Volume 44 Number 4 2007
Pages 547 — 552

Abstract - Reproducibility of noninvasive cardiac output during arm exercise in spinal cord injury

Jonathan Myers, PhD;1-2* Heather Brown, PT;3 Susan Smith, PT;3 Inder Perkash, MD;3 B. Jenny Kiratli, PhD3

1Cardiology Division, Department of Veterans Affairs (VA) Palo Alto Health Care System, Palo Alto, CA; 2Cardiology Department, Stanford University, Palo Alto, CA; 3Spinal Cord Injury Center, VA Palo Alto Health Care System, Palo Alto, CA

Abstract — The carbon dioxide (CO2) rebreathing method is a noninvasive technique to estimate cardiac output during exercise, but few data are available on the validity and reliability of this measure in individuals with spinal cord injury (SCI). Sixteen male subjects with SCI (mean age 45 +/- 9, seven paraplegic and nine tetraplegic) underwent three submaximal steady state arm ergometer exercise tests. We estimated cardiac output using the exponential CO2 rebreathing technique at an individualized exercise intensity approximating 50% of peak oxygen uptake. Mean values for the cardiac output measurements were 13.0 +/- 2.4, 13.3 +/- 2.0, and 13.4 +/- 1.7 L/min; the difference among the trials was not significant (p = 0.54). The typical error was 1.80 +/- 0.85 L/min, the limits of agreement were 11.3 to 15.3 L/min, the coefficient of variation was 5.4% +/- 3.4%, and the intraclass correlation coefficient was 0.85 (95% confidence interval = 0.70-0.94). The test-to-test variation in estimated cardiac output during arm ergometry in individuals with SCI is similar to that observed in studies that used this technique in ambulatory persons. The 5% relative variation between tests suggests that the CO2 rebreathing technique for estimating cardiac output can be performed in SCI individuals with acceptable reproducibility.

Key words: activity, autonomic function, cardiac output, exercise testing, heart disease, heart rate, paraplegia, oxygen uptake, reproducibility, spinal cord injury.

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