Laminar Airflow Ventilation Research Articles

Effect of laminar airflow ventilation on surgical site infections: a systematic review and meta-analysis

The role of the operating room's ventilation system in the prevention of surgical site infections (SSIs) is widely discussed, and existing guidelines do not reflect current evidence. In this context, laminar airflow ventilation was compared with conventional ventilation to assess their effectiveness in reducing the risk of SSIs. We searched MEDLINE, Embase, Cochrane Central Register of Controlled Trials, and WHO regional medical databases from Jan 1, 1990, to Jan 31, 2014. We updated the search for MEDLINE for the period between Feb 1, 2014, and May 25, 2016. We included studies most relevant to our predefined question: is the use of laminar airflow in the operating room associated with the reduction of overall or deep SSI as outcomes in patients of any age undergoing surgical operations? We excluded studies not relevant to the study question, studies not in the selected languages, studies published before Jan 1, 1990, or after May 25, 2016, meeting or conference abstracts, and studies of which the full text was not available. Data were extracted by two independent investigators, with disagreements resolved through further discussion. Authors were contacted if the full-text article was not available, or if important data or information on the paper's content was absent. Studies were assessed for publication bias. Grading of recommendations assessment, development, and evaluation was used to assess the quality of the identified evidence. Meta-analyses were done with RevMan (version 5.3). We identified 1947 records of which 12 observational studies were comparing laminar airflow ventilation with conventional turbulent ventilation in orthopaedic, abdominal, and vascular surgery. The meta-analysis of eight cohort studies showed no difference in risk for deep SSIs following total hip arthroplasty (330 146 procedures, odds ratio [OR] 1·29, 95% CI 0·98-1·71; p=0·07, I2=83%). For total knee arthroplasty, the meta-analysis of six cohort studies showed no difference in risk for deep SSIs (134 368 procedures, OR 1·08, 95% CI 0·77-1·52; p=0·65, I2=71%). For abdominal and open vascular surgery, the meta-analysis of three cohort studies found no difference in risk for overall SSIs (63 472 procedures, OR 0·75, 95% CI 0·43-1·33; p=0·33, I2=95%). The available evidence shows no benefit for laminar airflow compared with conventional turbulent ventilation of the operating room in reducing the risk of SSIs in total hip and knee arthroplasties, and abdominal surgery. Decision makers, medical and administrative, should not regard laminar airflow as a preventive measure to reduce the risk of SSIs. Consequently, this equipment should not be installed in new operating rooms. None.

Transmission of Mycobacterium chimaera from Heater-Cooler Units during Cardiac Surgery despite an Ultraclean Air Ventilation System.

Heater-cooler units (HCUs) were recently identified as a source of Mycobacterium chimaera causing surgical site infections. We investigated transmission of this bacterium from HCUs to the surgical field by using a thermic anemometer and particle counter, videotape of an operating room equipped with an ultraclean laminar airflow ventilation system, and bacterial culture sedimentation plates in a nonventilated room. Smoke from the HCU reached the surgical field in 23 s by merging with ultraclean air. The HCU produced on average 5.2, 139, and 14.8 particles/min in the surgical field at positions Off, On/oriented toward, and On/oriented away, respectively. Culture plates were positive for M. chimaera <5 m from the HCU in the test room. These experiments confirm airborne transmission of M. chimaera aerosols from a contaminated HCU to an open surgical field despite ultraclean air ventilation. Efforts to mitigate infectious risks during surgery should consider contamination from water sources and airflow-generating devices.

A numerical investigation of vertical and horizontal laminar airflow ventilation in an operating room

The effectiveness of vertical and horizontal ventilation systems in terms of reducing sedimentation and distribution of bacteria-carrying particles in an operating room is investigated. The exploration is carried out numerically using computational fluid dynamics. Both airborne particle concentration and sedimentation are simulated under different ventilation flow conditions. Model validation is performed through comparisons with experimental data from the literature. Achieved results reveal that the preferred selection between vertical and horizontal ventilation scenario in an operating room is highly depend on internal constellation of obstacles, work practice and supply airflow rate. Improper positioning of operating room personnel may remarkably reduce the ventilation efficiency. Increasing the airflow rate reduces particle concentration in the surgical zone. Efficient ventilation, however, is not only a matter of increasing airflow rate. Inappropriate airflow rates result in flow pattern transition from laminar to less efficient turbulent mixing. A laminar and well- organized (unidirectional) flow pattern is retired for a good result. Innovative further solutions are suggested to be found in cross-disciplinary collaboration.

