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The Surgical Mask: Are New Tests Relevant for OR Practice?
The Surgical Mask: Are New Tests Relevant for OR Practice? NATHAN L. BELKIN, PHD
S
ince the inception of surgical mask use more than a century ago, there has never been a universally accepted, standard test method for determining the filtering efficiency of surgical masks. In its guidance document for manufacturers who are filing a 510(k) for marketing approval of a new mask, the US Food and Drug Administration (FDA) recommends two types of tests for demonstrating that capability.1 One test measures particulate filtration efficiency using an unneutralized aerosol of 0.1-micrometer latex spheres at a challenge velocity between 0.5 cm/ second and 25 cm/second (ie, approximately 8 L/minute to 380 L/minute for a 9-cm radius mask).1-4 The other test measures bacterial filtration efficiency (ie, the mask’s ability to prevent the passage of aerosolized bacteria1), using an unneutralized 3 ± 0.3-micrometer Staphylococcus aureus aerosol at a flow rate of 28.3 L/minute.1,2,5-7 In neither case does the FDA require a minimum level of filter performance.2 This article explores the work done by a host of researchers in the development of both masks and filtering efficiency over the years and questions the relevance of these new tests to a surgical mask’s inuse conditions.
EARLY DEVELOPMENTS The work of Mikulicz8 and Flugge9 in 1897 demonstrated the presence of bacteria in droplets from the nose and mouth. Their finding was confirmed by the publication of Hamilton’s study10 in 1905, which demonstrated the importance of droplets of sputum in disseminating tuberculosis infection. This initiated research on the filtering capabilities of materials for masks that preceded © AORN, Inc, 2009
the use of masks in surgery. In 1918, Weaver11 published the results of his study on the role that a mask could have in preventing the spread of diphtheria, meningitis, pneumonia, and other diseases. He introduced the practice of wearing gauze masks covering the nose and mouth when caring for patients. Their use proved to be so successful that he recommended them for use in households in which those with diseases could spread the disease by nasopharyngeal discharge. As an extension of the practice, he also called for every patient entering an ambulance to don a mask and to continue wearing it until the patient reached his or her hospital bed. Later that year, Capps suggested a new dimension to mask use.12 Inasmuch as its use had proven to be effective in protecting health care workers from
ABSTRACT Since the turn of the 20th century, when researchers were discovering the presence of bacteria in droplets from the nose and mouth and the role these bacteria played in disease transmission, masks have been used as a method to protect both health care providers and patients from respiratory diseases. In 1926, the first study was published that indicated masks might also play a role in reducing the incidence of surgical site infections. That report spearheaded the development of new mask materials and designs and devices to demonstrate their filtering efficiency. This article provides a historical review of the work done by researchers over the years and examines whether tests to determine the filtering efficiency of surgical masks, including those recently adopted by the US Food and Drug Administration (FDA), are relevant to actual OR conditions. Key words: surgical masks, FDA guidance, filtering efficiency, in-use conditions. AORN J 89 (May 2009) 883-891. © AORN, Inc, 2009.
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contagion, it seemed reasonable that patients wearing a mask could similarly be protected from either primary contagion, or if they were already ill with an infection, from a second contagion.
TESTING
FOR
EFFECTIVENESS
All the attention was being directed simply on the use of masks not on the material of which they were made. Inasmuch as the material had heretofore only been identified on one occasion, it was believed that masks had all been made of the same type of material: gauze. Prompted by the fact that their masks were being procured from several sources, Haller and Colwell observed in 1918 that there were extreme variations in the number of layers of gauze used in the masks as well as in the quality of the gauze itself.13 They concluded that the amount of gauze placed in superimposed layers necessary to provide complete protection from those who were infected had to be the equivalent of 300 threads of fiber to the square inch. As for the size, masks were to be 8 inches long and 5 inches wide. They also developed and posted rules for contagious wards that included the use of the mask. The essential principle of their use was that patients out of bed and out of their cubicle were never to be unmasked, except when alone in the washroom. Although no data regarding the results of the practice were statistically recorded, they believed that it significantly lessened the incidence of cross infection. That same year, having defined the mask’s two-fold purpose as 1) protecting the wearer from infectious material from the respiratory passages of the patient and 2) protecting the patient from such material as the wearer may carry in his or her nose and mouth, Doust and Lyon14 proceeded to assess the efficiency of masks in preventing the dissemination of infectious material from the mouth during speaking or coughing. As the first study of its kind, the findings proved to be quite revealing. Whether the mask was made of as few as two or as many as 10 layers of coarse gauze, the results were not dramatically different. When masks made of from two to five layers of a mediumquality gauze were tested, the results proved to
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be more effective in all circumstances. This led Weaver15 to introduce a new dimension to testing the mask’s effectiveness in 1919. He reported on the mask’s influence on droplet infection in terms of the distance traveled by mouth droplets that had been driven out in forced respiratory efforts. He found that the effectiveness of the gauze was directly proportionate to the fineness of the weave and the number of layers used. Based on these findings, he adopted the use of a mask made of three layers of an absorbent gauze with a mesh thread count of 44 x 30. He found that the masks were not only useful as protection for health care workers but were also useful when worn by infected individuals to prevent contamination of their surroundings.
AN IN-VIVO SETBACK An outbreak of influenza in 1919 brought about a challenging situation for warranting compulsory use of the mask in attempts to mitigate an epidemic. Because influenza is a dropletborne infection, it appeared that wearing masks was a technique based on sound reasoning and that favorable results could be expected from their use. Their failure to prevent the spread of the disease was disappointing, although the use of masks was widespread. California health care officials Kellogg and MacMillan reported encountering a number of problems that had not been anticipated that seemed to account for this failure.16 These included use of a large number of improperly made masks; faulty wearing of the masks (eg, masks that were too small and covered only the mouth); and masks not worn at the proper times.
THE NEED
FOR A
MASK
IN
SURGERY
Up to this point, the use of a mask had been based on the findings reported by Mikulicz8 and Flugge9 in 1897. These focused on the transmission of bacteria found in droplets that were expelled from the nose and mouth. No mention had yet been made of mask use being able to influence the incidence of surgical site infection (SSI). Mask use in surgery gained considerable attention after the publication of Meleny’s first study in 1926, in which he reported having
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seen a reduction in the incidence of SSI when masks were worn by the surgical team.17 In his subsequent study published nine years later, however, Meleny reported that the rate of infection with the use of masks was closer to 15% than the 2% to 5% range that had been anticipated.18 The questions to be answered concerned the origin of the organisms and how they were able to gain a foothold in the tissues. After scrutinizing all the steps of sterile technique, Meleny determined that the important causes of SSIs were organisms from the • noses and throats of the members of the surgical team, • hands of the surgical personnel, • skin of the patient, • air in the OR, and • instruments and materials used in the procedure. Based on the findings, a series of changes were subsequently implemented that included the proper masking of the members of the surgical team.
THE “GERM-PROOF” MASK The first study that referred to the mask as a “surgical mask” was published by Walker in 1930.19 Prompted by a number of deaths in surgery, he surveyed 100 hospitals concerning the surgical masks they were using. Based on the results, he proposed the minimum capabilities for a surgical mask to be considered germproof: • it had to be comfortable and not overly warm when worn and cover both the nose and mouth; • it could not cause fogging or condensation of moisture on lenses of those wearing glasses; and • with both the nose and mouth covered, it would permit the wearer to talk for one hour, and when moistened for the last 15 minutes, would still maintain its filtering efficiency and not permit the passage of organisms. Despite the endless hours and exhaustive thought dedicated to all of his experiments, Walker admitted that he was not able to present the community with the ideal surgical mask. He
In 1926, Meleny reported a reduction in surgical site infections when masks were worn by members of the surgical team.
did, however, develop a surgical mask that included a 6-inch square of rubber taken from a discarded surgical glove that had been inserted between two layers of 10-inch squares of gauze, which he considered to be germ-proof. It was the germ-proof concept that prompted Blatt and Dale20 to construct a dust-proof tunnel to be used in determining a surgical mask’s effectiveness in 1935. Whereas comparative data led them to conclude that the surgical mask made of six layers of gauze was bacteriologically ineffective, they reported finding two layers of a new cellophane-and-gauze deflection-type mask to be comfortable, effective, nearly germ-proof, and inexpensive.
