Slashdot Mirror
Living Without a Pulse
SteamyMobile writes "Can you live without a pulse? Yes, now you can. The reason why we have a pulse is because it's hard for evolution to result in turbines or continuously spinning things. The next generation of artificial hearts may have no pulse. They also have no bearings, so they should last much longer than previous attempts. In fact, engineers don't give a predicted lifespan on these models. How would your life be different without a pulse?"
from the article:
"LVADs are not designed to replace the heart but are implanted alongside it under the rib cage."
Therefore your heart is still there beating. This is just a supplement to it.
While ths scenario is pretty funny...most CPR certified professionals check for breathing, not a pulse. And if they didn't, then they shouldn't be certified. Yes, they also check for a pulse, but not before they check for breathing. Depending on the body fat on a person, the pulse isn't always easily detected.
"Time is long and life is short, so begin to live while you still can." -EV
I think this has happened before (someone living without a pulse). There was some old man in Kentucky in the last year or so who was hooked up to an external blood pumping device. He was on the news because he lived for a few months, setting a record for the person who lived the longest without a heart. He was asked by a television reporter what it was like to not have a heart, and the guy said not having a pulse was the strangest thing he'd ever experienced. He said it was really really eerily quiet. Gross.
World's tallest building rises in the desert
... at the Doctors office without being able to take our pulse while they stall until there is a doctor available to see us?
You've never used the UK's National Health Service.
The nurses don't take your pulse while you wait for a doctor in our hospitals - after 4 hours of pulse taking, they would probably not have learnt a great deal more.
And that's the emergancy patients.
"Those who cast the votes decide nothing; those who count the votes decide everything." (attrib. Joseph Stalin)
most CPR certified professionals check for breathing, not a pulse.
Yup, ABC, Airway, Breathing, Circulation. One of the fist things they teach in First Aid class. You can have a hearbeat while not breathing, but you can't breathe without a heartbeat.
You are correct, what everyone is being trained to check for now (at least with the Red Cross CPR training I just took) is "signs of life", not a pulse. This includes breathing, possibly pulse, etc. This is probably due to the difficulty in checking for a pulse in obese people and those with a faint pulse.
Finkployd
Actually, current pacemakers can only be set to one speed, so people who have these devices already have the limitation of non-variable heartrate. While this is a setback for the pacemaker-using crowd, almost all agree that having a non-variable heart rate is better than having no heart rate at all.
Similarly, I recall seeing a documentary on this, which mentioned that the pulse may in fact be necessary to control and stimulate the growth of vessel walls. Anyone know if the opinion on this has changed?
Not a reliable indication. You'd be amazed how much peripheral circulation shuts down in patients in shock as the body attempts to maintain blood pressure in the core. At best, refill at the lobe will give you a general idea that the patient may be perfusing well, but lack of refill is certainly not an indication of pulselessness. Circulation out at the skin layer is one of the first things the body cuts back on in an attempt to combat shock.
(IMHO - however I speak from many years of experience as a Paramedic.)
There would still be a need for the valves in the veins for stopping backflow. The venous pressure is very low. If i remember right (my last physiology course was a long time ago), most of the return flow is added by movement (muscles squeezing the veins pushing blood through the valves and the breathing cycle which causes the large veins to expand and collapse which pulls blood back to the thorax and towards the heart.
This is a very simplistic explanation as I remember it, and I haven't had much coffee yet so the old gray matter is not ticking at full speed yet.
the procedure is actually to assess them first... something along the line of shaking them and asking "Annie! Annie! Are you OK?"
If they answer "yes," you're done.
I realize you were only joking, but the entire clinical picture needs to be taken into account.
My favorite EMS call is the patient with a minor head injury who is rushed in with a "blown pupil." When you go see the patient, they're awake and alert, not vomiting, not somnolent, etc. It's usually someone who's new, and doesn't understand the pathophysiology behind Uncal Herniation and 3rd nerve compression.
Back to the topic at hand... I wonder if the lack (or blunting) of the systolic peak and diastolic trough in the blood pressure would lead to any physiologic problems? According to the article, the device is actually a Left Ventricular Assist Device (the ole' intra-aortic balloon pump is the classic example of such a device). It steals blood from the left ventricle and steadily pumps it into the aorta... but I wonder if it has any effect on the coronary arteries?
