Table 3. Peak physiological response to exercise for patients with GOLD grade COPD by cluster.
| Parameter | Cluster I (n = 18) | Cluster II (n = 45) | Cluster III (n = 22) | p-value | ||
|---|---|---|---|---|---|---|
| Cluster I versus II | Cluster I versus III | Cluster II versus III | ||||
| Vʹo2 peak, mL•kg-1•min-1 | 26.3 ± 6.1 [23.2–29.3] | 23.7 ± 5.5 [22.1–25.4] | 24.5 ± 4.6 [22.4–26.5] | 0.22 | 0.56 | 0.85 |
| Vʹe, L•min-1 | 73 ± 25 [61–86] | 72 ± 25 [64–80] | 77 ± 19 [68–85] | 0.98 | 0.89 | 0.73 |
| Vʹe/MVV | 80 ± 17 [72–89] | 73 ± 15 [68–78] | 87 ± 7 [83–90] | 0.15 | 0.33 | <0.001 |
| Vt, % predicted VC | 56 ± 11 [51–62] | 54 ± 9 [52–57] | 61 ± 9 [58–65] | 0.71 | 0.23 | 0.01 |
| Bƒ, breaths•min-1 | 39 ± 8 [35–43] | 37 ± 7 [35–40] | 40 ± 7 [38–44] | 0.74 | 0.71 | 0.19 |
| Vʹe/Vʹo2 | 36 ± 5 [34–38] | 38 ± 7 [36–40] | 42 ± 5 [40–44] | 0.34 | 0.005 | 0.05 |
| Vʹe/Vʹco2 | 33 ± 4 [31–35] | 35 ± 6 [34–37] | 34 ± 5 [32–37] | 0.16 | 0.58 | 0.72 |
| RER | 1.11 ± 0.13 [1.04–1.17] | 1.09 ± 0.16 [1.04–1.14] | 1.23 ± 0.11 [1.18–1.28] | 0.88 | 0.01 | <0.001 |
| Dyspnea peak Borg score | 5.7 ± 1.4 [5.1–6.5] | 6.4 ± 2.5 [5.6–7.1] | 6.8 ± 1.5 [6.1–7.4] | 0.57 | 0.30 | 0.75 |
| Leg fatigue peak Borg score | 4.8 ± 2.4 [3.6–5.9] | 5.6 ± 2.7 [4.8–6.5] | 5.3 ± 2.3 [4.3–6.3] | 0.44 | 0.79 | 0.86 |
| Limiting factor dyspnea/legs/both/other, % | 28/55/17/0 | 24/38/38/0 | 59/23/18/0 | 0.02 | ||
Data are mean ± SD [95% confidence interval], unless otherwise specified.
Reported p-values for the ordinal variables (distribution) refer to Chi-Squared test values from the contingency analysis.
V′o2: oxygen uptake; V′e: minute ventilation; MVV: maximal voluntary ventilation by multiplying FEV1 by 35; Vt: tidal volume; VC: vital capacity; Bf: breathing frequency; V′co2: carbon dioxide output; RER: respiratory exchange ratio.