MAST Pants....

[Ace844]

(Reading Smart: Discovering What the Data Do and Don’t Say

By Elizabeth A. Criss @ RN, MEd)

When a commercial says "four out of five" people agree, what does that mean? The advertiser is hoping you think it means 80 percent of all people support that particular product or idea. But couldn’t it also mean something else? For instance, what if they had only asked five people for their opinions or mailed out only 10 surveys and received five responses – four people for, one against. There are many other possible combinations that could produce these numbers and still not represent 80 percent of the population. Is this wrong? It’s hard to say. The best response is probably that results, like beauty, are in the eyes of the beholder.

That’s all well and good for TV commercials, but this same "data torturing" can occur in medical research. Raw data generated by a project really doesn’t mean anything until it’s analyzed, and the tools used to analyze this information and the way data is compared determine what conclusions can be drawn. That can leave a lot of room for interpretation.

Let’s say you’re interested in finding the latest research on the pneumatic anti-shock garment (PASG). Flipping through the journals, you find a study evaluating the effect of PASGs on nontrauma patients. The abstract states this is a prospective study done on 300 patients during a 12-month period. The findings of the study indicate that PASGs are of little value in the treatment of nontrauma patients in the prehospital environment.

Intrigued by these findings, you read the article. The results section describes the 300 patients. You note that the study divided the patients into two groups: blood pressure (BP) > 60 mmHg and BP < 60 mmHg. To assist in understanding the results, the authors include Tables 1 through 3.

Moving on to the discussion, you note the authors’ conclusion: "For the majority of nontraumatic patients, the PASG is not beneficial and possibly increases mortality." To support their conclusion, there is a more lengthy and detailed explanation than you found in the abstract. Looking back over the information in Tables 1 and 2, you believe this to be a reasonable conclusion.

But what about Table 3? Didn’t it demonstrate that PASG use in these patients reduced mortality? It did, but the authors’ conclusions are still valid. It’s important to note that the authors said "in the majority of "patients," not that the results applied to all patients. So, why didn’t the authors make more reference to the group in Table 3?

Table 3 highlights a subgroup, patients, with a BP of < 60 mmHg that was positively affected by PASG use. Sometimes groups like this are left out due to the small number of patients in the subgroup; a small sample size does not allow the authors to calculate meaningful statistics or draw any significant conclusions. Without statistics, the most the authors can do is discuss the result as a possible trend. Nevertheless, the authors should at least mention this group as a potential area for future research. Another possibility for leaving subgroups out of a discussion is that they did not support the author’s original hypothesis. Although not entirely ethical, this has been done.

The point of all this is that it is important to understand that data can be manipulated. Researchers will sometimes drop patients who don’t fit the desired hypothesis or support a certain position. It is important for you, the reader, to scrutinize the literature and account for all the patients. If the authors say "majority," instead of "all," find out where the rest of the population went. Be suspicious. Ask yourself if these patients were deliberately left out, or if the sample was just too small to be meaningful.

Most of the research published today is well-controlled and scrutinized by professional review panels. However, it doesn’t hurt to become critical reader and ask questions.

Elizabeth Criss, RN, MEd, serves on the Prehospital Care Research Forum Board of Advisers, is a senior research associate at the University of Arizona in Tucson and a base hospital coordinator at University medical Center in Tucson.

This article was reprinted from JEMS, March 1994.

Table 1

All Study Participants

Number of Patients Number of Deaths Percent Mortality

PASG 165 50 30.3

No PASG 135 30 22.3

Table 2

Patients with BP>60 mmHg

Number of Patients Number of Deaths Percent Mortality

PASG 115 44 38.3

No PASG 102 22 21.6

Table 3

Patients with BP<60 mmHg

Number of Patients Number of Deaths Percent Mortality

PASG 50 6 12

No PASG 33 8 24.2

[Ridryder 911]

Ace, this is so important it should be a separate topic. I know 3 of the original authors of the Houstan MAST studies. They are renowned and I respect them very much... now with this saying, research on how this started, whom did the research, and the criteria, as well as the variables and population control etc.

THey hate to see me enter any symposium they are talking at.. there is a reason. Like all studies, one need to really understand research and statistics. As well the diversity of how studies are performed.

The PASG Houston study DID NOT describe there was a increase in deaths, or injuries, rather it demonstrated there was no increase in survivability. Rather or basically there was NO difference.

Now, one has to see what type of patients were studied, the application of PASG, the duration the patients had them on, as well as deflation procedures.

If I can recall part of the study involved application of the PASG suit until the "pop off" valves occur. Has anyone ever been able to do this? I have tried on mannequins, and have had the Velcro split or rip apart.. but as of yet NEVER had the pop-off valves sound. I can assure you the pressure required to do this is very high. As well, most medics knew the theory.. pressure increase the lumen of a wound... as well as we had figured out auto transfusion was a myth.

When examining the patients that was studied and the level of trauma they received, I doubt even a trauma sugeon being there in 3 minutes would change the outcome on some. (i.e multiple .357 hollowpoint to chest).

No, believe it or not I am not a big proponent of PASG. Yes, they assist and help in some shock syndromes and situations when applied and used appropriately, but very few cases. What I am passionate for is true an valid studies, having more EMS professionals understanding research and possessing the knowledge of how to truly read and interpret studies as well. Hopefully, we will not have a "knee jerk" reflex again.

* Ironically, PASG is now being marketed under a new name and used for O.B. situations for "hypotensive" patients. As funny, there is so many reports on how well this device works...lol

R/r 911

[AZCEP]

Honestly, if we are going to use them, we need to understand how the device works. Yet another problem to be solved through education.

For lower extremity fractures and unstable pelvic fx, there is nothing better. Aside from a full body vacuum splint, which few agencies can afford to part with.

Like every patient we need to manage, think the problem through and manage accordingly. Occasionally, you will find that the navel-down air splint (MAST/PASG) is the best tool for the job.

[AZCEP]

One of my co-workers made the mistake of asking where the MAST suit was located, and if I had ever actually used it. What followed was pretty entertaining.

We pulled it out, attached the pump, inflated the compartments--no pop-off valves to open--listened closely, and discovered the air bladders had dry rotted. We basically had a nylon encased, rubber swiss cheese.

As we are getting this mess taken care of, we respond to an elderly fall victim. When we arrive on scene we find our patient lying flat on her back on the floor, with her left femoral head obviously dislocated from the socket. IV/Pain meds later, patient moved to LSB with MAST in place. Took a few minutes to explain how to properly secure the velcro, inflated to just enough pressure to splint, and off to the hospital we go.

Arrive at the ER, and no one is able to understand why I didn't mention the patient had no blood pressure. I told them her pressure is fine, and the response was, "Why did you use the MAST suit?" A quick inservice later, the staff shaking their heads agreed that was probably the best way to immobilize this patient's injury.

[Ace844]

"azcep,"

This is slightly :

That's so You don't even know it!! :wink: 8) :shock:

[marq=down:e573d105a2]NICELY DONE!!![[/marq:e573d105a2]

:::

[bassnmedic]

We used to have them in our Cardiac Areest protocols back in Atlanta in the early 90's thru around 96 after that I haven't seen a set of PASG inflated on a patient.