Biofeedback

Just a few words about biofeedback in this entry. Many of these words will consist in my own speculations, so look on these parts as a sort of thinking aloud session.

I'm concerned with biofeedback for a couple of reasons--one being that the breathing exercises I've adopted as a means of (hopefully) counteracting high blood pressure are a form of biofeedback. At least they qualify in the opinion of this rank layman.

My question was just how biofeedback works. Not as in, how do you perform biofeedback--which I already know something about--but rather how to understand the cause and effect relation between the biofeedback activity and its influences on health. Specifically, how could breathing in a certain controlled way have an effect on blood pressure--which is connected with the circulatory system? Does breathing affect blood flow?

Well, yes it does. We have to breathe more heavily when we're exercising and our muscles are demanding more blood. But in this case it's more like muscle activity and the circulatory demands that creates is affecting breathing rather than breathing affecting the circulatory system. Does the converse make sense though, viz. that, if we could control our resting breathing rate, it could have an effect on the circulatory system? Broadly speaking, it seems to me that yes, it's possible it could have an effect. The questions are: what effect, how much control, and for how long do the effects last?

According to some things I've read, controlled breathing exercises performed for as little as 10 minutes, twice a day, can have an effect. On the surface, it sounds a little suspect, doesn't it? How could what you do during such a tiny percentage of--not to metnion your entire day, but only--your waking hours have much of an effect at all?

Well, rather than offering my own further speculations about this, here's a popular press article that presents one doctor's attempts to explain the "mechanism" by which this works:

Breathe deep to lower blood pressure, doc says
Experiment suggests slow breathing helps break down the salt we eat
updated 4:29 p.m. ET, Mon., July 31, 2006

WASHINGTON - Take a slow deep breath, then exhale just as slowly. Can you take fewer than 10 breaths a minute? Research suggests breathing that slowly for a few minutes a day is enough to help some people nudge down bad blood pressure.

Why would that brief interlude of calm really work? A scientist at the National Institutes of Health thinks how we breathe may hold a key to how the body regulates blood pressure — and that it has less to do with relaxation than with breaking down all that salt most of us eat.

Now Dr. David Anderson is trying to prove it, with the help of a special gadget that trains volunteers with hypertension to slow-breathe.

If he's right, the work could shed new light on the intersection between hypertension, stress and diet.

"If you sit there under-breathing all day and you have a high salt intake, your kidneys may be less effective at getting rid of that salt than if you're out hiking in the woods," said Anderson, who heads research into behavior and hypertension at the NIH's National Institute on Aging.

An estimated 65 million Americans have high blood pressure, putting them at increased risk of heart attacks, strokes, kidney damage, blindness and dementia. Many don't know it. Hypertension is often called the silent killer, because patients may notice no symptoms until it already has done serious damage.

Anyone can get high blood pressure, measured as a level of 140 over 90 or more. But being overweight and inactive, and eating too much salt — Americans eat nearly double the upper limit for good health — all increase the risk. Indeed, losing weight, physical activity and cutting sodium are the most effective lifestyle changes people can make to lower blood pressure. Still, most hypertension patients need medications, too.

Mysteries of high blood pressure

While they know risk factors, scientists don't fully understand the root causes of hypertension: What skews the body's usually finely tuned mechanisms for regulating the force of blood pounding against artery walls, until it can't compensate for some extra pounds on a couch potato? Understanding those mechanisms could point to better ways to prevent and treat hypertension.

Enter breathing.

Meditation, yoga and similar relaxation techniques that incorporate slow, deep breathing have long been thought to aid blood pressure, although research to prove an effect has been spotty.

Then in 2002, the Food and Drug Administration cleared the nonprescription sale of a medical device called RESPeRATE, to help lower blood pressure by pacing breathing. The Internet-sold device counts breaths by sensing chest or abdominal movement, and sounds gradually slowing chimes that signal when to inhale and exhale. Users follow the tone until their breathing slows from the usual 16 to 19 breaths a minute to 10 or fewer.

In clinical trials funded by maker InterCure Inc., people who used the slow-breathing device for 15 minutes a day for two months saw their blood pressure drop 10 to 15 points. It's not supposed to be a substitute for diet, exercise or medication, but an addition to standard treatment.

Why slow-breathing works "is still a bit of a black box," says Dr. William J. Elliott of Chicago's Rush University Medical Center, who headed some of that research and was surprised at the effect.

Slow, deep breathing does relax and dilate blood vessels temporarily, but that's not enough to explain a lasting drop in blood pressure, says NIH's Anderson.

Don't hold your breath

So, in a laboratory at Baltimore's Harbor Hospital, Anderson is using the machine to test his own theory: When under chronic stress, people tend to take shallow breaths and unconsciously hold them, what Anderson calls inhibitory breathing. Holding a breath diverts more blood to the brain to increase alertness — good if the boss is yelling — but it knocks off kilter the blood's chemical balance. More acidic blood in turn makes the kidneys less efficient at pumping out sodium.

In animals, Anderson's experiments have shown that inhibitory breathing delays salt excretion enough to raise blood pressure. Now he's testing if better breathing helps people reverse that effect.

"They may be changing their blood gases and the way their kidneys are regulating salt," he says.

If Anderson's right, it would offer another explanation for why hypertension is what he calls "a disease of civilization and a sedentary lifestyle."

Meanwhile, health authorities recommend that everyone take simple steps to lower blood pressure: by dropping a few pounds, taking a walk or getting physical activity, and eating less sodium — no more than 2,300 milligrams a day — and more fruits and vegetables.

This doctor's explanation of the "mechanism" doesn't offer a whole lot of promise for me since, so far as I can tell, my sodium intake is fairly low (for example I almost never use a salt shaker). Plus I'm pretty active: it's true that comparatively I'm a lot more sedentary now that at previous points in my life. But at the same time I'm probably more active than most of my peers.

But another source claims that "evidence . . . shows routinely performing certain breathing exercises can lower blood pressure by relaxing the muscles surrounding the small blood vessels and allowing the blood to flow more easily." This certainly looks like an alternate explanation of the "mechanism" by which these exercises influence blood pressure. So which is right?

I can't tell at this point whether one or other is more correct. I nonetheless plan to continue the breathing exercises for a time. It certainly can't hurt anything and is definitely relaxing.

In the future I may try another biofeedback technique, one that perhaps better typifies biofeedback and which involves holding a thermometer between two fingers and concentrating on causing the temperature to rise. The "mechanism" in this case seems more straightforward: to raise the temperature, blood flow has to be increased, and for blood flow to increase, the blood vessels have to be expanded (narrowed blood vessels being one of the factors causing blood pressure to rise, as was noted in my entry on seasonal blood pressure variation). So this technique is said to work in the same fashion as the breathing technique according to the alternate explanation offered above.

If I end up trying that I'll certainly be posting about it. Stay tuned . . .