Self-adjusting continuous positive airway pressure therapy based on the measurement of impedance - A comparison of free pressure variation and individually fixed higher minimum pressure

Background: Measurement of impedance using forced oscillation technique is a sensitive means of detecting airway obstructions, including the obstructi ve sleep apnea syndrome (OSAS). Objective: The present study was conducted to determine whether treatment with an automated impedance-controlled conti nuous positive airway pressure (CPAP) device (APAP(FOT)) is possible in pat ients with OSAS, and which is the best range of pressure variation in autom atical CPAP treatment. We investigated two modes of APAP(FOT) with differen t pressure ranges: (1) the widest technically possible pressure range and ( 2) a range with individually defined minimum pressure. Methods: Ten patient s [9 men, age 56.6 +/- 10.5 years, BMI 32.0 +/- 4.5 kg/m(2), apnea/hypopnea index (AHI) 18.2 +/- 13.3/h] had a diagnostic polysomnography (baseline). After manual titration of positive airway pressure they were submitted, in randomized order, to two modes of the APAP(FOT) device, namely pressure ran ge of 4.0-15.5 mbar (mode 1 free range) and an individually fixed higher mi nimum pressure with a maximum pressure of 15.5 mbar (mode 2). Results: Whil e the manually titrated pressure was 8.0 +/- 1.3 mbar, in mode 1 it was 5.6 +/- 2.1 mbar (p < 0.01); in mode 27.3 +/- 1.6 mbar (p < 0.05). Both of the se modes suppressed abnormal respiratory events (baseline AHI 18.2 +/- 13.3 /h; mode 1: 2.5 +/- 1.9; mode 2: 1.8 +/- 0.7, p < 0.01 in each case), and i ncreased slow wave sleep (baseline: 10.6 +/- 8.0%, mode 1: 20.2 +/- 10.4%, p < 0.05; mode 2: 22.3 +/- 9.3%, p < 0.01). In mode 1, the pressure was low er than that titrated manually in 73.2% of total sleep time, in mode 2 in 4 8.6%, while pressures higher than those derived manually were observed in 1 3.0% in mode 1 and in 19.1% in mode 2. Conclusions: The data indicate that impedance-controlled CPAP (APAP(FOT)) allows adequate treatment of OSAS pat ients at significantly lower pressures as compared with manually titrated p ressure. Differences between the two modes are only minor. Copyright (C) 20 00 S. Karger AG. Basel.