I was rather disappointed by the syringe design paper, perhaps because I rather enjoyed Dan Formosa’s talk to our class. The premise is nice: thoughtful design for ergonomic needs of the patient at hand; however, it’s not clear after reading the paper whether what they did was actually a good thing.
The test method is perhaps where I had the most issues. They are testing with a set of RA patients but do not make it clear where in their treatment they are at: at the time of testing, are they right after an injection/IV or about ready for a new one? There is not a lot of detail on the technical setup of the procedure; I was expecting diagrams with the placement of force sensors (dynamometers) for both types of syringes and perhaps a brief overview of the expected impact of new torsion (due to the wider grip) on the general forces of the system – none of this was in there. There was no discussion of how their artificial skin compared to real skin, especially in regards to resistance forces; furthermore, it wasn’t clear why they didn’t perform the procedure on actual skin (the introduction of a false, injectable surface introduces a psychological bias).
The results/discussion were confusing. The data and discussion all pointed to there being greater force exerted with the new design; however, they were attempting to produce a product that required less force to inject the medicine. Their discussion attempted to explain this by explaining that they were able to exert more force, but the data showed that more work was required by the new design – meaning they designed a syringe that was harder to press down! I believe they wanted to suggest that the design gives the user a better mechanical advantage in using the device, but by using a single isometric measurement they are only measuring the linear force involved (which shouldn’t be changing, work-wise, if their design functioned well). Getting a more granular measurement (i.e. pressure – force per area /finger) would be more appropriate.
A few other observations… There were quite a few typos and grammar mistakes – which doesn’t lend itself to being well-peer reviewed. They mention that “severity of arthritis had no statistically significant effect on the mean and maximum forces exertion [sic] during the injection,” which seems to have huge implications on their study; if the arthritis isn’t making a noticeable difference, they have no reason not to perform more intricate studies on a much better controlled setup. There was a “technical error” in their execution which resulted in almost 1/3 of the data not being captured for a large datapoint – this should have been enough reason to reset the experiment. Finally, there was a high p-value for their work and duration numbers in the results section, suggesting that the data wasn’t very clean.
All in all, it seems as though all they proved is that patient perception of a design in the style of (and perhaps bearing) the OXO brand gives a perception of better usability. I’m sure they could have proved a biomechanical benefit, but the paper suggests otherwise.
[Sheikhzadeh, Ali, et al. “The effect of a new syringe design on the ability of rheumatoid arthritis patients to inject a biological medication.” Applied Ergonomics 43.2 (2012): 368-375.]