Posts Tagged ‘PulseOX’

Replace the PulseOx test for CHD!

September 30, 2010

Just a few weeks ago the Pulse Oximetry test (also known as PulseOx) became part of the Newborn Screening Uniform Panel. In a post on this blog, we discussed how the PulseOx was a good test, but not perfect.

But what if we could discard the PulseOx, in favor of a better test?

Hot off the press – really, it hasn’t even been printed yet, it was electronically published before a print version is available – is a study by the University Medical Center in the Netherlands. Appearing in the European Journal of Clinical Investigation is a study (CLICK HERE to read the abstract) showing that certain biological markers do show up more often in children with Congenital Heart Defects! In the study, higher concentrations of S-adenosylmethionine, S-adenosylhomocysteine, and folate RBC were observed in children with heart defects.

(Don’t ask me to explain all that; it’s DNA and Molecular Biology with a little Chemistry thrown in for good measure!)

Could this test replace PulseOx? Perhaps… but not tomorrow. The study was a relatively small study, with only 329 children participating. (143 CHDers with 186 heart healthy children as a control group) The researchers themselves even stress that more research needs to be done.  But we could very well be looking at the first steps to a foolproof, 100% accurate “GOTCHA!” test for heart defects. And by studying the DNA changes that occur with a CHD, we could unlock the secret to how heart defects occur… and stop them before they begin!

Special thanks to Amy Basken for bringing this research to my attention. Amy is tireless, working for several different CHD groups. Today she represents Mended Little Hearts!

The PulseOx test – not perfect, but good

September 21, 2010

If you have been reading Facebook or Twitter this past weekend, you’ve probably seen the news: The Health and Human Services’  Secretary’s Advisory Committee on Heritable Disorders in Newborns and Children (SACHDNC) voted to recommend pulse oximetry screening for critical congenital heart disease be added to the newborn screening uniform panel.

According to what I have read, the Health and Human Services Secretary now has 180 days in which to consider the recommendation and decide to either accept it or reject it. Historically the Secretary acts fairly quickly and usually accepts the recommendations given by her advisors, so the major hurdle could well have been cleared. It could only be a matter of time before the Pulse Oximetry becomes standard practice.

No PulseOx testing protocol exists yet. The official recommendation by the Health Resources and Services Administration addresses this issue, by stating “The Health Resources and Services Administration shall guide the development of screening standards…

This will delay the process – with no testing protocol, the recommendation can’t be accepted on a Tuesday and the program begin at 12:01 AM Wednesday. For the results to mean anything, a medical test must be administered in the exact same manner each and every time it is given. For example, I need to have some blood drawn this week. The nurse will apply a tourniquet to my arm, inset a needle into a vein in the crook of my elbow, and draw three vials of blood. Everyone else, no matter where they are, who has those tests done will go through the same process. Protocols are an essential part of medical testing. As this 2008 report notes, “Nursing staff received in-service training in the screening protocol and performed the pulse-oximetry procedure.”

In this study the type of  Oximeter is specified (under the heading “Methods”). This is also an important part of the protocol – perhaps not the exact same type of testing equipment, but a standard that must be met, and probably an agreed on calibration procedure. If you step on and off a manual scale enough times, the pointer will no longer return to zero… and your weight will be inaccurate until the scale is “zeroed out.” A pound or two won’t make much difference, but a point or two difference on a PulseOx reading could mean alarmed parents and unneccessary testing. A proper testing protocol would even specify a testing location, as studies have shown slightly lower PulseOx readings when the test is performed on the foot. Fussy or crying babies also produced lower saturation numbers.

Despite what you may have heard, the PulseOx test isn’t that accurate when performed on heart defects that do not cause Cyanosis. Cyanosis (medical term: Hypoxemia) comes from the root word Cyan, meaning “blue,” and is caused by low levels of oxygen in the blood. Cyanosis can be hard to detect, as the oxygen level has to drop below 90% before it begins to appear. Cyanosis will cause the lips, fingers, and toes to have a blueish tinge. (SEE THIS ILLUSTRATION) Non-Cyanotic (also known as “acyanotic”) Heart Defects account for 70% of all defects. When these defects are present, blood oxygenation (and therefore the PulseOx reading) is usually normal. In fact, the recommendation is only meant for CCCHDs, or Critical (sometimes the word Complex is used) Cyanotic Congenital Heart Defects.

While the Pulse Oximetry screening test is not the complete answer for detecting Congenital Heart Defects; it is certainly part of the answer – another piece of the puzzle; another arrow in our quiver. My idea – and I don’t know if it is just a pipe dream, or a discovery we haven’t made yet – is to find a “bulletproof” test that indicates the presence of a heart defect. Does a defective heart release a gene, an enzyme, or any kind of biomarker into the bloodstream?   If we could find that marker and learn how to detect it… Gotcha!

