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Without evidence of benefit, an intervention should not be presumed to be beneficial or safe.

- Rogue Medic

Bad Advice on Masimo’s RAD-57 – Part II

Mon, 21 Feb 2011 06:30:17 -0500 by

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Also posted over at Paramedicine 101 (now at EMS Blogs). Go check out the rest of the excellent material there.

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Continuing from Bad Advice on Masimo’s RAD-57 – Part I.

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Medic Marshall adds this little bit of commentary to what was covered in Part I

When I dug a little deeper and looked at the study’s limitations, I saw that the authors noted approximately three quarters of the subjects were of Hispanic or African descent. The RAD-57 device has already been shown to have poor performance when measuring carboxyhemoglobin in dark-pigmented individuals. A significant potential for bias (at least in my humble opinion) exists in this study. Take it for what it’s worth; I personally don’t give it a whole lot of merit.[1]

Wow.

We should only use this on pale skinned people? Is that the idea?

Should Masimo avoid advertising this to fire departments with significant numbers of non-white firefighters?

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A significant potential for bias (at least in my humble opinion) exists in this study review. Take it for what it’s worth; I personally don’t give it a whole lot of merit.

He admits that the RAD-57 is inaccurate, but he claims that the inaccuracy of the RAD-57 is a demonstration of accuracy.

In the study being reviewed,[2] we have the RAD-57 being used in almost ideal circumstances – not in the poorly controlled EMS environment – and it is still not even close to accurate, but we shouldn’t criticize, because we don’t expect it to be accurate.

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Don’t criticize the RAD-57 for being inaccurate. Nobody expects it to be accurate.

That is not a defense I was expecting. This is a, Well that depends on what your definition of accuracy is, defense.

He does score pretty high on the chutzpah meter and that chutzpah meter doesn’t have objective confirmation of accuracy, either.

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To be continued in Bad Advice on Masimo’s RAD-57 – Part III and finished in Bad Advice on Masimo’s RAD-57 – Part IV.

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Footnotes:

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[1] RAD-57 Pulse Oximeter Performance – Study measures device’s readings comared with lab measurement
JEMS Street Science
by Keith Wesley, MD, FACEP and Marshall J. Washick, BAS, NREMT-P
Tuesday, February 15, 2011
Article

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[2] Performance of the RAD-57 pulse CO-oximeter compared with standard laboratory carboxyhemoglobin measurement.
Touger M, Birnbaum A, Wang J, Chou K, Pearson D, Bijur P.
Ann Emerg Med. 2010 Oct;56(4):382-8. Epub 2010 Jun 3.
PMID: 20605259 [PubMed – indexed for MEDLINE]

Free Full Text Article from Ann Emerg Med with links to Free Full Text PDF download

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Filed Under: Assessment, Critical Judgment, Ethics, Heresy, Masimo, Paramedicine 101, Research

Bad Advice on Masimo’s RAD-57 – Part I

Fri, 18 Feb 2011 06:30:20 -0500 by

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Also posted over at Paramedicine 101 (now at EMS Blogs). Go check out the rest of the excellent material there.

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Here is some bad advice from a review of the RAD-57 study. Research that showed just how flawed Masimo’s CO (Carbon monOxide) measuring technology is –

Medic Marshall: I’m not entirely sure how I feel about this study. I’m afraid people will look at it as saying the RAD-57 doesn’t really work, and a valuable tool for evaluating potential CO exposures for patients and firefighters in rehab will be discarded.[1]

Is the RAD-57 a valuable tool for evaluating potential CO exposures for patients and firefighters in rehab?

What would make it valuable?

Assume that we use the RAD-57 to measure the CO levels of firefighters in rehab. We want to determine if the firefighter should –

1. Go to the hospital.

2. Go back to the station/home/to the next fire, depending on dispatch.

3. Go back to fighting this fire.

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How do we determine which category the firefighter falls into?

1. Go to the hospital.

If the number on the RAD-57 is above whatever limit is established for the Go to the hospital decision, then there should be no question.

There is not a clear danger level for carboxyhemoglobin (COHb – CO bound to hemoglobin in the blood). In the study 15% was used. Whatever level is used, the important thing to know is whether the readings are accurate.

Most of the time, when the blood level of CO was over 15%, the RAD-57 was not accurate.

Most of the time, the RAD-57 missed the readings over 15%.

With a 15% carboxyhemoglobin level, the firefighter is presumed to be toxic. That toxicity probably occurred fighting this fire.

Most of the time, firefighters who should be told Go to the hospital, will be told, Everything’s OK. Go back and knock down that fire.

Most of the time, poisoned firefighters will be given bad advice if we trust the RAD-57.

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Is this safe?

Compared to what? Compared with juggling hand grenades with the pins pulled it is very safe, but that is not what I would call safe.

