Abstract
The Medical Device Regulation (MDR) of the European Union (EU) places greater emphasis on the usability of medical devices, with the goal of eliminating or reducing the risk of infection to patients. As this goal also is applicable to sterile packaging, ANSI/AAMI/ISO 11607-1:2019 introduced a usability evaluation requirement for aseptic presentation of terminally sterilized medical devices. In an effort to reduce contamination risks, this requirement focuses specifically on the sterile barrier system (SBS). However, research is limited on evaluating the usability of SBSs and their performance, from an aseptic presentation standpoint, in clinical settings. To address this research gap, we assessed 14 sterile medical devices with five different SBS configurations to elucidate how SBS configuration (type, size, and number of SBS layers) and user satisfaction levels affect usability. A total of 40 experienced clinical nurses participated in 280 individual trials (20 per SBS configuration), which were conducted in a simulated operating room. Ultraviolet fluorescent powder was used to simulate the contamination process and to evaluate the success or failure of the aseptic presentation. Pouch and tray configurations exhibited the best overall performance, while vent bags performed poorly and were considered less acceptable. Double SBS configurations outperformed single SBS configurations. The study highlighted the importance of appropriate SBS symbols to identify SBS layers, which is another patient safety–related requirement of the EU MDR. The current work also includes an analysis of the powder contamination method used in conducting the usability evaluation.
Background
Risk of Infection in Healthcare Settings
Healthcare-associated infections (HAIs) pose a serious worldwide health concern. According to the Centers for Disease Control and Prevention, on a daily basis, “approximately one in 31 U.S. patients contracts at least one infection in association with his or her hospital care.”1 This alarming statistic highlights the importance and urgency to improve existing patient care. Although much progress has been made, more needs to be done to prevent HAIs in healthcare facilities.
HAIs can be transmitted from a person to a patient, both directly and indirectly. By definition, “indirect transmission involves the transfer of an infectious agent through a contaminated intermediate object or person.”2 Specifically, one potential cause of HAI is “when a sterile medical device touches a nonsterile surface during aseptic presentation.”3
For a medical device packaged in a sterile barrier system (SBS), only the inside portion of the SBS or the inside of a double SBS (e.g., a whole inner pouch or tray) remains sterile during transportation, storage, and handling. During the transfer of the medical device from storage to the operating room (OR), the outside of the SBS will be exposed to various environmental conditions depending on when the protective packaging is removed. The higher the contamination on these external contact surfaces, the higher the likelihood of an indirect transfer of microbes in cases of inadvertent contact with sterile surfaces.3 Of further concern is the finding that some microorganisms, such as methicillin-resistant Staphylococcus aureus, “can survive on packaged goods for more than 38 months,”4 which can severely compromise patient outcomes. Contamination on the outside of the SBS may be transferred to the sterile medical device due to poor design features, storage and handling practices, and/or opening behavior affecting aseptic presentation.
Given the vital role of sterile packaging in patient care, conducting usability evaluations for aseptic presentation of medical devices currently on the market is important.
Regulatory Requirements
The European Union (EU) Medical Device Regulation (MDR) sought to improve the quality, safety, and reliability of medical devices and ensure patient safety. Specifically, the MDR states that the medical device design shall “allow easy and safe handling” and “prevent microbial contamination of the device or its content such as specimens or fluids.”5 One of the key features to consider is the SBS opening behavior and the ability to present medical devices aseptically. Another requirement of the EU MDR is related to information on the sterile packaging, which should include “an indication permitting the sterile packaging to be recognized as such.”5,6
To support conformity with requirements of the EU regulations, ANSI/AAMI/ISO 11607-1:2019, Packaging for terminally sterilized medical devices—Part 1: Requirements for materials, sterile barrier systems and packaging systems, sets requirements for usability evaluation.7 As outlined in section 7 of 11607-1, the usability evaluation for aseptic presentation is described as follows: “7.1 A documented usability evaluation shall be conducted to demonstrate that the sterile contents can be aseptically removed from the sterile barrier system for presentation. 7.2 The usability evaluation for aseptic presentation shall include an assessment of (a) the ability to identify where to begin opening, (b) the ability to recognize and perform the technique required to open the sterile barrier system without contaminating or damaging the contents, and (c) the ability to subsequently present the contents aseptically.”
