The air we breathe: Numerical investigation of ventilation strategies to mitigate airborne dispersion of MERS-CoV in inpatient wards.

Ventilation strategies for infection control in hospitals has been predominantly directed towards isolation rooms and operating theatres, with relatively less emphasis on perceived low risk spaces, such as general wards. Typically, the ventilation systems in general wards are intended to optimize patient thermal comfort and energy conservation. The emission of pathogens from exhalation activity, such as sneezing, by an undiagnosed infectious patient admitted to general wards, is a significant concern for infection outbreaks. However, the ventilation guidelines for general wards with respect to infection control are vague. This research article presents a numerical study on the effect of varying air change rates (3 h-1, 6 h-1, 9 h-1, 13 h-1) and exhaust flow rates (10%, 50% of supply air quantity) on the concentration of airborne pathogens in a mechanically ventilated general inpatient ward. The findings imply that the breathing zone directly above the source patient has the highest level of pathogen exposure, followed by the breathing zones at the bedside and adjacent patients close to the source patient. The dispersion of pathogens throughout the ward over time is also apparent. However, a key difference while adopting a lower ACH (3 h-1) and a higher ACH (13 h-1) in this study was that the latter had a significantly lower number of suspended pathogens in the breathing zone than the former. Thus, this research suggests high ventilation rates for general wards, contrary to current ventilation standards. In addition, combining a higher air change rate (13 h-1) with a high exhaust flow rate (50% of supply air) through a local exhaust grille dramatically reduced suspended pathogens within the breathing zone, further mitigating the risk of pathogen exposure for ward users. Therefore, this study presents an effective ventilation technique to dilute and eliminate airborne infectious pathogens, minimizing their concentration and the risk of infection.

Impact of thermal comfort on online learning performance.

Online learning has drawn much more attention since the outbreak of COVID-19. Most related studies have focused on online platform design and instructional design. However, the physical environment where online learning is conducted (e.g., students' homes) is rarely studied. To understand the thermal conditions in students' online learning environment and its impact on students' thermal comfort and their performance during online learning, an experiment, including both objective measurement and subjective assessment, was conducted in a student's apartment. Thirty university students participated in this experiment, and they were randomly assigned into six groups (three thermal conditions (i.e., control, cold, and hot) × two-course durations). Both environmental parameters (i.e., air temperature, radiant temperature, air velocity, etc.) and physiological parameters (i.e. skin temperatures) were measured at the same time. Besides, students' thermal sensation, acceptance, and learning performance were self-evaluated and collected through questionnaires. Results showed that participants' thermal sensation was positively correlated with their mean skin temperature (MST) and the operative temperature (To) in the apartment (MST: ρ = 0.94, p < 0.001; To: ρ = 0.91, p < 0.001), yet no significant relation with their personal characteristics was observed in the current study, which might be caused by the small sample size. Moreover, inverted U-shape relationships were identified between participants' perceived performance and their thermal sensation/MST/To. When students felt slightly cool (TSV = -0.3), they thought they could reach their best performance. This study revealed the impacts of the thermal environment on students' online learning performance, more performance tasks could be conducted in the future to examine the impacts in more detail.

A Novel IoT-Enabled Wireless Sensor Grid for Spatial and Temporal Evaluation of Tracer Gas Dispersion.

Current IoT applications in indoor air focus mainly on general monitoring. This study proposed a novel IoT application to evaluate airflow patterns and ventilation performance using tracer gas. The tracer gas is a surrogate for small-size particles and bioaerosols and is used in dispersion and ventilation studies. Prevalent commercial tracer-gas-measuring instruments, although highly accurate, are relatively expensive, have a long sampling cycle, and are limited in the number of sampling points. To enhance the spatial and temporal understanding of tracer gas dispersion under the influence of ventilation, a novel application of an IoT-enabled, wireless R134a sensing network using commercially available small sensors was proposed. The system has a detection range of 5-100 ppm and a sampling cycle of 10 s. Using Wi-Fi communication, the measurement data are transmitted to and stored in a cloud database for remote, real-time analysis. The novel system provides a quick response, detailed spatial and temporal profiles of the tracer gas level, and a comparable air change rate analysis. With multiple units deployed as a wireless sensing network, the system can be applied as an affordable alternative to traditional tracer gas systems to identify the dispersion pathway of the tracer gas and the general airflow direction.

