If you are breathless, you have difficulty in breathing properly, for example because you have been running or because you are afraid or excited.
e.g. I was a little breathless and my heartbeat was bumpy and fast...
e.g. We were breathless with anticipation.
'I'll go in,' he said breathlessly.
Asthma causes wheezing and breathlessness.
You use breathless for emphasis when you are describing feelings of excitement or exciting situations.
e.g. Technology has advanced at a breathless pace.
e.g. ...the breathless excitement of early 1988, when hundreds and thousands of citizens gathered nightly for political meetings.
Nancy waited breathlessly for him to go on.