Laminar Air Flow Unit Research Articles

Effect of laminar airflow unit diffuser size on pathogen particle distribution in an operating room

Operating room ventilation is quite important to protect patients from infection risk inside a surgical field. The laminar flow units (LAF) used in these applications contribute to removal of pathogen particles from the operation area by creating a protection zone on the surgical field. In this study, effect of LAF diffuse size on airflow and particle distribution in an operating room is investigated using computational fluid dynamics (CFD). Three different diffuser sizes (1.8 m x 2.4 m, 2.4 m x 2.4 m, 3.2 m x 3.2 m) and three different particle diameters (5 µm, 10 µm, 20 µm) are examined. In the modeling of airflow and particle motion, the Realizable k-ε turbulence model and Lagrangian approach are used, respectively. The distributions of airflow and particles originated from the surgical team are analysed. Also, the air change efficiency is predicted as for the entire operating room and for the breathing zone. The results reveal that the LAF diffuser size has a decisive role in air velocity and contaminant distribution in the operating room. It is seen that the amount of particles deposited on the operating table could be reduced up to 73% by increasing the diffuser size.

Effect of mobile laminar airflow units on airborne bacterial contamination during neurosurgical procedures

Surgical site infections (SSIs) after neurosurgery are potentially life-threatening and entail great costs. SSIs may occur from airborne bacteria in the operating room, and ultraclean air is desired during infection-prone cleaning procedures. Door openings and the number of persons present in the operating room affect the air quality. Mobile laminar airflow (MLAF) units, with horizontal laminar airflow, have previously been shown to reduce airborne bacterial contamination. To assess the effect of MLAF units on airborne bacterial contamination during neurosurgical procedures. In a quasi-experimental design, bacteria-carrying particles (colony-forming units: cfu) during neurosurgical procedures were measured with active air-sampling in operating rooms with conventional turbulent ventilation, and with additional MLAF units. The MLAF units were shifted between operating rooms monthly. Colony-forming unit count and bacterial species detection were conducted after incubation. Data was collected for a period of 18 months. A total of 233 samples were collected during 45 neurosurgical procedures. The use of MLAF units significantly reduced the numbers of cfu in the surgical site area (P<0.001) and above the instrument table (P<0.001). Logistic regression showed that the only significant predictor affecting cfu count was the use of MLAF units (odds ratio: 41.6; 95% confidence interval: 11.3-152.8; P<0.001). The most frequently detected bacteria were coagulase-negative staphylococci. MLAF successfully reduces cfu during neurosurgery to ultraclean air levels. MLAF units are valuable when the main operating room ventilation system is unable to produce ultraclean air in infection-prone clean neurosurgery.

Three-dimensional air distribution analysis of different outflow typed operating rooms at different inlet velocities and room temperatures

It is important to provide a regular unidirectional air distribution in an operating room to reduce the number of particles. Measurements were taken in the one of the operating rooms at Uludag University Medical School, with laminar air flow unit and two-cornered outlet which was thought to have some airflow problems. Moreover, a three-dimensional computational fluid dynamics model has been developed where the measurements were taken in. The distributions of air velocity, temperature, and relative humidity have been examined and compared with the measurements to validate the computational fluid dynamics analyses. In addition to present model, four-cornered outlet operating room has been analyzed and compared with the results of two-cornered one. It is concluded that the case of four-cornered outlet provides more suitable thermal distribution, which results in a reduction of the particle numbers in the interior. Although there is no significant change in temperature and relative humidity in the operating room, air distribution changes dramatically.

Comparison of three distinct clean air suits to decrease the bacterial load in the operating room: an observational study.

