Table 4. Advantages and disadvantages of portable monitoring devices (PMDs).

Advantages

Accessibility

Improved patient access

Easy self-application of monitoring (no technician required)

Possible impact on waiting list

Cost

Acceptability for patients

Patients with possible anxiety or who are uncomfortable sleeping alone in a laboratory bed, under medical guidance

Patient sleeps in his/her own bed

The effect of environmental factors on sleep variables is still unknown (the sleep pattern is probably more representative of everyday sleep)

Disadvantages

Reliability

Unattended portable monitoring is subject to data loss

Equipment malfunction

Sensor disconnections

Patient or family interference

Telephone-line interference (during modem transfer or playback)

Diagnostic limitations

Nonsleep-apnoea diseases

Underestimate of the AHI

No electrophysiological signals needed to score and stage sleep, no detection of hypopnoeas associated with arousals and no evaluation of the quality of sleep

PMD can vary according to:

Number and types of signals

Sensors used

Methods of scoring

Criteria used to define respiratory events

Cut-off of the AHI used to define diagnosis and severity of OSAS

AHI: apnoea/hypopnoea index; OSAS: obstructive sleep apnoea syndrome.