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A laboratory value of 15% carboxyhemoglobin was selected as the cutoff for determination of these performance characteristics according to proposed use of this RAD level for out-of-hospital triage of patients with possible carbon monoxide exposure in New York City.13[2]

The RAD device correctly identified 11 of 23 patients with laboratory values greater than or equal to 15% carboxyhemoglobin (sensitivity 48%; 95% CI 27% to 69%).[2]

Less than half of the patients with elevated COHb were correctly identified.

If we consider screening any fire fighter for COHb, then we should send that fire fighter to the hospital and do it the right way.

Or do firefighters not deserve accurate screening?

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If you’re evaluating a patient who happens to be a firefighter, and they’re exhibiting signs and symptoms of CO exposure but the RAD-57 device is reading in a normal range, you aren’t (or at least you shouldn’t) allow that firefighter to return to duty.[1]

This is true, but –

If you’re evaluating a patient who happens to be a firefighter, and they’re exhibiting signs and symptoms of CO exposure, then stop playing with the RAD-57 and take them to the hospital.

If you’re evaluating a patient who happens to be a firefighter, and they’re exhibiting signs and symptoms of CO exposure the RAD-57 provides an excuse to send that firefighter back to fighting that fire.

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The RAD-57 could justify refusing to cover illness due to on the job exposure to carbon monoxide.

If there were signs of CO toxicity, why didn’t the firefighter go to the hospital? The RAD-57 indicated no serious exposure, but it is inaccurate.

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Without the RAD-57, the firefighter stays safe.

With the RAD-57, the firefighter is in danger.

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This is exactly the opposite of what we want.

The problem is that CO toxicity does not present with clear symptoms. What is a symptom of CO toxicity could be any of dozens of other things. A low reading on the RAD-57 can convince people that the symptoms are due to something else.

The RAD-57 is dangerous.

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To be continued in Bad Advice on Masimo’s RAD-57 – Part II and later continued in Bad Advice on Masimo’s RAD-57 – Part III and finished in Bad Advice on Masimo’s RAD-57 – Part IV.

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Footnotes:

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[1] RAD-57 Pulse Oximeter Performance – Study measures device’s readings comared with lab measurement
JEMS Street Science
by Keith Wesley, MD, FACEP and Marshall J. Washick, BAS, NREMT-P
Tuesday, February 15, 2011
Article

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[2] Performance of the RAD-57 pulse CO-oximeter compared with standard laboratory carboxyhemoglobin measurement.
Touger M, Birnbaum A, Wang J, Chou K, Pearson D, Bijur P.
Ann Emerg Med. 2010 Oct;56(4):382-8. Epub 2010 Jun 3.
PMID: 20605259 [PubMed – indexed for MEDLINE]

Free Full Text Article from Ann Emerg Med with links to Free Full Text PDF download

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Filed Under: Assessment, Critical Judgment, Ethics, Heresy, Masimo, Paramedicine 101, Research

How TO Respond to Negative Research

Sun, 05 Dec 2010 06:30:41 -0500 by
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Also posted over at Paramedicine 101 (now at EMS Blogs). Go check out the rest of the excellent material at these sites. There is a new research podcast specifically for EMS – EMS Research Podcast. On episode 2 we discuss several topics, including the research on the RAD-57 non-invasive monitor.

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In the comments to How Not to Respond to Negative Research is this excellent example from daedalus2u of a response to negative research that is much better than the response by Dr. O’Reilly.

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I suspect that the problem is in the factory calibration of the device (the algorithms for calculating COHb from spectral information) which I think derives from a mistaken idea of what is important to determine.

The error seems to be due to the way the RAD-57 is calibrated.

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I suspect the factory calibration is being driven by marketing considerations, i.e. because the marketing people want to put “accurate to X%” on their glossy marketing brochures, rather than listen to those involved in treating patients as to what information they actually need to treat those patients.

I would be cynical, if I were to conclude that Dr. O’Reilly might not have considered this, and that he had a lot of input into the calibration marketing of the RAD-57. That is, if daedalus2u is correct in his analysis and if I am cynical. Clearly, these are impossibilities.

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The only purpose of measurements like this (and for any diagnostic test) is differential diagnosis which is only useful for differential treatment. A test does not need resolution better than the resolution necessary to provide differential treatment.

Why calibrate the RAD-57 to identify dangerous levels of carboxyhemoglobin, when the alternative is to calibrate the RAD-57 for only the appearance of accuracy?

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What is important to determine in a patient with COHb is not a low percentage deviation from the “true” amount of COHb, but rather what is the absolute amount of COHb within a certain range.

And here is the explanation –

If the “true” COHb level is 20%, getting a reading of 30% or 15% isn’t going to change the treatment, O2 and getting to a HBO2 facility (my guess, but IANAD).