BackgroundLowering air-borne bacteria counts in the operating room is essential in prevention of surgical site infections in orthopaedic joint replacement surgery. This is mainly achieved by decreasing bacteria counts through dilution, with appropriate ventilation and by limiting the bacteria carrying skin particles, predominantly shed by the personnel. The aim of this study was to investigate if a single use polypropylene clothing system or a reusable polyester clothing system could offer similar air quality in the operating room as a mobile laminar airflow device-assisted reusable cotton/polyester clothing system.MethodsProspective observational study design, comparing the performance of three Clean Air Suits by measuring Colony Forming Units (CFU)/m3 of air during elective hip and knee arthroplasties, performed at a large university-affiliated hospital. The amount of CFU/m3 of air was measured during 37 operations of which 13 were performed with staff dressed in scrub suits made of a reusable mixed material (69 % cotton, 30 % polyester, 1 % carbon fibre) accompanied by two mobile laminar airflow units. During 24 procedures no mobile laminar airflow units were used, 13 with staff using a reusable olefin fabric clothing (woven polypropylene) and 11 with staff dressed in single-use suits (non-woven spunbonded polypropylene). Air from the operating field was sampled through a filter, by a Sartorius MD8, and bacterial colonies were counted after incubation. There were 6–8 measurements from each procedure, in total 244 measurements. Statistical analysis was performed by Mann–Whitney U-test.ResultsThe single-use polypropylene suit reduced the amount of CFU/m3 to a significantly lower level than both other clothing systems.ConclusionSingle-use polypropylene clothing systems can replace mobile laminar airflow unit-assisted reusable mixed material-clothing systems. Measurements in standardized laboratory settings can only serve as guidelines as environments in real operation settings present a much more difficult challenge.

Sequence types of Staphylococcus epidermidis associated with prosthetic joint infections are not present in the laminar airflow during prosthetic joint surgery

Molecular characterization of Staphylococcus epidermidis isolates from prosthetic joint infections (PJIs) has demonstrated a predominance of healthcare-associated multi-drug resistant sequence types (ST2 and ST215). How, and when, patients acquire these nosocomial STs is not known. The aim was to investigate if sequence types of S. epidermidis associated with PJIs are found in the air during prosthetic joint surgery. Air sampling was undertaken during 17 hip/knee arthroplasties performed in operating theaters equipped with mobile laminar airflow units in a 500-bed hospital in central Sweden. Species identification was performed using MALDI-TOF MS and 16S rRNA gene analysis. Isolates identified as S. epidermidis were further characterized by MLST and antibiotic susceptibility testing. Seven hundred and thirty-five isolates were available for species identification. Micrococcus spp. (n = 303) and coagulase-negative staphylococci (n = 217) constituted the majority of the isolates. Thirty-two isolates of S. epidermidis were found. S. epidermidis isolates demonstrated a high level of allelic diversity with 18 different sequence types, but neither ST2 nor ST215 was found. Commensals with low pathogenic potential dominated among the airborne microorganisms in the operating field during prosthetic joint surgery. Nosocomial sequence types of S. epidermidis associated with PJIs were not found, and other routes of inoculation are therefore of interest in future studies.

Effect of a portable ultra-clean exponential airflow unit on the particle distribution in an operating room

The effects of a mobile laminar airflow unit on the concentration, deposition and distribution of bacteria-carrying particles in an operating room are investigated. The exploration is carried out using numerical calculation schemes (computational fluid dynamics approach). The model validation was performed through result comparisons with published measurement data from literature. Two types of mobile screen units were evaluated as an extension of turbulent-mixing operating-room ventilation. Airborne particle concentration/sedimentation was recorded with and without a screen unit on the operating table and two instrument tables. Both active and passive air sampling were examined and the results are compared. It was found that the additional mobile ultra-clean laminar airflow unit reduces the counts of airborne bacteria and surface contamination to a level acceptable for infection-prone surgeries.

Analytical characteristics of a qPCR-based molecular diagnostic assay - conceptual considerations for laboratory personnel.

Analytical characteristics of a qPCR-based molecular diagnostic assay - conceptual considerations for laboratory personnel.

Does a mobile laminar airflow screen reduce bacterial contamination in the operating room? A numerical study using computational fluid dynamics technique.