THE ERA
OF
NEW MATERIALS
AND
DESIGNS
The first change in the basic material as well as design was reported by Waters in 1936.21 The mask was made of a transparent, impermeable, lightweight, noncombustible substance—a cellulose derivative called “plastecele.” In addition to completely covering the mouth, chin, and nostrils, its design deflected breath spray away from the wound. In 1938, Arnold returned the focus from deflection back to the filtering capability.22 He tested masks made of a new material consisting of a combination of cotton and wood cellulose in the form of a creped wadding called “cellucotton.” His tests confirmed that the greatest source of oral bacterial flora occurred during loud talking, and they either escaped or were deflected above the mask and lateral to each side of the mask. Perhaps the most significant study published before World War II was reported by AORN JOURNAL •
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Hirshfield and Meyers,23 whose experiments were designed to test the efficiency of the masks themselves. Based on what they considered to be a shortcoming in the work done by their predecessors, they felt that a mask’s filtering efficiency should be assessed by its ability to prevent the passage of both droplets and droplet nuclei, the two mechanisms by which airborne infections could be transmitted. Using an airtight chamber, they tested a variety of masks of different materials under what they described as usual conditions of actual use. They found the masks to be grossly inadequate because they allowed large numbers of organisms to escape through or around them. They attributed these deficiencies to the inability to construct a mask capable of preventing the passage of all bacteria without making it so resistant to the passage of air that breathing through it would be arduous and the difficulty of fitting a mask to the face in such a way that air did not escape around it.
THE POST WORLD WAR II ERA For a period of some 20 years after the war, little work was done on either the development or efficacy of the surgical mask because of the surge in the improvement of surgical equipment and the prophylactic use of antibiotics. With the lack of evidence that masks could prevent SSI, doubts as to their need prevailed. Collected opinions ranged from a firm belief in their effectiveness to an equally definite disbelief. It was argued that during quiet breathing, few, if any, bacteria were expelled from the nose or mouth. On the other hand, it was generally agreed that during sneezing, and to a lesser extent during coughing and talking, particles, many of which had been shown to contain bacteria, were blown from the nose and mouth. All things considered, surgical masks were presumably viewed as being valuable if they shielded the patient’s wound from pathogenic bacteria from surgical team members’ noses and mouths. On that basis, the consensus was that the mask could do this by either filtering bacteria passing through it or by being impervious and deflecting the expired air so that it traveled behind the wearer’s head. The focus was increasingly
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on the cleanliness of the environment, however, and the surgical community directed its attention to the use of gloves, sterile gowns, and drapes.
TESTING NEW MATERIALS
AND
DESIGNS
Nevertheless, during this period, manufacturers introduced different materials and designs of surgical masks, and each manufacturer used different test methods to demonstrate the virtues of their product. This prompted a prestigious group of English clinical investigators, headed by Shooter, to try to validate the manufacturers’ claims in 1959.24 The first mask they examined was a filtration type of “basket-shaped” mask that fit fairly snugly over the nose and chin and was made of four layers of gauze with a thread count of 46 threads to the inch. The second type was a “tail-type” or deflection design, made of a “double thickness of closely woven cambric”24(p247) with a piece of paper inserted between the layers. A tail of the cambric was attached to the mask when worn so that in addition to the mask covering the nose, the mouth and chin would be covered and the tail would hang down the wearer’s neck and be tucked under the OR gown. It should be noted that the fit over the cheeks was loose. The third and last mask that the researchers examined was another deflection design made of paper with the intent that it would be worn once and then thrown away. It consisted of an outer and inner layer of paper that completely enveloped a pad of cellulose wadding. It covered the nose, mouth, and chin but fit loosely around the cheeks. Based on the results of their investigation, the group was able to confirm the conclusions of others to the effect that all three masks protected the area in front of the mouth from many of the wearer’s mouth and nose organisms, and increasing the thickness of the mask or improving its fit could lead to a point at which it would be difficult to breathe. Perhaps the most worthy of their observations was made possible by the uniqueness of their testing apparatus, which indicated that with the deflection type mask, it seemed probable that deflected, expired air would inevitably carry some of the bacteria
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behind the head. This may well have accounted Up to this point, although a considerable for the experiences reported earlier by others amount of work had been done to assess the who had not considered the deflective type of mask’s filtering efficiency, relatively little had mask acceptable because it did not reduce the been done in terms of measuring the quantitatotal count of bacteria in the room. tive bacterial contribution of nasopharyngeal It was also noted that the practice of lowerexpirations to the atmospheric environment. ing the mask around the neck created a risk of One of the shortcomings of the techniques was contaminating both the mask’s outer and inner that they failed to measure the very small surfaces. For that reason, it was suggested that droplets and droplet nuclei that were not proif a fresh mask could not be available for every jected any appreciable distance by virtue of situation, the hands should be washed each their lack of kinetic energy. time the soiled mask was touched.24 With the availability of the Andersen samThe following year, Rockwood and pler—a device that collects microscopic organO’Donoghue added a new dimension to the isms from the air using a series of filters—in the mask’s filtering efficiency.25 late 1950s, however, that deterSpecifically, this related to the mination could be made. With length of time a mask could the objective of advancing the be expected to maintain its test methodology, Greene and effectiveness while being Vesley introduced a testing In 1961, Castaneda worn. Based on the protocol chamber to best accommodate of their test, they concluded its use in 1962.28 Their tests led observed that the ideal that their mask could not be them to conclude that the mask still had not considered suitable for more mask’s filtering capability itself than three hours of use. Idealwas of little value unless combeen developed. ly, they recommended that the plete control of the environmask be changed after each ment could be provided. use regardless of the length of Still faced with concern for time it was worn. establishing a balance beAround the same time, tween the mask’s filtering effiKiser and Hitchcock26 introduced a newly ciency and wearer comfort, Ford and Peterson designed mask made of a flexible polyvinyl in 1963 introduced both a new material and testing device.29 Rather than testing masks plastic with wing-like cheek pieces to deflect air posteriorly. To trap moisture and bacteria, a while they were being worn by humans, they replaceable cotton and wool insert, intended to used the Andersen sampler with a compressed be changed after every use, was incorporated air source. Eleven different masks were evaluinto its construction. Despite its high filtering ated including one disposable mask made of efficiency, it was not ideal because the wearer spun glass. Although the more expensive, sinhad to speak quite loudly to make himself or gle-use mask was found to be the most effecherself heard. tive, the critical question was whether its perIn 1961, Castaneda observed that formance justified its cost. A year later, Nicholes30 reported on the The ideal mask has yet to be developed. None, results of his tests that used a proprietary new so far, has succeeded in combining comfort device to evaluate five masks made of a variwith bacteriologic security. . . . Even upon ety of different materials, including cotton the development of such a device, whether in gauze, a molded non-woven fabric, and fine the form of a more perfect mask or some bacglass fiber mats. The mask made of the fine tericidal medium, other aspects of surgical glass fiber mats proved to be superior to the technique and the care of the wound will others. Its thickness ranged from 1.5 mm to continue to be of paramount importance in 2 mm and it had the ability to remove 96% to the prevention of post-operative sepsis.27(p428) 98% of the bacteria or viruses from the aerosol AORN JOURNAL •
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The popularity of the first single-use, disposable mask spurred the design of other throw-aways. New masks were made of a number of different materials, including polypropylene fibers, polyester-rayon fibers, and cellulose fibers (ie, paper).
challenge; its design enlarged the total air diffusion but increased breathing comfort.
