Visi is a minimal patient contact `appropriate technology` system for sleep screening. Simplicity, economics and ease of use has made Visi the UK`s standard system with more than 170 installations since 1993.

The most important parameters for the assessment of Obstructive Sleep Apnoea Syndrome (OSAS) when considering patients for CPAP therapy or surgery, are measures of sleep fragmentation and the increase in upper airway resistance.

The Visi system uses audio/video and Masimo oximetry to generate measurements of sleep disturbance: body movement and heart rate changes, upper airway resistance: oxygen saturation and snoring/environmental sounds calibrated in decibels, allowing a comprehensive assessment of sleep disordered breathing and disturbed sleep.

Visi uses these signals in conjunction with ECG (EKG) to generate several further measures of sleep disturbance: ECG waveform and R-R interval, Pulse Transit Time and the Pulsatile Index (variablility in the size of the plethysmograph signal which follows arousal.

Oral/ nasal airflow by thermistry, two respiratory effort channels by inductance, body position and movement, pressure from a standard CPAP machine or mask, two leg channels and floating/ grounded inputs are also available.

The headbox (Black Shadow) is battery-powered and communicates wirelessly to the computer. It may also function without video.

Data is stored and displayed on a computer running Windows, audio/video recordings with picture-in-picture backing up the traces seen on the display, providing economic storage and viewing of the subject.