PT  - JOURNAL ARTICLE
AU  - Ming-Lung Chuang
AU  - I-Feng Lin, Dr.
AU  - Shih-Pin Chen
TI  - Kinetics of Changes in Oxyhemoglobin Saturation during Walking and Cycling Tests in Chronic Obstructive Pulmonary Disease
AID  - 10.4187/respcare.02494
DP  - 2013 Aug 13
TA  - Respiratory Care
PG  - respcare.02494
4099  - http://rc.rcjournal.com/content/early/2013/08/13/respcare.02494.short
4100  - http://rc.rcjournal.com/content/early/2013/08/13/respcare.02494.full
AB  - BACKGROUND AND OBJECTIVE: The patterns and kinetics of changes in oxyhemoglobin saturation measured with pulse oximetry (ΔSpO2) in six-minute walking test (6MWT) and cycling test has not been addressed in patients with chronic obstructive pulmonary disease (COPD). METHODS: Sixty COPD patients with FEV1 54±18%pred were evaluated for anthropometrics, oxygen-cost diagram (OCD) score, lung function tests, and the 6MWT and cycling test with SpO2 measurements. The ΔSpO2 were compared within individual tests and between both tests. The differences in the variables between desaturators and non-desaturators were compared. RESULTS: In the 6MWT, four patterns of SpO2 developed. Desaturation-re-saturation was the most common (46%). ΔSpO2 ≥3% occurred approximately at 1.2 minutes and the nadir re-saturated at 3.5 min. The ΔSpO2 between the start and the nadir (ΔSpO2SN) was greater than that between the start and the end (ΔSpO2SE) (p<0.0001). The desaturators had less inspiratory muscle strength (IMS), more dyspnea, and shorter distance on the 6MWT, while the re-saturators had greater FEV1/FVC and less functional residual capacity (all p<0.05). In the cycling test, three patterns of SpO2 developed. Desaturation was the most common (57%). The ΔSpO2 ≥3% and SpO2nadir occurred at 4.6 min and 6.6 min, respectively, of the 6.8-minute exercise duration. The desaturators had less body mass index, OCD score, IMS post-exercise, diffusing capacity, SpO2 and work on walking, and peak exercise performance (all p<0.05). In both tests, the ΔSpO2SN during the 6MWT was greater (p<0.05) but the ΔSpO2SE was similar (p=0.79). The desaturators in both tests had lower OCD scores (p<0.01) and poorer peak exercise performance. CONCLUSIONS: Measurement of ΔSpO2SN rather than ΔSpO2SE during the 6MWT is recommended because ΔSpO2SN is greater and the SpO2nadir is earlier. In both exercise tests, exertional desaturation can be predicted with the OCD scores and has more capability to predict peak exercise performance than the 6MWT.