THE DISPOSABLES Spooner’s historical review in 1967 31 summarized the fact that the filtering efficiency of gauze masks was negligible; that dampening further decreased their efficiency; that improper fitting permitted bacteria to escape from the sides of the mask; and that when made of multiple layers, they were most uncomfortable to wear. On the other hand, the deflector-type masks, although effective in preventing exhalation of bacteria directly in front of the wearer’s mouth, were again deemed inadequate because they did not contribute to a reduction in the number of colonies of bacterial count throughout the room. Because of the popularity of the first singleuse, disposable mask, several other throwaways were introduced. New masks were made of a number of different materials (eg, polypropylene fibers, polyester-rayon fibers, cellulose fibers [ie, paper]). These developments called for yet another method to ascertain which material provided the maximum level of protection for the patient. Two researchers, Madsen and Madsen,32 rose to the occasion in 1967, using the testing chamber designed by Greene and Vesley along with the Andersen sampler. Rather than using
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humans, they incorporated forced air and an artificial head (ie, manikin) that had a rigid nose bridle and soft cheeks. The mask’s filtering efficiency was expressed as the percentage of bacteria retained by the mask as compared to a control when the manikin was not wearing a mask. The relative efficiency of the masks was found to be, in descending order: polypropylene fibers, polyester-rayon fibers, glass fibers, and cellulose. At the same time, the results of the Ford, Peterson, and Mitchell three-phase, three-year study33 were released. The first phase was dedicated to a filtering test of 14 commercially available masks; the second phase examined the bacterial threat from the nasopharynx of the personnel to the patient’s open wound; and for the third phase, the researchers performed a bacteriological analysis of all the wound infections. Based on the results of the first phase, the researchers found that the mask made of fiberglass possessed a high filtering efficiency, and they used it exclusively for the three-year period. In the second phase, the organism most frequently found in 90% of the nasopharyngeal cultures of the surgical personnel was alpha hemolytic streptococcus. In the third phase, of the total of 2,987 clean procedures, 71 wound infections were reported. In that group, 31 infections were caused by S aureus, five by S epidermis, and the remaining by mixed flora. In the total of 1,092 clean-contaminated cases, there were a total of 58 infections, with 18 caused by S aureus alone, one by S epidermis, and the balance by mixed flora. Based on their findings, the investigators concluded that they had validated the use of a mask to protect the open surgical wound. They maintained, however, that in addition to filtering efficiency, many other factors were associated with mask use, including fit, breathability, lack of allergenicity, disposability, cost, product consistency, and availability. As comprehensive as the three-year study was, several questions remained. For example, there was the matter of how long a mask could be worn before its filtering efficiency would be reduced and whether a mask should be changed at certain fixed periods because it became ineffi-
Belkin
cient when wet. These issues were addressed by Dineen34 in 1971. Using a specially designed cloud chamber that included the use of the Andersen sampler, he examined 11 different masks. He tested new gauze masks that had been laundered once and new (ie, unused) disposable masks, testing all the masks after they were worn for periods ranging from one to eight hours during actual procedures. Only four of the single-use and the one gauze mask passed Dineen’s tests for filtration when he tested them both wet and dry. Although there were variances in their filtration efficiency, contrary to general belief, the more efficient masks did not lose their ability to filter after prolonged use and moistening. What was disconcerting were the variances in the filtering efficiency of the masks, not from one manufacturer to another, but in certain instances, from mask to mask from the same manufacturer. Then in 1975, Quesnal reported on his study on the filtering efficiency of six different masks of varying design and composition.35 Using an Andersen sampler and a testing chamber similar to that designed by Greene and Vesley, Quesnal collected and sized the contaminated particles through or around the mask while the wearer was talking. His data indicated that the gross efficiency of all the masks was high but that three proved to be distinctly better at small-particle filtration than the other three. The difference between the best and worst was significant. In 1983, a unique testing method was designed by Shah, Crompton, and Vickers.36 Testing the effectiveness of the masks photographically, they came to the realization that contrary to what most do instinctively, when the wearer coughed or sneezed, it was better for him or her to face the wound and not turn to the side, since the air was expelled from the side of the mask. That same year, Vesley, Langholtz, and Lauer reported on the efficacy of both a new design and a new polymeric-microfiber material.37 In addition to using an Andersen sampler, the researchers conducted testing in a chamber similar to the one developed by Greene and Vesley. In addition to enumerating microbial
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particles with the sampler, they quantified the particles with a laser spectrometer and found the mask’s filtering efficiency to be higher than 95%.
THE MASK TODAY As seen in this chronological review, the emphasis in mask development has historically been the concern for protecting the patient from the members of the surgical team. In the process, the focus has historically been on the mask’s filtering efficiency. The FDA’s recent recommendations also focus on that quality. Even with high filtering efficiency, some exhaled air will escape unfiltered around the edges of the mask—and that depends on how well the mask fits. Because of the escaping exhaled air, which can be as low as 5% or as high as 40%, a mask that is said to be 99.9% effective is essentially only 95% effective or less. Not to be overlooked as well is the fact that the filtering efficiency tests have been conducted in highly controlled environmental conditions unlike in-vivo conditions in today’s ORs, in which there are 15 to 20 air changes per hour in HEPA-filtered air circulatory systems.38,39 The key question is what is the effect of all of the improvements that have been made in masks? Have they contributed to a reduction in the incidence of SSIs? Obviously, mask improvements have increased their costs. Considering the rapidly escalating pressures to control costs, should a mask’s effectiveness be predicated on its filtering efficiency or its theoretical effectiveness?
CONCLUSION To date, the use of the surgical mask has not been evidenced based.40,41 Considering the myriad variables, it is highly doubtful that its efficacy will ever be conclusively demonstrated. Its use seems reasonable and the practice has simply been passed along on that basis. The FDA’s recommendation is the first one adopted by the regulatory agency for measuring the mask’s filtering efficiency. However, based on this chronological review, the recommendation does not seem to have taken into consideration the mask’s conditions in-use. It should be noted that one manufacturer has AORN JOURNAL •
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recently announced the availability of a new surgical mask that incorporates proprietary filtration media that meets the requirement of a totally different standard. Although the new mask is recommended for wearing in longer procedures for which comfortable, breathable masks are important, its testing protocol “does not reflect expected levels of filtration in actual in use conditions.”42 This then raises the question as to the significance of the FDA’s recommendations to perioperative personnel. On the surface, it appears that the only purpose the recommendations serve is to give manufacturers a point of reference for the quality of their products. No more, no less.