Einfluss der Fußbodendesinfektion auf die mikrobielle und partikuläre Belastung der Raumluft in Augen-OP-Räumen mit Verdrängungslüftungsbereichen

The necessity for routine disinfection of floors between two surgical procedures or disinfection only after visible contamination was assessed in two identical ophthalmological operating theatres equipped with laminar air flow ventilation. Over a period of four weeks, one of the two tested operating rooms was disinfected after every surgical procedure, and the other only in the case of visible contamination. This regimen was inverted every week. To compare the air quality, particle count and total bacteria count were measured inside and outside the laminar air flow. Additionally, bacteria count was measured in the operating field, consisting of the operating table and the instrument tray. Patients were monitored for surgical site infection over a period of one year after operation. No difference in particle count or number of viable bacteria was found between the two investigated procedures. Also, no wound infections were observed after one year of surveillance for surgical site infection. It appears that frequent cleaning disinfection of floors is not necessary if a laminar air flow ventilation system is installed. Under these conditions, targeted disinfection of visibly soiled surfaces appears to be sufficient. Generally, the duration of surgical procedures should be kept as short as possible.

Operating Room Ventilation With Laminar Airflow Shows No Protective Effect on the Surgical Site Infection Rate in Orthopedic and Abdominal Surgery

To evaluate whether operating room (OR) ventilation with (vertical) laminar airflow impacts on surgical site infection (SSI) rates. Retrospective cohort-study based on routine surveillance data. Sixty-three surgical departments participating voluntarily in the German national nosocomial infections surveillance system "KISS" were included (a total of 99,230 operations). Active SSI surveillance was performed according to the methods and definitions given by the US National Nosocomial Infection Surveillance system. Surgical departments were stratified according to type of OR ventilation used: (1) turbulent ventilation with high-efficiency particulate air-filtered air, and (2) HEPA-filtered (vertical) laminar airflow ventilation. Multivariate analyses were performed by the generalized estimating equations method to control for the following variables as possible confounders: (a) Patient-based: wound contamination class, ASA score, operation duration, patients' age and gender, endoscopic operation; (b) Hospital-based: the number of beds in the hospital, its academic status, operation frequency, and long-term participation in KISS. The risk for severe SSI after hip prosthesis implantation was significantly higher using laminar airflow OR ventilation (1.63 < 1.06; 2.52>), as compared with turbulent ventilation. The adjusted odds ratios for the other operative procedures analyzed were: knee prosthesis 1.76 < 0.80, 3.85>; appendectomy 1.52 < 0.91, 2.53>; cholecystectomy 1.37 < 0.63, 2.97>; colon surgery 0.85 < 0.49, 1.49>; and herniorrhaphy 1.48 < 0.67; 3.25>. Unexpectedly, in this analysis, which controlled for many patient and hospital-based confounders, OR ventilation with laminar airflow showed no benefit and was even associated with a significantly higher risk for severe SSI after hip prosthesis.