The coronary arteries mainly fill during diastole, when the aortic valve closes and blood floods the coronary sinuses on the aortic side of said valve... since this device essentially "steals" blood from the left ventricle and injects it somewhere downstream, I wonder if the coronaries get the same filling? (I suppose it's a question of where you place the downstream catheter.) It might not make a difference if you have clean coronaries, but if you've got a Left-main stenosis, it could be bad to drop that filling pressure...
In a perfect hydraulic system, it wouldn't matter, since pressure injected in one location would increase pressure in all locations... but arteries have compliance, and they can flex.
Interesting device... it'd be nice to know some more details.
Even if a man chops off your hand with a sword, you still have two nice, sharp bones to stick in his eyes.
When you're unconscious, you still breathe.
Mod point free since 2001
If you look at the internal surface of a major vein you will notice that it it is uneven. It does not allow blood to flow back and this works properly only with a pulse flow. It will not work properly with a constant flow.
But a flowback prevention device is only needed because of the pulsed flow. Without flowback prevention, blood could never reach the head as it would keep running back down the arteries as the heart cycled. As long as a continuous flow is of sufficient pressure, this problem is eliminated, and the need for flowback prevention is removed.
Apparently the reason they now teach this method is because it's more reliable for those who haven't had a great deal of training - i.e. most First Aiders.
Obviously the pulse check is only used after you've already checked for breathing.
the reason many times is more ominous than what you mention. Say you're operating on a patient who has received previous radiation therapy. Sometimes the vessels will be just like butter. you can't place a stitch without it tearing. Meanwhile you're trying to pump in blood faster than they are bleeding out.
say an artery is transected and the operating field fills with blood. They are bleeding out faster than 2 suckers can handle and you can't see to stop the bleed.
say there is a arterial-venous malformation making a venous lake. The entire operating field is all blood vessels and there is no where to place a stitch that will stop the bleeding and won't cause more...
Only arteries have a pulse. The blood flow is as follows: heart -> arteries -> capillaries -> veins -> heart. By the time the blood gets thru the capillaries to the veins the blood pressure is vastly reduced and the pulsatile flow generated by the heart is not felt in the veins. Hence veins do not have a pulse. The valves in the veins have nothing to do with the pulsatile flow of the heart and hence a constant flow heart will not affect the functioning of the veins in any way. Venous problems like varicose veins, cirrose like vena portalis deformities are not related to how the heart pumps.
They expand on the acronym in a couple of scenarios.
ATLS (Advanced Trauma Life Support, a program by the American College of Surgeons) expands that to ABCDE: Airway, Breathing, Circulation, Deficits in neurologic function, and Exposure (remove/cut off all clothing... easier to find injuries and wounds that way).
Also, the "C" in the old "ABC" acronym is also supposed to stand for Cerebral protection in addition to circulation. I've also heard CPR termed "cerebral pulmonary resuscitation." That's probably a fair substitution, since your main goal in CPR is to protect the brain by creating a low-flow rather than a zero-flow state (contrary to what some folks think, CPR doesn't restart the heart from a V-fib/V-tach arrest... generally only electricity can do that).
Once your brain's dead, you're dead... even if your heart, lungs, kidneys, etc are all working normally. Those folks become organ donors, or should...
Let me put in a plug here... PLEASE CONSIDER DONATING YOUR ORGANS. Please... talk to your family about it, get it on your driver's license or living will. Lots of people need organs, and if you don't need yours anymore (and you have no deep religious/philosophical objection), why not donate them? Just a thought...
Even if a man chops off your hand with a sword, you still have two nice, sharp bones to stick in his eyes.
Variable speed is unecessary. Not sure if you were saying that is the way and how it works when you replied, but you don't need to vary the speed at all. The speed of the pump is set to have the ability to deliver the maximum required flow and pressure (pump sizing exercise) and then the amount of flow is varied by the muslces that contract on the artieries. In other words, the body continues ot regulate the flow/need of the blood and the pump just supplies it. THat is the way a centrifigual pump works, the impeller goes the same speed all the time and has the potential to deliver the maximum flow, but does not deliver the maximum flow until the discharge valve (in this case the muscles the constrict the arteries) are open 100%. Simply put in the pump so that the blood flow capacity is there and then the bodies natural mechanisms that already directy the flow of blood would do the rest. Variable speed is near impossible (probably completely impossible) due to the control/decisions of speed/input needs etc that we don't know how to read from the human body.
