Hour-to-hour variability of oxygen saturation in sleep apnea.
OBJECTIVE
Methods used to express the severity of oxygen desaturation during polysomnography include the average oxygen saturation (AO2), lowest oxygen saturation (LO2), and the percent of the total time with oxygen saturation level lower than 90% (T<90%). We wanted to determine which one of these methods is least variable during different hours of monitoring.


METHODS
Prospective, observational study.


METHODS
Sleep center at a medical university.


METHODS
One hundred fifty patients with apnea-hypopnea index from 5 to 130.


METHODS
AO2, LO2, and T<90% were calculated during each of the 8 h of polysomnography. Data for each hour were compared and the Cronbach alpha coefficients were calculated.


RESULTS
There was a high degree of correlation among the three methods as well as between each method and the severity of sleep apnea. The mean+/-SD values for each method were as follows: AO2, 92.7+/-5.6; LO2, 68.5+/-19.3; and T<90%, 15.7+/-24.2. The alpha coefficients for these methods were AO2, 0.98; LO2, 0.88; and T<90%, 0.98. In all methods, the data of the first hour were significantly different from the data of the subsequent hours.


CONCLUSIONS
Both AO2 and T<90% methods show less hour to hour variability compared with LO2, and there is more variability in the first hour. Since the AO2 values >90% may not convey the severity of O2 desaturation, T<90% may be the best method of expressing oxygen saturation changes during polysomnography.
Chaudhary
B
B
Georgia Sleep Center, Medical College of Georgia, Augusta 30912-3137, USA.
Dasti
S
S
Park
Y
Y
Brown
T
T
Davis
H
H
Akhtar
B
B
D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood*; D017286:Polysomnography; D011446:Prospective Studies; D012891:Sleep Apnea Syndromes / Q000097:blood* / Q000503:physiopathology
D010100:Oxygen