Ventilation conditions and air-borne bacteria and particles in operating theatres: proposed safe economies

Indoor Air Quality in Inpatient Environments: A Systematic Review on Factors that Influence Chemical Pollution in Inpatient Wards

Introduction

Indoor air quality is one the main issues in which governments are focusing. In healing spaces, several research studies are reporting a growing number of data analysis and research works in order to guarantee and prevent health of users and workers. Currently the main investigations are about biological and physical risks; otherwise chemical ones are less investigated. Several countries are carrying out indoor air quality monitoring in those professional workplaces in which chemicals are used but also in some typically indoor (generic) spaces for the building hygiene assessment. The indoor air is affected by several factors that currently are analyzed punctually, without a whole scenario of all the variable performances. The authors have done a systematic review on the current state of the art and knowledge related to chemical pollution in healing spaces and the emerging strategies, supported by scientific literature, for healthy inpatient rooms and their indoor air.

Methodology

The systematic review has been done through the analysis of papers from SCOPUS, DOAJ, and PubMed databases. The survey sample considered 483 scientific articles, between 1989 and 2017, and starting the systematic reading and analysis of the abstracts, only 187 scientific papers were selected, and only 96 were accessible.

Discussion

Since scientific literature reports very different outputs and results, the resulting work from the survey is divided into specific fields of interest related to construction and finishing materials, installations, components, ventilation systems, processes, etc. Starting from the systematic reading, the paper classifies the factors of indoor air in four macroareas: outdoor air and microclimatic factors (temperature, relative humidity, air velocity, air change, etc.); management activities (management and maintenance activities, ventilation systems, HVAC, cleaning and disinfectant activities, etc.); design factors (room dimensions, furniture, finishing materials, etc.); and human presence and medical activities (users' presence, their health status, and medical activities carried out in inpatient rooms).

Conclusion

The systematic review gives rise to a broad scenario on the existing knowledge regarding the indoor air pollution, design, and management strategies for healthy spaces and several emerging topics. Although the aim of the investigation is strictly related to chemical pollution, several considerations from the biological point of view have been listed. The systematic review, supported by the existing scientific literature, becomes a starting point for considering the importance of the topic and to stimulate the knowledge around this field of interest for improving studies, analysis, and simulations.

Reduction of Particles in the Operating Room Using Ultraviolet Air Disinfection and Recirculation Units

BACKGROUND

Airborne bacteria are a major source for wound contamination during total joint arthroplasty. Crystalline ultraviolet C (C-UVC) filter units were designed to disinfect and recirculate air in the operating room (OR). This preliminary study assessed the particle reducing capacity of C-UVC units in a highly controlled OR setting.

METHODS

A particle counter was deployed in a positive-pressure OR to measure total and viable particle counts (TPC/VPC). Thirty 23-minute experiments were performed. At 4 designated times a person would walk through the door to mimic OR traffic. Ten experiments were performed as controls, 10 experiments used a C-UVC unit 4 meters (m) from the door, and 10 cases with the C-UVC unit at 8 m. Outcomes included overall, change (Δ), and maximum TPC/VPC. Mann-Whitney U-tests determined statistical differences in TPC/VPC.

RESULTS

Compared to controls, the cases with the C-UVC unit at 4 m had significantly lower particle levels. Overall TPC/VPC, changes in TPC/VCP, and maximum TPC/VPC were all significantly lower (P < .05) in the C-UVC unit (4 m) group compared to the controls. The C-UVC at 8 m significantly reduced TPC in all 3 outcomes (P < .05) compared to controls; however, it did not significantly reduce changes in VPC (P = .107) and maximum VPC (P = .052). There were no significant differences in any outcomes between the 4 m and 8 m group.

CONCLUSION

C-UVC units have shown to be capable of significantly reducing TPC and VPC in a highly controlled OR setting. Reducing airborne particles using C-UVC units may reduce infection rates following total joint arthroplasty.

