Sudden shortnes of breath @ 70

Question
I was on a recent dive trip and on my last dive of the trip I experienced something strange and scary. This was the sixth dive of the week, I was diving nitrox all week without issue. most dives were between 40 and 80 feet. On my last dive of the week in the afternoon, I descended to 75 feet with no issues, I was taking some pictures of a 7/11 crab and spent about 3 min getting the right shot, when I turned to join the rest of the divers I noticed stars in front of my eyes and felt out of breath and very panicked. I started to lose it a bit but regained control somewhat of my breathing, I think I may have been very close to hyper ventilating. I slowly started back to the boat mindful of the rate of my ascent. It was suggested that I may have been short breathing causing a lack of oxygen in my bloodstream, I don't recall doing this. Is there anything else that could have caused this issue?

Dave

Answer
David,

Excellent job on staying calm and getting control of your breathing!  Bad job on not staying with a buddy during your dive.

Before I even finished reading your question, the first thing that came to mind was skip breathing (that's the term I learned for what you call short breathing).  Consciously or unconsciously, underwater photographers often do this.  While concentrating on getting the "perfect" shot, one can forget to breath continuously, and even hold your breath to keep bubbles from affecting the shot.

Another cause may have been not exhaling forcefully enough to clear the second stage of built up CO2.  This would be a similar situation to skip breathing.

While there is the issue of residual oxygen build up with multiple Nitrox dives, I would think the small number of dives made over the course of a week would discount this as a cause.  You were certainly not diving deep enough to have any kind of depth-related oxygen toxicity (and your described symptoms do not match) on either of the standard Nitrox mixes.

In summary, the apparent cause of your symptoms would be skip (short) breathing.  To avoid this in the future, remember the basic rule of breathing continuously while on SCUBA.

Thanks for your inquiry,

Henry Babcock
AllExperts SCUBA Expert