Actually, since the RAD-57 is a non-invasive portable device advertised as capable of ruling out the possibility of unrecognized carbon monoxide toxicity, the choice is between identifying a need for transport to the hospital.

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I think the “problem” is that the device is tuned to give the most precise readings in the low COHb range where precision isn’t important because low COHb readings are the most common. Then when those measurements are compared and averaged, the precision at the low end dominates the average, but the precision at the low end isn’t at all important. What is important is the rare go/no go values at the high end.

At the hospital, a blood test will be done to confirm any elevated RAD-57 reading.

All that is needed is a Go/No Go decision. Go to the hospital vs. don’t go to the hospital.

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I don’t know anything about the details of how the device works, other than it uses some kind of spectral stuff, but it is inconceivable to me that the technique couldn’t be made to technically work, and technically work just by changing the software. I think the problem there is that because the device has to be FDA approved, changing the software turns it into a new device that needs new FDA approval even if it works better. I suspect that business considerations are preventing that from happening.

Sometimes knowing too much about the specifics may distract us from the relevant points.

With the way the FDA does things – occasionally too affected by politics – changing the software should be much more easily resolved than paying out some large settlements for unrecognized toxicity, but I don’t mean to criticize, if paying out large settlements is Masimo’s marketing strategy.

If this explanation is correct, I think that Masimo owes daedalus2u a lot of money.

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PS – Steve comments –

In this crazy world of online advertising, immediately after your damning post is… an ad for the Masimo Rad-57!! “Quick and Noninvasive Assessment of CO Levels in the Blood” it reads, and features a photo of a Fireman and a Medic. The Fireman has had a rough day; he’s seated, no helmet, with the Rad-57 clip attached to his finger. But you know in just a moment the Medic is going to tell him he’s A-OK and send him back to work – because the Rad-57 says he’s great! (Maybe…maybe not!)

Steve’s comment about the message communicated by the ad is correct.

Steve’s comment about the placement of the ad is not correct. I copied the ad into my post to make a point. The image of the Magic 8-Ball is right next to the RAD-57 image to make a counterpoint.

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Filed Under: Assessment, Critical Judgment, Ethics, Heresy, Masimo, Paramedicine 101

How Not to Respond to Negative Research – Addendum

Fri, 26 Nov 2010 13:45:39 -0500 by
–ResearchBlogging.org

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Also posted over at Paramedicine 101 (now at EMS Blogs) and at Research Blogging. Go check out the rest of the excellent material at these sites. There is a new research podcast specifically for EMS – EMS Research Podcast. On episode 2 we discuss several topics, including the research on the RAD-57 non-invasive monitor.

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In How Not to Respond to Negative Research, I forgot to address one of the more important problems with the response of Dr. Michael O’Reilly.

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Because the study used the same type of device and sensor and evaluated patients similar to those in previous studies, the differences in results were likely due to different methods by the investigators. The possible reasons for the discrepancy between the results reported in this study include multiple items addressed in the directions for use of the device and sensor, including:

•inappropriate finger positioning in the sensor

•inappropriately sized sensor for the subject’s finger

•timing of SpCO and COHb measurements not being exactly simultaneous

•increased methemoglobin level (which can be ruled out by measuring noninvasive methemoglobin levels [SpMet] with the Rad-57)

    •patient motion

    •external light interference

    •device or sensor malfunction (there were many zero readings by Rad57 in which HbCO was considerably higher, which could be due to device malfunction and may indicate a need for service)[1]

Dr. O’Reilly is telling us that the RAD-57 is too difficult to use in the ED (Emergency Department), but miraculously acquires accuracy and reliability at a fire scene.

timing of SpCO and COHb measurements not being exactly simultaneous

Exactly simultaneous?

Exactly?

Does carboxyhemoglobin vary that much that a few seconds later, the HbCO is wildly different?

If that is the case, why buy a machine that will only give us a snap shot of a rapidly fluctuating and unreliable number?

Is there any reason to believe that carboxyhemoglobin changes that rapidly and unpredictably?

No.

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Three RAD devices and training in their use were supplied by Masimo Corporation for the duration of the study. Clinicians underwent training in use of the RAD device before study initiation. Measurement of RAD carboxyhemoglobin was performed simultaneously with sampling of arterial or venous blood for laboratory determination of carboxyhemoglobin level.[2]

Simultaneously, but not exactly simultaneously?

Dr. O’Reilly is creating the impression that this is a difference. Should we believe that, in the ED, the levels of carboxyhemoglobin are rising dramatically between the application of the RAD-57 and the simultaneous drawing of blood, just because the word exact was not used?

The big problem with the RAD-57 was that it missed over half of the significantly elevated carboxyhemoglobin levels – some while indicating a carboxyhemoglobin level of zero. Did patients have a zero carboxyhemoglobin level one minute and a significantly elevated carboxyhemoglobin level the next minute?