However, a dearth of existing studies have considered these updated requirements; therefore, limited research exists regarding the relationship among SBS design, healthcare user behaviors, and, ultimately, patient outcomes.8 To comply with these requirements, the sterile packaging engineering industry should also use human factors methodologies and consider approaches,6 including the powder contamination method,9 to better understand how sterile packages are used by clinicians.
Study Background
We conducted a study with 40 healthcare professionals to demonstrate the usability evaluation process for 14 different sterile medical devices currently available on the market in China. These 14 devices had five different SBS configurations. The quantitative and qualitative data gathered in this study were used to analyze the effects of SBS configuration type, SBS size, number of SBS layers, and user satisfaction levels on the overall aseptic presentation failure rate.
Methods
This study sought to assess the role of several factors related to the SBS, including overall contamination rates and users’ handling, use, and opening behaviors. The study was conducted in a simulated OR among registered nurses. The overall experimental framework is adopted from Trier et al.9 However, this project used various commonly available sterile medical devices on the market in China. As a result, our study highlights the real-life performance of different SBS configurations and provides actionable insights for the sterile packaging industry.
Participants
A total of 40 OR nurses with clinical experience and broad demographics were recruited (Table 1). Participants were randomly divided into 20 groups. One nurse wearing contaminated gloves (hereafter referred to as the “nonsterile nurse”) and one nurse wearing sterile/uncontaminated gloves (hereafter referred to as the “sterile nurse”) were assigned for each group. Participants were affiliated with at least three different hospitals under two different hospital classifications. In China, hospitals are categorized into three classes based on the scale of the hospital (in terms of the size of the hospital building, amount of staff, and number of departments), technical ability of staff, medical devices used, and overall administrative capability.
Table 1.
Summary of participants' demographic and occupational information. Abbreviation used: OR, operating room.
The usability evaluations were conducted at Yuliman-SGS usability test lab in Suzhou, China, from July to August 2021 (Figure 1).
Figure 1.
The simulated operating room in the Yuliman-SGS usability test lab.
Packages and Medical Devices
A total of 14 medical devices from different manufacturers were divided into five groups according to different SBS configuration types, as shown in Figure 2: (1) header bag (items 1–3), (2) rigid tray (items 4 and 5), (3) vent bag (items 6 and 7), (4) pouch (items 8–12), and (5) form-fill seal (items 13 and 14).
Figure 2.
Different medical device packaging configurations used in the study.
Among the 14 sterile medical devices, two used a double SBS (items 4 and 12) and 12 used a single SBS. Double SBSs are mainly used for precise, heavy, or high-risk medical devices to reduce the risk of aseptic presentation or loss of sterility. To our knowledge, the proportion of single to double SBSs in this study reflects the real-world situation of the current medical device market.
Moreover, of the 14 types of medical devices, 12 were single-use medical devices from four different manufacturers. All types underwent ethylene oxide sterilization except items 11 and 12, which were packaged by the central sterile supply department at the Second Affiliated Hospital of Soochow University and sterilized by hydrogen peroxide low-temperature plasma.
Detailed information regarding the test packages is provided in Table 2.
Table 2.
Medical device packaging used in the study. Abbreviations used: LDPE, low-density polyethylene; PE, polyethylene; PET, polyethylene terephthalate; PTCA, percutaneous transluminal coronary angioplasty.
Simulation of Contamination Process
Ultraviolet (UV) fluorescent powder (Glo Germ Powder; Glo Germ, Moab, UT) was used to represent contamination. This method was first proposed by Crick et al.10 and adapted by Trier et al.9 to identify the “contact between package contents with nonsterile surfaces, specifically the provider’s hands and the outside of the pouch.” The brand of powder used in this study was developed to simulate the presence and transfer of real germs and demonstrate cases of contamination. It is a popular tool among schools, hospitals, and food services for training and education purposes.
The powder was applied to the outside of the SBS and gloves of nurses. After the device was transferred to the sterile field, it was scanned with UV light in a dark room to detect the transfer of the powder. Presence of powder particles was indicative of contact with the outside of the SBS or gloves (i.e., nonsterile surfaces) of the nurse. The UV scan in the dark room and samples under the UV lighting can be seen in the “UV Scan” column of Figure 3. Last, contamination was assessed and recorded by the researchers, and each sample was photographed (once on each side) to enable a post hoc review of sample contamination.
Figure 3.
Flow chart of test methods. Abbreviation used: UV, ultraviolet.