But until that day comes – if it ever comes – you throw everything but the kitchen sink into the fight.

Just in case…

August 26, 2010

I was very pleased – to say the least! – about my exam at the Emory Adult Congenital Heart Center yesterday. An Echocardiogram showed that my Left Ventricle is 6 Millimeters smaller than the original Echo done there in 2002. It was 82 Millimeters across in 2002; it is now 76. And in my case, a shrinking heart is a 100% Official Certified GOOD THING!

If there is trouble in the future, if my PulseOx numbers were to start dropping and I was feeling worn out all the time, there are a few options that we could try to help get me back on an even keel. A couple of them are invasive but do not involve heart surgery… surgery can be a risky (and quite possibly fatal) proposition for me.

First things first, remember that 1) I am not a doctor; I’m just trying to explain it to you as it was explained to me. 2) This applies only to my heart and my health situation. Every heart defect is different, and what works for me may not be such a good thing for you… and vice versa.

The general plan for me would be to increase the blood oxygenation… but when you do that, the heart is naturally going to work harder. The trick is to find a happy balance between a decently high PulseOx and the amount of work that the heart can do. Right now my PulseOx is in the low 80% range and I have that happy balance.

The first option I would have (and all this is way in the future, if at all!) is based on my unusual anatomy. Like many reading, I have the Glenn Shunt. But mine was done in 1967, and is a completely different operation. Let’s review the difference:

The Bi-directional Glenn Shunt, the operation usually performed today: The Superior Vena Cava is cut where it joins the heart and is sewn into the Pulmonary Artery. They usually try to sew it as close to the T formed by the Pulmonary Artery to deliver an equal amount of blood to both lungs.

The Classic Glenn Shunt, performed on me in 1967: The Superior Vena Cava stays where it is. Instead of being cut, it is sewn closed. The right branch of the Pulmonary Artery is cut and sewn into the side of the Superior Vena Cava, which means that all of the blood from the Superior Vena Cava is sent into the right lung.

Now in my case, the Vena Cava wasn’t sewn completely closed. I don’t know if that was an error or if a small opening was left to relieve pressure that got too high, but a small amount of blood gets through the chokepoint and into the Right Atrium. If I were to start having problems they could use a Catheter to plug that small hole. That would cause my PulseOx to climb but shouldn’t increase the heart’s workload too much, and would probably be my best option.

The second thing they could do would be to create a fistula in my right arm. Basically, they would “short-circuit” the circulatory system by connecting an artery directly to a vein. My blood would head down my right arm as usual, but would “turn around” and head back toward the heart before it normally would. (Don’t worry,there are lots of of arterial branches and veins…. my arm wouldn’t rot and fall off!) That would increase the PulseOx numbers… but would also increase the heart’s work load. It is probably my second best option.

The third option would be a combination of medications that could reduce the natural resistance inside my body. Part of the heart’s work comes from how far the blood travels – if you could take all of the blood vessels out of an average human child and place them end to end, you’d have about 60,000 miles of blood vessels! Part of the heart’s work is because of resistance – your blood also has to turn corners and flow through organs (“Scuse me! Comin’ through!”). The medication would “grease” my blood vessels and make the blood flow through them easier. This would cause my PulseOx to rise… but not as much as any other option. My heart would also work harder. With more effort but not as many benefits, this is my third and least attractive option.

But getting a good report now gives me something better than all three of these possibilities: time. Nothing has to be done now, nor for the foreseeable future. And if I do reach the point where something needs to be done, delaying it now means that another option  could be developed that might be even better than the three ideas currently on the table.

All part of the master plan to keep pushing that final day back!

UPDATE: See Heather’s comment below for a good laugh! 🙂  Thanks, Heather!

Pulse Oximetry explained

March 30, 2010

A Pulse Oximeter (PulseOx) is a useful tool, but exactly how does one work? Obviously, it’s not magic, though it might as well be. Very few people can tell you what happens in the couple of seconds that occur after you place it on your finger.

Pulse Oximeters were invented in the 1940’s by scientist Glen Milliken, who published his ideas in a research paper titled The oximeter: an instrument for measuring continuously oxygen-saturation of arterial blood in man. But it looked nothing like the Oximeters we have today: those wouldn’t appear until the Japanese refined the technology in 1972.

But the average person still wouldn’t have been able to purchase a Pulse Oximeter. Biox made it into a commercial product in 1981, and it was the late 1980’s before they really began to catch on in the United States.

So how do they work? A Pulse Oximeter emits light from two different sources: a red light that you can see, and an infrared light that you can’t see. As the PulseOx is placed on your finger or ear the lights activate automatically.

