Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2009 Jul;64(7):626-30.
doi: 10.1136/thx.2008.111393. Epub 2009 Apr 8.

Exercise peripheral oxygen saturation (SpO2) accurately reflects arterial oxygen saturation (SaO2) and predicts mortality in systemic sclerosis

J J Swigris  1 , X Zhou, F S Wamboldt, R du Bois, R Keith, A Fischer, G P Cosgrove, S K Frankel, D Curran-Everett, K K Brown
Affiliations

Exercise peripheral oxygen saturation (SpO2) accurately reflects arterial oxygen saturation (SaO2) and predicts mortality in systemic sclerosis

J J Swigris et al. Thorax. 2009 Jul.

Abstract

Background: Measures of oxygenation have not been assessed for prognostic significance in systemic sclerosis-related interstitial lung disease (SSc-ILD).

Methods: 83 subjects with SSc-ILD performed a maximal cardiopulmonary exercise test with an arterial line. The agreement between peripheral oxygen saturation (SpO2) and arterial oxygen saturation (SaO2) was examined and survival differences between subgroups of subjects stratified on SpO2 were analysed. Cox proportional hazards analyses were used to examine the prognostic capabilities of SpO2.

Results: At maximal exercise the mean (SD) difference between SpO2 and SaO2 was 2.98 (2.98) and only 15 subjects had a difference of >4 points. The survival of subjects with SSc-ILD whose maximum exercise SpO2 (Spo(2)max) fell below 89% or whose SpO2max fell >4 points from baseline was worse than subjects in comparator groups (log rank p = 0.01 and 0.01, respectively). The hazard of death during the median 7.1 years of follow-up was 2.4 times greater for subjects whose SpO2max fell below 89% (hazard ratio 2.4, 95% CI 1.1 to 4.9, p = 0.02) or whose SpO2max fell >4 points from baseline (hazard ratio 2.4, 95% CI 1.1 to 5.0, p = 0.02).

Conclusion: In patients with SSc-ILD, SpO2 is an adequate reflection of SaO2 and radial arterial lines need not be inserted during cardiopulmonary exercise tests in these patients. Given the ease of measurement and its prognostic value, SpO2 should be considered as a meaningful clinical and research outcome in patients with SSc-ILD.

PubMed Disclaimer

Figures

Figure 1
Figure 1
Plots of peripheral oxygen saturation (SpO2) against arterial oxygen saturation (SaO2) and Bland-Altman plots for subjects with fibrosing interstitial lung disease related to systemic sclerosis (SSc-ILD) at (A) baseline and (B) maximum exercise. (A) In the upper graph the diagonal line marks the line of unity, and in the lower graph the middle line marks the mean difference between SpO2 and SaO2 and the two outer lines mark twice the standard deviation in either direction. (B) In the upper graph the diagonal line marks the line of unity, and in the lower graph the middle line marks the mean difference between SpO2 and SaO2 and the two outer lines mark twice the standard deviation in either direction.
Figure 2
Figure 2
Kaplan–Meier survival curves for subjects with fibrosing interstitial lung disease related to systemic sclerosis (SSc-ILD) stratified on peripheral oxygen saturation at maximal exercise (SpO2max) <89% or ≥89%. The solid line represents subjects whose SpO2max remained ≥89% and the dashed line represents subjects whose SpO2max fell to <89%. Tic = censored observation. Median survival for the entire cohort = 9.5 years.
Figure 3
Figure 3
Relationship between peripheral oxygen saturation (SpO2) at maximum exercise and resting percentage lung carbon monoxide transfer factor (Tlco%).
See this image and copyright information in PMC

References

    1. Bouros D, Wells AU, Nicholson AG, et al. Histopathologic subsets of fibrosing alveolitis in patients with systemic sclerosis and their relationship to outcome. Am J Respir Crit Care Med. 2002;165:1581–6. - PubMed
    1. Morgan C, Knight C, Lunt M, et al. Predictors of end stage lung disease in a cohort of patients with scleroderma. Ann Rheum Dis. 2003;62:146–50. - PMC - PubMed
    1. Simeon CP, Armadans L, Fonollosa V, et al. Mortality and prognostic factors in Spanish patients with systemic sclerosis. Rheumatology (Oxford) 2003;42:71–5. - PubMed
    1. Steen VD, Medsger TA., Jr Severe organ involvement in systemic sclerosis with diffuse scleroderma. Arthritis Rheum. 2000;43:2437–44. - PubMed
    1. Goh NS, Desai SR, Veeraraghavan S, et al. Interstitial lung disease in systemic sclerosis: a simple staging system. Am J Respir Crit Care Med. 2008;177:1248–54. - PubMed