New medical devices are appearing at a furious pace. Some devices such as artificial heart valves or prosthetic joints require clinical trials before they come into clinical use, but other devices obtain approval through the 510(k) Food and Drug Administration mechanism, and no clinical data are available as to whether they actually work or how they compare with other predicate devices. Such was the case with the 2 alternating pressure seat cushion devices investigated in an n-of-1 trial done by Dr Barry Farr.1
The author found himself in the difficult situation of having recurrent Staphylococcus aureus furuncles develop over pressure points on his buttocks as his multiple sclerosis progressed. Initially, the furuncles developed only after each course of steroids for a multiple sclerosis exacerbation. Then, after he lost the ability to walk without a walker, the furuncles began appearing after prolonged periods of sitting on a hard surface without steroid use. Over the 9 years before the trial began, the furuncles required increasingly long periods of warm compress applications with resultant deterioration in his quality of life. Furthermore, given the potential likelihood that the furuncles might ultimately require incision and drainage or be accompanied by bloodstream infection and/or metastatic infection and require hospitalization, the author felt that a preventative solution was necessary.
As addressed in his report, all conventional antistaphylococcal approaches such as antibacterial soaps (including 4% chlorhexidine gluconate), staphylococcal decolonization by topical or systemic antibiotics, sitting on foam cushions, and gel-filled cushions either failed or were not feasible. After extensive research, the author felt that the most promising solution to his problem was the use of an alternating pressure seat cushion. These devices were developed to mimic hospital beds that attempt to prevent pressure sores. In patients with spinal cord injuries and elderly patients requiring wheel chairs, such devices have been shown to reduce the risk of pressure sores on the buttocks2,3; however, no data exist related to the prevention of staphylococcal furuncles in the same location. When the pace of technological advance is moving so rapidly that randomized clinical trials cannot keep up with determining what is optimal therapy or when randomized clinical trial are too expensive to perform, one approach that has been shown to be quite valuable is an n-of-1 trial.
A recent review of 108 n-of-1 clinical trials reported and published in peer reviewed medical journals between 1985 and 2010 concluded that n-of-1 trials are a useful tool for enhancing therapeutic precision in a range of conditions and should be conducted more often.4 Of note, only half the trials had a statistically significant end point, with the other half using a graphical comparison or a clinical significance end point. It has been particularly emphasized that an n-of-1 trial allows the optimization of a treatment approach for single patients.5 This is especially true in areas where substantial heterogeneity exists in the study population.4 Potential problems with this approach include the following: (1) many journals will not publish n-of-1 trials for unclear reasons, (2) the interventions frequently cannot be blinded (as in this study) introducing the potential for bias, and (3) there is substantial potential for wash-over, which is best addressed, if feasible, by having a washout period.4,5
Using the repeated crossover design with an A-B-A-B design recommended by many for n-of-1 trials, the author found that cushion B (Ease Cushions [Paradise, Calif]: Ease G-100 or Ease Stage 1) was associated with 6 abscesses, whereas cushion A (Aquila Airpulse PK [Aquila Corp, Homen, Wis]) was only associated with a single abscess in a similar period of use. This end point was quite definitive, was statistically significant, and clearly accomplished the goal of improving his quality of life. Of additional note, the Aquila cushions prevented buttock discomfort from developing, whereas the 2 Ease cushions were much less effective at preventing buttock discomfort. This suggests that unmitigated pressure, with its accompanying reduction in local blood flow, is a fundamental part of the pathogenesis of furuncles in this setting. Without this trial, the author’s ability to continue to perform things important to him, such as writing, would have been greatly curtailed.
One consideration that may not be obvious to the reader and thus bears emphasizing is that, to a well-trained infectious disease physician/epidemiologist (such as Dr Farr), in this unblinded study design, it would become quite clear long before the study reached statistical significance that one cushion was better than the other cushion. Thus, to reach the desired statistical end point, the investigator/patient had to knowingly continue to experience all of the pain and suffering that occurred with each new furuncle. This puts Dr Farr in the same company with a long list of other physicians who have experimented on themselves to improve the greater good. In acknowledgment of your sacrifice in such a way that it will improve the lives of others, Dr Farr, I solute you.
1. Farr B. Preventing recurrent, pressure-related furuncles with an alternating air cushion. Infect Dis Clin Pract
. 2013; 21: 21–24.
2. Gil-Agudo A, De la Pena-Gonzalez A, Del Ama-Espinosa A, et al.. Comparative study of pressure distribution at the user-cushion interface with different cushions in a population with spinal cord injury. Clin Biomech
. 2009; 24: 558–563.
3. Brienza D, Kelsey S, Karg P, et al.. A randomized clinical trial on preventing pressure ulcers with wheelchair seat cushions. J Am Geriatr Soc
. 2010; 58: 2308–2314.
4. Gabler NB, Duan N, Vohra S, Kravitz RL. N-of-1 trials in the medical literature: a systematic review. Med Care
. 2011; 49: 761–768.
5. Lillie EO, Patay B, Diamant J, et al.. The n-of-1 clinical trial: the ultimate strategy for individualizing medicine? Per Med
. 2011; 8: 161–173.