- What is pulse oximetry?
Dr. Koppel: Pulse oximetry is a technology that’s been around for quite a long time, it was developed in the 1970s. It’s a noninvasive way of measuring the oxygen saturation of a patient’s blood. And it relies on transmitting a specific wave length of red light through an extremity, such as a hand or foot or a fingertip. The device is able to interpret the amount of light that passes through the extremity and convert that in to a percentage of red blood cells that are carrying oxygen. It displays a number that’s called oxygen saturation.
- Why is it needed?
Dr. Koppel: Well it’s very useful for all patients in terms of a vital sign that gives us an assessment of the oxygen status of the patient. And what we’ve known for some time now is that it can also be useful as a screening test to detect subtle degrees of decreased oxygen in babies who may have critical congenital heart disease. These are babies that may look pink to us when we just look at them using our eyes but in fact our eyes can deceive us. Although the babies look pink to us their oxygen levels may be slightly low and that might be an indication that they have a critical congenital heart defect.
- How easy is the procedure?
Dr. Koppel: It’s very simple. It’s a procedure that’s done on patients in the hospital very routinely, and is completely painless, and noninvasive. It simply involves placing a probe that has a red light on one side and a sensor on the other, and a cable that attaches to a device. And it gives us a display that tells us the patient’s heart rate with the oxygen saturation, and it all can be done in less than a minute.How long have you been doing this here?Dr. Koppel: We were very early adopters of pulse oximetry screening. The initial reports came out in the spring of 1995 and by 1998 we undertook a clinical trial here at Long Island Jewish Medical Center. So we’ve been doing this for fifteen years. We’ve published our data and it’s been incorporated into the collection of world literature that has now reached a point where governments, ministries of health, and departments of health have been able to endorse the use of pulse oximetry as a screen for critical congenital heart disease. It’s really very quick; it takes only about a minute to get a reading, but we measure in two locations. We measure in the right hand as well as one of the feet. So the estimate is that the screen itself takes about five minutes from start to finish. It is completely painless; it’s nothing more than wrapping something that looks like a band aide around the hand or the foot.
- Are all of them the same?
Dr. Koppel: The nature of the test is that it can be done in one extremity, in which case it should be the foot but the current national recommendation is to do the right hand as well. The feeling is that by doing the right hand together with one of the feet you can increase your detection of one of the more common of the critical heart defects called coarctation of the aorta. The problem is that you might increase your risk of having a false positive result by doing two measurements. But on balance, the feeling is that if you can increase the sensitivity of the test to find the most common defect then it’s worth the risk of having a few more false positives cases.
- What can be found and can these conditions be deadly?
Dr. Koppel: The nature of congenital heart disease is that it’s quite common; there are about one in 100 babies that have some type of heart defect. Thankfully, three-quarters of them are not considered critical. They might cause problems after a few weeks or months but they’re not likely to be lethal. However, one in four babies with a heart defect has what’s called critical congenital heart disease. That’s defined as a heart defect that requires some type of intervention during the first year of life. So the problems that we’re screening for with the pulse oximetry are for that category, the critical congenital heart disease. Most of those babies can be picked up with pulse oximetry because these are conditions that result in a decreased oxygen level. But there are some that may not and for that reason pulse oximetry screening was never intended to replace the physical examination. Pediatric caregivers are still expected to perform a detailed physical examination and discharge instructions to families should include instructions on signs to watch out for.The signs to watch out for might be blue discoloration or difficulty feeding, rapid breathing, etc.
- So mom, or mom and dad come in; tell me how the process works, when do you guys tell them about it? And when does this baby get tested?
Dr. Koppel: Well, this is part of our routine newborn screening process. Which New York State has been a leader in since the very beginning when newborn screening first started in the 1960s. Most newborn screening is traditionally based on the collection of dried blood spots from a heel stick. And the blood is sent off to a lab in the state’s public health lab where screening is done for over 45 different disorders. But more recently, newborn screening has expanded to include physiologic testing for conditions such as hearing loss. And now pulse oximetry screening is added to that list of other conditions for which we screen babies. So the way we do it here at our hospital, is we wait until the babies are at the time point where they need to have their blood spots collected for the state screening. At that point, we bring the baby back to the nursery and before we obtain the blood spots we put the pulse oximetry probes on the baby and perform the screening tests at that time. It’s recommended to wait until after 24 hours for the blood spot collection. And in addition, if we delay the pulse oximetry screening beyond 24 hours we minimize the risk of having a false positive result. That is the time point at which we do the screening.