Dr. O’Reilly seems to be indicating that carboxyhemoglobin operates on the same principle of uncertainty as Scrödinger’s Cat, but with a free random number generator.

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There are several problems with researching EMS equipment in the much more stable environment of the ED.

The ED environment has much less variability than the EMS environment.

If vasoconstriction is a problem, the warmer ED is much less likely to produce vasoconstriction than being out in the cold, which is often where the RAD-57 will be used.

The people using the equipment are generally paying much more attention to what they are doing, if only because they have to document compliance with study protocols.

As stated in the study, the participants are often trained by the people most familiar with the equipment – not somebody who read a package insert, or watched a video, or was once trained by someone from the manufacturer.

Compared with use in the EMS environment, the ED environment can be seen as much closer to the ideal testing environment.

Is Dr. Reilly complaining that Masimo provides bad training on the use of the RAD-57?

If our device does not work in your hands, it’s your fault.

It is always a pleasure to deal with someone who stands behind a product and is looking out for the patients assessed/treated with that product.

Dr. Michael O’Reilly, who is Executive Vice President of Masimo Corporation, an officer of the corporation, and holds stock options in Masimo[1], is not that person.

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The RAD-57 may have some role in identifying elevated carboxyhemoglobin levels, but so far nobody can tell what that role is. As I pointed out earlier –

Less than half of the patients with elevated COHb were correctly identified.

If we screen a fire fighter for COHb, then we need to keep that fire fighter out of the fire.

Should anyone ever use a low RAD-57 reading to justify returning a fire fighter to a fire?

No.

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Footnotes:

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[1] Performance of the Rad-57 pulse co-oximeter compared with standard laboratory carboxyhemoglobin measurement.
O’Reilly M.
Ann Emerg Med. 2010 Oct;56(4):442-4; author reply 444-5. No abstract available.
PMID: 20868919 [PubMed – indexed for MEDLINE]

Free Full Text of letter and author reply from Ann Emerg Med with links to Free Full Text PDF download

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[2] Performance of the RAD-57 pulse CO-oximeter compared with standard laboratory carboxyhemoglobin measurement.
Touger M, Birnbaum A, Wang J, Chou K, Pearson D, Bijur P.
Ann Emerg Med. 2010 Oct;56(4):382-8. Epub 2010 Jun 3.
PMID: 20605259 [PubMed – indexed for MEDLINE]

Free Full Text Article from Ann Emerg Med with links to Free Full Text PDF download

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O’Reilly M (2010). Performance of the Rad-57 pulse co-oximeter compared with standard laboratory carboxyhemoglobin measurement. Annals of emergency medicine, 56 (4) PMID: 20868919

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Touger, M., Birnbaum, A., Wang, J., Chou, K., Pearson, D., & Bijur, P. (2010). Performance of the RAD-57 Pulse Co-Oximeter Compared With Standard Laboratory Carboxyhemoglobin Measurement Annals of Emergency Medicine, 56 (4), 382-388 DOI: 10.1016/j.annemergmed.2010.03.041

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Filed Under: Assessment, Critical Judgment, EMS Research Podcast, Ethics, Heresy, Masimo, Paramedicine 101, Research Blogging

How Not to Respond to Negative Research

Fri, 26 Nov 2010 06:30:12 -0500 by
–ResearchBlogging.org

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Also posted over at Paramedicine 101 (now at EMS Blogs) and at Research Blogging. Go check out the rest of the excellent material at these sites. There is a new research podcast specifically for EMS – EMS Research Podcast. On episode 2 we discuss several topics, including the research on the RAD-57 non-invasive monitor.

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Continuing from The RAD-57 Pulse Co-Oximeter – Does It Work – Part I and from The RAD-57 Pulse Co-Oximeter – Does It Work – Part II. More on the use of the RAD-57.

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To the Editor:

Masimo Corporation is the manufacturer of the Rad-57, a multiwavelength pulse carbon monoxide oximeter that measures noninvasive carboxyhemoglobin (SpCO) in the blood. The Rad-57 is the subject of a study by Touger et al1 and an accompanying editorial2 in this edition of Annals. Masimo appreciates the journal’s willingness to publish these comments about the study and editorial.[1]

So far, so good.

Since the introduction of the Rad-57 in 2005, Masimo has received countless reports from clinicians that the device has enabled them to save lives and limit the damaging effects of carbon monoxide poisoning.[1]

Only the second paragraph and Dr. O’Reilly is already wandering into the street corner sales pitch. This is what the alternative medicine charlatans always seem to say.

Countless? Why is it that none of the people making these anecdotal claims are able to count, but they expect us to trust them with our lives?