Cardiac bypass, used commonly during a CABG (coronoary artery bypass graft) operation, involves an external pump, pumping blood around the body after gas exchange has occured outside the body (ie. carbon dioxide removed and oxygen added, plus some other bits'n'pieces). (Bypass is required during CABG because the operations are commonly performed with the heart 'stopped' for 30-60 minutes while the surgeon attaches the grafts. 'Off-pump' CABGs are sometimes performed where the surgeon operates on the beating heart, avoiding the need for bypass).
Anyway - the bypass pump commonly delivers continuous (ie. non-pulsatile) flow, even though most modern machines have the capability to deliver pulsatile flow. Research is somewhat inconclusive as to whether there is any disadvantage in delivering non-pulsatile flow in this setting, although in most situations where someone has poor kidney function the machine will be set to deliver a pseudo-pulsatile flow, in an attempt to mimic the normal physiology.
The rationale here is that some (inconclusive) research suggests that the kidney's may be damaged by non-pulsatile flow. As the kidney's receive such a large proportion of cardiac output (25% !), it;s wouldn't be surprising.
I would be surprised if a non-pulsatile flow didn't throw up some unexpected problem - but also, my time as an anaesthetist (or anaesthesiologist in the US) continually demonstrates the impressive adaptability of the human body!
(and regardless, being on bypass does all sorts of unpleasant things to the body, independent of the presence/absence of pulsatile pressures.)
From the ventracor website:
"The VentrAssist(TM) LVAS has the potential to become as commonplace and reliable as pacemakers."
That seems to be a pretty bold statement considering that implanting one of these is a pretty invasive procedure and that the implant leaves you with wires penetrating the skin leaving a path for infection. This technology combined with the AbioCor (did I get that right) transdermal battery would be pretty cool.
I also do not see any valve in the design, so if the battery were to fail, the heart would not be able to pump.
There are pacemaker / defibrillator (CRT) devices on the market today that offer, long term, effective treatment for several types of heart failure (see the new england journal of medicine), they require a minimally invasive procedure, are completely implanted - no external wires, and the heart maintains some pumping ability in the event of a device failure. Also, the patient regains a quality of life and independence that you could not have with worrying about keeping your batteries charged and wires protruding from your abdomen.
The design of the device is novel and very interesting and , without a doubt, will benefit a small population of patients. I am waiting, however, for the next generations of treatments that target the tissue and biology repsonsible for the pathology. Gene therapy, stem cells, etc. offer greater hope and better long term outcomes for patients. Pumps are only for sustaining until something better can be found.
The device you're thinking of is an AED, Automated External Defibrillator. Basically what it does is read the patient's EKG, compare it against a list of known arrhythmias, and decide whether it should deliver a jolt. I was skeptical about them at first -- being an EMT-D, i.e. an EMT with additional training to use manual defibs (and years of ER experience, not just a four-week class) I had been taught that human judgement was the gold standard -- but the fact is they've saved a lot of lives, and their judgement is often better than that of stressed-out emergency personnel.
The correlation between ignorance of statistics and using "correlation is not causation" as an argument is close to 1.
But that is not a peer reviewed article either. It was written by a geology graduate student from UCSB.
Biology in the Subjunctive Mood:
A Response to Nicholas Matzke
By William A. Dembski
On October 11, 2003, the Talk Reason website posted an article by Nicholas Matzke titled "Evolution in (Brownian) Space: A Model for the Origin of the Bacterial Flagellum" (http://www.talkreason.org/articles/flagellum.cfm) . Talk Reason advertises itself as a website that "presents a collection of articles which aim to defend genuine science from numerous attempts by the new crop of creationists to replace it with theistic pseudo-science under various disguises and names." The most obvious target here is intelligent design. Indeed, Matzke's article attempts to rebut one of the main challenges that intelligent design has raised against Darwinian evolution, namely, how to explain the emergence of irreducibly complex biochemical machines like the bacterial flagellum.
