[A modified unit for detecting sleep apnea]

A comprehensive diagnostic work-up of patients with a suspected sleep apnea syndrome must include conventional polysomnographic monitoring during the night. On account of the considerable staff and technical requirement, however, this definitive diagnostic measure is not suitable for use as a screening programme. For this reason we undertook to develop a device for the computer-aided recording of sleep apnea. The heart of the unit is a 65816 microprocessor with an address capacity of 16 Mbytes. The oro-nasal airflow is recorded with the aid of thermistors, and, after digital filtering, the respiratory rate is continuously recorded on the basis of this signal. Continuous recording of the heart rate and oxygen saturation, is also effected, the recorded data being stored in the microprocessor. On conclusion of the data acquisition phase, evaluation and a compressed display is shown on any conventional personal computer. Our preliminary experience reveals that the algorithm employed is extremely reliable for the detection of respiration rate and apnea, even in the presence of unfavourable signal forms. Clinically relevant deviations from manual evaluation do not occur. As was to be expected, processing of the signals for heart rate and oxygen saturation presented no problems.