REFERENCES 1. Oberg T, Brosseau LM. Surgical mask filter and fit performance. Am J Infect Control. 2008; 36(4):276-282. 2. Guidance for Industry and FDA Staff: Surgical Masks—Premarket Notification [510(k)] Submissions. Washington, DC: US Department of Health and Human Services, Food and Drug Administration, Center for Devices and Radiological Health; 2004. 3. ASTM F1215-89. Test Method for Determining the Initial Efficiency of a Flatsheet Filter Medium in an Airflow Using Latex Spheres [Withdrawn 1998]. West Conshohocken, PA: ASTM International; 1989. 4. ASTM F2299-03. Standard Test Method for Determining the Initial Efficiency of Materials Used in Medical Face Masks to Penetration by Particulates Using Latex Spheres. West Conshohocken, PA: ASTM International; 2003. 5. Military Specifications: Surgical Masks, Disposable, MIL-M-36945C 4.4.1.1.1. Washington, DC: Department of Defense; June 12, 1975. 6. Greene VW, Vesley D. Method for evaluating effectiveness of surgical masks. J Bacteriol. 1962;83: 663-667. 7. ASTM F2101-01. Standard Test Method for Evaluating the Bacterial Filtration Efficiency (BFE) of Medical Face Mask Materials Using a Biological Aerosol of Staphylococcus aureus. West Conshohocken, PA: ASTM International; 2001. 8. Mikulicz J. Das operiren in sterilisirten Zwirnhandschuhen und mit Mundbinde. Zentralblatt für Chirurgie. 1897;24:713-717. 9. Flügge C. Ueber luftinfection. Zeischrift für Hygiene und Infektionskrankheiten. 1897;25:179-193. 10. Hamilton A. Dissemination of streptococci through invisible sputum; in relation to scarlet fever and sepsis. JAMA. 1905;44:1108-1011. 11. Weaver GH. The value of the face mask and other measures. JAMA. 1918;71:76-78. 12. Capps JA. A new adaptation of the face mask in 890 • AORN JOURNAL
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control of contagious disease. JAMA. 1918;70:910-911. 13. Haller DA, Colwell RC. The protective qualities of the gauze face mask; experimental studies. JAMA. 1918;71:1213-1215. 14. Doust BC, Lyon AB. Face masks in infections of the respiratory tract. JAMA. 1918; 71:1216-1219. 15. Weaver GH. Droplet infection and its prevention by the face mask. J Infect Dis. 1919;24:218-230. 16. Kellogg WH, Macmillan G. An experimental study of the efficacy of gauze face masks. Am J Public Health. 1920;10:34-42. 17. Meleny FL, Stevens FA. Postoperative haemolytic Streptococcus wound infections and their relation to haemolytic Streptococcus carriers among operating personnel. Surg Gynecol Obstet. 1926; 43:338-342. 18. Meleny FL. Infection in clean operative wounds: a nine year study. Surg Gynecol Obstet. 1935;60:264-275. 19. Walker IJ. How can we determine the efficacy of the surgical mask? Surg Gynecol Obstet. 1930;50:266-270. 20. Blatt ML, Dale ML. A bacteriological study of the efficiency of face masks. Surg Gynecol Obstet. 1933;57:363-368. 21. Waters EG. Adequate surgical masking: problem and solution. Am J Surg. 1936;32:474-477. 22. Arnold L. A new surgical mask. Arch Surg. 1938;37:1008-1016. 23. Hirshfield JW, Laube PJ. Surgical masks: an experimental study. Surgery. 1941;9:720-730. 24. Shooter RA, Smith MA, Hunter CJ. A study of surgical masks. Br J Surg. 1959;203(47):246-249. 25. Rockwood CA Jr, O’Donoghue DH. The surgical mask: its development, usage, and efficiency. Arch Surg. 1960;80:963-971. 26. Kiser JC, Hitchcock CR. Comparative studies with a new plastic surgical mask. Surgery. 1958; 44(5):936-939. 27. Castaneda A. Historic development of the surgical mask. Surgery. 1961;41:423-428. 28. Greene VW, Vesley D. Method for evaluating effectiveness of surgical masks. J Bacteriol. 1962;83: 663-667. 29. Ford CR, Peterson DE. The efficiency of surgical face masks. Am J Surg. 1963;106:954-957. 30. Nicholes PS. Comparative evaluation of a new surgical mask medium. Surg Gynecol Obstet. 1964; 118:579-583. 31. Spooner JL. History of surgical face masks. AORN J. 1967;5(1):76-80. 32. Madsen PO, Madsen RE. A study of disposable surgical masks. Am J Surg. 1967; 114(3):431-435. 33. Ford CR, Peterson DE, Mitchell CR. An appraisal of the role of surgical face masks. Am J Surg. 1967;113(6):787-790. 34. Dineen P. Microbial filtration by surgical masks. Surg Gynecol Obstet. 1971;133(5):812-814. 35. Quesnel LB. The efficiency of surgical masks of varying design and composition. Br J Surg. 1975;62 (12):936-940.
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36. Shah M, Crompton P, Vickers MD. The efficiency of face masks. Ann R Coll Surg Engl. 1983;65(6): 380-381. 37. Vesley D, Langholtz AC, Lauer JL. Clinical implications of surgical mask retention efficiencies for viable and total particles. Infect Surg. 1983;2(7): 531-536. 38. Davis WT. Filtration efficiency of surgical face masks: the need for more meaningful standards. Am J Infect Control. 1991;19(1):16-18. 39. Weber A, Willeke K, Marchioni R, et al. Aerosol penetration and leakage characteristics of masks used in the health care industry. Am J Infect Control. 1993;21(4):167-173. 40. Belkin NL. A century after their introduction,
are surgical masks necessary? AORN J. 1996;64(4): 602-607. 41. Belkin NL. Masks, barriers, laundering, and gloving: Where is the evidence? AORN J. 2006;84(4): 655-664. 42. 3M™ Filtron™ Duckbill Design Tie-On Surgical Mask. 3M. http://solutions.3m.com/wps/portal/3M /en_US/SH/SkinHealth/products/catalog/?PC_7_R JH9U5230GE3E02LECFTDQG2O7_nid=GBW2PJCH KQbeVHK1T0WDSNgl. Accessed April 1, 2009.
Nathan L. Belkin, PhD, is retired from the health care industry. He resides in Largo, FL.
Atypical Antipsychotic Drugs May Cause Sudden Cardiac Death
A
study funded by the Agency for Healthcare Research and Quality (AHRQ) has determined that patients ages 30 to 74 who took atypical antipsychotics had a significantly higher risk of sudden death from cardiac arrhythmias and other cardiac causes than patients who were not taking these medications, according to a January 14, 2009, news release from the AHRQ. Higher dosages of the medications increased the risks to the patient. The most common uses for atypical antipsychotic medications (eg, risperidone, quetiapine, olanzapine, clozapine) are to treat schizophrenia and bipolar disorders. They also are used “off label” to treat agitation,
anxiety, psychotic episodes, and obsessive behaviors. The researchers found that patients currently taking these medications were twice as likely to experience a sudden cardiac death as those who were not. This rate is comparable to patients taking typical antipsychotics (eg, haloperidol, thioridazine). The researchers concluded that atypical antipsychotics are not a safe alternative to typical antipsychotics in preventing sudden cardiac death. Use of atypical antipsychotic drugs increases risk of sudden cardiac death in adults [news release]. Rockville, MD: Agency for Healthcare Research and Quality; January 14, 2009.
Demethylation Could Trigger Cancer
D
emethylation, a process that reverses the buildup of chemical bonds on certain cancer-promoting genes, may also trigger more than half of all cancers, according to a March 23, 2009, news release from Johns Hopkins Kimmel Cancer Center, Baltimore, Maryland. Currently, demethylating medications are used to treat cancer, but they may actually cause new cancers. Scientists at Johns Hopkins studied normal and cancer cells from the human mouth, nose, and throat. These cells were treated with the demethylating medication 5-azacytidine. Scientists then recorded information regarding which genes were activated as a result. Findings from this study indicated that important regulators of gene activity occur both outside and inside DNA in a cell’s nucleus. A single con-
nection among the 106 activated genes was discovered through analysis of these results. The BORIS gene acts as a “master regulator” by recruiting other proteins to demethylate a coordinated set of genes, thereby signaling the development of cancer. Nearly 60% of cancers, including head, neck, and lung cancers, have high levels of the BORIS gene. In the future, a combination of agents like 5-azacytidine and a “Boris Blocker,” which has yet to be developed, may provide protection for patients who need demethylating treatments. Genetic changes outside nuclear DNA suspected to trigger more than half of all cancers [news release]. Baltimore, MD: Johns Hopkins Kimmel Cancer Center; March 23, 2009.
