Do Double-fan Surgical Helmet Systems Result in Less Gown-particle Contamination Than Single-fan Designs?
Authors: Vermeiren Alex , Verheyden Maarten , Verheyden Frank 
Published: January 2020

Abstract

Background
Surgical helmet systems commonly are stand-alone systems with a single fan blowing air into the suit, creating positive pressure that blows particles out through areas of low resistance, possibly contaminating surgical attire and the surgical field. Two-fan systems were developed more recently to release spent air, also theoretically lowering pressure in the suit and decreasing the aforementioned risk of particle contamination. To our knowledge no study to date has measured the potential differences in gown particle contamination to support this hypothesis.

Questions/purposes
We compared a commonly used single-fan system versus a two-fan system and asked: (1) Which fan system results in less gown particle contamination? (2) Are there differences between the systems in the location of contamination?

Methods
Using an existing experimental study model, two surgeons performed five 30-minute TKA simulations comparing a single-fan to a double-fan helmet system after applying fluorescent powder to the hands, axillae, and chest. Both are two-piece hood and gown systems. The single-fan sits on top of the helmet blowing air into the suit; the double-fan system has a second fan positioned at the rear blowing out spent air. Ultraviolet light-enhanced photographs were subsequently obtained of the flexor and extensor surfaces of the arms, axillary areas, and front and back of the chest. We chose these locations because they all contain either a seam or an overlap between gown and hood or gloves through which particles can escape. The images were scored for contamination on a scale of 1 (zero specks) to 4 (> 100 specks) by three independent observers. Interobserver correlation was assessed through Spearman’s test yielding 0.91 (95% CI 0.86 to 0.94; p < 0.0001), 0.81 (95% CI 0.73 to 0.87; p < 0.0001) and 0.87 (95% CI 0.80 to 0.91; p < 0.0001) between observers 1 and 2, observers 1 and 3, and observers 2 and 3, rendering the used scale reliable. Results of the observers were averaged and compared using the Mann-Whitney U test.

Results
There was no difference in overall gown particle contamination between the systems (overall single-fan median contamination score 2.5 of 4 [interquartile range Q1-Q3 0-3.42] versus double fan 1 out of 4 (Q1-Q3 0-3); p = 0.082), but all tests showed there was contamination at the gown-glove interface. In general, there were few differences between the two systems in terms of location of the contamination; however, when comparing only the axillary regions, we found that the single-fan group (median score 3.67 [Q1-Q3 3-4]) showed more contamination than the double-fan group (2.33 [Q1-Q3 0-3.08]); p = 0.01.

Conclusion
We found no difference in gown particle contamination between a single-fan and a double-fan helmet design. However, we note that contamination was present in all tests with both systems, so surgeons should not assume that these systems provide a contamination-free environment.

Clinical Relevance
When using such helmets, the surgeon should not place items close to the axillary region because the seam of the gown may have low resistance to particle contamination. Gown designs could be improved by creating better seals, especially at the arm-body seam.