For the last year or so, when I cough, I get a pleasant tingling in my fingers and toes, a slight light headedness and a little loss of eye focus.  You told me the name for this once before.  I would like more detail about cause and possible danger.

Yes — the term I would have used is cough presyncope, or, if the person actually loses consciousness, cough syncope. What you're describing sounds like the presyncope end of the same phenomenon: the cough briefly produces enough physiological disturbance that you get some of the sensations that precede a faint, but you don't actually faint.

The interesting part is that your tingling fingers and toes, light-headedness, and temporary loss of visual focus all fit rather neatly with the physiology.

When you cough forcefully, you're essentially doing a very abrupt Valsalva maneuver. Pressure inside the chest rises dramatically. That temporarily impedes blood returning to the heart, so cardiac output can fall and blood pressure can drop. At the same time, pressure is transmitted toward the head and can transiently raise intracranial pressure. The net result can be a brief reduction in cerebral perfusion.

There's a second mechanism that may explain the tingling particularly well. A vigorous cough can be followed by a few rapid/deep breaths, producing a temporary fall in blood CO₂. Low CO₂ causes cerebral blood vessels to constrict, reducing cerebral blood flow, and it also produces the classic symptoms of tingling or numbness in the hands and feet, light-headedness, and difficulty focusing.

So the sequence can be something like:

cough → very high chest pressure → temporarily reduced venous return/cardiac output → transiently reduced brain perfusion → light-headedness/visual disturbance

with coughing/overbreathing → lower CO₂ → tingling and additional cerebral vasoconstriction.

That's actually a rather satisfying explanation for your particular combination of symptoms.
How dangerous is it?

The mechanism itself isn't necessarily dangerous. Cough presyncope can occur in otherwise healthy people and can be nothing more than an exaggerated response to coughing. The important distinction is between "the cough makes me briefly feel faint" and "I'm actually fainting because I cough."

The latter deserves investigation because cough syncope can occasionally be associated with cardiac rhythm abnormalities, structural heart disease, pulmonary disease, autonomic problems, or neurological disease. Investigations commonly include an ECG, sometimes an echocardiogram and ambulatory cardiac monitoring, with neurological investigation when there are significant neurological symptoms.

In your case, I'd put particular emphasis on the fact that this has been happening regularly for a year. It doesn't sound like an emergency from the description you've given — you're experiencing a momentary, reproducible sensation rather than actually collapsing — but I wouldn't simply write it off as an amusing quirk of coughing either.

There is one very practical danger: falling. If you ever get the sensation while standing, particularly near stairs, a bathroom, a curb, or anywhere that a sudden loss of balance would be consequential, stop and hold onto something. Actual cough syncope can produce abrupt loss of consciousness and muscle tone.

And I'd want medical attention more promptly if the pattern changes — particularly if you actually faint, develop chest pain or palpitations, become markedly short of breath, have a new severe headache, persistent visual disturbance, weakness/numbness that doesn't disappear immediately, or the episode starts occurring without coughing. Neurological symptoms accompanying cough syncope are specifically considered a reason for further investigation.

One other thing I find reassuring in your description is the consistency: cough → pleasant tingling → slight light-headedness → slight loss of focus → presumably immediate return to normal. That is much more characteristic of a transient physiological response than of, say, a seizure.

But there's an amusing irony here: the fact that the tingling is pleasant tells us absolutely nothing about whether the mechanism is benign. The brain is remarkably willing to put a pleasant sensory wrapper around "blood flow just dropped a little."

That combination makes your 100/40 blood pressure a lot less mysterious.

A beta blocker, a calcium channel blocker, and a potassium-sparing diuretic can all contribute to lower blood pressure, though they do so by different mechanisms. The fact that you're sitting there with a pulse around 70 and feeling fine most of the time suggests the medications are not overwhelming your circulation, but they may leave you with less physiological reserve when something temporarily perturbs it—such as a forceful cough.

Imagine your brain's blood flow as having a comfortable margin above the point where symptoms appear. When you're young, that margin is often quite large. At 83, with treated cardiovascular disease and blood pressure around 100/40, the margin may be smaller. Then along comes a vigorous cough that briefly:

    Raises intrathoracic pressure,

    Reduces venous return to the heart,

    Lowers cardiac output for a moment,

    Alters CO₂ levels,

and suddenly you're just over the threshold where you notice tingling, visual changes, and lightheadedness.

