The Science Journal of the American Association for Respiratory Care

2002 OPEN FORUM Abstracts

THE REPRODUCIBILITY AND VARIABILITY OF RESPIRATORY GAS EXCHANGE MEASUREMENTS DURING EXERCISE IN THE PATIENTS.

Yong Yu Zhang, M.D., RPFT, Harbor-UCLA Research and Education Institute, Torrance, CA 90502

Exercise test results are frequently the standard used to evaluate the efficacy of the pharmacological intervention and rehabilitation. The reproducibility and variability of the respiratory gas exchange measurement during exercise was evaluated in this study for seeking the criteria. Thirteen patients with primary pulmonary hypertension (PPH), 30 patients with stable chronic heart failure (CHF) and 43 patients with renal failure (RF) underwent two progressive incremental exercise tests on cycle ergometer to a symptom-limited maximum between one and 26 days. The expired gas analysis was measured by using breath-by-breath. The Peak Yo2 was determined by the average of Yo2 at the last 30 second of the exercise and anaerobic threshold (AT) was evaluated by the V-slope method. The Peak Yo2 (m±SD), on test 1 and 2, respectively, was 1.098±0.436L/min and 1.138±0.450L/min (p<0.001). The Yo2 at AT (m±SD) was 0.742±0.267L/min and 0.738± 0.272L/min (p<0.001) respectively. The test-to-test reproducibility of Peak Yo2 (r=0.95, SEE=0.015L/min) and AT (r=0.92, SEE=0.012L/min) was high. The table showed the Peak Yo2 and AT (m± SD) on test 1 and 2 among PPH, CHF and RF groups. There was no significant difference in the Peak Yo2 and AT between test 1 and 2 among the three groups. There was high reproducible in Peak Yo2 (PPH: r=0.94, CHF: r=0.92 and RF: r=0.96) and AT (PPH: r=0.95, CHF: r=0.85 and RF: r=0.95). The inter-individual variability of Peak Yo2 and AT was 9.3± 7.6% and 10.2± 10.0%, respectively. These variations were not significantly correlated with Peak Yo2 or AT. This suggested that the variable exercise result was not affected by the extent of the exercise capacity. The variation of the Peak Yo2 was less than 24% in the 95% of the patients.

Conclusion: the measurement of respiratory gas exchange during exercise is an objective and reproducible method for evaluating the efficacy of the pharmacological intervention and rehabilitation. For evaluating an individual patient a variation in Peak Yo2 > 24% would represent a significant alteration.

 
Peak Yo2 ( L/min)
AT (L/min)
Test 1 Test 2 p Test 1 Test 2 p
PPH .70±.16 .76±.18 >.05 .53±.13 .53±.14 >.05
CHF 1.26±.44 1.31±.45 >.05 .84±.27 .86±.30 >.05
RF 1.11±.42 1.14±.44 >.05 .74±.26 .72±.24 >.05

OF-02-008

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