Wednesday, May 31, 2006

Just out in NEJM: old news about pulmonary embolism (PIOPED II)

Despite popular opinion CT pulmonary angiography has not emerged as the diagnostic modality of choice for PE. Finally, 16 years after PIOPED was reported in JAMA and 9 months after I posted the PIOPED II findings here PIOPED II is reported in NEJM.

Detailed findings, discussed in my earlier post, will not be repeated here. Suffice it to say that although CT is a useful addition to the diagnostic armamentarium it does not emerge as a clear cut stand alone modality of choice. Just as with V/Q scanning, the predictive power of CT is poor when test results are discordant with pre-test probability. A Bayesian approach using an integrated clinical algorithm is still the best method. There is a 17% false negative rate with CT. Fortunately small peripheral emboli, of questionable clinical significance, account for the majority of these false negatives. This is inferior to nuclear scanning which, if normal (as distinguished from “low probability”), demonstrated 100% sensitivity in PIOPED. Put another way, no patient in PIOPED with a normal perfusion scan had PE. Editorial comment in the same NEJM issue is here.

Tuesday, May 30, 2006

Questions raised by firing of CMAJ editors

Heated discussion continues about the Canadian Medical Association Journal (CMAJ) since my post May 20. The bitter dispute between the journal owners and the editors raises fundamental questions.

What should a medical journal strive to be?
As pointed out in this BMJ editorial from several years ago a journal’s niche could occupy any point on a broad spectrum, “from being like Brain, a forbidding, research based journal, to Cosmopolitan, a magazine full of froth and colour.” But such a niche needs specific definition. Confusion results when a journal tries to be too many things. Therein lies part of the problem at CMAJ. The journal should define what it intends to be---a scholarly research journal, a medical news magazine or a political rag. It can’t be all those. Who, for example, would think of publishing peer reviewed research in Medical Economics?

What is the appropriate role of an editor?
Perhaps that depends on the type of journal in question. If the journal purports to be a scholarly scientific publication the editor should be objective, neutral and “disinterested.” There should be no social or political agenda and no personal bent that might bias the selection or editing of articles. Dr. John Hoey, though, seems to have other ideas. In the May 11 NEJM piece in which he recounts his firing from CMAJ he writes that “the defining characteristic of an editor is quixotic idealism….” Quixotic idealism? Well, whatever that means it sounds anything but objective or neutral. Concerning the attributes of an editor he writes that “An eager propensity to poke a stick into something or somebody is also useful.” Useful, perhaps, for The American Spectator.

What is editorial independence and are there limits?
Dr. Hoey’s absolute notion of editorial independence amounts to a lack of editorial accountability. But editorial independence must be balanced against accountability. In a May 23 piece in CMAJ the interim editors write “Editorial independence should not confer immunity from accountability.” In that same article the authors note that the World Association of Medical Editors (WAME), which Hoey cites in defense of his views, has reconsidered the concept of editorial independence. Indeed, in its May 15 2006 revision, the section titled "Editorial Independence" has been retitled "The Relationship Between Journal Editors-in-Chief and Owners."

Is Hoey’s concept of absolute independence realistic? As pointed out in a recent Lancet editorial on this matter “The CMA might legitimately argue that they should not be saddled indefinitely with an editor whose policies and perspectives were not in keeping with its own views. The publisher of The Economist might not hire the editor of The Nation, and vice versa. So what is the voice that should be reflected in a journal owned by a medical association?” Consider the American Medical Association and its lobbying efforts for tort reform. Suppose the editor of JAMA, the AMA’s general medical journal, wrote and selected articles predominantly in opposition to tort reform. Would it be appropriate for the AMA to intervene? It would in such political issues where the membership had a stake, as opposed to purely scientific questions in which detached neutrality is essential. The only way to avoid such a conflict is to avoid mixing political commentary and science in the same journal.