Updating Indoor Air Quality (IAQ) Assessment Screening Levels with Machine Learning Models.

Indoor air quality (IAQ) standards have been evolving to improve the overall IAQ situation. To enhance the performances of IAQ screening models using surrogate parameters in identifying unsatisfactory IAQ, and to update the screening models such that they can apply to a new standard, a novel framework for the updating of screening levels, using machine learning methods, is proposed in this study. The classification models employed are Support Vector Machine (SVM) algorithm with different kernel functions (linear, polynomial, radial basis function (RBF) and sigmoid), k-Nearest Neighbors (kNN), Logistic Regression, Decision Tree (DT), Random Forest (RF) and Multilayer Perceptron Artificial Neural Network (MLP-ANN). With carefully selected model hyperparameters, the IAQ assessment made by the models achieved a mean test accuracy of 0.536-0.805 and a maximum test accuracy of 0.807-0.820, indicating that machine learning models are suitable for screening the unsatisfactory IAQ. Further to that, using the updated IAQ standard in Hong Kong as an example, the update of an IAQ screening model against a new IAQ standard was conducted by determining the relative impact ratio of the updated standard to the old standard. Relative impact ratios of 1.1-1.5 were estimated and the corresponding likelihood ratios in the updated scheme were found to be higher than expected due to the tightening of exposure levels in the updated scheme. The presented framework shows the feasibility of updating a machine learning IAQ model when a new standard is being adopted, which shall provide an ultimate method for IAQ assessment prediction that is compatible with all IAQ standards and exposure criteria.

Ongoing effects of eConsultation in nephrology on hospital referral rates: An observational study.

INTRODUCTION: eConsultation in nephrology is an innovative way for general practitioners (GPs) to consult a nephrologist. Studies have shown that questions from GPs can be answered and intended referrals can be avoided by eConsultation. However, follow-up data are lacking. The primary aim of this study was therefore to assess whether patients for whom a referral to the outpatient clinic of a medical specialist was avoided in the short term were not then referred for the same problem within one year after the eConsultation. METHODS: All eConsultations sent between June 2017 and April 2018 to seven nephrologists in three different hospitals in The Netherlands were included. Exclusion criteria were duplications and missing data on follow-up. Data were obtained from the eConsultation application forms and from GP medical records. RESULTS: A total of 173 eConsultations were included. Of the 32 patients for whom a referral was initially prevented, 91% (95% confidence interval 75-98) had not been referred to a specialist for the same problem within one year after the eConsultation. DISCUSSION: eConsultation in the field of nephrology can prevent referrals in the long term. It can therefore contribute to a more modern and efficient health-care system in which chronic care is provided by GPs in close proximity to patients, while specialist support is easily available and accessible through eConsultation when necessary.

Time-Variant Positive Air Pressure in Drainage Stacks as a Pathogen Transmission Pathway of COVID-19.

Time-variant positive air pressure in a drainage stack poses a risk of pathogenic virus transmission into a habitable space, however, the excessive risk and its significance have not yet been sufficiently addressed for drainage system designs. This study proposes a novel measure for the probable pathogenic virus transmission risk of a high-rise drainage stack with the occurrence of positive air pressure. The proposed approach is based on time-variant positive air pressures measured in a 38 m high drainage stack of a full-scale experimental tower under steady flow conditions of flow rate 1-4 Ls-1 discharging at a height between 15 m to 33 m above the stack base. The maximum pressure and probabilistic positive air pressures in the discharging stack ventilation section with no water (Zone A of the discharging drainage stack) were determined. It was demonstrated that the positive air pressures were lower in frequency as compared with those in other stack zones and could propagate along the upper 1/3 portion of the ventilation pipe (H' ≥ 0.63) towards the ventilation opening at the rooftop. As the probabilistic positive pressures at a stack height were found to be related to the water discharging height and flow rate, a risk model of positive air pressure is proposed. Taking the 119th, 124th, 140th and 11,547th COVID-19 cases of an epidemiological investigation in Hong Kong as a baseline of concern, excessive risk of system overuse was evaluated. The results showed that for a 20-80% increase in the frequency of discharge flow rate, the number of floors identified at risk increased from 1 to 9 and 1 to 6 in the 34- and 25-storey residential buildings, respectively. The outcome can apply to facilities planning for self-quarantine arrangements in high-rise buildings where pathogenic virus transmission associated with drainage system overuse is a concern.

