Kinetics of changes in oxyhemoglobin saturation during walking and cycling tests in COPD.

Abstract

BACKGROUND:

The patterns and kinetics of changes in SpO2 in the 6-min walk test (6MWT) and cycling test have not been addressed in patients with COPD.

METHODS:

We studied 60 COPD subjects, with a mean ± SD FEV1 of 54 ± 18% of predicted. We compared the changes in SpO2 (ΔSpO2) within and between the 2 tests, and the differences between the desaturators and non-desaturators.

RESULTS:

In the 6MWT there were 4 patterns of SpO2. Desaturation then resaturation was the most common (46%). ΔSpO2 ≥ 3% occurred at approximately 1.2 min, and the nadir was at 3.5 min where resaturation occurred thereafter. The ΔSpO2 between the start and the nadir (start-vs-nadir ΔSpO2) was greater than the start-vs-end ΔSpO2 (P < .001). The desaturators had less inspiratory muscle strength, worse dyspnea, and shorter 6-min walk distance, whereas the resaturators had greater FEV1/FVC and less functional residual capacity (all P < .05). In the cycling test there were 3 patterns of SpO2. Desaturation was the most common (57%). The ΔSpO2 ≥ 3% and nadir SpO2 occurred at 4.6 min and 6.6 min, respectively, of the 6.8-min cycling exercise duration. The desaturators had lower body mass index, lower oxygen-cost diagram score, less post-exercise inspiratory muscle strength, lower diffusing capacity, lower SpO2, lower work during 6MWT, and lower peak exercise performance (all P < .05). In both tests, the start-vs-nadir ΔSpO2 during the 6MWT was greater (P = .02) but the start-vs-end ΔSpO2 was similar (P = .79). The desaturators in both tests had lower oxygen-cost-diagram scores (P < .01) and poorer peak exercise performance.

CONCLUSIONS:

Measurement of start-vs-nadir ΔSpO2 rather than start-vs-end ΔSpO2 during the 6MWT is recommended, because start-vs-nadir ΔSpO2 is greater, and the nadir SpO2 is earlier. In both the 6MWT and the cycling exercise test, desaturation can be predicted with the oxygen-cost-diagram score, which has more capability to predict peak exercise performance than the 6MWT.

• Authors: Ming-Lung Chuang, I-Feng Lin, Shih-Pin Chen
• Journal: Respiratory care (Respir Care) Vol. 59 Issue 3 Pg. 353-62 (Mar 2014) ISSN: 1943-3654 [Electronic] United States
• PMID: 23942752 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Oxyhemoglobins

Topics

• Aged
• Bicycling (physiology)
• Exercise Test
• Female
• Forced Expiratory Volume (physiology)
• Humans
• Male
• Middle Aged
• Oxyhemoglobins (metabolism)
• Pulmonary Disease, Chronic Obstructive (blood, physiopathology)
• Vital Capacity (physiology)
• Walking (physiology)