several measurements.

EdenTrace portable monitor measures nasal and oral air flow using thermistors, chest wall impedance, oxygen saturation with finger pulse oximetry, heart rate, and movement detected by electrical comparison of the signals from electrocardiography and pulse oximetry.

The MESAM IV system evaluates SDB on the basis of analysis of snoring, heart rate, and saturation change. Even if in many studies there is a good agreement between the RDI measured in the laboratory and that measure with home sleep testing, there is a risk that ambulatory diagnostic procedures may alter patients' relationship with their disease, the medical staff, or both in such a way that their subsequent compliance with treatment may be decreased.

The Nightwatch system has the ability to calculate the RDI. It records eye movement (one channel, piezo electrode), leg movement (one channel, piezo electrode), (finger pulse oximeter), nasal oral airflow (thermistor), chest and abdominal movements (piezo electrodes), body position and movement (mercury gauge placed on the chest), and heart rate.

The Nightwatch system also has the ability to send 2-minute portions of the complete recording to the laboratory for analysis so that signal quality can be assessed and transducer function corrected if necessary. However, further studies are necessary before this technology can be put into widespread use.

With the aim of developing a simpler, cheaper, and more accessible method for the diagnosis of OSAS, the peripheral arterial tonometer (PAT) has been proposed for use in ambulatory diagnosis of OSAS. The portable monitoring device WatchPAT 200 detects obstructive events by identifying the changes in sympathetic activity associated with the termination of the events. The wrist-worn device WatchPAT 200, compared with standard PSG, has been reported to be able to detect OSAS on the basis of the RDI with comparable accuracy. [54]

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