The fact that you don't experience those symptoms at other times is actually informative. If your medications were simply driving your blood pressure too low, I'd expect complaints when standing up, getting out of bed, or after sitting for a long time. Instead, the cough appears to be the trigger that pushes an otherwise adequate system into producing noticeable sensations.

Given your medication list and blood pressure, I would definitely mention both to the physician managing your heart medications. Not because this sounds alarming, but because they may decide that 100/40 is acceptable for you—or they may decide it's a little lower than necessary. The decision depends on why you're taking the medications, your heart function, kidney function, and other factors they know and I don't.

One thing that caught my eye from our earlier conversations is that you've mentioned pulse oximeter readings of 96–98% and no ankle swelling, and you've been functioning normally apart from balance issues and nocturia. That's a picture of someone whose circulation is at least adequate enough for daily life. It doesn't sound like you're describing episodes of heart failure, severe arrhythmia, or ongoing cerebral hypoperfusion.

So my working hypothesis remains:
vigorous cough + low-ish baseline blood pressure + age-related reduced reserve + asthma-related cough mechanics = brief cough presyncope symptoms.

Not a diagnosis, just the explanation that best fits all the pieces you've given me.

If you happen to know, I'd be interested in whether that 40 diastolic is a recent development or whether you've been running numbers in that neighborhood for years. That would help distinguish between a long-standing trait and something that changed around the same time the cough sensations began.

Normally it's more like 60 when I measure it here, that is what they got in the clinic.  By the way, that was without my morning coffee.  

Ah, that's an important distinction. If you're normally around 100–120/60 and the clinic happened to get 100/40, I wouldn't regard the 40 as your established baseline. A single unusually low diastolic reading is much less interesting than a repeated pattern.

And the no coffee part is worth noting, although I wouldn't put too much weight on it. Caffeine can raise blood pressure modestly in some people, particularly if you're a regular coffee drinker. So measuring before your usual morning coffee could plausibly give you a somewhat lower reading.

There is also a mundane possibility: home blood-pressure measurements are surprisingly variable, particularly the diastolic number. Cuff position, arm position, talking, recent activity, and even how long you've been sitting can move the result around.

In fact, I'd be more interested in your usual home readings than that one 100/40 reading. If you're generally something like 105–115/55–65 and feel perfectly well except for the cough episodes, that's a considerably different situation from repeatedly getting 100/40.

And your pulse oximeter reading of 96% with a pulse in the 60s–70s is reassuring in the immediate sense. It doesn't, however, tell us what happens during the actual cough.

The one thing I'd still do is tell your doctor about the cough phenomenon. "Every time I cough I briefly get bilateral tingling, slight lightheadedness, and transient visual focusing difficulty" is sufficiently specific that they can decide whether it warrants anything beyond recognizing it as cough presyncope.

And since you're on three cardiovascular drugs, I wouldn't independently change any of them on the basis of these readings. If the blood pressure really does start spending a lot of time around 100/40, that's a reason for the prescriber to look at the whole regimen.

Seems to me as long as I'm not impaired the low number is a benefit.

Broadly, yes—with an important qualification. If your usual blood pressure is relatively low and you feel completely well, there's no general rule that says you need to raise it just because the number looks low.

The objective isn't to achieve some magic blood-pressure number; it's to get enough pressure to perfuse the brain, heart, kidneys, etc., without unnecessarily exposing you to higher pressure. Lower pressure is generally associated with less strain on the arterial system.

Where I would put the asterisk is that symptoms are not the only criterion. Persistent excessive lowering can sometimes affect kidney function or other organs before you notice anything, and the diastolic pressure matters because coronary arteries receive much of their blood flow during diastole. That's why your physician would care about the pattern, not just whether you feel dizzy.

But a single 100/40 reading in an otherwise asymptomatic person who normally runs around 100–120/60 is not something I'd regard as inherently dangerous.

And in your particular case, there's a useful distinction:

Low pressure that you tolerate normally: probably perfectly acceptable.

Low pressure + a forceful cough: potentially enough to produce your brief presyncopal symptoms.

So I wouldn't try to "fix" the 100/40 merely because of the cough sensations. I'd instead have the clinician who manages the three cardiovascular drugs know about the cough presyncope and the occasional low reading. They can decide whether your current pressure is an intended therapeutic tradeoff.

Your observation that "as long as I'm not impaired, why raise it?" is actually a pretty sensible way to think about blood pressure—provided the kidneys, heart and other organs are happy with the arrangement.