February 28, 2009

Cough syncope or vaso-vagal response

Something I left out of today's earlier post is that two nights ago, I had a bought of coughing that made me pass out. This has happened only once before and I didn't fully pass out at the time - that is, I didn't lose consciousness completely, but my senses did shut down for a few seconds and I was left sitting upright and aware, but blind, deaf, and numb briefly, until sensation returned. This was, oh, about 18 months ago. Well, two nights ago, I had a fit that knocked me right out. Again, I was out for only a few seconds, I think, but I woke up slumped way over in my desk chair, about to head for the floor.

The weird thing is, my heart rate and breathing rate were calm and steady right after these episodes. Usually, a hard coughing fit raises my heart rate and breathing rate and it takes a few minutes to recover, but not with these two attacks that sent me over the edge.

So I've taken some time to research what's going on and believe it is called cough syncope, or vaso-vagal response. Essentially, the vessels in the neck press so hard on the vagal nerve that passes through the neck that it sends the wrong signals to the body, causing the heart to slow and blood vessels in the legs to open up. Blood pressure drops, the brain gets deprived of oxygen, and the cougher passes out. This is a simplified explanation, of course. There are other elements at work, too, including imbalances in blood pressure between the thoracic and intracranial cavities, causing intracranial blood flow to reverse or stop. I am fascinated by the thought that even a brief cough, if hard enough, can instantly put the whammy on one's entire cardiovascular system.

The good news is that there is no damage to the system and recovery is rapid. In fact, I felt just fine after I woke back up, but remained concerned about what this implies. What if this happens while I'm driving? That's my main concern.

As it happens, this is also a concern elsewhere. I found a study from England re: syncope in heavy goods vehicle (HGV) drivers. Syncope has been the underlying cause of many accidents, some fatal. What the study identified was that the vast majority of sufferers were overweight smokers, and that smoking cessation was successful in alleviating further bouts of syncope. Young asthmatics were also susceptible to syncope. All very intersting, but what caught my eye was that the department of vehicles there updated their regulations such that to be licensed as a HGV driver, you have to be free of episdes of syncope for ten years, similar to the requirements for epileptic seizures.

I have to admit that my very first thoughts after consciousness returned was not what passing out meant for my immediate health - I wasn't worried about that - but what it meant for my motorcycle riding. I have had some doozies of coughing fits while driving. For the most part, all I have to is ...well, not pass out. Keep the bike pointed straight ahead, which involves nothing more than sitting there and keeping the throttle steady. But going unconscious for even a few seconds could prove deadly.

I did fall asleep at the handlebars once, for a few seconds. It was during the first night of a group of us doing an IronButt ride from Long Beach, CA to the east coast. This one was a 2000-miles in 48 hours ride and we completed that requirement somewhere around Knoxville, TN I think. Anyway, about 20 hours in, I had a moment where I fell asleep, the bike wandered onto the shoulder, the vibrations woke me up and I saw the end of a guardrail coming right at me. I twitched my arm and corrected my course and managed to avoid the guardrail, but it was close - way, way too close for comfort. One of the other riders commented on the episode at our next gas stop and I shrugged it off, but made sure to get a jolt of caffeine into me. The rest of the ride was uneventful and I entered that land beyond tiredness where I could stay awake more easily than at that 20-hour window. Still, I nearly crashed that night. Could have died, conceivably. The fact that I was on two wheels is not important - it would have been just as bad in a four-wheeled vehicle.

So, the point is, what if a coughing fit in the future shuts my brain off for a few seconds while I'm on the bike? I am concerned this could result in an accident; a fatality. :(

We'll see how things go over the next couple months. I'd hate to think I have to remove myself from the driving pool because of a tendency toward syncope. I am otherwise an excellent driver and America needs more drivers like me on the road, not less!