Laminar Air Flow System Research Articles

Operating room ventilation with laminar air flow ceiling and a local laminar air flow system near the operating table for the patient

The aim of this study is to determine how the air flow from a unidirectional air flow (UAF) system and a local ventilation system will interact with each other. The study analyzes the air circulation near the operating table at different air flow velocities from both systems. The air flow velocities correspond to the usual range of velocities that are recommended by norms and guidelines. The research was approached by numerical and experimental studies. The thermal plume of the patient was measured by Particle Image Velocimetry (PIV) and thermography (IR) and compared with the results from the numerical case. A mesh independency study was made for the numerical case. The study showed that velocities ≥0.2 m/s from the UAF, depending on the height of the room, can overcome the thermal plume generated by a human subject with a moderate activity (100÷120W). The velocities from the local ventilation system need to be higher with at least one step, in accordance with the distance from the ventilation system to the operating wound, in order to avoid disturbances generated from the UAF system.

Influence of the Arrangement of Surgical Light Axes on the Air Environment in Operating Rooms.

Purpose Surgical lights in the operating rooms are typically installed in a single axis in the center of the room or in two axes on both sides of the operating table. In the single-axis installation, the air-conditioning outlet cannot be placed in the center of the ceiling, which may affect the air current. Therefore, we measured the air current and cleanliness in two equivalent operating rooms using a vertical laminar airflow system equipped with either single-axis or double-axis surgical lights. Methods Air current was measured using a three-dimensional ultrasonic anemometer. Cleanliness was evaluated by measuring the amount of dust before and after air-conditioner activation. To visualize the air current, smoke was illuminated on a sheet of laser light while the air-conditioning was stopped, and changes after air-conditioning activation were observed. Results In the single-axis room, an oblique fast air current flowing from the surrounding air outlet toward the center was observed, and the flow velocity fluctuated greatly. In the double-axis room, uniform downward laminar airflow was observed. The amount of dust at the center decreased significantly faster in the double-axis room; thus, the cleanliness at the center was higher in the double-axis room. Persistent stagnation of smoke was observed below the single-axis lighting, whereas smoke below the double-axis lighting was immediately dispersed and the air cleared even when surgical lights were in the position for surgery. Conclusion Uniform vertical laminar airflow was formed and high cleanliness was achieved in the center of the room when the surgical lights were arranged in two axes.

Laminar airflow and mixing ventilation: Which is better for operating room airflow distribution near an orthopedic surgical patient?

There has been little research on the performance of laminar airflow (LAF) and mixing ventilation (MV) systems regarding clean airflow distribution near a surgical patient in operating rooms (ORs). The objective of this study was to examine the performance of LAF and MV systems in ORs at St Olavs Hospital in Norway. Experimental measurements were conducted in 2 ORs equipped with LAF and MV systems. Under real operating conditions, airflow distribution from the LAF system was disrupted, and airflow velocity became significantly lower than that of MV above the lying patient. Airflow pattern was observed as distributed vertically downward and horizontally with LAF and MV, respectively. Turbulence intensity of supply airflow from LAF was much lower than that of MV. The airflow distribution by LAF system in close proximity to a patient is greatly affected by thermal plumes generated above incisions by both patients and surgical facilities. The effect of surgical facilities on airflow distribution by using MV is not significant compared to LAF ventilation. New guidelines are needed for the design of clean airflow distribution systems in the vicinity of surgical patients in ORs.

Effect of laminar air flow and building construction on aspergillosis in acute leukemia patients: a retrospective cohort study

