Dietary nitrate supplementation opposes the elevated diaphragm blood flow in chronic heart failure during submaximal exercise

Chronic heart failure (CHF) results in a greater cost of breathing and necessitates an elevated diaphragm blood flow (BF). Dietary nitrate (NO₃‾) supplementation lowers the cost of exercise. We hypothesized that dietary NO₃‾ supplementation would attenuate the CHF-induced greater cost of breathing and thus the heightened diaphragm BF during exercise. CHF rats received either 5 days of NO₃‾-rich beetroot (BR) juice (CHF + BR, n = 10) or a placebo (CHF, n = 10). Respiratory muscle BFs (radiolabeled microspheres) were measured at rest and during submaximal exercise (20 m/min, 5% grade). Infarcted left ventricular area and normalized lung weight were not significantly different between groups. During submaximal exercise, diaphragm BF was markedly lower for CHF + BR than CHF (CHF + BR: 195 ± 28; CHF: 309 ± 71 mL/min/100 g, p = 0.04). The change in diaphragm BF from rest to exercise was less (p = 0.047) for CHF + BR than CHF. These findings demonstrate that dietary NO₃‾ supplementation reduces the elevated diaphragm BF during exercise in CHF rats thus providing additional support for this therapeutic intervention in CHF.