- How much is the piece of equipment to do it?
Dr. Koppel: The device itself varies according to manufacture, but it’s generally on the order of about $2000 per instrument. The probes may either be reusable or disposable probes. And the guidance from national agencies is that either is acceptable. There can be significant cost savings by using reusable probes that just need to be wiped down with alcohol between patients. Other hospitals however choose to go with disposable probes. So by using reusable probes the per patient cost works out to approximately 50 cents, and disposable probes range between six to thirteen dollars each.
- And these are something that you would bill to insurance or if they don’t have insurance, the patient would be charged for it? How much is it for the test to be done?
Dr. Koppel: National agencies are currently working with the insurance industry to try to develop an appropriate system for billing for this procedure. In the meantime, governments have mandated that the screening be performed, and it often becomes an unfunded mandate which hospitals pick up. But then hospitals, in all likelihood, transfer this into other patient costs. There was a paper that appeared in a pediatrics journal paper out of the CDC that illustrated how cost-effective pulse oximetry screening is compared to many others screening mortalities. And in fact, of the costs per patient to perform the screen and the cost per quality life year that saved by detecting heart defects, the performance of pulse oximetry as a screening test is extremely favorable.
- So you weren’t surprised?
Dr. Koppel: That’s right. The report came as no surprise because the test is so easy to administer at such a low-cost with excellent performance characteristics in terms of sensitivity and specificity. The treatment is so effective at saving lives that it was very obvious from the outset that the cost-effectiveness data would be favorable. Having said that I should point out that in metropolitan regions pediatric echocardiography is widely available. There have always been concerns voiced about implementing this type of screening in suburban and rural locations across the country where pediatric echocardiography may not be as easily available and where abnormal pulse oximetry screening test may require ambulance transport of the patient to a larger center. But these fears are turning out to be unwarranted because the data is being collected from programs all across the country, indicating that it’s in fact very rare for a baby to have to move by ambulance.
- And the few babies that are moved by ambulance do turn out, in the vast majority of cases, to have a critical congenital heart defect that would have required transport even if the baby had become symptomatic.How much of a lifesaver is the pulse oximetry?
Dr. Koppel: It’s difficult to know because up until this point, where pulse oximetry screening has now been recommended for wide split–widespread implementation, the data collection mechanisms have been somewhat incomplete. But we have estimates that the number of lives that we can expect to be saved each year in the United States with universal pulse oximetry screening will be somewhere between 20 and 100 babies saved each year. That is, protection of somewhere between 20 and 100 babies from death, but that doesn’t include the expected number of babies who will be protected from severe neurologic injury among survivors of the late diagnosis of critical congenital heart disease.
- What’s the downside of pulse oximetry?
Dr. Koppel: Well the downside is that it is not yet at a point where it’s able to detect all types of critical heart disease. The one that is most common is a condition called coarctation of the aorta where there’s a narrowing in the aorta and we’re only able to find about half of those cases using our current method. So there is the need for ongoing research to develop additional tests to improve our sensitivity for finding babies with coarctation. The only other downside is that, like any other screening tests there is the risk of a false positive where we think that the baby has disease but ultimately we do electrocardiogram in find out, in fact, there is no disease. And conversely, there’s a risk of a false negative where, as in the case of coarctation, the test results are normal but the baby still has the disease that has gone undetected.
- Anything else you want to add?
Dr. Koppel: Well, I would simply say that we’re at a point we are able to do so much for babies who have congenital heart disease. And it’s very disappointingif we have a baby that has fallen through multiple layers of safety in terms of detection of the critical heart defect. We have a duty to diagnose. And if there’s anything that we can do to improve our clinical abilities and we have to overcome this idea that we’re outstanding clinicians that can detect lewd discoloration using our eyes only. So we need the help of the pulse oximeter as an instrument that aids in the detection of low oxygen levels.
This information is intended for additional research purposes only. It is not to be used as a prescription or advice from Ivanhoe Broadcast News, Inc. or any medical professional interviewed. Ivanhoe Broadcast News, Inc. assumes no responsibility for the depth or accuracy of physician statements. Procedures or medicines apply to different people and medical factors; always consult your physician on medical matters.
If you would like more information, please contact:
Robert Koppel, MDMedical DirectorRegional Perinatal CenterCohen Children’s Medical Center of New YorkAssociate Professor of PediatricsHofstra North Shore – LIJ School of Medicine