BackgroundThe preventive effect of laminar air flow (LAF) on aspergillosis has been observed in patients with hematological malignancies. However, the short follow-up period limits the interpretation of study results.MethodsTo assess the preventive effect of long-term LAF use on aspergillosis in its long-term use, we retrospectively analyzed 124 acute leukemia patients at our hospital between January 2005 and March 2016. We compared the incidence of aspergillosis before (May 2008) and during the construction of a new building (June 2008–January 2010) and in the early (February 2010–March 2014) and late (April 2014–March 2016) periods after moving to a new hematology ward with an LAF system. The 2008 European Organization for Research and Treatment of Cancer and Mycosis Study Group criteria were used for the diagnosis of aspergillosis.ResultsFourteen patients were diagnosed with possible, probable, or definite aspergillosis. Cumulative incidence rates of aspergillosis at day 180 were 12.4, 24.9, 9.3, and 25.1% before construction, during construction, in the early period after moving to a new ward, and in the late period after moving to a new ward, respectively (p = 0.106). Multivariate analysis showed that the LAF system tended to reduce the risk of aspergillosis in the early period (before construction vs. early period; hazards ratio (HR) = 1.97, p = 0.463 and during construction vs. early period;HR = 3.42, p = 0.184), but the risk increased in the late period (late vs. early period, HR = 5.65, p = 0.035).ConclusionsBuilding construction might increase the risk of aspergillosis. Short-term LAF use might reduce aspergillosis risk, but its long-term use is inadequate, although we could not exclude the possibility of increased risks in the recent period due to continued improvements in the different areas of our hospital. Strict maintenance, more effective LAF system, and optimization of aspergillosis prophylaxis may be necessary.

Influence of Ceiling Height on Airflow and Particle Distribution in an Operating Room

Bacteria-carrying particles released by surgical staff are the main factors leading to surgical site infections (SSI). Operating rooms must be designed to reduce risks of such infections. In this numerical study, the effect of different ceiling heights on particle dispersion and deposition are studied for an operating room with laminar airflow (LAF) system. Two different particle diameters (12 and 20 ìm) are tested under three different ceiling heights (2.43–2.8–3.0 m) at a constant air change rate (ACH=20). Numerical predictions are performed by using the commercial software ANSYS Fluent 16.0. The results reveal that decreasing of the ceiling height reduces the amount of particle deposited on the surgical table.

Do surgeons and surgical facilities disturb the clean air distribution close to a surgical patient in an orthopedic operating room with laminar airflow?

Airflow distribution in the operating room plays an important role in ensuring a clean operating microenvironment and preventing surgical site infections (SSIs) caused by airborne contaminations. The objective of this study was to characterize the airflow distribution in proximity to a patient in an orthopedic operating room. Experimental measurements were conducted in a real operating room at St. Olav's Hospital, Norway, with a laminar airflow system. Omnidirectional anemometers were used to investigate the air distribution in the operating zone, and 4 different cases were examined with a real person and a thermal manikin. This study showed that the downward airflow from the laminar airflow system varies in each case with different surgical arrangement, such as the position of the operating lamp. The results indicate that the interaction of thermal plumes from a patient and the downward laminar airflow may dominate the operating microenvironment. The airflow distribution in proximity to a patient is influenced by both the surgical facility and the presence of medical staff. A thermal manikin may be an economical and practical way to study the interaction of thermal plumes and downward laminar airflow. The provision of higher clean airflow rate in the operating microenvironment may be an effective way to prevent the development of SSIs caused by indoor airborne contamination.

Operating Room Traffic Increases Aerosolized Particles and Compromises the Air Quality: A Simulated Study

BackgroundStrategies to prevent bacterial fallout and reduce particle count in the operating room (OR) are key components of preventing periprosthetic joint infection. Although OR traffic control is an important factor, a quantitative study has not been performed to investigate the influence of personnel and door opening on OR air quality. This simulated study aimed to examine the influence of these 2 factors on particle density in OR with and without the laminar air flow (LAF). MethodsBoth experiments took place within an empty OR of an arthroplasty unit equipped with an LAF system. First, the number of particles in the air was counted using a particle counting apparatus while 9 persons entered the room, one every 15 minutes. Second, the door was opened and closed starting with zero door openings per minute and increasing to 4 in 15-minute increments. Both experiments were performed once with the LAF turned on and once without. ResultsThe number of personnel in the OR and the number of door openings per minute correlate with the density of particles. Both relationships were significantly reduced by turning the LAF on (correlation coefficients <0.4). With the LAF being turned on, the particle density per person decreased from 211.19 to 18.19 particles/ft3 (P < .001) and the particle density per rate of door openings declined from 117.80 to 1.90 particles/ft3 (P = .017). ConclusionThis study confirms that personnel and door opening are a major source of particles in the OR air. Controlling traffic is critical for reduction of particles and is likely to be a key preventative strategy in reducing periprosthetic joint infection. LAF is protective against the negative influence of number of people and door openings.