Trials
A total of 40 experienced clinical nurses participated in 280 individual trials (20 per SBS configuration), which were conducted in a simulated OR. Each test session lasted up to 2.5 hours. Each test session involved five modules corresponding to five different SBS configuration types. For each module, participants worked in groups for each SBS configuration type. After each module, the researcher asked open-ended questions to collect participants’ subjective assessments of the SBS. The researcher also asked participants to assess the SBS’s ease of use and safety via a five-point Likert-type scale (ranging from 1 [unsafe] to 5 [safe]). The flowchart of each session is shown in Figure 3.
In the preparation stage, powder was applied to the exterior of the gloves immediately before a module. The powder also was applied to test SBSs just prior to being handed to test participants, as shown in the “Preparation” column of Figure 3.
Specifically, a researcher wearing contaminated gloves, which were selected by the nurse before the start of the test session, submerged the fingertips of the gloves into a tray containing powder, thereby coating the fingertips of the gloves. Then, the researcher touched the outside of the SBS with the contaminated gloves and covered the surface of the SBS with powder. The criteria for powder coating required that all parts of the packaging system intended to be opened at the point of use must be evenly and fully covered in a very thin layer of powder. After coating, the individual with the contaminated gloves used the UV light to confirm that the contamination had coated the package and gloves. Last, the researcher took off his/her gloves and placed the gloves on the cart.
Next, during the aseptic presentation stage, the cart with gloves and test SBS were moved outside of the OR by the researcher. Outside of the OR, the researcher guided the nonsterile nurse to wear the gloves and then pushed the cart inside the OR. Another researcher prepared the drape to represent the sterile field. Then, as shown in the “Aseptic Preparation” column of Figure 3, the nonsterile nurse opened the SBS with the powdered (contaminated) glove and the sterile nurse transferred the content from the SBS to the sterile field. To ensure consistency with real-world settings, we asked all participants to use the same speed and pace with the aseptic presentation as they would in a regular OR setting. In addition, we randomly shuffled the order of SBSs presented for each group of participants to avoid a potential bias resulting from fatigue. After the presentation, this researcher then transported the contents and drape to the darkroom to be scanned by UV light. In the darkroom, the researcher counted the number of aseptic presentation failures. After each test session, the researcher used UV light to inspect the simulated OR to ensure that it was free of contaminants.
For the final stage of the study, researchers reviewed the process with the nurse participants and collected their feedback. As noted in the “Interview" column of Figure 3, the survey questions sought to gain nurses’ feedback regarding ease of opening packaging systems, ease of understanding packaging labels, and overall safety of packaging. Follow-up discussion with the nurses helped researchers understand their needs and concerns about different types of SBSs, as well as the root causes for failures during aseptic presentation.
Acceptance Criteria of Aseptic Presentation
The success/failure of the aseptic trial was determined by the presence of UV fluorescent powder. Specifically, if any powder appeared on the contents or unopened second layer of the SBS sterile field, aseptic presentation was considered to have failed.
However, our criteria in the evaluation of all packages during the study, which determines any presence of powder to be a failure case, may lead to higher number of false-positives. Thus, in conducting future research, it is important to be aware of the potential sensitivity of this method while evaluating the packaging system during the aseptic trial.
Results
Statistical Methods
We collected data from a total of 278 trials for five configurations. Data collected included product name, SBS layer, SBS configuration, and aseptic presentation failure rate. For analysis, we looked at the effects of SBS configuration, size, and layer type in relation to failure rate, as well as the relation between the failure rate and three objectively recorded measurements. We also assessed the effect of SBS configuration on some of these variables. Specifically, we used Pearson’s correlation coefficient to study the relationships among variables. Data analysis was performed on RStudio version 1.4.1717 ("Juliet Rose," 2021-05-24 for macOS).
Overall Data
Data for the five types of SBSs are provided in Table 3. Within each type of SBS, different types of medical devices and their corresponding failure rates were reported. As noted previously, the failure of an aseptic trial was defined by the presence of UV fluorescent powder. The failure rate of one type of SBS is calculated as the failure number divided by the number of valid data, which is the number of trials conducted in total.
Table 3.
Aseptic presentation failure rate. *Average failure rate for group. Abbreviation used: PTCA, percutaneous transluminal coronary angioplasty.