Given this accuracy specification, approximately 95% of SpCO measurements are expected to be within 2 SDs of the COHb value. If this specification were applied to limits of agreement calculation, the accuracy could be stated as 5.9% to +5.9%. The study by Touger et al1 stated: “We determined a priori that a difference of ±5% carboxyhemoglobin would be considered clinically significant.” No rationale for the ±5% threshold was provided, but we do not believe it is appropriate to initiate a study with expectations greater than the stated performance of a device or drug. In short, there was a strong likelihood the study would result in a negative conclusion by the investigators before it even started.[1]

Accuse the ones performing the study of approaching things with a bias.

So, what did the study state about the reasons for their range?

Finally, the selection of ±5% carboxyhemoglobin as a boundary for acceptable limits of agreement was based on presumed clinical significance but may be considered somewhat arbitrary. The actual limits of agreement (–11.6% to 14.4% carboxyhemoglobin) demonstrated in our study substantially exceeded this value, suggesting that the inference would have been the same even if a larger value, eg, ±10% carboxyhemoglobin, had been chosen.[2]

Dr. O’Reilly is complaining that ±5% is narrower than the ±5.9% that he states should be used as the limit of 2 standard deviations. Dr. Touger points out that ±5.9% would not make the RAD-57 look good. Even ±10% wouldn’t make the Rad-57 look good.

The study results are significantly different from those of other available studies, as well as from Masimo’s internal test data from subjects with 1% to 40% COHb levels. However, the study results by Touger et al1 are discussed as being representative of device performance, and strong conclusions are made by both the authors and the editors according to the study results.[1]

This study was of real emergency department patients (at a burn center with a hyperbaric chamber) being evaluated for possible CO (Carbon monOxide) poisoning. As far as being different from other available studies, that is not true.

Here is another study, which does not encourage faith in the RAD-57 readings.

A total of 36.4% of the patients transported during the study had SpCO documented. Of the 1,017 adults included in this group, 11 (1.1%) had an SpCO >15%.[3]

1% of the patients included in the study had RAD-57 levels above 15%.

Of the 11 patients with a SpCO >15%, 10 were transported to a hospital for which the investigators had institutional review board (IRB) approval to review the patient’ s medical record. Of those 10, none had confirmatory venous carboxyhemoglobin levels. The two patients with an SpCO level of 21% did have a repeat SpCO documented at triage upon arrival to the emergency department. Their repeat levels were 8% and 2%. None of the 10 patients with levels >15% ultimately were diagnosed with and treated for carbon monoxide exposure or toxicity.[3]

The medical records were available for 91% of that 1%.

None of the 10 patients with levels >15% ultimately were diagnosed with and treated for carbon monoxide exposure or toxicity.

But, none of them had blood drawn to check carboxyhemoglobin levels.

Were they misdiagnosed?

More important. Did the researchers let the hospitals know that they were studying the ability of the RAD-57 to identify carboxyhemoglobin?

From the study, the answer appears to be, No.

Do we know if the RAD-57 missed any patients with elevated carboxyhemoglobin?

No.

This study does not appear to have been designed to identify patients missed by the RAD-57.

Data obtained from other studies indicate that there are false positive results using the new technology, but the benefit of identifying true positive CO toxic patients outweighs the burden of false positive results.3 In this cohort, there were at least two patients who had discordant results when a repeat SpCO was obtained, further emphasizing that all positive results obtained with the non-invasive method should be confirmed with a blood carboxyhemoglobin level.[3]

The RAD-57 readings were inconsistent. The patients with high readings were not diagnosed with, or treated for carbon monoxide toxicity. This does not support Dr. O’Reilly’s claims that the RAD-57 is accurate and just being unfairly evaluated.

The RAD-57 may have some role in identifying elevated carboxyhemoglobin levels, but so far nobody can tell what that role is. As I pointed out earlier –

Less than half of the patients with elevated COHb were correctly identified.

If we screen a fire fighter for COHb, then we need to keep that fire fighter out of the fire.

Should anyone ever use a low RAD-57 reading to justify returning a fire fighter to a fire?

No.

Masimo stands by its products’ performance and knows that when SpCO-enabled devices are used according to their directions for use, they provide accurate SpCO measurements that provide significant clinical utility, helping clinicians detect carbon monoxide poisoning in patients otherwise not suspected of having it and rule out carbon monoxide poisoning in patients with suspected carbon monoxide poisoning.[1]

That advice from Dr. O’Reilly may encourage us to return fire fighters to an environment that has already made them toxic, but with the mistaken belief that they have carboxyhemoglobin levels of zero, when their carboxyhemoglobin is really very high.

Dr. O’Reilly’s advice is bad for Masimo investors.

Dr. O’Reilly’s advice is bad for patients.

Dr. O’Reilly’s advice misrepresents the research.

Find a way to make the RAD-57 reliable, then sell a lot of them. Right now, it isn’t reliable.

Right now, the RAD-57 is an accident waiting to happen.

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Continued in How Not to Respond to Negative Research – Addendum and in How TO Respond to Negative Research.