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ince the inception of surgical mask use more than a century ago, there has never been a universally accepted, standard test method for determining the filtering efficiency of surgical masks. In its guidance document for manufacturers who are filing a 510(k) for marketing approval of a new mask, the US Food and Drug Administration (FDA) recommends two types of tests for demonstrating that capability.1 One test measures particulate filtration efficiency using an unneutralized aerosol of 0.1-micrometer latex spheres at a challenge velocity between 0.5 cm/ second and 25 cm/second (ie, approximately 8 L/minute to 380 L/minute for a 9-cm radius mask).1-4 The other test measures bacterial filtration efficiency (ie, the mask’s ability to prevent the passage of aerosolized bacteria1), using an unneutralized 3 ± 0.3-micrometer Staphylococcus aureus aerosol at a flow rate of 28.3 L/minute.1,2,5-7 In neither case does the FDA require a minimum level of filter performance.2 This article explores the work done by a host of researchers in the development of both masks and filtering efficiency over the years and questions the relevance of these new tests to a surgical mask’s inuse conditions.
EARLY DEVELOPMENTS The work of Mikulicz8 and Flugge9 in 1897 demonstrated the presence of bacteria in droplets from the nose and mouth. Their finding was confirmed by the publication of Hamilton’s study10 in 1905, which demonstrated the importance of droplets of sputum in disseminating tuberculosis infection. This initiated research on the filtering capabilities of materials for masks that preceded © AORN, Inc, 2009
the use of masks in surgery. In 1918, Weaver11 published the results of his study on the role that a mask could have in preventing the spread of diphtheria, meningitis, pneumonia, and other diseases. He introduced the practice of wearing gauze masks covering the nose and mouth when caring for patients. Their use proved to be so successful that he recommended them for use in households in which those with diseases could spread the disease by nasopharyngeal discharge. As an extension of the practice, he also called for every patient entering an ambulance to don a mask and to continue wearing it until the patient reached his or her hospital bed. Later that year, Capps suggested a new dimension to mask use.12 Inasmuch as its use had proven to be effective in protecting health care workers from
ABSTRACT Since the turn of the 20th century, when researchers were discovering the presence of bacteria in droplets from the nose and mouth and the role these bacteria played in disease transmission, masks have been used as a method to protect both health care providers and patients from respiratory diseases. In 1926, the first study was published that indicated masks might also play a role in reducing the incidence of surgical site infections. That report spearheaded the development of new mask materials and designs and devices to demonstrate their filtering efficiency. This article provides a historical review of the work done by researchers over the years and examines whether tests to determine the filtering efficiency of surgical masks, including those recently adopted by the US Food and Drug Administration (FDA), are relevant to actual OR conditions. Key words: surgical masks, FDA guidance, filtering efficiency, in-use conditions. AORN J 89 (May 2009) 883-891. © AORN, Inc, 2009.
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contagion, it seemed reasonable that patients wearing a mask could similarly be protected from either primary contagion, or if they were already ill with an infection, from a second contagion.
TESTING
FOR
EFFECTIVENESS
All the attention was being directed simply on the use of masks not on the material of which they were made. Inasmuch as the material had heretofore only been identified on one occasion, it was believed that masks had all been made of the same type of material: gauze. Prompted by the fact that their masks were being procured from several sources, Haller and Colwell observed in 1918 that there were extreme variations in the number of layers of gauze used in the masks as well as in the quality of the gauze itself.13 They concluded that the amount of gauze placed in superimposed layers necessary to provide complete protection from those who were infected had to be the equivalent of 300 threads of fiber to the square inch. As for the size, masks were to be 8 inches long and 5 inches wide. They also developed and posted rules for contagious wards that included the use of the mask. The essential principle of their use was that patients out of bed and out of their cubicle were never to be unmasked, except when alone in the washroom. Although no data regarding the results of the practice were statistically recorded, they believed that it significantly lessened the incidence of cross infection. That same year, having defined the mask’s two-fold purpose as 1) protecting the wearer from infectious material from the respiratory passages of the patient and 2) protecting the patient from such material as the wearer may carry in his or her nose and mouth, Doust and Lyon14 proceeded to assess the efficiency of masks in preventing the dissemination of infectious material from the mouth during speaking or coughing. As the first study of its kind, the findings proved to be quite revealing. Whether the mask was made of as few as two or as many as 10 layers of coarse gauze, the results were not dramatically different. When masks made of from two to five layers of a mediumquality gauze were tested, the results proved to
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be more effective in all circumstances. This led Weaver15 to introduce a new dimension to testing the mask’s effectiveness in 1919. He reported on the mask’s influence on droplet infection in terms of the distance traveled by mouth droplets that had been driven out in forced respiratory efforts. He found that the effectiveness of the gauze was directly proportionate to the fineness of the weave and the number of layers used. Based on these findings, he adopted the use of a mask made of three layers of an absorbent gauze with a mesh thread count of 44 x 30. He found that the masks were not only useful as protection for health care workers but were also useful when worn by infected individuals to prevent contamination of their surroundings.
AN IN-VIVO SETBACK An outbreak of influenza in 1919 brought about a challenging situation for warranting compulsory use of the mask in attempts to mitigate an epidemic. Because influenza is a dropletborne infection, it appeared that wearing masks was a technique based on sound reasoning and that favorable results could be expected from their use. Their failure to prevent the spread of the disease was disappointing, although the use of masks was widespread. California health care officials Kellogg and MacMillan reported encountering a number of problems that had not been anticipated that seemed to account for this failure.16 These included use of a large number of improperly made masks; faulty wearing of the masks (eg, masks that were too small and covered only the mouth); and masks not worn at the proper times.
THE NEED
FOR A
MASK
IN
SURGERY
Up to this point, the use of a mask had been based on the findings reported by Mikulicz8 and Flugge9 in 1897. These focused on the transmission of bacteria found in droplets that were expelled from the nose and mouth. No mention had yet been made of mask use being able to influence the incidence of surgical site infection (SSI). Mask use in surgery gained considerable attention after the publication of Meleny’s first study in 1926, in which he reported having
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seen a reduction in the incidence of SSI when masks were worn by the surgical team.17 In his subsequent study published nine years later, however, Meleny reported that the rate of infection with the use of masks was closer to 15% than the 2% to 5% range that had been anticipated.18 The questions to be answered concerned the origin of the organisms and how they were able to gain a foothold in the tissues. After scrutinizing all the steps of sterile technique, Meleny determined that the important causes of SSIs were organisms from the • noses and throats of the members of the surgical team, • hands of the surgical personnel, • skin of the patient, • air in the OR, and • instruments and materials used in the procedure. Based on the findings, a series of changes were subsequently implemented that included the proper masking of the members of the surgical team.
THE “GERM-PROOF” MASK The first study that referred to the mask as a “surgical mask” was published by Walker in 1930.19 Prompted by a number of deaths in surgery, he surveyed 100 hospitals concerning the surgical masks they were using. Based on the results, he proposed the minimum capabilities for a surgical mask to be considered germproof: • it had to be comfortable and not overly warm when worn and cover both the nose and mouth; • it could not cause fogging or condensation of moisture on lenses of those wearing glasses; and • with both the nose and mouth covered, it would permit the wearer to talk for one hour, and when moistened for the last 15 minutes, would still maintain its filtering efficiency and not permit the passage of organisms. Despite the endless hours and exhaustive thought dedicated to all of his experiments, Walker admitted that he was not able to present the community with the ideal surgical mask. He
In 1926, Meleny reported a reduction in surgical site infections when masks were worn by members of the surgical team.
did, however, develop a surgical mask that included a 6-inch square of rubber taken from a discarded surgical glove that had been inserted between two layers of 10-inch squares of gauze, which he considered to be germ-proof. It was the germ-proof concept that prompted Blatt and Dale20 to construct a dust-proof tunnel to be used in determining a surgical mask’s effectiveness in 1935. Whereas comparative data led them to conclude that the surgical mask made of six layers of gauze was bacteriologically ineffective, they reported finding two layers of a new cellophane-and-gauze deflection-type mask to be comfortable, effective, nearly germ-proof, and inexpensive.