A numerical study of ventilation strategies for infection risk mitigation in general inpatient wards.

Aerial dispersion of human exhaled microbial contaminants and subsequent contamination of surfaces is a potential route for infection transmission in hospitals. Most general hospital wards have ventilation systems that drive air and thus contaminants from the patient areas towards the corridors. This study investigates the transport mechanism and deposition patterns of Middle East Respiratory Syndrome Coronavirus (MERS-CoV) within a typical six bedded general inpatient ward cubicle through numerical simulation. It demonstrates that both air change and exhaust airflow rates have significant effects on not only the airflow but also the particle distribution within a mechanically ventilated space. Moreover, the location of an infected patient within the ward cubicle is crucial in determining the extent of infection risk to other ward occupants. Hence, it is recommended to provide exhaust grilles in close proximity to a patient, preferably above each patient's bed. To achieve infection prevention and control, high exhaust airflow rate is also suggested. Regardless of the ventilation design, all patients and any surfaces within a ward cubicle should be regularly and thoroughly cleaned and disinfected to remove microbial contamination. The outcome of this study can serve as a source of reference for hospital management to better ventilation design strategies for mitigating the risk of infection.

GUIDE, a structured pre-dialysis programme that increases the use of home dialysis.

BACKGROUND: Despite the many advantages it offers, the percentage of dialysis patients that receive home dialysis [peritoneal dialysis (PD) or home haemodialysis (HHD)] in the Netherlands has declined over the last decade. Pre-dialysis education could stimulate the use of home dialysis. This article presents the results of the pre-dialysis programme GUIDE, with regard to the following question: Does the implementation of a structured pre-dialysis programme with a home-focused approach increase the number of pre-dialysis patients that choose and receive home dialysis? METHODS: The GUIDE process starts when a patient has an eGFR of 15 mL/min/1.73 m2. The process begins with a home visit from a case manager and the completion of questionnaires by the patient, the case manager and the nephrologist. A multidisciplinary meeting (MDM) is held to determine a specific patient profile (or treatment recommendation). This is followed by patient education, a second MDM and finally the selection of the treatment by the patient and the nephrologist. This retrospective observational study describes the selection process of all patients that received a treatment recommendation between 12 September 2013 and 18 December 2014 at Meander Medical Centre. Data were collected by file research and analysis of questionnaires. RESULTS: One hundred and two patients were included. They started the process at a mean eGFR of 12.3 mL/min/1.73 m2. Home dialysis was recommended for 62.8% of the patients who were advised to have dialysis treatment. Of the patients that opted for dialysis, 34.2% chose PD and 8.2% chose HHD; 22.9% started home dialysis as their first therapy, compared with 17.6% in the months before implementation of GUIDE. Finally, 32.1% of the patients that received dialysis therapy received home dialysis. In the months before GUIDE, an average of just 19.5% of the patients that received dialysis received home dialysis. CONCLUSIONS: In comparison to historical data, the pre-dialysis programme GUIDE increases the number of patients that choose and receive home dialysis.

Evaluation of Indoor Air Quality Screening Strategies: A Step-Wise Approach for IAQ Screening.

Conducting a full indoor air quality (IAQ) assessment in air-conditioned offices requires large-scale material and manpower resources. However, an IAQ index can be adopted as a handy screening tool to identify any premises (with poor IAQ) that need more comprehensive IAQ assessments to prioritize IAQ improvements. This study proposes a step-wise IAQ screening protocol to facilitate its cost-effective management among building owners and managers. The effectiveness of three IAQ indices, namely θ1 (with one parameter: CO2), θ2 (with two parameters: CO2 and respirable suspended particulates, RSP) and θ3 (with three parameters: CO2, RSP, and total volatile organic compounds, TVOC) are evaluated. Compared in a pairwise manner with respect to the minimum satisfaction levels as stated in the IAQ Certification Scheme by the Hong Kong Environmental Protection Department, the results show that a screening test with more surrogate IAQ parameters is good at identifying both lower and higher risk groups for unsatisfactory IAQ, and thus offers higher resolution. Through the sensitivity and specificity for identifying IAQ problems, the effectiveness of alternative IAQ screening methods with different monitoring parameters is also reported.