Impact of surgical lights on the velocity distribution and airborne contamination level in an operating room with laminar airflow system

The presence of surgical lights disturbs the flow of ultraclean air in operating rooms (ORs) with vertical laminar airflow systems (LAF) by creating a wake downstream of the lights. The wake may be characterised by velocities low enough to directly influence the level of airborne microbe-carrying particles (MCP) close to the surgical site in an OR, eventually leading to surgical site infections (SSIs). The influence of surgical lights on airflow distribution during non-operating conditions and on airborne contamination level close to the operating table during mock surgeries was analysed in ORs with vertical LAF systems. The velocity and turbulence intensity (TI) distributions were recorded through a cross-sectional grid of points under surgical lights during non-operating conditions. In order to detect microbiological contamination during operating conditions, four mock surgeries were performed mimicking real surgeries on a porcine tissue. Three of the surgeries were performed under different types of surgical lights and one surgery did not include surgical lights at all. The mean velocity under all three surgical lights was significantly lower (≤0.07 m/s) compared with the mean velocity measured when the LAF was not obstructed by lights (0.24 m/s). At several points in the grid under all three lights, velocities as low as ≤0.02 m/s were measured. Air sampling during mock surgeries recorded at least 1 CFU/m3 for 43% of the samples (n = 16; mean = 1.25; range 0–4) using surgical lights, while not a single bacteria count was recorded without the use of lights (n = 7).

Airborne bacterial contamination during orthopedic surgery: A randomized controlled pilot trial

Study objectiveSeveral factors such as lack of unidirectional, turbulent free laminar airflow, duration of surgery, patient warming system, or the number of health professionals in the OR have been shown or suspected to increase the number of airborne bacteria. The objective of this study was to perform a multivariate analysis of bacterial counts in the OR in patients during minor orthopedic surgery. DesignProspective, randomized pilot study. SettingMedical University of Vienna, Austria. PatientsEighty patients undergoing minor orthopedic surgery were included in the study. InterventionsSurgery took place in ORs with and without a unidirectional turbulent free laminar airflow system, patients were randomized to warming with a forced air or an electric warming system. MeasurementThe number of airborne bacteria was measured using sedimentation agar plates and nitrocellulose membranes at 6 standardized locations in the OR. Main resultsThe results of the multivariate analysis showed, that the absence of unidirectional turbulent free laminar airflow and longer duration of surgery increased bacterial counts significantly. The type of patient warming system and the number of health professionals had no significant influence on bacterial counts on any sampling site. ConclusionORs with unidirectional turbulent free laminar airflow, and a reduction of surgery time decreased the number of viable airborne bacteria. These factors may be particularly important in critical patients with a high risk for the development of surgical site infections.

FIELD MEASUREMENT OF AIRBORNE PARTICULATE MATTERS CONCENTRATION IN A HOSPITAL’S OPERATING ROOM

In a hospital operating room, adequate air flow and cleanliness are crucial to protect the patient from surgical site infection (SSI) during a procedure. The probability of the patient to get the infection is related to the concentration of bacteria carrying particles inside the room. This paper presents a field measurement study to quantify the concentration of particulate matters (PM) in a hospital operating room which complies with the ISO Class 7 requirements. The operating room was equipped with High Efficiency Particulate Air (HEPA) filters and a vertical laminar air flow (LAF) system. The measurements were conducted at three height levels from the floor namely 1.2 m, 1.8 m and 2.4 m. The data was logged at a rest condition, in accordance to the ISO 14644-1 requirements. A HPC300 particle counter was used to measure the concentrations of particulate matters namely PM0.5, PM1 and PM5. The results show that the concentrations of all particulate matters were higher at the height level of 1.2 m compared to other height levels. The concentration of PM0.5 was relatively higher than PM1 and PM5 in the vicinity of operating table.