What are the risks of political influence in a scholarly scientific journal?
Science influenced by any sort of agenda is biased and corrupt. I have given examples in the pages of this blog here, here and here. Orac gives an example here. Scientific discourse differs so fundamentally from political debate that the two are hardly compatible. The former involves objective discussion between disinterested parties while the latter involves impassioned contests between those with competing interests, with participants bolstering their positions according to their own biases. But as I posted on May 20, Hoey seems to have no problem mixing scientific inquiry with politics.

Should there be a demarcation between scientific reporting and other content such as journalism and political commentary?
Although the essential importance of demarcation should be self evident, not all agree. Another Lancet editorial on the firing said “To distinguish between a journal's responsibility to publish peer-reviewed research and investigative journalism is false.” But all sorts of problems emerge when the distinction is not clear. As the same Lancet editorial points out, “According to the CMAJ, the journal's publisher ordered a news article containing a survey of women's experiences of trying to obtain the Plan B morning-after pill (levonorgestrel) to be withheld, after receiving a complaint from the Canadian Pharmacists Association. The CMA's withdrawal request was justified on the grounds that the survey of women's experiences constituted scientific research, rather than journalism, and the editorial team should therefore have sought ethical counsel and peer review of the article.” Jerome P. Kassirer and others in this CMAJ editorial disagreed with “Contrary to the claims of the CMA that the Plan B article could be construed as a scientific study and was subject to all the requirements of such an investigation, in the opinion of the Committee, the report (both as it was intended to be published and as it eventually appeared) does not meet the definition of 'research' as understood in medical science.” Though the informal survey of women seeking emergency contraception was not research these comments indicate that the point was in dispute. The distinction was blurred, and one of the essential points of contention between the publisher and the editors was whether it did in fact constitute research. Perhaps a clear distinction would have averted the crisis.

Are there solutions?
Political debate, medical journalism and rigorous scientific reporting, each of which has an important role, are best played out in separate venues. This not only avoids confusing the different forms of writing but also minimizes conflicts of interest by keeping politics and personal bias at arm's length from scientific inquiry. Structures are already in place to accomplish this. Most professional societies have companion publications which serve separate purposes. I’ll draw an example from my own specialty organization, the Society of Hospital Medicine, which has just launched its scientific journal, The Journal of Hospital Medicine. It is a pristine, scientifically rigorous publication devoid of politics, self-promotion or items of personal or economic interest to hospitalists. The Society’s companion tabloid style publication, The Hospitalist, contains all those things. That’s just fine, because it makes no pretense at being a scholarly scientific journal.

Sunday, May 28, 2006

Heparin for ischemic stroke: still not evidence based

This study looked at low molecular weight heparin in various subsets of patients with atrial fibrillation, published in Stroke. Outcomes were not improved.

Platelets and vascular events

This bench to bedside review in Mayo Clinic Proceedings covers clinical trials of platelet antagonists and discusses the biologic mechanisms. Open access to the full text of this article is available 6 months after publication date.

Friday, May 26, 2006

Kudos to Medpundit

I knew there was another reason to miss Medpundit. She was, on occasion, willing to challenge the PC orthodoxy in medicine. In researching my post on the CMAJ mess I overlooked this.

Straight to the guts of the issue, she said: “Well, it is the Canadian Medical Association's journal, so they're well within their rights to tell the editors to tone down the politics, aren't they? It happens all the time to
political writers and editors. It isn't as if the Association asked the editors of the CMAJ to suppress scientific research papers. Political proselytizing, like religious proselytizing, doesn't belong in a scientific journal. And if the editors want to make the journal political, then they should realize they have to play by the same rules as every other political editor.”

Wish I’d said it.

Wednesday, May 24, 2006

Are state medical boards becoming draconian?

Perhaps so, opines Chris Rangel. State boards, suffering from an image of being too lax, are under public pressure to police the medical profession more aggressively. And, according to Dr. Rangel, at least in the state of Texas, an increasing frequency of complaints to medical boards, often frivolous, may be an unintended consequence of successful tort reform in that state. He writes that physicians in Texas fear the board is getting out of control and notes the case of one doctor who was “fined $500, ordered to take classes on documentation, publicly reprimanded, and all for forgetting to time and date an addendum note in a chart.” (Though I have no hard data I’ve heard of instances of this sort of thing).