THE ERA
OF
NEW MATERIALS
AND
DESIGNS
The first change in the basic material as well as design was reported by Waters in 1936.21 The mask was made of a transparent, impermeable, lightweight, noncombustible substance—a cellulose derivative called “plastecele.” In addition to completely covering the mouth, chin, and nostrils, its design deflected breath spray away from the wound. In 1938, Arnold returned the focus from deflection back to the filtering capability.22 He tested masks made of a new material consisting of a combination of cotton and wood cellulose in the form of a creped wadding called “cellucotton.” His tests confirmed that the greatest source of oral bacterial flora occurred during loud talking, and they either escaped or were deflected above the mask and lateral to each side of the mask. Perhaps the most significant study published before World War II was reported by AORN JOURNAL •
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Hirshfield and Meyers,23 whose experiments were designed to test the efficiency of the masks themselves. Based on what they considered to be a shortcoming in the work done by their predecessors, they felt that a mask’s filtering efficiency should be assessed by its ability to prevent the passage of both droplets and droplet nuclei, the two mechanisms by which airborne infections could be transmitted. Using an airtight chamber, they tested a variety of masks of different materials under what they described as usual conditions of actual use. They found the masks to be grossly inadequate because they allowed large numbers of organisms to escape through or around them. They attributed these deficiencies to the inability to construct a mask capable of preventing the passage of all bacteria without making it so resistant to the passage of air that breathing through it would be arduous and the difficulty of fitting a mask to the face in such a way that air did not escape around it.
THE POST WORLD WAR II ERA For a period of some 20 years after the war, little work was done on either the development or efficacy of the surgical mask because of the surge in the improvement of surgical equipment and the prophylactic use of antibiotics. With the lack of evidence that masks could prevent SSI, doubts as to their need prevailed. Collected opinions ranged from a firm belief in their effectiveness to an equally definite disbelief. It was argued that during quiet breathing, few, if any, bacteria were expelled from the nose or mouth. On the other hand, it was generally agreed that during sneezing, and to a lesser extent during coughing and talking, particles, many of which had been shown to contain bacteria, were blown from the nose and mouth. All things considered, surgical masks were presumably viewed as being valuable if they shielded the patient’s wound from pathogenic bacteria from surgical team members’ noses and mouths. On that basis, the consensus was that the mask could do this by either filtering bacteria passing through it or by being impervious and deflecting the expired air so that it traveled behind the wearer’s head. The focus was increasingly
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on the cleanliness of the environment, however, and the surgical community directed its attention to the use of gloves, sterile gowns, and drapes.
TESTING NEW MATERIALS
AND
DESIGNS
Nevertheless, during this period, manufacturers introduced different materials and designs of surgical masks, and each manufacturer used different test methods to demonstrate the virtues of their product. This prompted a prestigious group of English clinical investigators, headed by Shooter, to try to validate the manufacturers’ claims in 1959.24 The first mask they examined was a filtration type of “basket-shaped” mask that fit fairly snugly over the nose and chin and was made of four layers of gauze with a thread count of 46 threads to the inch. The second type was a “tail-type” or deflection design, made of a “double thickness of closely woven cambric”24(p247) with a piece of paper inserted between the layers. A tail of the cambric was attached to the mask when worn so that in addition to the mask covering the nose, the mouth and chin would be covered and the tail would hang down the wearer’s neck and be tucked under the OR gown. It should be noted that the fit over the cheeks was loose. The third and last mask that the researchers examined was another deflection design made of paper with the intent that it would be worn once and then thrown away. It consisted of an outer and inner layer of paper that completely enveloped a pad of cellulose wadding. It covered the nose, mouth, and chin but fit loosely around the cheeks. Based on the results of their investigation, the group was able to confirm the conclusions of others to the effect that all three masks protected the area in front of the mouth from many of the wearer’s mouth and nose organisms, and increasing the thickness of the mask or improving its fit could lead to a point at which it would be difficult to breathe. Perhaps the most worthy of their observations was made possible by the uniqueness of their testing apparatus, which indicated that with the deflection type mask, it seemed probable that deflected, expired air would inevitably carry some of the bacteria
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behind the head. This may well have accounted Up to this point, although a considerable for the experiences reported earlier by others amount of work had been done to assess the who had not considered the deflective type of mask’s filtering efficiency, relatively little had mask acceptable because it did not reduce the been done in terms of measuring the quantitatotal count of bacteria in the room. tive bacterial contribution of nasopharyngeal It was also noted that the practice of lowerexpirations to the atmospheric environment. ing the mask around the neck created a risk of One of the shortcomings of the techniques was contaminating both the mask’s outer and inner that they failed to measure the very small surfaces. For that reason, it was suggested that droplets and droplet nuclei that were not proif a fresh mask could not be available for every jected any appreciable distance by virtue of situation, the hands should be washed each their lack of kinetic energy. time the soiled mask was touched.24 With the availability of the Andersen samThe following year, Rockwood and pler—a device that collects microscopic organO’Donoghue added a new dimension to the isms from the air using a series of filters—in the mask’s filtering efficiency.25 late 1950s, however, that deterSpecifically, this related to the mination could be made. With length of time a mask could the objective of advancing the be expected to maintain its test methodology, Greene and effectiveness while being Vesley introduced a testing In 1961, Castaneda worn. Based on the protocol chamber to best accommodate of their test, they concluded its use in 1962.28 Their tests led observed that the ideal that their mask could not be them to conclude that the mask still had not considered suitable for more mask’s filtering capability itself than three hours of use. Idealwas of little value unless combeen developed. ly, they recommended that the plete control of the environmask be changed after each ment could be provided. use regardless of the length of Still faced with concern for time it was worn. establishing a balance beAround the same time, tween the mask’s filtering effiKiser and Hitchcock26 introduced a newly ciency and wearer comfort, Ford and Peterson designed mask made of a flexible polyvinyl in 1963 introduced both a new material and testing device.29 Rather than testing masks plastic with wing-like cheek pieces to deflect air posteriorly. To trap moisture and bacteria, a while they were being worn by humans, they replaceable cotton and wool insert, intended to used the Andersen sampler with a compressed be changed after every use, was incorporated air source. Eleven different masks were evaluinto its construction. Despite its high filtering ated including one disposable mask made of efficiency, it was not ideal because the wearer spun glass. Although the more expensive, sinhad to speak quite loudly to make himself or gle-use mask was found to be the most effecherself heard. tive, the critical question was whether its perIn 1961, Castaneda observed that formance justified its cost. A year later, Nicholes30 reported on the The ideal mask has yet to be developed. None, results of his tests that used a proprietary new so far, has succeeded in combining comfort device to evaluate five masks made of a variwith bacteriologic security. . . . Even upon ety of different materials, including cotton the development of such a device, whether in gauze, a molded non-woven fabric, and fine the form of a more perfect mask or some bacglass fiber mats. The mask made of the fine tericidal medium, other aspects of surgical glass fiber mats proved to be superior to the technique and the care of the wound will others. Its thickness ranged from 1.5 mm to continue to be of paramount importance in 2 mm and it had the ability to remove 96% to the prevention of post-operative sepsis.27(p428) 98% of the bacteria or viruses from the aerosol AORN JOURNAL •
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The popularity of the first single-use, disposable mask spurred the design of other throw-aways. New masks were made of a number of different materials, including polypropylene fibers, polyester-rayon fibers, and cellulose fibers (ie, paper).
challenge; its design enlarged the total air diffusion but increased breathing comfort.