Comparison between mixed and laminar airflow systems in operating rooms and the influence of human factors: Experiences from a Swedish orthopedic center

The importance of laminar airflow systems in operating rooms as protection from surgical site infections has been questioned. The aim of our study was to explore the differences in air contamination rates between displacement ventilation and laminar airflow systems during planned and acute orthopedic implant surgery. A second aim was to compare the influence of the number of people present, the reasons for traffic flow, and the door-opening rates between the 2 systems. Active air sampling and observations were made during 63 orthopedic implant operations. The laminar airflow system resulted in a reduction of 89% in colony forming units in comparison with the displacement system (P < .001). The air samples taken in the preparation rooms showed high levels of bacterial growth (≈ 40 CFU/m(3)). Our study shows that laminar airflow-ventilated operating rooms offer high-quality air during surgery, with very low levels of colony forming units close to the surgical wound. The continuous maintenance of laminar air flow and other technical systems are crucial, because minor failures in complex systems like those in operating rooms can result in a detrimental effect on air quality and jeopardize the safety of patients. The technical ventilation solutions are important, but they do not guarantee clean air, because many other factors, such as the organization of the work and staff behavior, influence air cleanliness.

532Effect of mobile unit ultra-clean laminar air flow system (LAF) on microbial contamination in urological surgery procedures. Preliminary results

532Effect of mobile unit ultra-clean laminar air flow system (LAF) on microbial contamination in urological surgery procedures. Preliminary results

Reduction of Infection after Cardiac Surgery: A Clinical Trial

Between January 1, 1975, and June 1, 1984, 3,275 patients underwent cardiac operations with cardiopulmonary bypass. No operations were performed in 1978. In Phase I of the study, general operating rooms were used for cardiac operations, and standard methods of antisepsis and asepsis were used. Phase II began in January, 1979, with the opening of two specially constructed operating rooms with complete separation of incoming and outgoing personnel and supplies, and with a laminar airflow system. All personnel scrubbed 3 minutes and changed into autoclaved clothing before entering the operating suite, and scrubbed again for 5 minutes before putting on gowns. By Phase III, which began in July, 1982, all additional protocols against infection were in place including strict techniques in the intensive care unit and a continuous antiinfection surveillance program. In Phase I, 7.3% (70% confidence limits [CL] 6.4 to 8.2%) of patients had an infectious complication; in Phase II, 2.7% (CL 2.3 to 3.2%), and in Phase III, 0.8% (CL 0.5 to 1.2%). The reductions were similar in the four subtypes of infection (superficial presternal infection, mediastinitis, endocarditis, and septicemia). The study indicates that improving the surgical environment, improving the surgical and operating room protocols, and increasing the awareness of the dangers of infection among the personnel can strikingly reduce the incidence of infections after cardiac operations.

Airborne Contamination in Orthopedic Surgery

The question arises whether, on the basis of our studies, the laminar flow system and aspiration suit should be considered as useful and effective components of the overall proctocol to prevent postoperative surgical infections. Our observations do not permit a definitive answer. This would obviously depend on the demonstration of a reduction of the incidence of postoperative infection by means of a large controlled study. The infection rate encountered in this study can not be used to draw any conclusion as to the efficacy of the laminar flow systems, since there are too many uncontrollable variables which may be influential in causing a post operative wound infection. Published reports and present data seem to indicate that the airborne route of transmission is of little significance in modern surgery and that the amount of wound contamination is not necessarily a reflection of airborne contamination. Thus, the use of the laminar air flow system and aspiration suits, which are clearly designed to prevent wound infection by the airborne route, does not seem to be justified on this basis at the present time. On the other hand, the use of laminar air flow system and/or aspiration suit by necessity imposes a strict discipline in those operating rooms, where multiple personnel are routinely involved; i.e., they reduced the number of personnel in contact with patient, reduce the traffic about the surgical patient, etc., which may have significant benefits towards the control of surgical wound infections. This enforced discipline may very well account for the significant decrease in the number of positive intraoperative wound cultures in this study when laminar air flow systems and/or aspiration suits were in use.