The red light (which has a wavelength of 660 nm) shines through the finger and is absorbed by hemoglobin. The problem is, everything else in the body absorbs light, also. So the infrared light is used too – it has a higher wavelength and is absorbed at a different rate than the red light. A receiver picks up the light waves from both sources as they leave the body, and the Oximeter’s computer chip compares the two. The comparison values are entered into a mathematical formula (CLICK HERE and page down to see the formula that makes Pulse Oximetery possible) and the answer is displayed on the screen – all in a matter of moments!

If I had to do the math to figure out the Oxygenation level, It would take all day to get one reading!

Oximetery does have its limitations: while most people think it is a beat to beat accurate measurement, it is not. It is an average over time. Another big drawback is that it can be fooled by Carbon Monoxide poisoning. hemoglobin mated with Carbon Monoxide responds like oxygen mated Hemoglobin, so a patient dying of Carbon Monoxide poisoning will give a PulseOx reading of 90% or higher.  Also, dark skin could cause inaccurate readings. This 2007 report contends that it does; later reports either report no effect or draw inconclusive results.

SQUIDs could replace PulseOx!

February 6, 2010

LATE ANNOUNCEMENT: Hypoplastic Right Hearts will sponsor a showing of the movie Hearts of Hope at the Children’s Hospital of Denver. The showing will be at 2:00 PM Denver time on the second floor in the Mt. Oxford Room.

Pulse Oximetry tests on newborns may soon be a thing of the past.

Researchers at The University of Leeds have developed a new portable magnetometer that is so sensitive, it can detect heart abnormalities in a fetus. The new unit is smaller, faster and cheaper than other magnetometers that are available, and it is better it can detect heart problems earlier than any technology now in use.

The human heart produces a magnetic “signature” as it beats, one that can be detected with the right equipment. A magnetometer measures magnetic fields, and this one is a special type of device known as a SQUID (Superconducting QUantum Interference Device) that is super-sensitive. In fact, the reason that they are not used more often is that they are too sensitive – the patient has to be inside of a magnetic shield or the magnetometer might pick up other magnetic fields. The new SQUID gets around that problem by better shielding the detector unit. It is also simple to use, so almost anyone with the proper training can conduct the test. (Though I am sure that they will still have to be read by a Magnetocardiologist.)

“We don’t do PulseOx tests anymore,” A nurse may tell you one day. “The prenatal SQUID test tells us everything we need to know.”

Another look at Pulse Oximetery

December 2, 2009

There is a growing movement in the Congenital Heart Defect (CHD) family pushing for the inclusion of testing newborns with a Pulse Oximeter before being released from the hospital. Such a test would provide a fast, inexpensive way to determine if a CHD is present; if the situation warrants, further tests can be conducted.

Back in July I wrote a blog post about an article that appeared in the medical journals Circulation and Pediatrics that stated that Pulse Oximetery should not be supported as a routine test for newborns.

Many readers have misinterpreted that post, the Circulation/Pediatrics articles do not say that the PulseOx test should be discarded, but that more research is needed. (Very few readers click the links in each post, I do not know why. That’s where a lot of extra information about the subject can be found. And sometimes I just might surprise you!)

Seriously, let’s visit the subject of the PulseOx again for a few moments. It’s a pretty good idea – a quick reading of the child’s blood oxygenation level can be determined by a Pulse Oximeter (sometimes called a PulseOx). The test is quick (ten seconds at the most), painless, and inexpensive. Any blood oxygenation level reading below 90%  usually triggers a follow-up test: usually an Echocardiogram or an ECG.

While the medical journal article cites its own reason why there needs to be more research into the use of PulseOx, I can see one major flaw they did not mention: A PulseOx test can only detect a Cyanotic Heart Defect. And only about 25% of all heart defects cause Cyanosis.

So what we need, in my opinion, is overlapping tests: PulseOx combined with an Echocardiogram AND an ECG. And perhaps add a Fetal Echocardiogram for mothers who are in high risk groups.

But when you do all that, the CHD test for newborns is no longer fast, and certainly not inexpensive.

And the bad news is that even with overlapping tests, a few CHDs will still slip through. On May 4 of this year I blogged about Nick Heine, the police officer who died of an undiagnosed Congenital Heart Defect while answering a call. Nick had a problem in his heart’s electrical conduction system, and certainly he had undergone a complete physical exam before becoming a police officer. He probably had to have physicals all during his career, but that heart defect never showed itself until the instant it killed him.

So this is where research comes in. Keep looking at the results of the PulseOx; the more we know, the better we can make the test. Research will also make other medical procedures – of all types – better, faster, and less expensive. So perhaps one day there will be one single test, cheap, fast, and reliable, to determine if a child has a Heart Defect.