Before reviewing and critiquing Matzke's article, I want to offer a few remarks about Matzke himself and my past interactions with him. Matzke's day job is as a geography graduate student at the University of California at Santa Barbara. Nonetheless, he is also one of the most active participants in online discussions concerning evolution and intelligent design (the sheer volume of text that he is able to generate is remarkable). In such forums, he tends to go by various pseudonyms. His main one until a year or two ago, when he blew his cover by publicly attacking Jonathan Wells at UCSD, was "Nic Tamzek." On the ARN bulletin board (www.arn.org) he has used "Niiicholas." On the ISCID bulletin board (www.iscid.org), through which I know him best, he goes by "Yersinia." He uses still other pseudonyms in other forums (as in the Talk Origins newsgroup).
Matzke's interest in intelligent design and evolution goes back at least to his undergraduate days at Valparaiso University, a Christian school in Indiana. As far back as 1996 (and perhaps earlier) he was posting online in the American Scientific Affiliation's evolution discussion forum. All these discussions are archived, and it appears that at the time Matzke was still keeping his options open about where he would come down in the debate over biological origins. In the last four years or so, however, his views have ossified so that his defense of Darwinian evolution and his attacks on intelligent design have become unswerving if not predictable.
I learned of Matzke's latest article through a New Zealand biochemist named Robert Mann. Mann maintains an Internet mailing list critical of intelligent design. Like many, Mann worries that intelligent design, in claiming to show that biological systems exhibit signs of intelligence that lie beyond the reach of the Darwinian mechanism, is committing an argument from ignorance. Thus, in his most recent email to me, he wrote, "Admittedly, the submicroscopic details of the flagellum, or a fortiori the chloroplast, remain unexplained by neo-Darwinian theory. The logical gist of IDT is a 'designer of the gaps' inference from lack (pro tem) of scientific knowledge. This is open to getting filled in, as a neophyte has recently suggested at http://talkreason.org/articles/flagellum.cfm." The neophyte Mann cites is Nicholas Matzke.
So has Matzke in fact filled in the gaps that intelligent design claims are insurmountable for the Darwinian selection mechanism? In particular, has he provided a detailed, testable, step-by-step Darwinian model for the origin of the bacterial flagellum? Matzke claims that he has. Thus we read at the beginning of his article: "This article will propose a detailed model for the evolutionary origin of the bacterial flagellum." And at the end of his article we read: "Finally, in light of the organized complexity and apparent 'design' of the flagellum, the very fact that a step-by-step Darwinian model can be constructed that is plausible and testable significantly weakens the suggestion that extraordinary explanations [read intelligent design] might be required."
In fact, such claims by Matzke about wha
You guys are not looking hard enough. Artificial heart was surgeon's last hope of saving Julie's Life
I paid the going retail price for a Windows screen reader and got a free Unix computer!
Well, this is a well-deserved flame.
Darwin doesn't even mention mousetraps in the chapter from which the individual whose propaganda you are parroting lifted this passage.
It's pretty clear that calebb is just another not-so-honest creationist who has taken (probably nth-hand) out-of-context a passage from a book he's possibly never even seen. Even if he has seen it, he certainly hasn't read it for comprehension.
Now, let's look at the rest of that passage, shall we? (emphasis added)
If it could be demonstrated that any complex organ existed, which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down. But I can find out no such case. No doubt many organs exist of which we do not know the transitional grades, more especially if we look to much-isolated species, round which, according to my theory, there has been much extinction. Or again, if we look to an organ common to all the members of a large class, for in this latter case the organ must have been first formed at an extremely remote period, since which all the many members of the class have been developed; and in order to discover the early transitional grades through which the organ has passed, we should have to look to very ancient ancestral forms, long since become extinct.
We should be extremely cautious in concluding that an organ could not have been formed by transitional gradations of some kind. Numerous cases could be given amongst the lower animals of the same organ performing at the same time wholly distinct functions; thus the alimentary canal respires, digests, and excretes in the larva of the dragon-fly and in the fish Cobites. In the Hydra, the animal may be turned inside out, and the exterior surface will then digest and the stomach respire
It's absolutely appalling to see such worthless rubbish like calebb's post here modded up to a score greater than -1.
