If you're curious about this subject, there's a fairly new book [0] by James Nestor who argues for what you're talking about and quite a bit more. He did an exp

If you're curious about this subject, there's a fairly new book [0] by James Nestor who argues for what you're talking about and quite a bit more. He did an experiment where he had his nose sealed to force mouth breathing and found that it caused a number of nasty health consequences, including elevated heart rate. So it's likely that your anecdote is representative of an actual causal relationship between nasal breathing and heart rate. He did a promotional appearance [1] for the book with Joe Rogan that covers a bunch of the material, but the book is interesting beyond what gets discussed in the interview. [0] https://www.mrjamesnestor.com/breath https://www.mrjamesnestor.com/breath [1] https://www.youtube.com/watch?v=U5o9b2RVC2E https://www.youtube.com/watch?v=U5o9b2RVC2E