Surgeon Personal Protection: An Underappreciated Benefit of Positive-pressure Exhaust Suits

BACKGROUND

Positive-pressure exhaust suits cost more than standard surgical gowns, and recent evidence suggests that they do not decrease infection risk. As a result, some hospitals and surgeons have abandoned positive-pressure exhaust suits in favor of less expensive alternatives. We propose that in addition to their original purpose of decreasing infection rates, positive-pressure exhaust suits may also improve personal protection for the surgeon and assistants, perhaps justifying their added costs.

QUESTIONS/PURPOSES

(1) Do positive-pressure exhaust suits decrease exposure to particulate matter during TKA? (2) What areas covered by gowning systems are at risk of exposure to particulate matter?

METHODS

Three surgical gowning systems were tested: (1) surgical gown, face mask, surgical skull cap, protective eyewear; (2) surgical gown, face mask, surgical protective hood, protective eyewear; and (3) positive-pressure exhaust suit. For each procedure, a cadaver knee was injected intraarticularly and intraosseously with a 5-µm fluorescent powder mixed with water (1 g/10 mL). After gowning in the standard sterile fashion, the primary surgeon and two assistants performed two TKAs with each gowning system for a total of six TKAs. After each procedure, three independent observers graded skin exposure of each surgical participant under ultraviolet light using a standardized scale from 0 (no exposure) to 4 (gross exposure). Statistical analysis was performed using Friedman's and Nemenyi tests. The interrater reliability for the independent observers was also calculated.

RESULTS

The positive-pressure exhaust suits had less surgeon and assistant exposure compared with other systems (p < 0.001). The median overall exposure grade for each gowning system was 4 for System 1 (range, 3-4), 2.5 for System 2 (range, 2-3), and 0 for System 3 (range, 0-0). In pairwise comparisons between gowning systems, the positive-pressure exhaust suits had less exposure than gowning System 1 (difference of medians: 4, p < 0.001) and gowning System 2 (difference of medians: 2.5, p = 0.038). There was no difference found in exposure between Systems 1 and 2 (difference of medians: 1.5, p = 0.330). When gowning Systems 1 and 2 were removed, particulate matter was found in places that were covered such as the surgeon's beard, lips, inside the nostrils, behind the protective eyewear around the surgeon's eye, and in both eyebrows and eyelashes.

CONCLUSIONS

The positive-pressure exhaust suits provided greater personal protection with each procedure than the other two gowning systems.

CLINICAL RELEVANCE

With conventional gowns, particulate matter was found in the surgeon's eyelashes, under the face mask around the mouth, and inside the nostrils. Despite recent evidence that certain types of positive-pressure exhaust suits may not decrease infection, there is a clear benefit of surgeon protection from potentially infectious and harmful patient substances. Despite their added costs, hospitals and surgeons should weigh this protective benefit when considering the use of positive-pressure exhaust suits.

Sources and dynamics of fluorescent particles in hospitals

Fluorescent particles can be markers of bioaerosols and are therefore relevant to nosocomial infections. To date, little research has focused on fluorescent particles in occupied indoor environments, particularly hospitals. In this study, we aimed to determine the spatial and temporal variation of fluorescent particles in two large hospitals in Brisbane, Australia (one for adults and one for children). We used an Ultraviolet Aerodynamic Particle Sizer (UVAPS) to identify fluorescent particle sources, as well as their contribution to total particle concentrations. We found that the average concentrations of both fluorescent and non-fluorescent particles were higher in the adults' hospital (0.06×10⁶ and 1.20×10⁶  particles/m³ , respectively) than in the children's hospital (0.03×10⁶ and 0.33×10⁶  particles/m³ , respectively) (P<.01). However, the proportion of fluorescent particles was higher in the children's hospital. Based on the concentration results and using activity diaries, we were able to identify sources of particle production within the two hospitals. We demonstrated that particles can be easily generated by a variety of everyday activities, which are potential sources of exposure to pathogens. Future studies to further investigate their role in nosocomial infection are warranted.

The Gown-glove Interface Is a Source of Contamination: A Comparative Study

BACKGROUND

The original Charnley-type negative-pressure body exhaust suit reduced infection rates in randomized trials of total joint arthroplasty (TJA) decades ago. However, modern positive-pressure surgical helmet systems have not shown similar benefit, and several recent studies have raised the question of whether these gowning systems result in increased wound contamination and infections. The gown-glove interface may be one source of particle contamination.