BTW, "On the Origin of Species..." can be found in its entirety on-line at http://www.talkorigins.org/faqs/origin.html.
You can have a heartbeat while not breathing, but you can't breathe without a heartbeat.
Yes you can have breathing without a pulse. It is called agonal respiration.
Just because it CAN be done, doesn't mean it should!
What? Almost all current generation pacemakers are rate responsive - they have a minimum rate, max rate, and rate curves, and they use various sensors (usually activity (movement) from what I understand, but also breathing rate) to change from one setpoint to another.
I've been with my Dad when they check the programming of the resting and exercise rates on his pacemaker, and set them, and the transition point - It's all done with an inductive coil that is places over the main module of the pacemaker - they can even check the settings by phone
-- 73 de KG2V For the Children - RKBA! "You are what you do when it counts" - the Masso
The page linked to Intelligent Design actually goes on to refute the idea that the Bombardier Beelte is an example of inteligent design. It is quite plausible that the beetle developed it's defense mechanism through natural selection.
"What the American public doesn't know is what makes them the American public." -Ray Zalinsky (Tommy Boy)
or Adenocard (trade name in the US).
It can induce asystole for a few seconds... I've never seen it last for 30 seconds.
Patient reports of the adenosine experience vary greatly. Some don't mind it... others would rather have you cut their heart out than get adenosine. I'll never forget a biker guy I saw a couple of times for recurrent SVT (SuperVentricular Tachycardia). He hated adenosine (though it always worked); said it made him feel like he was dying. He was a great big muscular tattoo-covered man, and would cry like a little baby when you brought out the drug, literally weeping in terror.
To see a grown man reduced to that... my heart really went out to the poor guy.
Even if a man chops off your hand with a sword, you still have two nice, sharp bones to stick in his eyes.
I'll bite: I'm not golfing because I don't have the patience. IAAS (I am a Surgeon) and it would not be that difficult to measure a continuous flow generated pressure instead of a pulsed pressure. Plus you wouldn't have to teach us about turbines and such. For example, currently a patient in the ICU may have their blood pressure measured with an indwelling arterial line rather than a transduced cuff. We follow Mean Arterial Pressure (MAP) in this setting. Here's a quick definition: http://www.globalrph.com/map.htm (It was easier to google than find a textbook but this is short and sweet)- "Equation: MAP = [(2 x diastolic)+systolic] / 3 Diastole counts twice as much as systole because 2/3 of the cardiac cycle is spent in diastole. An MAP of about 60 is necessary to perfuse coronary arteries, brain, kidneys. Usual range: 70-110." We could still measure the equivalent of a MAP with a continuous pump. Some of the bioengineers who commented above probably know better, but whatever the range of pressure in the system from continuous pumping (whether it's always the same or if there's a smaller variation than the normal systolic/diastolic) it could still be accounted for and easily monitored and used to guide therapy. Probably the bigger problems are those already mentioned: baroreceptors that will now be in a new range, changes in coagulation, and destruction of blood borne cellular elements.
in some countries... I believe China still harvests organs from prisoners.
In the US there's so much oversight that I can't see it even being possible. Many transplants aren't even done in-house... the organ gets flown to where it needs to go (I've flown on a couple of those... you get to jump to the front of the line on the taxiway, even if there are 30 planes waiting to take off).
Seriously, there are so many ethical questions, paperwork to be filled out, different physicians involved... declaring someone brain-dead and pulling the plug is a big deal, even more so if it's an equivocal case; it requires multiple physicians to sign off, consultation with the family (and their physician), appropriate consultations and diagnostic testing, and often a review from the hospital ethics committee. Hell, half of the doctors that sit on those committees don't even like one another... they just tolerate each other. There's NO WAY they'd all agree, in some nepotistic star-chamber fashion, to something as evil as wrongfully terminating someone's life and harvesting their organs. No way.
I can't see that caper ever being pulled off and not coming to light.
Even if a man chops off your hand with a sword, you still have two nice, sharp bones to stick in his eyes.
No. Your dentist is actually doing the right thing.