Effect of SBS Configuration
Considerable differences in the failure rate of aseptic presentation emerged among the five SBS configurations, as shown in Figure 4. The vent bag had the highest failure rate (85%), followed by the header bag (72%). Therefore, in this study, the medical devices packaged by these two configurations were difficult to present aseptically, thus increasing the probability of contamination. Pouch and rigid tray designs performed better, with lower failure rates, demonstrating that they allow easier and safer handling compared with other configurations.
Figure 4.
Failure rate for different sterile barrier system (SBS) configurations (left) and different SBS layer types (right).
In addition, Figure 5 shows the best- and worst-performing samples among the trial kits. Overall, we found that surgical kits packaged in vent bags demonstrated the worst performance among the five configurations tested. Contamination of contents was clearly visible under UV light (Figure 5, second image from left). Observation indicated that this performance was mostly linked to the design of the vent bags; however, the size of the device was another aspect to consider. For example, as reflected by the nurse participant feedback shown in Table 4, contamination from vent bags could occur due to an irregular tear opening, a plastic opening that rolled inward, or confusion caused by the middle seal. Table 4 also includes possible reasons of failure for the header bags, such as the opening area being too narrow and the device being too big. The performance of header bags certainly could be optimized by a focused design effort. However, given the current design of the vent bag, efforts to optimize the design would be more difficult.
Figure 5.
The worst- and best-performing SBS samples for contamination results, displayed under ultraviolet lighting. The first and second images show surgical kits packaged by vent bags; these were among the worst-performing SBS samples. The third and fourth images show hemostat forceps packaged by double pouch; these were among the best-performing SBS samples.
Table 4.
Summary of feedback provided by nurse participants. Abbreviation used: NA, not applicable; SBS, sterile barrier system.
On the other hand, as shown in Figure 5 (right), the hemostat packaged by double pouch demonstrated excellent results, with no aseptic presentation failure in all 20 samples.
The quantitative and qualitative results described here provide insight into potential design modifications that could improve both the usability and safety of different SBS configuration types. Given the scope of this work in terms of the number of SBS types and the sample size, we hope to raise awareness of these important SBS design consideration. However, drawing conclusions about whether some types should be qualified or disqualified would be premature and was not the intent of this work.
Effect of Single versus Double SBS
The use of double SBSs is increasingly common among manufacturers and hospital sterile processing departments to aid in controlling and preventing contamination of medical devices during transportation, storage, and handling. In this section, we compare single and double SBS in terms of their effects in preventing contamination. As displayed in Figure 5 (right), the results showed that a multilayer SBS could provide considerably better protection against contamination during aseptic presentation.
Effect of SBS Size
The relation between SBS size and failure rate is shown in Figure 6 (left). A moderate positive correlation (r = 0.573) was observed between the two variables, as shown by the trendline of best fit (with one outlier disregarded in the figure). One sample (esophageal stent) was designated as an outlier due to concern for its ratio of length to width (1,600/145 = 11.03), which was much higher compared with the rest of the data. Because the goal was to ensure a roughly similar shape and shape proportion across all samples, the inclusion of this sample may lead to bias in this particular analysis.
Figure 6.
Left: Relation of total packaging size to failure rate. Right: Relation of safety of packaging system to failure rate. *Participants were asked to rate the safety of packaging systems by assigning a score from 1 (unsafe) to five (safe) (i.e., five-point Likert-type scale).
Subjective Evaluations of SBSs
We also collected subjective scores (ranging from 1 [unsafe] to 5 [safe]) from participants regarding the safety of SBSs (Figure 6, right). The scores were plotted with corresponding failure rates, along with the line of best fit (r = –0.53). Overall, packaging systems considered safer by the user tended to have lower failure rates. This observation suggested that subjective ratings may be a potential key factor associated with product failure.
SBS Configuration Preference
We asked each of the 40 participants to rank SBS configuration from most to least preferred (Figure 7). The y-axis shows the number of participants who ranked the corresponding SBS configuration as the most preferred configuration (of five). Overall, tray configurations were the most preferred (28 positive ratings and only one negative rating). Vent bag configurations received the highest number of unfavorable ratings and no positive ratings.
Figure 7.
Distribution of rating for best-performing SBS configurations. Abbreviation used: FFS, form-fill seal.
Effect of Medical Device Design in Relation to Packaging
Optimizing the SBS in relation to the specific medical device and the intended use is an important task for packaging designers. However, in this study, we did not analyze the effect of the medical device design in relation to its packaging. Therefore, no conclusions can be drawn to that effect, as all of the medical devices in the study were different.