Rangel writes that board investigators tend to take the attitude that the doctor is guilty until proven innocent. If that’s not already true one influential consumer activist group wants the standard to move in that direction. The Public Citizen Health Research Group wants “A reasonable statutory framework for disciplining doctors (preponderance of the evidence rather than beyond reasonable doubt or clear and convincing evidence).” And just how “reasonable” is preponderance of evidence as a standard for disciplinary hearings? I had that standard of explained to me by a plaintiff attorney when I was on jury duty a few years ago. He asked prospective jurors to imagine preponderance as analogous to “one thousand and one grains of sand” balanced on the scales of justice against “one thousand grains of sand.” Wow. Two grains of sand shy of guilty until proven innocent.

Related post here.

Tuesday, May 23, 2006

Just the FACTTs (Fluid and Catheter Treatment Trial)

Just in: For patients with ALI and ARDS, pull the PA catheter and keep ‘em dry. These long awaited results have been posted on line ahead of print in NEJM along with related editorials here and here.

We’ve long suspected the dry strategy was better. However up to now the jury was still out on the PA cath.

I’ve previously commented on the PA catheter and the wet-dry debate.

Medical webcast: physician-Pharma relationships

My latest find is Internal Medicine Grand Rounds (traditional Grand Rounds that is) at the University of Nebraska.


Dr. Martin Tobin spoke on April 14. We know Dr. Tobin as a leader in pulmonary and critical care medicine and the originator of the “Tobin index” for liberation from mechanical ventilators (frequency to tidal volume ratio) but on this occasion he spoke on “Patients, Pharma, Physicians.” This defense of the No Free Lunch position is eloquent but listen closely for the specious arguments and generalizations. (E.g., promotion influences prescribing; is this always bad? Industry-profession relationships deserve rigorous scrutiny, but should all industry supported publications and CME be rejected out of hand? Though individuals may be unduly influenced is it fair to characterize doctors as puppets?).

An interesting tidbit from Tobin’s presentation was the extent of Eli Lilly’s involvement in the Surviving Sepsis Campaign guidelines and the closely related IHI sepsis bundle. The commercial interest in these lofty initiatives deserves exposure (here’s the inside story on ties between Surviving Sepsis and a Lilly supported public relations campaign). Some take the cynical position that these guidelines are hopelessly tainted by industry influence. I take the moderate position of skepticism which looks to the primary sources of evidence while acknowledging value in the documents.

Despite flaws in the arguments there’s enough good material in the webcast to make for worthwhile viewing. Tobin presents foundational issues with a clarity that will help sharpen one’s perspective on the ethics of physician-Pharma relationships no matter which side of the debate one adheres to.

Background: Additional medical webcasts have been cited by me as well as Clinical Cases and Images. You can find more by entering your favorite medical subject into a Yahoo search under the video tab. Over time more and more institutions are posting video archives of their grand rounds.

Most physicians don’t know a long QT when they see one

Not even cardiologists, according to this study from last year in Heart Rhythm. There are many pitfalls. Sometimes the T wave is not well demarcated, and in many cases is fused with the U wave (an arrhythmogenic situation in and of itself which may have the same significance as a long QT). Many times the computer doesn’t correctly make the call.

This is concerning, because proper recognition can be life saving. It’s a basic skill we should all master. As a primary care physician or emergency physician you may be the first person to see the electrocardiogram of a patient with LQTS.

Essentials of blood banking

Here’s what takes place when you order blood products. From CMAJ.

Saturday, May 20, 2006

Fired CMAJ editor rants in NEJM

Politics versus science, editorial independence versus accountability

Dr. John Hoey wants editorial independence. Maybe he should start a blog. In the May 11 on line edition of the New England Journal of Medicine (NEJM) he recounts his dismissal as editor of the Canadian Medical Association Journal (CMAJ) and the related shake up that resulted in additional dismissals and resignations, virtually decimating the journal’s editorial staff.

