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 obstructive sleep apnea syndrome (OSAS).


OBJECTIVE
The present study was conducted to determine whether treatment with an automated impedance-controlled continuous positive airway pressure (CPAP) device (APAP(FOT)) is possible in patients with OSAS, and which is the best range of pressure variation in automatical CPAP treatment. We investigated two modes of APAP(FOT) with different pressure ranges: (1) the widest technically possible pressure range and (2) a range with individually defined minimum pressure.


METHODS
Ten patients [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 range of 4.0- 15.5 mbar (mode 1 free range) and an individually fixed higher minimum pressure with a maximum pressure of 15.5 mbar (mode 2).


RESULTS
While 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 2 7.3+/-1.6 mbar (p< 0.05). Both of these 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 increased 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 lower than that titrated manually in 73.2% of total sleep time, in mode 2 in 48.6%, while pressures higher than those derived manually were observed in 13.0% 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 patients at significantly lower pressures as compared with manually titrated pressure. Differences between the two modes are only minor.
Randerath
W
W
Klinik Ambrock/Hagen, Clinic for Pneumology, Allergology and Sleep Medicine, Witten/Herdecke University, Hagen, Germany.
Parys
K
K
Lehmann
D
D
Sanner
B
B
Feldmeyer
F
F
Rühle
K H
KH
D000328:Adult; D000368:Aged; D017097:Electric Impedance; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010358:Patient Participation; D017286:Polysomnography; D011175:Positive-Pressure Respiration / Q000379:methods*; D011336:Probability; D012129:Respiratory Function Tests; D012680:Sensitivity and Specificity; D012891:Sleep Apnea Syndromes / Q000175:diagnosis / Q000628:therapy*; D018709:Statistics, Nonparametric; D016896:Treatment Outcome