Respiratory rate and thumps

[Debbyly <Debbyly@aol.com>]

I  would like to get opinions, especially from vets, about respiratory rate
and thumps.  I have a seven year old Arabian gelding who has had a moderate
amount of conditioning.  He has done 650 miles of endurance, mostly multidays.
He has a very high respiratory rate.  He seems to breathe shallow and starts
to breathe rapidly as soon as he starts any work.  His pulse rate is
comparable to other Arab endurance horses and his pulse recovery is good.  His
respiratory recovery takes longer than his pulse recovery.

He has thumped three times in training; all three times after going moderately
hard uphill for a fairly long distance.  He did not go hard enough or long
enough to be exhausted or to have lost significant amount of electrolytes
through sweating.

I think that possibly the thumping in this case is caused by hyperventilation.
Can thumps be caused by a respiratory alkalosis and a problem with the
distribution of calcium rather than an actual calcium deficiency?

Does anyone have any suffestions for training to improve respiratory rate and
depth of respiration?

Thank you,

Debby Lyon