QUESTIONS/PURPOSES

The purpose of this study was to compare particle contamination at the gown-glove interface in several modern surgical helmet systems and conventional surgical gowns.

METHODS

A 5-μm fluorescent powder was evenly applied to both hands to the level of the wrist flexion crease. After gowning in the standard fashion, the acting surgeon performed a 20-minute simulated TJA protocol. Each of the five gowning systems was run through five trials. The amount of gown contamination at the gown-glove interface then was measured by three observers under ultraviolet light using a grading scale from 0 (no contamination) to 4 (gross contamination). Statistical analysis was carried out with Minitab 15. Friedman's test was used to compare the levels of contamination across trials for each gown and the Mann-Whitney test was used post hoc to perform a pairwise comparison of each gown.

RESULTS

All gown-glove interfaces showed some contamination. Friedman's test showed that there was a significant difference in contamination between gowns (p = 0.029). The Stryker T5 Zipper Toga system showed more contamination than the other gowns. The median contamination score and range for each gowning setup was 1.8 (range, 1-4; conventional Kimberly-Clark MicroCool gown without helmet), 4 (range, 3-4; Stryker T5 Zipper Toga), 3.6 (range, 0-4; Stryker helmet with conventional gown), 1.6 (range, 0-2; Stryker Flyte Toga), and 3.0 (range, 2-3; DePuy Toga). A Mann-Whitney test found no difference among any of the gowns except for the Stryker T5 Zipper Toga, which showed more contamination compared directly with each of the other four gowns (p < 0.001 for each gown-to-gown comparison).

CONCLUSIONS

Particle contamination occurs at the gown-glove interface in most commonly used positive-pressure surgical helmet systems. The Stryker T5 Zipper Toga exhibited more contamination than each of the other gowning systems.

CLINICAL RELEVANCE

The gown-glove interface is prone to particle contamination and all surgeons should be aware of this area as a potential source of surgical site infection. Although future studies are needed to clarify the link between particle contamination through this route and clinical infection, surgeons should consider using gowning systems that minimize the migration of fomites through the gown-glove interface.

Observing and quantifying airflows in the infection control of aerosol- and airborne-transmitted diseases: an overview of approaches

With concerns about the potential for the aerosol and airborne transmission of infectious agents, particularly influenza, more attention is being focused on the effectiveness of infection control procedures to prevent hospital-acquired infections by this route. More recently a number of different techniques have been applied to examine the temporal-spatial information about the airflow patterns and the movement of related, suspended material within this air in a hospital setting. Closer collaboration with engineers has allowed clinical microbiologists, virologists and infection control teams to assess the effectiveness of hospital isolation and ventilation facilities. The characteristics of human respiratory activities have also been investigated using some familiar engineering techniques. Such studies aim to enhance the effectiveness of such preventive measures and have included experiments with human-like mannequins using various tracer gas/particle techniques, real human volunteers with real-time non-invasive Schlieren imaging, numerical modelling using computational fluid dynamics, and small scale physical analogues with water. This article outlines each of these techniques in a non-technical manner, suitable for a clinical readership without specialist airflow or engineering knowledge.

Some aspects of the airborne transmission of infection

The relationship between the human body and the dissemination of potentially pathogenic particles and droplets is described. Airborne transmission of infection in operating theatres and a burns unit and the part played by the human microclimate and its interaction with ventilating air flows is discussed. The mechanisms by which different garment assemblies used for surgery can enhance particle dispersion are illustrated and the way that floor cleaning can increase the concentration of airborne organisms is described. The development of the successful use of ultra-clean air systems in orthopaedic implant surgery is reviewed. Relationships between contact and airborne transmission of disease are explored and ways by which containment strategies and metrics used in pharmaceutical and electronics manufacturing can be applied to the design and monitoring of healthcare areas is discussed. It is suggested that currently available techniques involving architectural, ventilation and operational aspects of healthcare provision, when properly applied, can markedly improve treatment outcomes that may otherwise be compromised by hospital-acquired infections involving both bacteria and viruses.