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Footnotes:

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[1] Performance of the Rad-57 pulse co-oximeter compared with standard laboratory carboxyhemoglobin measurement.
O’Reilly M.
Ann Emerg Med. 2010 Oct;56(4):442-4; author reply 444-5. No abstract available.
PMID: 20868919 [PubMed – indexed for MEDLINE]

Free Full Text of letter and author reply from Ann Emerg Med with links to Free Full Text PDF download

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[2] Performance of the RAD-57 pulse CO-oximeter compared with standard laboratory carboxyhemoglobin measurement.
Touger M, Birnbaum A, Wang J, Chou K, Pearson D, Bijur P.
Ann Emerg Med. 2010 Oct;56(4):382-8. Epub 2010 Jun 3.
PMID: 20605259 [PubMed – indexed for MEDLINE]

Free Full Text Article from Ann Emerg Med with links to Free Full Text PDF download

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[3] Non-invasive carboxyhemoglobin monitoring: screening emergency medical services patients for carbon monoxide exposure.
Nilson D, Partridge R, Suner S, Jay G.
Prehosp Disaster Med. 2010 May-Jun;25(3):253-6.
PMID: 20586019 [PubMed – indexed for MEDLINE]

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O’Reilly M (2010). Performance of the Rad-57 pulse co-oximeter compared with standard laboratory carboxyhemoglobin measurement. Annals of emergency medicine, 56 (4) PMID: 20868919

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Touger, M., Birnbaum, A., Wang, J., Chou, K., Pearson, D., & Bijur, P. (2010). Performance of the RAD-57 Pulse Co-Oximeter Compared With Standard Laboratory Carboxyhemoglobin Measurement Annals of Emergency Medicine, 56 (4), 382-388 DOI: 10.1016/j.annemergmed.2010.03.041

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Nilson D, Partridge R, Suner S, & Jay G (2010). Non-invasive carboxyhemoglobin monitoring: screening emergency medical services patients for carbon monoxide exposure. Prehospital and disaster medicine : the official journal of the National Association of EMS Physicians and the World Association for Emergency and Disaster Medicine in association with the Acute Care Foundation, 25 (3), 253-6 PMID: 20586019

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Filed Under: 'Alternative' Medicine, Assessment, Critical Judgment, EMS Research Podcast, Ethics, Heresy, Masimo, Paramedicine 101, Research Blogging

The RAD-57 Pulse Co-Oximeter – Does It Work – Part II

Wed, 17 Nov 2010 06:30:11 -0500 by
–ResearchBlogging.org

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Also posted over at Paramedicine 101 (now at EMS Blogs) and at Research Blogging. Go check out the rest of the excellent material at these sites. There is a new research podcast specifically for EMS – EMS Research Podcast. On episode 2 we discuss several topics, including the research on the RAD-57 non-invasive monitor.

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Continuing from The RAD-57 Pulse Co-Oximeter – Does It Work – Part I. More on the use of the RAD-57 non-invasive monitor.

The ad says, Quick and Noninvasive Assessment of CO Levels in the Blood.

I do not disagree with those claims. The problem is not speed.

I don’t mind taking more time, if it leads to greater accuracy.

This study does not encourage confidence in the accuracy of the assessment provided by the RAD-57.

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Median laboratory carboxyhemoglobin level was 2.3% (interquartile range 1% to 8.5%), with a range of 0% to 38%. Median RAD carboxyhemoglobin level was 3.0% (interquartile range 0% to 7.5%).[1]

Even with properly trained people and repeating the test, the RAD-57 does not appear to be accurate. Most of the laboratory readings were near zero, so guessing zero for everyone would have been a pretty good guess. A Pet Rock™ can even more consistently provide the same zero reading.

Type of exposure, . . . . . . . . . . . . . . . . . . . . . . . No. (%)
Smoke inhalation . . . . . . . . . . . . . . . . . . . . . . . 68 (57)
Improperly vented fuel burning device. . . . . . 47 (39)
Unknown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 (4)[1]

Most of the people assessed were in the ED (Emergency Department) for smoke inhalation.

One of the uses for this is to assess fire fighters – look at the Masimo ad.

Should anyone ever use a low RAD-57 reading to justify returning a fire fighter to a fire?

No.

If that fire fighter has elevated COHb, that probably occurred while fighting the fire. Even if we screen every fire fighter before the fire, a zero reading on the RAD-57 does not mean that a fire fighter does not already have elevated COHb.

Sending a fire fighter, with a not yet detected elevated COHb, back into the fire is probably only sending that fire fighter back into the same environment that produced the not yet detected elevated COHb.

This is not the way to make good things happen.

