Ambulatory polysomnography using a new programmable amplifier system with on-line digitization of data: technical and clinical findings.

A new system for polysomnographic recording at home is presented. It consists of a 12 to 24-channel amplifier system with direct digitization of the polygraph signals using a portable computer. Sampling frequency, amplification and filter settings can be defined by the user, and the signals are evaluated at bedside. Technical testing proved a high signal/noise ratio, linear amplification and a good signal quality. Clinical testing of the first 100 recordings showed that they were acceptable for conventional sleep scoring in 98 cases. A comparison of two consecutive recordings was done in 9 healthy subjects and 11 patients with rheumatic disorders. Using conventional sleep staging, only a slight "first night effect" (FNE) was demonstrated in the sleep architecture. Power spectral analysis using autoregressive modeling demonstrated only a difference of power between the 2 nights in the beta (14.5-25 Hz) band. In conclusion, the usability and technical advantages make the system very suitable for ambulatory recordings and only a minimal FNE should be considered when results are evaluated.