THE DISPOSABLES Spooner’s historical review in 1967 31 summarized the fact that the filtering efficiency of gauze masks was negligible; that dampening further decreased their efficiency; that improper fitting permitted bacteria to escape from the sides of the mask; and that when made of multiple layers, they were most uncomfortable to wear. On the other hand, the deflector-type masks, although effective in preventing exhalation of bacteria directly in front of the wearer’s mouth, were again deemed inadequate because they did not contribute to a reduction in the number of colonies of bacterial count throughout the room. Because of the popularity of the first singleuse, disposable mask, several other throwaways were introduced. New masks were made of a number of different materials (eg, polypropylene fibers, polyester-rayon fibers, cellulose fibers [ie, paper]). These developments called for yet another method to ascertain which material provided the maximum level of protection for the patient. Two researchers, Madsen and Madsen,32 rose to the occasion in 1967, using the testing chamber designed by Greene and Vesley along with the Andersen sampler. Rather than using
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humans, they incorporated forced air and an artificial head (ie, manikin) that had a rigid nose bridle and soft cheeks. The mask’s filtering efficiency was expressed as the percentage of bacteria retained by the mask as compared to a control when the manikin was not wearing a mask. The relative efficiency of the masks was found to be, in descending order: polypropylene fibers, polyester-rayon fibers, glass fibers, and cellulose. At the same time, the results of the Ford, Peterson, and Mitchell three-phase, three-year study33 were released. The first phase was dedicated to a filtering test of 14 commercially available masks; the second phase examined the bacterial threat from the nasopharynx of the personnel to the patient’s open wound; and for the third phase, the researchers performed a bacteriological analysis of all the wound infections. Based on the results of the first phase, the researchers found that the mask made of fiberglass possessed a high filtering efficiency, and they used it exclusively for the three-year period. In the second phase, the organism most frequently found in 90% of the nasopharyngeal cultures of the surgical personnel was alpha hemolytic streptococcus. In the third phase, of the total of 2,987 clean procedures, 71 wound infections were reported. In that group, 31 infections were caused by S aureus, five by S epidermis, and the remaining by mixed flora. In the total of 1,092 clean-contaminated cases, there were a total of 58 infections, with 18 caused by S aureus alone, one by S epidermis, and the balance by mixed flora. Based on their findings, the investigators concluded that they had validated the use of a mask to protect the open surgical wound. They maintained, however, that in addition to filtering efficiency, many other factors were associated with mask use, including fit, breathability, lack of allergenicity, disposability, cost, product consistency, and availability. As comprehensive as the three-year study was, several questions remained. For example, there was the matter of how long a mask could be worn before its filtering efficiency would be reduced and whether a mask should be changed at certain fixed periods because it became ineffi-
Belkin
cient when wet. These issues were addressed by Dineen34 in 1971. Using a specially designed cloud chamber that included the use of the Andersen sampler, he examined 11 different masks. He tested new gauze masks that had been laundered once and new (ie, unused) disposable masks, testing all the masks after they were worn for periods ranging from one to eight hours during actual procedures. Only four of the single-use and the one gauze mask passed Dineen’s tests for filtration when he tested them both wet and dry. Although there were variances in their filtration efficiency, contrary to general belief, the more efficient masks did not lose their ability to filter after prolonged use and moistening. What was disconcerting were the variances in the filtering efficiency of the masks, not from one manufacturer to another, but in certain instances, from mask to mask from the same manufacturer. Then in 1975, Quesnal reported on his study on the filtering efficiency of six different masks of varying design and composition.35 Using an Andersen sampler and a testing chamber similar to that designed by Greene and Vesley, Quesnal collected and sized the contaminated particles through or around the mask while the wearer was talking. His data indicated that the gross efficiency of all the masks was high but that three proved to be distinctly better at small-particle filtration than the other three. The difference between the best and worst was significant. In 1983, a unique testing method was designed by Shah, Crompton, and Vickers.36 Testing the effectiveness of the masks photographically, they came to the realization that contrary to what most do instinctively, when the wearer coughed or sneezed, it was better for him or her to face the wound and not turn to the side, since the air was expelled from the side of the mask. That same year, Vesley, Langholtz, and Lauer reported on the efficacy of both a new design and a new polymeric-microfiber material.37 In addition to using an Andersen sampler, the researchers conducted testing in a chamber similar to the one developed by Greene and Vesley. In addition to enumerating microbial
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particles with the sampler, they quantified the particles with a laser spectrometer and found the mask’s filtering efficiency to be higher than 95%.
THE MASK TODAY As seen in this chronological review, the emphasis in mask development has historically been the concern for protecting the patient from the members of the surgical team. In the process, the focus has historically been on the mask’s filtering efficiency. The FDA’s recent recommendations also focus on that quality. Even with high filtering efficiency, some exhaled air will escape unfiltered around the edges of the mask—and that depends on how well the mask fits. Because of the escaping exhaled air, which can be as low as 5% or as high as 40%, a mask that is said to be 99.9% effective is essentially only 95% effective or less. Not to be overlooked as well is the fact that the filtering efficiency tests have been conducted in highly controlled environmental conditions unlike in-vivo conditions in today’s ORs, in which there are 15 to 20 air changes per hour in HEPA-filtered air circulatory systems.38,39 The key question is what is the effect of all of the improvements that have been made in masks? Have they contributed to a reduction in the incidence of SSIs? Obviously, mask improvements have increased their costs. Considering the rapidly escalating pressures to control costs, should a mask’s effectiveness be predicated on its filtering efficiency or its theoretical effectiveness?
CONCLUSION To date, the use of the surgical mask has not been evidenced based.40,41 Considering the myriad variables, it is highly doubtful that its efficacy will ever be conclusively demonstrated. Its use seems reasonable and the practice has simply been passed along on that basis. The FDA’s recommendation is the first one adopted by the regulatory agency for measuring the mask’s filtering efficiency. However, based on this chronological review, the recommendation does not seem to have taken into consideration the mask’s conditions in-use. It should be noted that one manufacturer has AORN JOURNAL •
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recently announced the availability of a new surgical mask that incorporates proprietary filtration media that meets the requirement of a totally different standard. Although the new mask is recommended for wearing in longer procedures for which comfortable, breathable masks are important, its testing protocol “does not reflect expected levels of filtration in actual in use conditions.”42 This then raises the question as to the significance of the FDA’s recommendations to perioperative personnel. On the surface, it appears that the only purpose the recommendations serve is to give manufacturers a point of reference for the quality of their products. No more, no less.