A laboratory value of 15% carboxyhemoglobin was selected as the cutoff for determination of these performance characteristics according to proposed use of this RAD level for out-of-hospital triage of patients with possible carbon monoxide exposure in New York City.13[1]

The RAD device correctly identified 11 of 23 patients with laboratory values greater than or equal to 15% carboxyhemoglobin (sensitivity 48%; 95% CI 27% to 69%).[1]

Less than half of the patients with elevated COHb were correctly identified.

If we screen a fire fighter for COHb, then we need to keep that fire fighter out of the fire.

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If these results are typical of what could be expected on a fire scene?

This is a big if – but still a much safer if than ignoring these results.

Out of 23 fire fighters with greater than 15% COHb, 12 might be told to go back in and to breathe in more CO.

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I am not a lawyer, but I detect some significant legal fees in Masimo’s future, unless they make some things very clear.

The RAD-57 is not appropriate for the screening of large asymptomatic populations, except to come up with a reason to encourage those with elevated COHb readings on the RAD-57 to go to the hospital. Extrapolating from the results of this study, this will only identify about half of those with elevated COHb, so what do we do for the other half with elevated COHb?

The RAD-57 should not be thrown out, but the RAD-57 should never be used to justify discouraging someone from going to the hospital.

The RAD-57 should not be thrown out, but the RAD-57 should never be used to justify sending a fire fighter back into a fire.

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Does the RAD-57 work?

Maybe, but this study does not inspire confidence in the RAD-57.

We should not ignore this study.

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Continued in How Not to Respond to Negative Research and in How Not to Respond to Negative Research – Addendum.

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Footnotes:

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[1] Performance of the RAD-57 pulse CO-oximeter compared with standard laboratory carboxyhemoglobin measurement.
Touger M, Birnbaum A, Wang J, Chou K, Pearson D, Bijur P.
Ann Emerg Med. 2010 Oct;56(4):382-8. Epub 2010 Jun 3.
PMID: 20605259 [PubMed – indexed for MEDLINE]

Free Full Text Article from Ann Emerg Med with links to Free Full Text PDF download

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Touger, M., Birnbaum, A., Wang, J., Chou, K., Pearson, D., & Bijur, P. (2010). Performance of the RAD-57 Pulse Co-Oximeter Compared With Standard Laboratory Carboxyhemoglobin Measurement Annals of Emergency Medicine, 56 (4), 382-388 DOI: 10.1016/j.annemergmed.2010.03.041

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Filed Under: Assessment, Critical Judgment, EMS Research Podcast, Heresy, Masimo, Paramedicine 101, Research Blogging

The RAD-57 Pulse Co-Oximeter – Does It Work – Part I

Fri, 12 Nov 2010 09:24:12 -0500 by
–ResearchBlogging.org

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Also posted over at Paramedicine 101 (now at EMS Blogs) and at Research Blogging. Go check out the rest of the excellent material at these sites. There is a new research podcast specifically for EMS – EMS Research Podcast. On episode 2 we discuss several topics, including the research on the RAD-57 non-invasive monitor.

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Non-invasive monitoring for CO (Carbon Monoxide) toxicity seems to be the hot topic right now. Annals of Emergency Medicine has made its main paper, from October, on the RAD-57 non-invasive monitor free for everyone. The Doctor’s Channel has a brief video on the RAD-57 paper. The Poison Review has a brief print review of the RAD-57 paper. JEMS (Journal of EMS) has an entire supplement devoted to CO toxicity. On the EMS Research Podcast, we debate this for a while.

So, does the Masimo RAD-57 non-invasive monitor work?

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First, is there a need for some kind of non-invasive monitor?

Symptoms of carbon monoxide poisoning are nonspecific and include headache, fatigue, malaise, confusion, nausea, dizziness, visual disturbances, chest pain, shortness of breath, loss of consciousness, and seizures. Although carboxyhemoglobin levels are inconsistently related to the degree of toxicity, in the absence of a clear history, detection in the blood may be the only means of confirming suspected exposure.1[1]

Many of these can be described as flu-like symptoms. Another problem is hypochondria. When people are told that they have been exposed to something, they frequently imagine symptoms. At the other end of the spectrum, we have fire fighters wanting to go back in to fight a fire and denying that they have any symptoms. with such a diverse mix of presentations, it would be nice to have something more portable and less invasive than a hospital laboratory.

If the RAD-57 can do this, that would be a great thing for fire departments, for EMS, and for patients.

Demonstration of adequate agreement between measurements made with the RAD device and standard laboratory measurement is essential before this noninvasive method of carbon monoxide detection can appropriately be substituted for arterial or venous measurement in clinical care.[1]

Essential?

Is there any other method of assessing the validity of the non-invasive measurements of CO levels?

Not yet.

