[Variability of the treatment pressure under continuous positive airway pressure treatment in obstructive sleep apnea syndrome].
BACKGROUND
Selfadjusting CPAP therapy is mostly employed if constant CPAP does not sufficiently suppress respiratory disturbances or is not accepted by the patient. The number of respiratory disturbances and thus the pressure need varies with sleep stages and body position during sleep. However, the analysis of the pressure profile during automatic CPAP therapy indicates a relevant variability of treatment pressure which is independent of the above mentioned criteria. Therefore, we aimed to quantify the pressure variability and its significance in patients with obstructive sleep apnea syndrome (OSAS).


METHODS
We analysed the pressure profile during a six-week treatment period with selfadjusting CPAP therapy based on the measurement of the impedance (APAP FOT ). The variability index (VI) was calculated from the deviations of the treatment pressure from the mean pressure. The variability was considered to be low and clinically irrelevant if the VI did not exceed 0.75 as a mean value and in more than 10 % of the nights.


METHODS
20 patients (male 19, age 55.5 +/- 10.9 years, BMI 36.6 +/- 26.5 kg/m (2), AHI 36.9 +/- 21.3/h) who were treated with APAP FOT because of intolerance or inefficiency of constant CPAP.


RESULTS
The VI was 0.9 +/- 0.7 (range 0.27 +/- 0.05 to 1.95 +/- 0.83). The number of nights with a figure >/= 0.75 reached 17.6 +/- 13.8 (range 0 - 40). In 50 % of the patients the mean VI was lower than 0.75. However, in 7 of these 10 patients the VI exceeded 0.75 in more than 10 % of the nights (4 - 15). Only 3 of 20 patients fulfilled both criteria of pressure stability. The VI showed a significant correlation with P mean (r: 0.66, p < 0.001).


CONCLUSIONS
In most patients with difficult-to-treat OSAS a variability of the treatment pressure can be found.
Randerath
W
W
Klinik Ambrock, Klinik für Pneumologie, Allergologie und Schlafmedizin, Universität Witten/Herdecke. winfried.randerath@dland.de
Rocholl
C
C
Feldmeyer
F
F
Galetke
W
W
D001331:Automation; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration / Q000379:methods*; D011312:Pressure; D015203:Reproducibility of Results; D020181:Sleep Apnea, Obstructive / Q000503:physiopathology / Q000628:therapy*; D013997:Time Factors; D016896:Treatment Outcome