Is your uncle a heart failure patient? Furosmide is medication as a diuretic to prevent congested heart failure. The medication should provide relief for shortness of breath, and the only association with shortness of breath would be that medication is not effective and there is some pulmonary edema and the heart is not pumping effectively.... the blood is backing up into the lungs and causing SOB (relative to the diuretic ineffective).
There could be other causes for shortness of breath, and the underlying cause should be found and treated especailly if it is related to the heart...The doctor should revisit the possible causes for the SOB.
Thanks for sharing, and if you have any further questions or comments you are welcome to respond. Take care,
Ken