BackgroundAir-borne bacteria in the operating room (OR) may contaminate the surgical wound, either by direct sedimentation from the air or indirectly, by contaminated sterile instruments. Reduced air contamination can be achieved with an efficient ventilation system. The current study assesses the additive effect of a mobile laminar airflow (MLAF) unit on the microbiological air quality in an OR supplied with turbulent-mixing air ventilation.MethodsA recently designed OR in NKS (Nya Karolinska Sjukhuset, Stockholm, Sweden) was the physical model for this study. Simulation was made with MLAF units adjacent to the operating table and the instrument tables, in addition to conventional turbulent-mixing ventilation. The evaluation used numerical calculation by computational fluid dynamics (CFD). Sedimentation rates (CFU/m2/h) were calculated above the operating table and two instrument tables, and in the periphery of the OR. Bacterial air contamination (CFU/m3) was simulated above the surgical and instrument tables with and without the MLAF unit.ResultsThe counts of airborne and sedimenting, bacteria-carrying particles downstream of the surgical team were reduced to an acceptable level for orthopedic/implant surgery when the MLAF units were added to conventional OR ventilation. No significant differences in mean sedimentation rates were found in the periphery of the OR.ConclusionsThe MLAF screen unit can be a suitable option when the main OR ventilation system is unable to reduce the level of microbial contamination to an acceptable level for orthopedic implant surgery. However, MLAF effect is limited to an area within 1 m from the screen. Increasing air velocity from the MLAF above 0.4 m/s does not increase the impact area.

Mobile laminar air flow screen for additional operating room ventilation: reduction of intraoperative bacterial contamination during total knee arthroplasty

BackgroundSurgical site infections are important complications in orthopedic surgery. A mobile laminar air flow (LAF) screen could represent a useful addition to an operating room (OR) with conventional turbulent air ventilation (12.5 air changes/h), as it could decrease the bacterial count near the operating field. The purpose of this study was to evaluate LAF efficacy at reducing bacterial contamination in the surgical area during 34 total knee arthroplasties (TKAs).Materials and methodsThe additional unit was used in 17 operations; the LAF was positioned beside the operating table between two of the surgeons, with the air flow directed towards the surgical area (wound). The whole team wore conventional OR clothing and the correct hygiene procedures and rituals were used. Bacterial air contamination (CFU/m3) was evaluated in the wound area in 17 operations with the LAF unit and 17 without the LAF unit.ResultsThe LAF unit reduced the mean bacterial count in the wound area from 23.5 CFU/m3 without the LAF to 3.5 CFU/m3 with the LAF (P < 0.0001), which is below the suggested limit for an OR with ultraclean laminar ventilation. There were no significant differences in the mean bacterial count in the instrument table area: 28.6 CFU/m3 were recorded with the LAF (N = 6) unit and 30.8 CFU/m3 (N = 6) without the LAF unit (P = 0.631). During six operations with LAF and six without LAF, particle counts were performed and the number of 0.5 μm particles was analyzed. The particle counts decreased significantly when the LAF unit was used (P = 0.003).ConclusionWhen a mobile LAF unit was added to the standard OR ventilation, bacterial contamination of the wound area significantly decreased to below the accepted level for an ultraclean OR, preventing SSI infections.

