TABLE 15

Night-to-Night Variability in Polysomnographic Respiratory Parameters

Time Between EvaluationsSourceLevelNo.Findings
1–4 wkKatz et al103I30 suspected OSASNo significant group difference in the AHI between nights. Those with the highest AHI had the most variability. However, no patient was reclassified as primary snoring versus OSAS on the basis of the second study
7–50 dGoodwin et al101IV12Used unattended home PSG. Studies were successful in 10. No difference in AHI between nights in this small sample
Consecutive nightsScholle et al105III131 OSASNo difference in AHI between nights
Consecutive nightsLi et al104III46 obeseAHI was greater on night 2
44 controlsThe first night would have correctly identified 11 (85%) of the 13 cases of OSAS if the worst obstructive apnea index over any single night was used as the criterion. However, the 2 cases that would have been missed by the single PSG had only borderline OSAS
Consecutive nightsVerhulst et al 106I70 suspected OSASFirst night classified OSAS correctly in 91% of subjects, if the worst AHI over any night was used as the diagnostic criterion. All but 1 of those who were missed had an AHI <5/h