Measurement was obtained with the RAD by clipping the appropriate (adult or pediatric) probe onto the digit for a period of approximately 15 seconds and reading the carboxyhemoglobin value from the handheld device screen. Immediately after this measurement, the device was removed from the finger, replaced on the same finger, and allowed to recalibrate, and a repeated carboxyhemoglobin level was recorded from the device. Arterial or venous blood was obtained with the first RAD measurement and sent to the hospital laboratory in a heparinized syringe for direct measurement of whole blood carboxyhemoglobin, using co-oximetry (Siemens Rapidlab 1200 blood gas analyzer). Clinicians were asked to record whether the RAD measurement was technically difficult and whether the low signal quality indicator on the device was illuminated for each subject.[1]

That seems reasonable.

Let’s skip to the results.

A nice chart, but what does it mean?

The numbers on the left are the RAD-57 readings, while the numbers on the bottom are the laboratory readings. The readings should be the same. The laboratory readings are considered to be accurate. The difference between the laboratory value, or real COHb (carboxyhemoglobin – CO in the blood), and the RAD-57 value is the way inaccuracy is determined. The gray diagonal line in the middle should be about where all of the results end up, if the readings agree (if the RAD-57 is accurate).

For example, 5% from the RAD-57 (draw a horizontal line from 5 on the left) and 5% from the laboratory (draw a vertical line from 5 on the bottom), we would put a dot on the line where the two lines meet. If we take away all the lines and leave the dots, we have this chart of all 120 patient readings.

Two more examples are taken from Table 3. Laboratory and RAD COHb values(laboratory value ≥15% COHb and RAD value <15% COHb). I use the first two.

Zero% from the RAD-57 (draw a horizontal line from 0 on the left) and 19.8% from the laboratory (draw a vertical line from 19.8 [round off to 20] on the bottom), we would put a dot on the line where the two lines meet.

Zero% from the RAD-57 (draw a horizontal line from 0 on the left) and 35.2% from the laboratory (draw a vertical line from 35.2 [round off to 35] on the bottom), we would put a dot on the line where the two lines meet.

Since very few of the dots are going to be exactly on the line, we include a range of acceptable variance. I changed the gray line to a thick red line and put a thin red line on each side, parallel to the thick red line. This allows the number to be higher or lower by 5, for a total range of 10 around the laboratory reading.

This really does not make clear where the problems are likely to be. If the RAD-57 gives a false high reading and we take somebody to the hospital, that is an inconvenience, but it is not likely to lead to a bad medical outcome. The problems are when the RAD-57 gives false low readings that encourage EMS to tell the patients that there is no problem. If these patients do not receive treatment, there may be problems. The chart below shows that area. I drew a line to indicate that the upper left corner that would be included in the allowable variance range.

Even more potentially dangerous may be the patients with RAD-57 readings that are below 5, while their laboratory readings are more than 10. Do we really think that some EMS personnel will not look at these low numbers and tell patients that they have nothing to worry about?

Then there is the problem of all of the zero readings on the RAD-57. Everybody in this study was being evaluated for suspected carbon monoxide poisoning. There does not appear to have been any zero laboratory reading when the RAD-57 had a non-zero reading. There are a bunch of very low laboratory readings, but the only zero laboratory reading(s) coincide with a RAD-57 zero reading(s).

The RAD-57 zero readings are in the Pet Rock™ Area. I could run some wires and a fancy probe to a Pet Rock™. I would obtain the same result the RAD-57 did for all of these patients, who had laboratory readings of up to 35.2.

Lab   =   35.2

RAD-57   =   0

Pet Rock™   =   0

That’s not even close enough for government work.

The Pet Rock™ doesn’t need batteries or maintenance.

Is the RAD-57 that difficult to use properly?

Or

Is the RAD-57 that inaccurate?

Or

Is the RAD-57 both inaccurate and difficult to use?

Or

Something else?

Those are a lot of zeros that should not be zeros.

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Continued in The RAD-57 Pulse Co-Oximeter – Does It Work – Part II and in How Not to Respond to Negative Research as well as in How Not to Respond to Negative Research – Addendum.

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Footnotes:

–

[1] Performance of the RAD-57 pulse CO-oximeter compared with standard laboratory carboxyhemoglobin measurement.
Touger M, Birnbaum A, Wang J, Chou K, Pearson D, Bijur P.
Ann Emerg Med. 2010 Oct;56(4):382-8. Epub 2010 Jun 3.
PMID: 20605259 [PubMed – indexed for MEDLINE]

Free Full Text Article from Ann Emerg Med with links to Free Full Text PDF download

–

Touger, M., Birnbaum, A., Wang, J., Chou, K., Pearson, D., & Bijur, P. (2010). Performance of the RAD-57 Pulse Co-Oximeter Compared With Standard Laboratory Carboxyhemoglobin Measurement Annals of Emergency Medicine, 56 (4), 382-388 DOI: 10.1016/j.annemergmed.2010.03.041

.

Filed Under: Assessment, Critical Judgment, EMS Research Podcast, Heresy, Masimo, Paramedicine 101, Research Blogging
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