Clean operating rooms for optimizing surgical outcome

The National President of orthopedic surgeons of India has dedicated his efforts this year to surgical training in order to optimize surgical outcome. With the ongoing technological advances taking leaps and bounds worldover, our concern has always been to keep pace with the art and science of surgery. Many of the rituals and beliefs about practices in the operation theater were derived from wishful thinking and good ideas rather than scientific evidence. In an effort to develop these guidelines it would be good to know the standards of practice worldover. In this editorial I hope to review few facts in world literature and would expect your thoughtful minds to be stimulated regarding this important issue. WHO has come out with guidelines for safe surgery and have propagated – Safe surgery saves life, surgical site infection being one of the important issues. Surgical wound infection accounts for 20% of all nosocomial infections which most commonly occur because of contamination of wound during surgery. 1 Improvement in theater techniques, antibiotics, theater clothings and ventilation has reduced postoperative infection to as low as 0.3%. 2 Wound contamination can be reduced by a number of practices including: Limiting the number of personnel in the operation theater, Disrupting the flow of bacteria to the wound, Filtering the bacteria from the theater air, Disinfecting the air and the wound, Use of systemic antibiotics and Removing bacteria by physical methods such as disinfection and surgical techniques. The traffic in and out of the operating room should be restricted and the number of personnel should also be minimized. It is known that addition of 5 operating room personnel increased the microbiological counts by more than 15 folds. Also bacterial contamination in an operating room has been shown to increase significantly when the door is left open to the corridor. 3 The contamination rate of surgical instruments exposed to the air in an operation theater was 1.18 times higher than that of instruments that have been covered with a sterile guard. 4 The exposure time also had a positive correlation with bacterial contamination rate. Research on the clean air technology has brought certain facts which can help designing the operating rooms. Firstly vertical laminar airflow units generally reduce airborne contamination better than horizontal units. Secondly there is an inconsistent relationship between the surface and air bacterial counts, indicating that measurement of air contamination represents an unhelpful method for assessment of

Assessment of horizontal laminar air flow instrument table for additional ultraclean space during surgery

The area in a vertical ultraclean laminar air flow (LAF) theatre is usually too small to accommodate all the equipment needed for major surgery. We investigated the addition of an instrument table supplied with fixed ultraclean LAF and placed alongside the existing main LAF unit, to determine its physical and bacteriological effect on the main unit. In phase 1, with two investigators but without a patient, smoke tests showed no intrusion of air from the table into the main unit and particle counts did not show any adverse effect on the main LAF unit. In phase 2, during patients undergoing two total knee replacements, the LAF table and a table without LAF were placed alongside the main LAF unit. The tables were subjected to the activity of an extra operating room (OR) nurse working from inside the main LAF vigorously simulating handling of instruments. During this activity, the >5μm particle counts were 275/m(3) at the instrument table with LAF and 8550/m(3) at the table without LAF (P<0.0001). Also, without the OR nurse activity, the particle counts, just inside the main unit and adjacent to the LAF table, were significantly reduced (P<0.03-0.003). Sedimentation plates on the LAF table and in the main unit registered 22 and 25cfu/m(2)/h respectively compared with 45cfu/m(2)/h at the instrument table without LAF. In conclusion, the results from the smoke tests, particle counts and bacteriological evaluation showed that the additional instrument table supplied with LAF is efficient and can be safely used as an extension additional to a main OR LAF unit.

A mobile laminar airflow unit to reduce air bacterial contamination at surgical area in a conventionally ventilated operating theatre

The aim of this study was to evaluate the efficacy of a mobile laminar airflow (LAF) unit in reducing bacterial contamination at the surgical area in an operating theatre supplied with turbulent air ventilation. Bacterial sedimentation was evaluated during 76 clean urological laparotomies; in 34 of these, a mobile LAF unit was added. During each operation, settle plates were placed at four points in the operating theatre (one at the patient area and three at the perimeter), a nitrocellulose membrane was placed on the instrument table and an additional membrane near the wound. During four operations, particle counting was performed to detect particles > or =0.5 microm. Mean bacterial sedimentation on the nitrocellulose membrane on the instrument table was 2730 cfu/m(2)/h under standard ventilation conditions, whereas it decreased significantly to a mean of 305 cfu/m(2)/h when the LAF unit was used, i.e. within the suggested limit for ultraclean operating theatres (P=0.0001). The membrane near the wound showed a bacterial sedimentation of 4031 cfu/m(2)/h without the LAF unit and 1608 cfu/m(2)/h with the unit (P=0.0001). Particle counts also showed a reduction when the LAF unit was used. No significant difference was found at the four points in the operating theatre between samplings performed with, and without, the LAF unit. Use of a mobile LAF unit with turbulent air ventilation can reduce bacterial contamination at the surgical area in high-risk operations (e.g. prosthesis implant).

