I am one of the patients that developed breathing symptoms when I was doing Sprint Triathlons (swim portion). I went to PCP. PCP ordered CT and saw some areas of concern and referred me to Pulmonology.
Pulmonology had me do a very extensive pulmonology exam. Nothing came back. Saw first pulmonologist and quite frankly not much advise. So went back to PCP and said try Atrovent. Atrovent actually made is worse. So my other doctors said try albuterol. This seem to help some but did not stop it.
Then PCP said try Advair. This seemed to really help but was an ongoing every day treatment that I was concerned with as contains a steroid powder.
So back to another appt. with pulmonolgist (different one). This pumonolgist said my lungs and physical condition were good. However was quite frankly the test they do cannot specifically always determine if you have asthma or other disease as you cannot duplicate the same triggers. I was given 3 different mists to breathe in that represent the normal triggers but does not duplicate what your actually triggers are.
This pulmonolgist said use albuterol prior to race and not the daily advair. So you can see I have been all over the treatment scene. I have not had a sprint triathlon yet to see if the albuterol will work. Personally, and it just my opinion not a medical diagnosis, is that I have a psychological response to the swimming portion as you are over your head in water and I freeze up. The reason I say this is that I can swim a mile in a lap pool without incident.
In the past I had no issues at sprint triathons during the swim. I got injured sliding off a dock into water tearing up the back of my legs and was the first time I had the breathing problem and could not finish swim. So I think that epiosode started the trigger and the swim triggered that reaction again
Thus you can see why the pulmonary test I was given could not duplicate the trigger. I think important for all with breathing problems to try and see what triggers them and the try to address them with the medical help of your medical providers.
I used to do triathlons and agree that open water swimming is far more psychologically stressful than the pool, add a negative association to that, like an injury and it makes perfect sense to me that the stress of open water swimming could trigger physical symptoms, such as shortness of breath in your case. In addition to inhalers, are you working on your mind? There are a lot of resources these days on sports psychology, mindfulness, etc. It may be helpful to add a daily practice, if you aren’t already, that you can call upon when you hit the open water.