新しい移動式水平層流clean bedによる急性白血病の治療

In spite of using antibiotics, patients with acute leukemia undergoing cytotoxic therapy have a high incidence of infectious complications. In order to reduce the risk of acquiring infections from the environment, patient isolator has recently been developed. The design of a new portable clean bed with laminar air flow system, a collaborative effort by the Kinki University and Nihon Ikakikai Inc., is specifically for experimental leukemia chemotherapy, but is adaptable as a protective environment to other problems in medical management.The wall of the head side consists of high efficiency particulate air (HEPA)-filter capable to removing 99.97% of all particles greater than 0.3 p. in diameter. The wall of the foot side consists of prefilter. The air passes through the bed from head- to foot side in a horizontal direction at a velocity of 0.5 m per second and the filtered air is recirculated via ceiling of the apparatus. The noise is 50 phone and the temperature is possible in moderate adjustment.Bacteriological samples from the environment were taken by means of exposed settle-plates laid at the two sites (head- and foot side) of the ventilated clean bed and in open wards (single and six beds room). As culture medium was used Tryptosoy agar containing 6-8% sheep blood, and the plates of 86 mm in diameter were exposed for 9 hours.Significant differences in the bacteriological results could be detected between the samples from the clean bed and from open wards. That is, comparing colony counts per one hour by sedimentation technique, 1.01 colonies at the head side, 1.19 at the foot side, 12.3 in single bed rooms and 25.05 in six beds rooms were observed respectively.According to the classification of air cleanliness classes (standard of U. S. A., No.209), 100-1000 classes were obtained by the slit sampler method regardless of frequency of medical staff entering.Identification of viable particles from the clean bed revealed staphylococcus epidermidis, coryn. ebacterium, γ-streptococcus and etc., being common skin flora.Six patients with acute leukemia have been nursed in the clean bed. Cleansing procedures by chlorhexidine significantly reduced but not eliminated the organisms on the skin.Despite of severe neutropenia during their stay in the clean bed, four of the six patients achieved remission of their leukemia without developed infection. One patient became feverish and died of endotoxic shock on the 14th day after the staff was forced to stop the fan of the apparatus because of his mental disorders. The other 5 patients were prevented from psychological disorders, such as sleeping disturbance, anxiety or irritation, by familiar staff-patient contact and by reforming of noise.

Bacterial contamination of the surgical knife.

Two hundred and eight skin knives and 374 deep knives were evaluated in 153 clean orthopedic cases with and without a horizontal wall-less laminar air-flow system. There was no statistical difference in contamination frequency between the skin and the deep knives with and without the laminar air-flow. However, the knife blades were found to be contaminated less than laminar air-flow was used than when it was not (P less than 0.005). No correlation could be made between the cultures of the wound edges and the depth of the wound with the contaminated knife blades.

A systems analysis approach to postoperative wound infections. Phase I. Evaluation of a horizontal wall-less laminar air flow system.

A systems analysis approach to postoperative wound infections. Phase I. Evaluation of a horizontal wall-less laminar air flow system.

Medical applications of dust-free rooms. 3. Use in an animal care laboratory.

Bacterial air sampling in an animal care laboratory showed that dense aerosols are generated during cage changing and cage cleaning. Reyniers and Andersen sampling showed that the airborne bacteria numbered 50 to 200 colony-forming units (CFU)/ft(3) of air. Of the viable particles collected by Andersen samplers, 78.5% were larger than 5.5 mum. A low velocity laminar air flow system composed of high-efficiency particulate air (HEPA) filters and a ceiling distribution system maintained the number of airborne viable particles at low levels, generally less than 2 CFU/ft(3). Vertical air flow of 15 ft/min significantly reduced the rate of airborne infection by a strain of Proteus mirabilis. Other factors shown to influence airborne infection included type of cage utilized, the use of bedding, the distance between cages, and the number of animals per cage.

Medical Applications of Dust-free Rooms. III. Use in an Animal Care Laboratory

Bacterial air sampling in an animal care laboratory showed that dense aerosols are generated during cage changing and cage cleaning. Reyniers and Andersen sampling showed that the airborne bacteria numbered 50 to 200 colony-forming units (CFU)/ft(3) of air. Of the viable particles collected by Andersen samplers, 78.5% were larger than 5.5 mum. A low velocity laminar air flow system composed of high-efficiency particulate air (HEPA) filters and a ceiling distribution system maintained the number of airborne viable particles at low levels, generally less than 2 CFU/ft(3). Vertical air flow of 15 ft/min significantly reduced the rate of airborne infection by a strain of Proteus mirabilis. Other factors shown to influence airborne infection included type of cage utilized, the use of bedding, the distance between cages, and the number of animals per cage.