A limited diagnostic investigation for obstructive sleep apnea syndrome. Oximetry and static charge sensitive bed.

A simplified sleep apnea investigation consisting of combined oximetry and respiration movement monitoring was compared with conventional polysomnography. These two types of recordings were performed simultaneously during one night in 77 patients with suspected obstructive sleep apnea syndrome (OSAS). A static charge sensitive bed (SCSB) was used in the simplified recording because it provides a comfortable and reliable means of recording respiration movements. Periods of obstructive apneas gave a diamond-shaped periodic respiration movement pattern in the SCSB, usually accompanied by repetitive oxygen desaturations. The average number of desaturations greater than or equal to 4 percent per sleeping hour was termed the oxygen desaturation index (ODI) and compared with the apnea index (AI). In the whole population they were well correlated (p less than 0.0001, R2 = 0.41), but in individual cases there were considerable discrepancies. Patients with periodic respiration movements less than 18 percent of total sleeping time and ODI less than 2 never had AI greater than or equal to 5, whereas patients with periodic respiration greater than 45 percent and ODI greater than 6 always had AI greater than or equal to 5. Fifty-one of the 77 patients fulfilled these criteria. A bradycardia response to apneas was absent in 29 percent of patients with AI greater than or equal to 5. A combination of respiration movement and oximetry recording thus seems to give sufficient information to confirm or negate a diagnosis of OSAS in a majority of patients with clinical symptoms. In borderline patients, further investigations should be performed.