Abstract
Pulse oximetry is a simple tool used to assess suspected SDB. Currently focus is mainly on using 4% hypoxic dips/hr, although other indices exist.
Aim: To determine the use of pulse oximetry in the assessment of SDB using 4 indices and the value of using 2 nights of assessment
Methods: 150 consecutively referred patients had 2 nights of oximetry at home (Minolta 300i). Data was analysed (Download 2001; Stowood Scientific, UK), by experienced Physiologists and artefact removed. The 4% and 3% dips/hr, cumulative %time at SpO2< 90% (CT90; Olson et al, J Sleep Res 1999;8:51-55) and Δindex>0.6 (Levy et al, Chest 1996;109:395-99) were obtained for each night. Results: 132 patients gave usable data, 39F and 93M, aged 50 yrs (19 - 79).
The median(range) differences between the two nights (N1 - N2) for the group were: 4% dips/hr: -0.78 (-29.5 to 19.9), 3% dips/hr: -1.2 (-15.6 to 20.2), CT90: -0.12 (-21.9 to 29.7) and Δindex: -0.04 (-10.4 to 1.2). Using a combination of these indices, 26/132 (20%) were negative for all 4, 66 (50%) positive for all 4, 10 for any 3, 12 for any 2 and 18 for any one.
Conclusions: To use pulse oximetry
1) requires analysis by experienced practitioners to ensure accuracy of data;
2) requires two nights, resulting in a > 23% increase in a positive diagnosis from the second night;
3) with a combination of the 4 indices, all of which have good sensitivity and specificity for SDB, gives an indication of the likelihood of SDB being present. Using a combination of any 3 or all 4 accounts for 77% of the patients assessed.
- © 2012 ERS