Effects of inhaled furosemide on CO2 ventilatory responsiveness in humans

We previously showed that inhaled furosemide improves experimentally induced dyspnea. In order to test the possibility that inhaled furosemide may alter the CO2 chemosensitivity and thereby reduce the dyspneic sensation, the effect of inhaled furosemide on CO2 chemosensitivity was evaluated with a double-blinded, randomized crossover design in 10 healthy subjects. The CO2 chemosensitivity was measured by the steady-state and rebreathing methods before and after the inhalation of placebo (normal saline) and furosemide aerosols (40 mg). In addition, subjects were asked to rate their sensation of respiratory discomfort using a visual analog scale (dyspneic VAS) during the measurement of CO2 chemosensitivity with the steady-state method. Our results showed that (1) inhaled furosemide does not affect the breathing patterns of resting breathing, (2) inhaled furosemide does not affect the slope and intercept of the CO2 response curve, regardless of whether the CO2 chemosensitivity is measured by the steady-state technique or rebreathing technique and (3) inhaled furosemide improves the dyspneic sensation produced during hypercapnic hyperpnea. These results suggest that the mechanism of the improvement of dyspnea by inhaling furosemide is not associated with the decrease in the ventilatory drive to CO2 (C) 2002 Elsevier Science Ltd. All rights reserved.