Aerobiology in the operating room and its implications for working standards

Two novel operating room (OR) ventilation concepts, i.e. the upward displacement or thermal convection system and the exponential ultra-clean laminar air flow (LAF) designed to function without extra walls, were evaluated from a bacteriological point of view. The thermal convection system (17 air changes/h) was compared with conventional ventilation (16 air changes/h) with an air inlet at the ceiling and evacuation at floor level. The exponential LAF was compared with the vertical ultra-clean LAF and the horizontal ultra-clean LAF, both with extra side walls. The comparison was made using strictly standardized simulated operations and, except for the horizontal LAF, it was performed in the same OR where the type of ventilation was changed. In the different areas important for surgical asepsis, the thermal system resulted in a twofold to threefold increase in bacterial air and surface counts compared to the conventional system (statistical significance = p < 0.05-0.0001). The bacteriological efficiency of the exponential LAF was equal to the horizontal and vertical LAF units with extra walls in the OR, and all three systems easily fulfilled the criteria for ultra-clean air, i.e. bacteria-carrying particles < 10/m3. In the areas important for surgical asepsis the turbulent ventilation systems yielded highly significant correlation between air and surface contamination (p < 0.02-0.0006). No such correlation existed in the LAF systems.

Abandoning Care in Laminar Air Flow (LAF) Units and Routine High Dose Intravenous Immunoglobulines (IVIG) in Allogeneic Hematopoietic Stem Cell Transplantation (HSCT) Does Not Increase Mortality and Rate of Infections.

Nursing in LAF units and routine high dose IVIG were considered essential elements and standard of care in allogeneic HSCT during the 1980s. They were abandoned by many teams in view of high costs, lack of formal proof of evidence and improved diagnostic and therapeutic interventions against viral and fungal infections. A recent prospective study showed no benefit of routine IVIG but few data have analysed the consequences of the combined change in practice. We made these changes at our institution in two stages during a 10-year period: change from care in LAF rooms to single rooms (SR) and change from routine high dose IVIG to targeted IVIG replacement according to CDC guidelines. Basic strategies in supportive care and data collection remained unchanged. This resulted in a retrospective analysis of 357 allogeneic HSCT in three cohorts, i.e. LAF + IVIG, SR + IVIG and SR − IVIG (Table). Endpoints analysed were survival, transplant related mortality (TRM), relapse rate, incidence and severity of GvHD and infectious complication rates defined as: sepsis, septic thrombosis, urinary tract infections, pneumonias, and CMV reactivation. Results were adjusted by multivariate analyses for all the changes over time (see Table *significant difference between groups). There were more patients in advanced stage of disease and with higher age in more recent years. There were significantly fewer septicemias per hospital day but not per day in neutropenia in the LAF + IVIG group without impact on survival. There were no significant differences in any of the other outcomes analysed. Abandoning LAF and routine high dose IVIG use did not impact negatively on HSCT outcome. These data support current practice.GroupLAF + IVIGSR + IVIGSR, no IVIGTotalN116134107357Male55%51%62%59%Age, years*34344035Median, range4–582–621–6235Diagnosis*Leukemias85%83%82%84%Lymphoproliferative7%13%15%11%Others8%4%3%5%Early disease*46%38%29%–Late disease54%72%71%66%% RIC*0%10%32%–Days in hospital*53322838Days in neutropenia*16151114Day 100 TRM18%20%22%20%

Lack of influence of body exhaust gowns on aerobic bacterial surface counts in a mixed-ventilation operating theatre. A study of 62 hip arthroplasties