Although a confidentiality agreement prevents both sides from divulging details there were known to be repeated clashes between the editors and the owners of the Journal, the Canadian Medical Association (CMA). By most accounts it’s about not only editorial independence but also politics and the mixing of scientific content with journalism.

It all came to a head with the Journal’s publication of articles in March and December of 2005 about how Canadian pharmacists question and counsel women seeking behind the counter access to levonorgestrel (Plan B). The articles were highly critical of the Canadian Pharmacists Association (CPA) which, apparently getting wind of the December story before publication from one of the reporters, complained to the CMA and responded in the journal thusly.

The March editorial asserted that counseling by pharmacists makes women “fair game for unwanted questioning and unsought advice — at their own expense” and characterized involvement by pharmacists as a “lingering paternalism.” The response from George Murray, president of CMA, made these points: “Imagine the outrage if the Canadian Pharmacists Association (CPhA) were to suggest that doctors should not ask a woman her name if she is asking for EC, or that they not be paid for the service they provide. Further, for CMAJ to suggest that the information a pharmacist collects is not kept confidential is irresponsible. Any information provided is private, secure and confidential, which would not be the case if the product was available in a convenience store or supermarket.” And this: “CMAJ's position flies in the face of the medical professions' recognition of the importance of collaborative, interprofessional practice where physicians and other health care providers have a clearly identified and valued role.”

But there are larger questions. First, is political content appropriate for a scholarly medical journal? I would disagree strongly with Dr. Hoey and argue that it is not. Such politicization occurs in the form of opinion pieces under the guise of “scientific journalism” or in less transparent forms of editorial mischief such as publication bias or the acceptance of tainted articles. How does this pollute science? For example after example read Steve Milloy’s Junk Science Judo. On page 46 he writes: “When faced with alarming ‘news’ about a new health threat (especially one that might benefit some third party), keep the slow, steady ho-hum scientific method in mind. Boring? Sure. Tedious? You betcha. Slow and deliberative? Be grateful.” It’s dangerous to mix science with public debate. Sure, science can and should inform such debate, but it should never be the other way around, and the lines of demarcation should be clear. Political discourse should not influence science. The doing and the reporting of science should be pure, pristine and sterile. Once scientific results are released from scholarly journals public debate can then be played out in other more appropriate venues.

I like the way Milloy characterizes the process of science. Tedious. Boring. Ho-hum. But Hoey takes a different view. In the May 11 NEJM piece he writes “The ability of an editor to edit depends to an important degree on the editor's own outlook and self-assurance (often mistakenly interpreted as arrogance).” (My translaton: The ability of an editor to edit depends to an important degree on the editor’s own agenda). He goes on with “An eager propensity to poke a stick into something or somebody is also useful. It is a characteristic so widespread, at least among the editors I have known, members of the ICMJE and others, that it may be essential. But the defining characteristic of an editor is quixotic idealism, a characteristic that makes publishers nervous.” Hmmm. An eloquent defense of the eternal right of journal editors to function as loose cannons.

Hoey seems to have a double standard concerning politics in medical journals. Apparently it’s OK for the editors but not for the journal owners. That untenable position is articulated in this paragraph from the May 11 article: “The notion that politically sensitive topics can be expunged from a medical journal is folly. It is also irresponsible. Physicians and their patients must have faith that professional journals facilitate a discourse unencumbered by the economic and political interests of their owners.”

