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Respir Med. 2008 Jul;102(7):1026-32. doi: 10.1016/j.rmed.2008.02.004. Epub 2008 Mar 17.

Time to desaturation in the 6-min walking distance test predicts 24-hour oximetry in COPD patients with a PO2 between 60 and 70mmHg.

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Pulmonary Department, Respiratory Research Unit, NS Candelaria University Hospital, Carretera del Rosario 145, 38010 Santa Cruz de Tenerife, Tenerife, Spain.



The 6-min walking distance (6MWD) test is a useful tool for assessing patients with chronic obstructive pulmonary disease (COPD), but little is known about the changes in oxygen saturation that occur during the test.


To predict the oximetry profile during daily living activities by the time to desaturation in the 6MWD test in COPD-affected patients.


We studied 67 COPD patients with moderate hypoxemia performing a 6MWD test and a 24-hour ambulatory pulse oximetry (24-hr PO). We determined the time to desaturation (SatO290%) in the 6MWD test, in the daytime, nighttime and 24-hr PO. We then estimated the time to desaturation that better predicts desaturation in diurnal, nocturnal and 24-hour oximetries using the ROC type II analysis.


The patients who desaturated after 3'30min have a 100% probability not to desaturate during diurnal, nocturnal and 24-hr PO. Those patients who desaturated during the first minute of the 6MWD test have a 74% probability to desaturate in these oximetries.


The time to desaturation in the 6MWD test can discriminate early desaturators who desaturate during their daily living activities and late desaturators who do not desaturate. Ambulatory oximetry would thus only be necessary in patients with a time to desaturation that ranges between 1 and 3'30''.

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