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Comparison of Continuous and Discrete Measurements of Dyspnea During Exercise in Patients With COPD and Normal Subjects: Discussion

Comparison of Continuous and Discrete Measurements of Dyspnea During Exercise in Patients With COPD and Normal Subjects: DiscussionTable 3 presents summary data for the parameters of the linear regression analyses and absolute thresholds for the independent variables of power production, V02, and VE, respectively. There were no significant differences for the slopes and intercepts for the three independent variables and breathlessness ratings between the methods. Absolute thresholds could only be calculated with the continuous method.
Comparison Between Patients With COPD and Healthy Subjects
As expected, the peak exercise values for all three independent variables attained by the patients with COPD were significantly lower than that attained by the healthy subjects (Table 1). However, both the patient group and the healthy control subjects reported similar peak breathlessness ratings (approximately 6 on the Borg scale) [Table 2].
Patients with COPD exhibited significantly higher slopes compared to the healthy subjects for all three independent variables (Table 3). The x-intercepts were lower for patients with COPD for the independent variables of power production and V02, but were higher for VE compared with the healthy subjects (Table 3). canadian neighbor pharmacy com

The onset (absolute threshold) of breathlessness occurred significantly sooner (3.6 ± 0.9 min) for patients than for healthy subjects (5.5 ± 1.8 min). The absolute thresholds were lower in patients than in control subjects for power production and V02, but were similar for VE (Table 3). The Ekman fractions were similar between the two groups (Table 2).
The major findings of this study were as follows: (1) there was excellent test-retest reliability for all of the parameters of interest; (2) the continuous method yielded significantly more ratings during exercise compared with the discrete method, and enabled calculation of an absolute threshold and JNDs; (3) patients with COPD exhibited significantly higher slopes and lower x-intercepts for power production and V02 (as independent variables) with breathlessness (as the dependent variable) compared with healthy subjects; (4) patients with COPD had lower absolute thresholds for power production and V02 compared with healthy subjects; and (5) the Ekman fraction was similar between the two groups of subjects.
Table 3—Linear Regression Parameters and Absolute Thresholds Obtained for Patients With COPD and for Healthy Subjects During Exercise

Variables COPD Healthy
Discrete Method Continuous Method Discrete Method Continuous Method
Power production
Slope 0.11 ± 0.06т 0.10 ± 0.04т 0.06 ± 0.04 0.06 ± 0.03
Intercept 9.7 ± 40.8т 19.5 ± 13.5т 37.4 ± 27.6 44.7 ± 24.0
Absolute threshold 21.4 ± 13.0т 50.04 ± 26.9
V02
Slope 0.79 ± 0.48т 0.74 ± 0.36т 0.43 ± 0.34 0.37 ± 0.16
Intercept 5.5 ± 6.3т 7.7 ± 2.3т 8.5 ± 6.8 10.5 ± 4.0
Absolute threshold 8.2 ± 2.3т 11.7 ± 4.8
Ve
Slope 0.29 ± 0.17т 0.28 ± 0.14т 0.15 ± 0.16 0.12 ± 0.04
Intercept 13.8 ± 15.0т 19.3 ± 5.8т 10.9 ± 14.6 16.1 ± 9.2
Absolute threshold 21.1 ± 5.9 23.7 ± 8.8