Scholarly medical journals should, of course, avoid all political agendas, no matter whose. The problem can take various forms. An editor may have a political bent which the journal owners dislike, perhaps the case at CMAJ. Equally dangerous is an editorial agenda in lockstep with that of the owners, apparently the case at the Journal of American Physicians and Surgeons (JPANDS). Orac recently touched on this problem in connection with a controversial JPANDS paper purporting to demonstrate a link between mercury containing vaccines and autism. (Note that the Association of American Physicians and Surgeons opposes mandatory vaccination). The JPANDS example may be extreme but it’s nevertheless illustrative of what can happen when a medical journal cozys up to political interests. Such political affiliation has cost JPANDS a great deal in credibility as illustrated by this article by Terry Krepel (caution: ad hominem attacks here). Ironically, Hoey’s defenders seem to invoke the credibility argument in defense of more political content.

The debate about mixing journalism and politics with scholarly reporting of science was played out a few years ago in the British Medical Journal (BMJ) when that journal decided to emulate Cosmopolitan. The announcement from the pages of the January 5 2002 issue read: “The BMJ might be on a long march from being like Brain, a forbidding, research based journal, to Cosmopolitan, a magazine full of froth and colour. The trick is deciding how fast to go. Most current BMJ readers would be appalled by a BMJ that was like either Brain or Cosmopolitan, but some--- those who regret what they see as a constant "dumbing down" in our culture--- would like a journal more like Brain, while others longing for more accessibility and readability want something closer to Cosmopolitan. Today the BMJ introduces a few changes that take us closer to Cosmopolitan.” If readers wanted a dumbing down, BMJ did not disappoint. (Its heavy content of pseudoscientific fluff has earned it a venerable place on Quackwatch’s list of non-recommended periodicals).

Of course no discussion of medical politics and editorial mischief would be complete without mention of the George Lundberg incident at the Journal of the American Medical Association (JAMA). Briefly, an 8 year old study on whether oral sex is generally perceived as “sex” was suddenly selected for publication just in time to influence public debate on allegations surrounding President Clinton. Not surprisingly, Hoey and others, in the February 23 1999 issue of CMAJ weighed in with: “General medical journals are not just a repository of science….” and statements such as “policy makers, among others, crave the contributions of ‘science’” (it’s rather telling here that the authors put the word science in quotation marks). It goes on with “Moreover, it is na├»ve to think that scientific inquiry is conducted on a rarefied plane free of values and political perspectives in the first place.”

Wow. Let’s parse that statement. First, what is meant by “values?” Basic values such as scientific integrity and honesty, as well as ethical dealings with research subjects, are essential. But I would submit that “political perspectives” have no place in scientific inquiry. (Imagine the howls of indignation if that same statement was made by a Big Pharma leader with the phrase “money interests” substituted for “political perspectives).”

Finally, what about editorial independence? A reasonable view would be that journal owners should hire the editors and then let them do their job unencumbered. But just what is the job of an editor? Most would agree that it is to critically review submitted manuscripts and impartially select those that withstand rigorous scrutiny in order to ensure high scientific quality. Yes, journal owners must let editors do their job. But what is a journal to do when editors fail that job and create a conflict of interest by straying into the political arena? Nothing, apparently, according to Dr. Hoey. Dr. Hoey seems to be asking for more than editorial independence. He wants complete freedom from accountability.

Background: An expose by Michael Fumento on the tainting of science by politics as played out in medical journals.

Tuesday, May 16, 2006

How far do you have to jog to burn off that Big Mac?

Try the on line calculators at calories per hour.

The Medical Algorithms Project

Since I last checked a few years ago this resource has become a gem. It’s a vast and easy to navigate collection of reference material—more than just algorithms. Primary sources are thoroughly cited. Some of the material is dated. Nevertheless there’s enough good stuff here to include it in my favorites. It’s free but requires registration.

Playing with Google calculator

1 light year in angstroms

1 ml in bushels

9th root of 4

360 joules in BTUs

Monday, May 15, 2006

Wait times in Canada spur new industry: medical travel agencies

The Canadian Institute for Health Information has released its first survey on health care wait times, reported here in CMAJ. The wait for hip and knee replacement was reported to be around 3 months---quite a long time, but shorter than I had previously heard.