The efficiency of an air filtration system in the hospital ward

A study was conducted to ascertain the efficiency and effectiveness of an air filtration system (Electromedia Model 100C, Clean Air UK, UK) in the hospital ward. The sampling was conducted using a portable Surface Air Sampler (Cherwell Laboratories, Bicester, UK) in conjunction with settle plates. Samples were taken two days before and two days following activation of the filtration system and results compared. A clear, demonstrable, statistically significant reduction in microbial organisms following the activation of the filtration systems is evident (81% settle plates; 24% Surface Air Sampler). This study has implications for the improved health and welfare of patients and healthcare workers who may benefit through the implementation of such a system.

Inefficiency of upward displacement operating theatre ventilation

A new thermally based ventilation system ('Floormaster') with inlet of cool clean air at floor level, and evacuation at the ceiling of the air warmed by activity in the room (upward displacement ventilation, 17 air changes/h) was compared with a standard positive pressure (plenum) ventilation system with air supply through an inclined perforated screen along one wall at the ceiling and evacuation at floor level (conventional turbulent or mixing system, 16 air changes/h). The study was made during rigidly standardized sham operations (N = 20) performed in the same operating room by a six-member team wearing non-woven disposable or cotton clothing. In general the upward displacement system removed dust particles too small to carry bacteria (0.16-<0.3 microm, 0.001<P<0.01) more efficiently than the conventional system. However, the displacement system also yielded two to threefold higher air and surface bacterial counts in areas important for surgical asepsis (wound area, instrument table) especially with regard to bacterial sedimentation (0.001<P<0.05). The major shortcoming of the displacement system was insufficient elimination of the larger bacteria-carrying particles. The type of clothing worn by the members of the team did not influence the overall results. We conclude that an upward displacement system will lead to increased counts of airborne and sedimenting bacteria and thus increase the risk of postoperative infection in comparison with conventional operating room ventilation systems.

Electronic particle counting for evaluating the quality of air in operating theatres: a potential basis for standards?

Airborne particle counting in eight size ranges (0.5- greater than 20 microns), by computerized electronic equipment, was compared with the numbers of bacteria-carrying particles (BCP) assessed by slit sampling in ultra-clean and turbulently ventilated operating theatres. In the ultra-clean theatre the number of particles of 5-7 microns size range correlated with BCP while peaks in the numbers of particles less than 3 microns and greater than 15 microns corresponded with activity. Comparative relationships also occurred in the turbulently ventilated theatre but the use of this equipment in that environment cannot yet replace counts of airborne bacteria. We consider that electronic particle counting in the 0-20 microns size range may be used to judge the performance of a clean air operating theatre distribution system, including efficiency and integrity of the filter/seal systems and the presence or absence of entrainment of bacteria and other particles. The sampling techniques and analysis of particle concentration results described here may be a suitable basis for standards.

Air bacterial and particle counts in total hip replacement operations using non-woven and cotton gowns and drapes

Air bacterial and particle counts were obtained in a conventionally ventilated operating theatre, during 8 operations for total hip replacement performed using synthetic non-woven fabrics as drapes for the patients and gowns for the staff (trousers and stockings were of conventional cotton material), ('non-woven' group), and in 8 corresponding operations using conventional cotton fabrics ('cotton' group). No significant difference between the groups with regard to air bacterial counts was observed. The use of cotton fabrics was associated with substantially higher particle counts, probably due to particles from the cotton textiles themselves. No significant correlation was observed between the bacterial and particle counts, indicating that these came from different sources and that the particles were mainly of sterile origin. Thus, the benefit of the synthetic, non-woven fabrics in hip replacement surgery, when these fabrics are used to cover theatre staff only partially in the form of gowns, seems questionable with regard to the reduction of air bacterial counts. On the other hand, the surgical textiles of non-woven material improve the purity of the operating theatre since unlike cotton fabrics they do not produce and disperse particles in the air.