Aerobic bacterial surface contamination was studied with and without the use of body exhaust gowns in an operating room equipped with mixed/turbulent ventilation and separate operating and anaesthetic areas during 62 hip joint arthroplasties. In 31 operations conventional gowns were used, and 31 were performed with body exhaust gowns. Bacterial surface contamination was monitored in the operating and anaesthetic area using 9 cm diameter settle plates (1+1) and nitrocellulose membranes (2+2) transferred after sampling to nutrient pads. Compared with conventional clothing, the use of body exhaust gowns did not significantly reduce the microbial contamination ( P=0.1–0.7). On the settle plates 1 m from the patient 279±326 cfu/m 2/h were observed with conventional clothing compared with 142±227 cfu/m 2/h with body exhaust gowns. The first membrane located on the patient in the sterile area detected 250±590 cfu/m 2/h with conventional clothing and 210±320 cfu/m 2/h with exhaust gowns. For the second membrane on the floor, the counts were 1790±2700 and 1590±1590 cfu/m 2/h. For all operations the settle plates yielded 210±287 cfu/m 2/h in the operating area and 720±564 cfu/m 2/h in the anaesthetic area ( P=0.01). Compared with the membrane placed on the anaesthetic equipment the counts on the membrane placed on patient were also significantly lower ( P=0.01) while the membranes placed on the floor in each area showed no difference in counts. In conclusion, compared with conventional clothing, the use of body exhaust gowns could not be proven to provide more protection against microbial contamination. The low number of colony forming units found in the operating area was similar to that expected from an ultraclean laminar airflow unit, although achieved with a cheaper and more energy saving system.

Surgical area contamination – comparable bacterial counts using disposable head and mask and helmet aspirator system, but dramatic increase upon omission of head-gear: an experimental study in horizontal laminar air-flow

The effect of different head coverings on air-borne transmission of bacteria and particles in the surgical area was studied during 30 strictly standardized sham operations performed in a horizontal laminar air flow (LAF) unit. The operating team members wore disposable gowns plus either a non-sterile head covering consisting of a squire type disposable hood and triple laminar face mask, a sterilized helmet aspirator system or no head cover at all.In the wound area both types of head cover resulted in low and comparable air (means of 8 and 4cfu/m3) and surface contamination (means of 69 and 126cfu/m2/h) rates. Omission of head-gear resulted in a three- to five-fold increase (P≥0.01− 0.001), depending on site sampled air contamination rate (mean of 22cfu/m3) whereas the bacterial sedimentation rate in the wound area increased about 60-fold (P≥0.0001). A proper head cover minimized the emission of apparently heavy particles that were not removed by the horizontal LAF and contained mainly streptococci, presumably of respiratory tract origin. Dust particle counts revealed no differences between the three experimental situations. No correlation between air and surface contamination rates or between air contamination and air particle counts was found.We conclude that, from a bacteriological point of view, disposable hoods of squire type and face masks are equally as efficient as a helmet aspirator system and both will efficiently contain the substantial emission of bacteria-carrying droplets from the respiratory tract occurring when head cover is omitted. Finally, the use of bacterial air counts to assess surgical site surface contamination in horizontal LAF units must be seriously questioned.

Inconsistent correlation between aerobic bacterial surface and air counts in operating rooms with ultra clean laminar air flows: proposal of a new bacteriological standard for surface contamination

The relationship between surface contamination (cfus/m2/h) with particles carrying aerobic bacteria and corresponding air contamination rates (cfus/m3) was evaluated in operating rooms (OR) equipped with ultra clean vertical or horizontal laminar airflow (LAF). For the evaluation we collected data during strictly standardized sham operations using non-woven disposable or cotton clothing. Air contamination in the wound and instrument areas (Casella slit sampler) was related to the surface contamination rate (settle plates) in the same areas and in addition, on the patient chest.Typically, the mean surface counts were 20–70 cfus/m2/h and the air counts 1–2 cfus/m3in disposable clothing experiments, whilst the use of cotton clothing resulted in higher counts of 100–200 cfus/m2/h (wound P>0·05, patient P>0·05, instruments P<0·01) and 4 cfus/m3(P<0·02–0·001). In the vertical LAF, taking both disposable and cotton clothing operations together, the surface and air contamination rates (surface/air ratio SAR) were highly correlated (P =0·02–0·004) and the ratio varied between 18:1 and 50:1 with a mean for wound air of 36:1. Using only disposable clothing in the vertical LAF, the number of significant correlations was reduced. With cotton clothing experiments in vertical LAF and in the horizontal LAF using disposable clothing, no significant correlation between surface and air contamination was found.The wide variation of SAR values and the inconsistent relationship between surface and air counts indicates that measurement of OR air contamination represents an unhelpful method for assessment of surgical site contamination in LAF units. We propose instead that colony counts on sedimentation plates is a clinically more relevant indicator of bacterial OR contamination in LAF units. In addition to the current bacteriological standard for ultra clean OR air of (<10 cfus/m3) we suggest a corresponding standard for the surface contamination rate of <350 cfus/m2/h.