Meanwhile, companies such as Timely Medical Alternatives are responding to Canadians’ frustration with waiting lists by booking more rapid treatment in nearby U.S. hospitals. Another company,, is sending patients to India and France because of lower costs in comparison to the U.S. (Reported here in the same issue of CMAJ).

Thursday, May 11, 2006

Any med students listening in?

At least one, over at Medskool, who offers this take on basic science in medical school.

JAMA reprints CDC distortion on chelation deaths

This week’s JAMA republished the March 3 MMWR piece on chelation associated deaths being investigated by the CDC. This was spun by the CDC as a case of medication error due to “look alike, sound alike” medications and JAMA makes no effort to correct the distortion. Here’s my take from last March.

Wednesday, May 10, 2006

Medical school basic science---a follow up

Somehow I can’t quite let this go. Dr. Rangel’s post and my reply on the question of how much basic science should be taught in medical school sparked several discussion threads on other blogs.


Orac weighed in with a lengthy post of his own. One of his commenters referenced my statement about hydrophobic and hydrophilic amino acids and illustrated the self-correcting nature of the blogosphere with---

Pedantically, however, this:"some [amino acids] are hydrophobic and comprise membrane lipid bilayers" is wrong. Lipid bilayer membranes comprise phospholipids. Hydrophobic amino acid sidechains are exposed in integral membrane proteins, allowing the protein to embed within the phospholipid bilayer. Mea culpa. Sloppy terminology on my part. The principal components of cell membranes are phospholipids. Various proteins, the exposed amino acids of which tend to be hydrophobic, may traverse or be embedded in the lipid bilayer. Post revised.

Reflecting on the article about compromised basic science education in Australia’s medical schools Orac observes similar trends in the U.S.---

None of this was news to me, or, I daresay, to most surgeons. When I quiz third year medical students about anatomy in the operating room, even very basic anatomy, far more frequently than I like, I'm amazed at how little some of them know or, with the exception of students going into surgical specialties, seem to care. I've never seen a student quite as clueless as the ones described in the Australian article, but it's nonetheless clear to me that the deemphasis of anatomy and basic science in medical education is not a phenomenon confined to Australia. Indeed, the above article only echoes and amplifies complaints that I've heard for a long time right here in the good old U.S.A.

Though not in academic medicine and therefore unable to directly observe such trends I’ve suspected this sort of thing for some time. Constant tinkering with curricula and the increasing encroachment of pseudoscience in med school courses has been a long time concern of mine.

DB links to the discussion and wonders if we need a new Flexner report. As I said before Abraham Flexner may be turning over in his grave over the current state of medical education. I agree medical education needs another housecleaning. I only hope the next Flexner doesn’t have this vision for medical training proposed a few years ago in BMJ: “….gone will be the days of freestanding courses in biochemistry, physiology and anatomy” and “There will be no exams in anatomy, physiology, or biochemistry, and no one will need to learn by rote the entire Krebs cycle or the names of all those little holes in the skull.”

Thursday, May 04, 2006

Is the hospitalist movement a product of intelligent design?

A letter to the Annals of Internal Medicine seems to suggest it is. Dr. Ashok Daftary writes “Academic medicine is the carpenter that fashioned the coffin of internal medicine. Instead of re-engineering internal medicine to accommodate change it cannibalized the discipline reducing its worth, creating the hospitalist and ambulatory care internist.”

Although Retired Doc, DB and Kevin have this issue well covered I’ll weigh in as a representative of the hospitalist movement. I have to agree with DB that the movement was nobody’s grand scheme—it arose out of economic pressure as I pointed out earlier this year:

"Finally, to remind readers of the historical perspective, the hospitalist movement is a bit like the blogosphere, arising not by anyone’s personal agenda but almost as if out of thin air. About a decade ago changing practice patterns in pockets of California with heavy managed care penetration captured the attention of Robert Wachter and Lee Goldman who published this prescient
article in NEJM in which the term “hospitalist” was coined. Economic pressures were the initial driving force. As the movement gained momentum it came to be driven more and more by its original detractors, the family docs who, for a variety of reasons, chose to eliminate their hospital practices."

