A new maximal bicycle test using a prediction algorithm developed from four large COPD studies

A new protocol for exercise testing in COPD; improved prediction algorithm for WMAX and validation of the endurance test in a placebo-controlled double bronchodilator study

Background:

Two new protocols have been developed for bicycle exercise testing in chronic obstructive pulmonary disease (COPD) with an individualized cardiopulmonary exercise test (ICPET) and subsequent customized endurance test (CET), which generate less interindividual spread in endurance time compared with the standard endurance test. Main objectives of this study were to improve the prediction algorithm for W_MAX for the ICPET and validate the CET by examining treatment effects on exercise performance of indacaterol/glycopyrronium (IND/GLY) compared with placebo.

Methods:

COPD patients, with forced expiratory volume in 1 s (FEV₁) 40–80% predicted, were recruited. Pooled baseline data from two previous studies (n = 38) were used for the development of an improved W_MAX prediction algorithm. Additional COPD patients (n = 14) were recruited and performed the ICPET, using the new prediction formula at visit 1. Prior to the CET at visits 2 and 3, they were randomized to a single dose of IND/GLY (110/50 µg) or placebo.

Results:

The improved multiple regression algorithm for W_MAX includes diffusing capacity for carbon monoxide (DLCO), FEV₁, sex, age and height and correlated to measured W_MAX (R² = 0.89 and slope = 0.89). Treatment with IND/GLY showed improvement in endurance time versus placebo, mean 113 s [95% confidence interval (CI): 6–220], p = 0.037, with more prominent effect in patients with FEV₁ < 70% predicted.

Conclusion:

The two new protocols for ICPET (including the new improved algorithm) and CET were retested with consistent results. In addition, the CET showed a significant and clinically relevant prolongation of endurance time for IND/GLY versus placebo in a small number of patients.

Reduced Variability of Endurance Time in New Protocols for Exercise Tests in COPD

Purpose

For exercise testing of COPD patients, a standard endurance test (ET) with constant workload is recommended. The test suffers from large inter-individual variability and need for large sample sizes in order to evaluate treatment effects.

Methods

A new protocol for ET in COPD was designed. In contrast to the standard ET, the new ET involved an increasing workload in order to reduce the standard deviation of endurance time. Two new ETs were compared with the standard ET. In Study A, the new ET started at 75% of the patient’s maximum workload (W_MAX) and increased stepwise with 3%/2 min until exhaustion. Study B started at 70% of W_MAX and increased linearly with 1%/min.

Results

In Study A, that included 15 patients, the standard deviation and range for endurance time and work capacity were narrower for the new versus the standard ET. However, the higher mean workload at end and the low mean work capacity relative to the standard ET indicated that the stepwise increase was too aggressive. In Study B, that included 18 patients, with a modified protocol, the averages for endurance time, workload at end and work capacity were similar for new and standard ET, while the standard deviations and ranges for endurance time and work capacity were kept more narrow in the new ET. The variances for endurance time were not equal between the standard ET and the two new ETs (p<0.05 for both according to Levene’s test).

Conclusion

The new ET reduced the number of patients with extreme endurance times (short and long) compared to the standard test. The new test showed a significant lower variance for endurance time, which potentially can lead to fewer patients needed in comparative studies. The overall best results were observed with a low linear increase during endurance.