And until then, we work with what we have – PulseOx.

Pulse Oximemetry: Not Recommended

July 13, 2009

A new scientific statement from the American Heart Association and American Academy of Pediatrics will not recommend using Pulse Oximetery to screen for Congenital Heart Defects (CHDs).

Despite repeated pleas from the CHD community (including a post on the Funky Heart blog) the authors of the scientific statement feel there are too many variables that can affect the test. They are not saying that the test should be abandoned completely; in fact they encourage facilities that are already performing the test to continue – and to compare results.

Pulse Oximetery is a simple, painless test that can be used to detect the presence of a Congenital Heart Defect in a newborn infant – but is it too simple? The Pulse Oximeter can detect low levels of oxygen in the blood, which is called Cyanosis and is a recognized sign of a complex heart defect. But only 25% of heart defects cause Cyanosis. And as simple as it is, the Oximeter can be misused.

If you want an accurate test, you have to standardize the the testing procedure. A child born in a hospital in Denver will naturally have a slightly lower PulseOx reading than a child born in Washington, DC – would we have to have a “Normalized PulseOx reading” for different sections of the country?

What we need is more statistical information about the accuracy of Pulse Oximeter testing, and perhaps an even better screening test. A test that is just as fast and just as inexpensive.

That’s one of the reasons that ongoing CHD research is so important.

Appointment went well!

October 8, 2008

My appointment at Emory went well! I have been feeling good and am not aware of any problems (and that is a problem itself: a heart that is getting sicker won’t always make you feel bad. A cardiac chamber that is failing won’t cause you any pain, but it will enlarge and cause you to not function as well as you once did. The loss of function happens so slowly that it can easily be passed off as the normal effects of age, and there is no way to detect a changing heart chamber without an x-ray and/or and ECG.) but for some reason I was extremely nervous before my appointment today. We’re not talking just the normal doctor’s office anxiety, but really, really nervous. If someone had slammed a door, you probably would have had to peel me off the ceiling.

And even though I was so nervous, my blood pressure was great. 102/57, which is pretty astounding. For some reason, even with a Funky Heart and blood vessels that interconnect more than the Los Angeles Freeway, my BP has always been close to perfect.

After the BP and the PulseOx test, the nurse brought in the ECG machine and hooked me up. There have really come a long way — today it takes about 20 seconds to produce the ECG sheet; it actually takes longer to place all the sticky pads on the patient than it does to run the test! When I was an infant, you couldn’t even touch the patient or the test (printed on yards of cash register receipt paper) would be invalid. The patient couldn’t move, either, which meant screamin’ young’uns like myself were very difficult. The folks finally came up with a way to get me to hold still without touching me: they’d let me starve! Whenever it was ECG time, they’d put me on the table and hold my bottle right over my mouth. I’d start sucking, being perfectly still the entire time. (Hey, eating is hard work! You have to concentrate!)

I was also able to get my flu shot! I was sitting there waiting on the doctor – you know, those few minutes that they leave you alone after the nurse finishes her examination, but before the doctor gets to you – when the nurse comes in again and asks if I want the flu shot. That was on my list of questions to ask the doctor; I had seen an ad for a drugstore that was distributing the shot a few days before and meant to ask about it. The nurse said that they were recommending them, AND had a supply reserved for the Congenital patients, so I signed the forms and got my shot!

Then my doc comes in and examines me. He always has permission to bring some of his students, so usually he enters the room with three or four young people in tow. Today is no different. I actually enjoy his teaching sessions; he switches back and forth between English and med-talk enough that I’m getting an education, too!

This has changed over the years, too. It used to be that a doctor would ask if he/she could bring a medical student into the room because “We don’t see very many cases like you.” Now he’s bringing in students because the students are choosing Adult Congenital Cardiology. And even if they don’t go that route, studying people like me will help that one day in the future when a sick kid comes into the Emergency Department and no one can make heads or tails of what’s going on. Hopefully that former student will be able to say “Wait a minute, I’ve seen something like this before…”

And although I was nervous – scared to death, actually – everything went great! I’m due back in 4 months. I will see my doctor at the Adult Congenital Heart Association’s (ACHA) Lobby Day 2009 in Washington, DC, and I hope to interview him for the Funky Heart blog. I’m sure that if I had asked today he would have sat down with me right then, but I hadn’t set anything up in advance. And to take up an extra 30 minutes of his time that I didn’t need would not be fair to his other patients, so I’ll do the interview another day.

Tonight’s musical selection is Tom Petty’s Won’t Back Down. I heard this when we stopped at a store on the way to Atlanta; I hadn’t heard it in a while and had almost forgotten how good a song it is. I hope you enjoy it too.