I’ll be the first to admit that the movement is too self promoting at times, but as DB aptly put it, it was “not a nefarious plan or conspiracy.”

Wednesday, May 03, 2006

CPAP and BiPAP in acute pulmonary edema---evidence based and ready for prime time

ER and critical care docs I’ve worked around seem to have figured this out some time ago, and now we have high level evidence to support the use of these modalities in acute cardiogenic pulmonary edema (ACPE). The meta-analysis just published in Critical Care provided robust evidence that non invasive (usually via face mask) continuous positive airway pressure (CPAP) and non invasive continuous positive pressure ventilation (NPPV, more popularly known as BiPAP), when combined with standard medical therapy (SMT) reduce mortality and the need for intubation when compared to SMT alone.

Absolute risk reductions were striking, with numbers needed to treat (NNT) for CPAP of 4.5 in preventing need for intubation and 8 to save one life. For NPPV the NNTs were 5.6 and 14 respectively. All of those results were statistically significant except for the effect of NPPV on mortality, in which the confidence interval overlapped zero. A few studies in the analysis compared the two modalities, showing a non statistically significant trend in favor of NPPV.

The authors conclude that these modalities, which already had a class IIa recommendation in the 2005 guidelines for management of acute heart failure from the European Society of Cardiology, are first line interventions and should be considered “mandatory.”

Tuesday, May 02, 2006

Refining our approach to pulmonary embolism

From the February 27 issue of Archives of Internal Medicine come three studies and an editorial on this subject.

A prediction rule using history, physical exam and arterial oxygen saturation identified PE patients at low risk. Echocardiographic assessment of right ventricular function was not required. This is appealing because the safety of initial out patient treatment of PE is not clear. The authors caution that validation of the rule in additional studies is necessary before it can be recommended as a clinical tool to select patients for out patient treatment.

In this study of emergency room patients with prior history of venous thromboembolism a negative D-dimer test (VIDAS D-Dimer Exclusion) seemed to safely exclude a recurrent event. The relatively low number of patients with prior thrombosis who have a negative D-dimer limits the applicability of this approach.

Multimodal bedside testing was as good as V/Q scanning in ruling out PE in this study. A negative clinical score combined with a negative D-dimer safely excluded PE. If these two modalities were discordant, bedside determination of alveolar dead space fraction excluded some additional patients.

It was all nicely synthesized in this accompanying editorial.

Monday, May 01, 2006

What’s the best level of PEEP for ARDS?

The struggle to make a dent in the mortality of acute respiratory distress syndrome (ARDS) has frustrated clinicians and researchers for decades. It is perhaps for this reason that there has been much tinkering with a vast array of technological advances and novel modalities, most of which have not been supported by high level clinical studies. Among the latest approaches to fail the rigorous test of evidence based medicine was the use of high “recruitment” levels of positive end expiratory pressure (PEEP). This was discussed in my recent post about ARDS.

As a follow up I should mention the paper by Gattonini and colleagues in the April 27 issue of NEJM (also recently cited by Pulmonary Roundtable). Gattonini has done pioneering work to help advance understanding of the pathophysiology of ARDS. The investigators demonstrated a method of CT imaging to determine the amount of recruitable lung in patients with ARDS. Not surprisingly patients were heterogeneous in the amount of recruitable lung present. A significant number of patients had little recruitable lung. Such patients might be harmed by high levels of PEEP. For those patients with larger degrees of recruitable lung, this study does not tell us how much PEEP is optimal.

An accompanying editorial discusses physiologic rationale and contains illustrations (with a video clip in the on line version) of ex vivo rat lung ventilation with and without PEEP, demonstrating dramatically how PEEP restores homogeneity of aeration by recruiting atelectatic areas. Striking as this illustration is the editorial writer reminds us that the ARDSnet study found no benefit of high level PEEP compared with conventional PEEP.

So what approach should we use? The best guide is still the ARDSnet PEEP scale.