REFERENCES 1. Oberg T, Brosseau LM. Surgical mask filter and fit performance. Am J Infect Control. 2008; 36(4):276-282. 2. Guidance for Industry and FDA Staff: Surgical Masks—Premarket Notification [510(k)] Submissions. Washington, DC: US Department of Health and Human Services, Food and Drug Administration, Center for Devices and Radiological Health; 2004. 3. ASTM F1215-89. Test Method for Determining the Initial Efficiency of a Flatsheet Filter Medium in an Airflow Using Latex Spheres [Withdrawn 1998]. West Conshohocken, PA: ASTM International; 1989. 4. ASTM F2299-03. Standard Test Method for Determining the Initial Efficiency of Materials Used in Medical Face Masks to Penetration by Particulates Using Latex Spheres. West Conshohocken, PA: ASTM International; 2003. 5. Military Specifications: Surgical Masks, Disposable, MIL-M-36945C 4.4.1.1.1. Washington, DC: Department of Defense; June 12, 1975. 6. Greene VW, Vesley D. Method for evaluating effectiveness of surgical masks. J Bacteriol. 1962;83: 663-667. 7. ASTM F2101-01. Standard Test Method for Evaluating the Bacterial Filtration Efficiency (BFE) of Medical Face Mask Materials Using a Biological Aerosol of Staphylococcus aureus. West Conshohocken, PA: ASTM International; 2001. 8. Mikulicz J. Das operiren in sterilisirten Zwirnhandschuhen und mit Mundbinde. Zentralblatt für Chirurgie. 1897;24:713-717. 9. Flügge C. Ueber luftinfection. Zeischrift für Hygiene und Infektionskrankheiten. 1897;25:179-193. 10. Hamilton A. Dissemination of streptococci through invisible sputum; in relation to scarlet fever and sepsis. JAMA. 1905;44:1108-1011. 11. Weaver GH. The value of the face mask and other measures. JAMA. 1918;71:76-78. 12. Capps JA. A new adaptation of the face mask in 890 • AORN JOURNAL
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control of contagious disease. JAMA. 1918;70:910-911. 13. Haller DA, Colwell RC. The protective qualities of the gauze face mask; experimental studies. JAMA. 1918;71:1213-1215. 14. Doust BC, Lyon AB. Face masks in infections of the respiratory tract. JAMA. 1918; 71:1216-1219. 15. Weaver GH. Droplet infection and its prevention by the face mask. J Infect Dis. 1919;24:218-230. 16. Kellogg WH, Macmillan G. An experimental study of the efficacy of gauze face masks. Am J Public Health. 1920;10:34-42. 17. Meleny FL, Stevens FA. Postoperative haemolytic Streptococcus wound infections and their relation to haemolytic Streptococcus carriers among operating personnel. Surg Gynecol Obstet. 1926; 43:338-342. 18. Meleny FL. Infection in clean operative wounds: a nine year study. Surg Gynecol Obstet. 1935;60:264-275. 19. Walker IJ. How can we determine the efficacy of the surgical mask? Surg Gynecol Obstet. 1930;50:266-270. 20. Blatt ML, Dale ML. A bacteriological study of the efficiency of face masks. Surg Gynecol Obstet. 1933;57:363-368. 21. Waters EG. Adequate surgical masking: problem and solution. Am J Surg. 1936;32:474-477. 22. Arnold L. A new surgical mask. Arch Surg. 1938;37:1008-1016. 23. Hirshfield JW, Laube PJ. Surgical masks: an experimental study. Surgery. 1941;9:720-730. 24. Shooter RA, Smith MA, Hunter CJ. A study of surgical masks. Br J Surg. 1959;203(47):246-249. 25. Rockwood CA Jr, O’Donoghue DH. The surgical mask: its development, usage, and efficiency. Arch Surg. 1960;80:963-971. 26. Kiser JC, Hitchcock CR. Comparative studies with a new plastic surgical mask. Surgery. 1958; 44(5):936-939. 27. Castaneda A. Historic development of the surgical mask. Surgery. 1961;41:423-428. 28. Greene VW, Vesley D. Method for evaluating effectiveness of surgical masks. J Bacteriol. 1962;83: 663-667. 29. Ford CR, Peterson DE. The efficiency of surgical face masks. Am J Surg. 1963;106:954-957. 30. Nicholes PS. Comparative evaluation of a new surgical mask medium. Surg Gynecol Obstet. 1964; 118:579-583. 31. Spooner JL. History of surgical face masks. AORN J. 1967;5(1):76-80. 32. Madsen PO, Madsen RE. A study of disposable surgical masks. Am J Surg. 1967; 114(3):431-435. 33. Ford CR, Peterson DE, Mitchell CR. An appraisal of the role of surgical face masks. Am J Surg. 1967;113(6):787-790. 34. Dineen P. Microbial filtration by surgical masks. Surg Gynecol Obstet. 1971;133(5):812-814. 35. Quesnel LB. The efficiency of surgical masks of varying design and composition. Br J Surg. 1975;62 (12):936-940.
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36. Shah M, Crompton P, Vickers MD. The efficiency of face masks. Ann R Coll Surg Engl. 1983;65(6): 380-381. 37. Vesley D, Langholtz AC, Lauer JL. Clinical implications of surgical mask retention efficiencies for viable and total particles. Infect Surg. 1983;2(7): 531-536. 38. Davis WT. Filtration efficiency of surgical face masks: the need for more meaningful standards. Am J Infect Control. 1991;19(1):16-18. 39. Weber A, Willeke K, Marchioni R, et al. Aerosol penetration and leakage characteristics of masks used in the health care industry. Am J Infect Control. 1993;21(4):167-173. 40. Belkin NL. A century after their introduction,
are surgical masks necessary? AORN J. 1996;64(4): 602-607. 41. Belkin NL. Masks, barriers, laundering, and gloving: Where is the evidence? AORN J. 2006;84(4): 655-664. 42. 3M™ Filtron™ Duckbill Design Tie-On Surgical Mask. 3M. http://solutions.3m.com/wps/portal/3M /en_US/SH/SkinHealth/products/catalog/?PC_7_R JH9U5230GE3E02LECFTDQG2O7_nid=GBW2PJCH KQbeVHK1T0WDSNgl. Accessed April 1, 2009.
Nathan L. Belkin, PhD, is retired from the health care industry. He resides in Largo, FL.
Atypical Antipsychotic Drugs May Cause Sudden Cardiac Death
A
study funded by the Agency for Healthcare Research and Quality (AHRQ) has determined that patients ages 30 to 74 who took atypical antipsychotics had a significantly higher risk of sudden death from cardiac arrhythmias and other cardiac causes than patients who were not taking these medications, according to a January 14, 2009, news release from the AHRQ. Higher dosages of the medications increased the risks to the patient. The most common uses for atypical antipsychotic medications (eg, risperidone, quetiapine, olanzapine, clozapine) are to treat schizophrenia and bipolar disorders. They also are used “off label” to treat agitation,
anxiety, psychotic episodes, and obsessive behaviors. The researchers found that patients currently taking these medications were twice as likely to experience a sudden cardiac death as those who were not. This rate is comparable to patients taking typical antipsychotics (eg, haloperidol, thioridazine). The researchers concluded that atypical antipsychotics are not a safe alternative to typical antipsychotics in preventing sudden cardiac death. Use of atypical antipsychotic drugs increases risk of sudden cardiac death in adults [news release]. Rockville, MD: Agency for Healthcare Research and Quality; January 14, 2009.
Demethylation Could Trigger Cancer
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emethylation, a process that reverses the buildup of chemical bonds on certain cancer-promoting genes, may also trigger more than half of all cancers, according to a March 23, 2009, news release from Johns Hopkins Kimmel Cancer Center, Baltimore, Maryland. Currently, demethylating medications are used to treat cancer, but they may actually cause new cancers. Scientists at Johns Hopkins studied normal and cancer cells from the human mouth, nose, and throat. These cells were treated with the demethylating medication 5-azacytidine. Scientists then recorded information regarding which genes were activated as a result. Findings from this study indicated that important regulators of gene activity occur both outside and inside DNA in a cell’s nucleus. A single con-
nection among the 106 activated genes was discovered through analysis of these results. The BORIS gene acts as a “master regulator” by recruiting other proteins to demethylate a coordinated set of genes, thereby signaling the development of cancer. Nearly 60% of cancers, including head, neck, and lung cancers, have high levels of the BORIS gene. In the future, a combination of agents like 5-azacytidine and a “Boris Blocker,” which has yet to be developed, may provide protection for patients who need demethylating treatments. Genetic changes outside nuclear DNA suspected to trigger more than half of all cancers [news release]. Baltimore, MD: Johns Hopkins Kimmel Cancer Center; March 23, 2009.
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