Other Findings
In this study, researchers found that 37 of 40 nurses failed to correctly differentiate between SBS and protective packaging for a double-layered packaging system of a coronary drug stent. To illustrate this, samples of protective packaging and an SBS are shown in Figure 8. ANSI/AAMI/ISO 11607-1:2019, subclause 6.1.8, requires that if the packaging system to be opened at the point of use consists of more than one layer, the SBS(s) should indicate that this is the case. SBS symbols are provided in ISO 15223-1:2021, subclauses 5.2.11 through 5.2.14.11 In our case, no SBS symbols were marked on the package to guide the users, which is one possible reason that this package resulted in poor usability performance.
Figure 8.
Examples of samples using protective packaging (left image) and an SBS (right image). A total of 37 of 40 nurses failed to correctly differentiate between protective packaging and an SBS for a double-layered packaging system of a coronary drug stent. The new SBS symbols included on the right, which are described in ISO 15223-1:2021,11 are intended to prevent such situations from occurring in the future.
Interview Results and Summary
Verbal feedback from nurse participants is summarized in Table 4.
Limitations
A limitation of this study was the choice of UV fluorescent powder to detect contamination. We initially ruled out lotion, despite it being a common method, because it may cause the gloves and the packaging to become slippery, making the handling difficult and therefore biasing the results. However, as we later discovered, powder can be easily dispersed, which may in turn contaminate the sterile environment and lead to false-positives. To address this limitation, after each test session, researcher used UV light to inspect the OR to confirm whether it was clean and free of powder. In addition, before each trial, a designated individual put a new clean drape on the table to present a sterile field.
Another limitation was that measurement bias may have occurred due to inconsistent application of the powder by different participants. The fact that the powder can be easily dispersed also means that the sensitivity of the test method may be higher compared with real-world conditions. To achieve more consistent and accurate comparisons of different designs, it is necessary to collaborate with industry experts to standardize the quantity of powder dispersed and to define how to establish, for example, the failure limit.
Another potential limitation was that this study did not use slow-motion video capture for detecting contamination.12 This method avoids the pitfalls of both powder and lotion but is considerably more expensive. However, slow-motion video allows location- and time-dependent data to be acquired, thereby making it possible to extend our studies with more types of analysis.
A final limitation was related to the selection of test participants. For example, factors such as participant hand preference and height could be important factors when opening SBSs. However, we ensured that our participant pool represented a random sample of the larger population; thus, the distributions of hand preference and participant height should mimic those of the actual OR nurse population. Nevertheless, future work should consider these potentially confounding factors in usability studies.
Conclusion
In this study, we conducted usability evaluations of various types of SBSs in terms of their potential contamination failure rates and offered extensive analyses and insights about the attributes of these packages. Most notably, double-pouch SBSs were the best performing, while vent bags were the worst performing. In addition, we found that including appropriate SBS symbols to differentiate an SBS from protective packaging was vitally important.
Although further work in this area is needed, we hope that this study can enable the sterile packaging community to identify possible opportunities to improve medical package design for easy and safe handling. Optimizing SBSs in relation to specific medical devices and their intended use can help minimize risk of microbial contamination. This study demonstrates that it is incumbent upon the medical device industry and standards-developing organizations to develop rigorous aseptic presentation evaluation procedures for SBSs. In particular, defining appropriate pass and failure criteria for the broader industry will help device designers and medical device manufacturers follow and evaluate their products before entering the market and hospitals. In turn, this can benefit the downstream users of these products in important ways.
Developing a tighter association with the clinical risk analysis of the packaged medical devices also will be essential. The Spaulding Classification of separating patient care items into three categories (noncritical, semicritical, and critical) is widely recognized. As appropriate aseptic technique is particularly important for categorizing critical items, will it be appropriate to consider a further subdivision of this category to recognize that different procedures have different risk profiles? Additional focused research is needed to elucidate these topics.
ASTM Committee F02 on Primary Barrier Packaging has initiated a new work item (WK7785) to develop a guidance document on usability assessments for medical packaging, with the focus mainly being on methodology. This is an important and encouraging initiative. Contributions such as this will allow medical device manufacturers and SBS designers to have the necessary standards to evaluate and validate their packaging system designs.
Funding
Financial support to conduct this study was received from the China Medical Device Packaging Committee.
Acknowledgments
The authors thank the registered nurse participants for their knowledge of handling and opening techniques for numerous medical device packaging systems.
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