Your dad has a valve problem in his heart, and dental work does cause a transient bacteremia (bacteria being released into the bloodstream). Most of the time your immune system will clear out those bacteria, no problem... most of the time.
If you have a damaged heart valve, those bacteria can infect the valve, leading to a condition called Bacterial Endocarditis. The bacteria grow on the valve, and can destroy that valve, as well as throwing infected bits downstream in your circulation, leading to brain abscesses, kidney and lung infections, and general sepsis.
Endocarditis is a nasty, nasty condition... probably most of the cases I've seen were IV drug users. It's a hell of a life; some of those folks will shoot up anything they can find, regardless of what's in it (ie. foreign material loaded with bacteria). Also, when they are re-using needles, the needles will eventually dull, and sometimes barb (painful!). To detect a barb, addicts will sometimes lick the needle tip, then shoot up if no barb is felt with the tongue... you can see where I'm going with this. The human mouth is only slightly less dirty than the human anus... they end up injecting tons of bacteria, and develop Endocarditis. To make matters worse, they never go to the doctor, except when they try to scam more narcotics, or inadvertantly overdose. By the time they do show up, their valves are shot, and they're almost dead. If they survive, they end up needed open-heart surgery and valve replacement.
Anyway, that's probably more than you wanted to know... but as far as dental procedures go, the antibiotics your dad takes are effective in preventing Endocarditis. He'd be well-advised to keep taking them as prescribed.
I don't think the original poster was referring to Endocarditis though... I'm fairly sure he was referring generally to Atherosclerotic Disease.
Even if a man chops off your hand with a sword, you still have two nice, sharp bones to stick in his eyes.
No one has linked to this yet? Are you kidding me?
_ cont.ht ml
Just in case you missed it, fascinating stuff. (Possible complications aside)
http://www.ventrassist.com/news/VentrAssist.pdf
from
http://www.ventrassist.com/product/descrip
I've never understood why surgeons can't do the same with blood vessels - the patient is bleeding from a major artery, and it never occurs to them that the could slice the artery in half and connect the ends with surgical tubing?
The answer is that vascular surgeons have been doing exactly this since the 1950s.
Common procedures nowadays include replacing part of an aneurysmal abdominal aorta with a "Dacron" graft or bypassing stenosed or occluded arteries in the lower limbs with synthetic grafts.
There is no place like ~!
This is rather off-topic, but from what I understand the average age of menarche has always been roughly between 12 and 14 years of age, including in places like ancient Rome.
The reason people thought that it has been dropping is that the doctors who were compiling information on in the 19th century were studying undernourished women who were in poor health.
However, there has been a slight (6 months or so) drop in the average age of menarche in recent years which has been attributed to artificial estrogen-like chemicals in the environment. Also, it has been shown that on average, girls who live in families afflicted by domestic violence reach menarche earlier.
On the other hand, low body fat and vigorous excercise will delay menarche: for gymnasts the average age is 14 to 15.
As for your comment about rampant teenage sex: people forget that they had an easy way to deal with teenage sex in the middle ages: they married the girls off extremly young. Even quite recently women would marry at 18 or even younger. I imagine "waiting until you are married" is a bit easier under those circumstances.
You have it exactly backwards. The theory of evolution is just that, a theory. This is how science works. One postulates a hypothesis. Only if it is useful, that is, it furthers our understanding, and allows testing against, is it kept. Theories that are not testable, like intelligent design, are not scientific, they are matters of faith. Theories can easily be proved false, all one needs is a single concrete counter example, but being mere theories, they are never quite proved true. If after years and years of being tested (and not once being false), and continuously demonstrated as being useful, theories are accepted as fact. The creationists like to put this backwards: concluding that since scientist cannot prove evolution, the competing model (ID) is on equal footing. ID is faith, it is by definition not testable, and it is not useful in science. You can feel free to believe it you wish, but your conclusion is not based on logic. Scientific models, laws even, do not have to be fully understood to be useful. The effects of gravity, for example, are well understood -- and we have plenty of equations for it -- even though science hasn't quite explained where gravity comes from (except that it is an intrinsic feature of mass). Gravity isn't mentioned in the Bible, so the religious nuts don't feel compelled to manufacture un-testable competing theories.
I paid the going retail price for a Windows screen reader and got a free Unix computer!