TABLE 2

Parameters during the treadmill exercise tests

Blockage of peripheral opioid receptors (methylnaltrexone)Blockage of peripheral and central opioid receptors (naloxone)No blockage (normal saline)Mean difference between methylnaltrexone and placebo (95% CI)Overall p-value#p-value for treatment difference
Peak values
VO2 mL·kg−1·min−119.1±6.418.8±4.919.1±6.4−0.21 (−2.22–1.79)0.8630.822
VE L·min−148.4±13.850.4±14.650.4±19.3−2.04 (−7.07–2.99)0.7860.358
VCO2 L·min−11.2±0.61.2±0.71.1±0.70.01 (−0.10–0.12)0.5650.872
 Breathlessness intensity8.4±2.28.3±2.28.5±2.10.20 (−0.67–1.07)0.3390.631
 Breathlessness unpleasantness8.2±2.48.2±2.08.9±1.9−0.27 (−0.74–0.21)0.6300.251
 Leg fatigue8.4±2.07.5±2.98.4±2.30.13 (−0.54–0.81)0.3850.678
Endurance time, min16.0 (5.8)15.2±5.616.1±7.9−1.00 (−3.90–1.90)0.7910.472
Reason for stopping
 Breathlessness8119+
 Leg fatigue8§69+
Regression slopes
 Breathlessness intensity VO20.37±0.350.45±0.270.46±0.44−0.08 (−0.32–0.16)0.9190.498
 Breathlessness intensity VE0.05±0.340.13±0.340.06±0.63−0.02 (−0.19–0.16)0.8730.850
 Breathlessness unpleasantness VO20.35±0.350.41±0.300.51±0.44−0.14 (−0.37–0.08)0.5360.199
 Breathlessness unpleasantness VE0.05±0.330.13±0.390.07±0.63−0.03 (−0.22–0.15)0.8840.722
 Leg fatigue VO20.31±0.290.34±0.370.45±0.46−0.14 (−0.36–0.09)0.5730.218

Data are presented as mean±sd or n, unless otherwise stated. VO2: oxygen consumption; VE: minute ventilation; VCO2: carbon dioxide production. #: p-value for the test of the overall treatment effect from a random effects model for cross-over designs; : p-value for the test of difference between methylnaltrexone and placebo from a paired t-test; +: one participant selected both leg fatigue and breathlessness; §: one result missing.