Influence of protective isolation on outcome of allogeneic bone marrow transplantation for leukemia.

Various isolation strategies are used to prevent infections during bone marrow transplantation; data on their efficacy are lacking. We studied whether use of high efficiency particulate air filtration (HEPA) and/or laminar airflow (LAF) units affect transplant-related mortality (TRM) or survival in the first year after allogeneic transplantation. 5065 patients with leukemia receiving bone marrow transplants from an HLA identical sibling (n = 3982) or alternative related or unrelated donors (n = 1083) between 1988 and 1992 were reported to the International Bone Marrow Transplant Registry by 222 teams. Two types of isolation were considered: (1) conventional protective isolation with single patient room and any combination of hand-washing, gloves, mask and gown; and (2) HEPA and/or LAF. Cox proportional hazards regression models were used to determine the relative risks (RRs) of transplant-related mortality (TRM) and of deaths from any cause in patients treated in HEPA/LAF units compared to patients treated in conventional isolation. HLA-identical sibling and alternative donor transplants were analyzed separately. Risks of TRM and overall mortality in the first 100 days post-transplant were significantly lower among patients treated in HEPA/LAF units than in those treated conventionally. RRs of TRM were 0.76 (P = 0.009) for recipients of HLA-identical sibling transplants and 0.65 (P = 0.003) for recipients of alternative donor transplants. Correspondingly RRs of overall mortality were 0.80 (P = 0.02) and 0.65 (P = 0.0006). Decreased risks of TRM and of death in the first 100 days post-transplant resulted in significantly higher 1-year survival rates in patients treated in HEPA/LAF rather than in conventional isolation units. Use of HEPA and/or LAF to prevent infections decreases TRM and increases survival after allogeneic bone marrow transplants for leukemia.

Ultraclean Laminar Airflow ORs

To minimize postoperative infections, ultraclean laminar airflow (LAF) units equipped with high-efficiency particulate air filters developed for electronic and aerospace technology have been adapted for ORs. Traditionally, the airflow was either vertical or horizontal and, to function properly, encompassed extra side walls inside the OR. Recently, new airstream technology has provided zoned down-flow units that provide an exponential airflow (i.e., resembling an upside-down trumpet mouth). The exponential airflow allows for omission of extra side walls, making them more versatile in clinical use. Each different type of LAF requires knowledge of airstream patterns and how OR team members need to dress and work to prevent contamination of the sterile air and the aseptic areas. This article discusses different LAF systems and related demands on OR clothing and behavior.

Zoned vertical ultraclean operating room ventilation: A novel concept making long side walls unnecessary

We evaluated a novel concept of High Efficiency Particulate Air (HEPA)-filtered vertical Laminar Air Flow (LAF) for operating room ventilation, designed to be used without side-walls. The LAF-unit has a central zone with an airflow of 0.4 m/s and a peripheral zone with an airflow of 0.2 m/s. The design provides an exponential downflow of air resembling an upside-down trumpet mouth and it was claimed to prevent entrainment of peripheral contaminated air. The unit was evaluated with regard to elimination of particles with focus on bacteria-carrying particles (colony-forming units = cfu) during rigidly standardized sham operations. Three different lengths of walls/enclosures (short-ending 2.0 m, medium 1.0 m and long 0.2 m above the floor) were tested. It provided a high degree of bacteriological cleanliness (0.05-4 cfu/m3 of air and 7-64 cfu/m2/h surface contamination) and its efficiency was proved to be independent of the length of the enclosures. We conclude that the novel zoned ultraclean vertical LAF unit is versatile, as it allows for omitting long side-walls, without compromising bacteriological safety.