Post-transplant infections: single center experience from the developing world

To describe our experience of post-transplant infections in allogeneic stem cell transplants at the Armed Forces Bone Marrow Transplant Centre, Rawalpindi, Pakistan. From July 2001 to September 2006, patients with malignant and non-malignant hematological disorders having human leukocyte antigen (HLA)-matched sibling donors were selected for transplant. Pre-transplant infection surveillance was carried out, and strict prophylaxis against infection was observed. After admission to the hospital, patients were kept in protective isolation rooms, equipped with a HEPA filter positive-pressure laminar airflow ventilation system. Bone marrow and/or peripheral blood stem cells were used as the stem cell source. Cyclosporin and prednisolone were used as prophylaxis against graft-versus-host disease (GVHD). The engraftment was monitored with cytogenetic/molecular analysis and change of blood group. Survival was calculated from the date of transplant to death or last follow-up. One hundred and fifty-four patients received allogeneic stem cell transplants from HLA-matched siblings for various hematological disorders at the Armed Forces Bone Marrow Transplant Centre, Rawalpindi, Pakistan between July 2001 and September 2006. Indications for transplant included aplastic anemia (n=66), beta-thalassemia major (n=40), chronic myeloid leukemia (n=33), acute leukemia (n=8), and miscellaneous disorders (n=7). One hundred and twenty patients were male and 34 were female. The median age of the patient cohort was 14 years (range 1 1/4-54 years). One hundred and thirty-six patients and 135 donors were cytomegalovirus (CMV) IgG-positive. One hundred and forty patients (90.9%) developed febrile episodes in different phases of post-transplant recovery. Infective organisms were isolated in 150 microbiological culture specimens out of 651 specimens from different sites of infections (23.0% culture positivity). Post-transplant infections were confirmed in 120 patients (77.9%) on the basis of clinical assessment and microbiological, virological, and histopathological examination. Mortality related to infections was 13.0%. Fatal infections included CMV disease (100% mortality, 6/6), disseminated aspergillosis (66.7% mortality, 4/6), pseudomonas septicemia (42.9% mortality, 9/21), and tuberculosis (25% mortality, 1/4). More than 90% of our patients developed febrile episodes with relatively low culture yield. The majority of infections were treated effectively, however CMV, aspergillosis, and pseudomonas infections remained problematic with high mortality.

P15.07 Laminar Air Flow (LAP) Ventilation in Operating Room: the Need for a Control System to Ensure the Usefulness of its Installation

P15.07 Laminar Air Flow (LAP) Ventilation in Operating Room: the Need for a Control System to Ensure the Usefulness of its Installation

Invasive Aspergillus infections in hematologic malignancy patients.

The incidence of invasive Aspergillus (IA) infections in patients with hematologic malignancies continues to increase. The most common species include Aspergillus fumigatus (approximately 90% of cases), A. flavus, A. niger, A. terreus, and A. nidulans. Most infections involve the pulmonary parenchyma, though systemic dissemination of the fungus from a primary pulmonary focus or the paranasal sinuses after hyphal invasion into blood vessels is frequent. Early diagnosis and initiation of appropriate antifungal therapy has been shown to improve the prognosis of patients afflicted with this condition. The definitive diagnosis of IA is based on showing the hyphal invasion in tissue specimens together with a positive culture for Aspergillus species from the same specimen. The detection of circulating fungal antigens and DNA seems to be a promising, rapid, and sensitive diagnostic tool for early diagnosis of aspergillosis. The current antifungals available for the treatment of IA include amphotericin B deoxycholate and lipid formulations, itraconazole and caspofungin acetate. New investigational antifungal drugs include the triazoles voriconazole, posaconazole and ravuconazole, liposomal nystatin, and 2 echinocandin derivatives (anidulafungin [VER-002] and micafungin [FK463]). Preventive measures include reduction of environmental exposure of patients from sources of infection and anti-fungal prophylaxis. Specialized air-handling systems capable of excluding Aspergillus spores, such as high-efficiency particulate air (HEPA) filtration with or without laminar air flow ventilation has proven to be very efficacious. Targeted antifungal prophylaxis for hematologic patients who are at high risk for developing invasive fungal infections is not currently standardized.

Delirium in burn patients isolated in a plenum laminar air flow ventilation unit

The incidence of psychological morbidity associated with delirium was compared between burn patients isolated in a bed-size plenum laminar air flow ventilation unit (PLAFVU) and matched control burn patients treated in standard open cubicles. In patients with burn sizes of less than 60 per cent of body surface area, delirium developed in 40 per cent of the patients treated in the PLAFVU, but only in 7 per cent of the matched control patients (P = 0.04). Most of the patients with burn sizes of 60 per cent or greater exhibited delirium regardless of the method of treatment. The development of psychological morbidity was more strongly associated with treatment in the PLAFVU than with common causes such as hyponatraemia or septicaemia. The present study suggests that in the majority of burn patients, i.e. those with less than 60 per cent burns, the development of psychological morbidity may in fact be influenced by types of treatment which affect patient psychology, rather than being solely the result of physiological derangements.