Impact of incidental renal artery stenosis on long-term mortality in patients with peripheral arterial disease undergoing vascular procedure.

OBJECTIVE: In peripheral arterial disease (PAD), mortality is high. Incidental renal artery stenosis (RAS) is a predictor of mortality in PAD patients undergoing angiography. This might be relevant for risk-benefit assessment when vascular surgery is considered, both in terms of perioperative risk, and in terms of life expectancy. METHODS: We studied the prognostic impact of incidental RAS in 488 subjects (334 men, 154 women; mean follow-up 6.0 ± 3.4 years) who underwent angiography for PAD in a single center between 1997 and 2000. Renal arteries were visualized and follow-up data concerning vascular procedures were analyzed. RESULTS: RAS (diameter reduction >50%) was present in 26%. Forty-six percent of study patients underwent a vascular procedure (85% vascular surgery, remainder underwent amputation). Patients that underwent vascular surgery had a better renal function at baseline, less history of stroke, and a larger proportion of smokers. Overall mortality was similar for patients that underwent surgery (54.5%) and those without surgery (49.6%). There was no difference in 90-day postoperative mortality for patients without or with RAS (7.2% vs 10.3%; NS). For subjects that underwent bypass surgery, long-term mortality was substantially and significantly higher among those with RAS (65.1%) vs those without RAS (43.5%). On Cox regression analysis, age was the only independent predictor of 90-day postoperative mortality. The well-known cardiovascular risk factors of age, diabetes mellitus, history of prior peripheral vascular disease, smoking, prior myocardial infarction, prior stroke, and amputation, as well as presence of RAS, were independent predictors for overall mortality. CONCLUSION: In PAD, incidental RAS predicts long-term mortality independent of other risk factors. The elevated mortality is not due to a higher postoperative risk. Subjects presenting with PAD and RAS can therefore undergo vascular procedures with the same risk as other patients.

Influence of indoor air quality (IAQ) objectives on air-conditioned offices in Hong Kong.

It is costly to sample all air pollutants of a general community. Air sampling should be conducted based on a practical assessment strategy and monitoring plan. In Hong Kong, the Environmental Protection Department (HKEPD) launched an Indoor Air Quality (IAQ) certification scheme to grade workplace IAQ as 'Excellent' or 'Good' by measuring the levels of nine common indoor air pollutants, namely carbon dioxide (CO(2)), carbon monoxide (CO), respirable suspended particulates (RSP), nitrogen dioxide (NO(2)), ozone (O(3)), formaldehyde (HCHO), total volatile organic compounds (TVOC), radon (Rn), and airborne bacteria count (ABC). Although average office IAQ performance has been improved since the implementation of this certification scheme, there are still resource issues and technical difficulties. To streamline the assessment of office IAQ performance, this study proposes a simple index of IAQ benchmarks formulated in compliance with the HKEPD requirements. In particular, three of the nine listed common air pollutants were selected as the 'representatives' for the overall satisfactory IAQ. Together with the assessment results of 422 Hong Kong air-conditioned offices, the index was evaluated in terms of test sensitivity, specificity and predictive values. Proved to be feasible to describe the IAQ of some air-conditioned offices, this IAQ index would be a useful tool for policymakers, building owners and professionals to quantify IAQ performance in offices and to make decisions on resources and manpower management for efficient mitigation actions.

Atherosclerotic renovascular disease and renal impairment: can we predict the effect of intervention?

Atherosclerotic renal artery stenosis (ARAS) is associated with hypertension, ischemic nephropathy, and high cardiovascular risk. We review the data on revascularization of the renal artery by percutaneous transluminal renal angioplasty (PTRA) and pharmacological therapy. In patients with severe ARAS and poorly controlled hypertension, PTRA can improve blood pressure control. In patients with rapid renal function loss and severe ARAS, PTRA can improve short-term renal function, but there is no evidence for long-term renoprotection. Recent evidence indicates that ARAS, and incidental renal artery stenosis, considerably increases cardiovascular risk, independent of blood pressure, renal function, and prevalent risk factors. This suggests that revascularization might potentially improve overall prognosis, but no data are available currently. The high cardiovascular risk warrants aggressive pharmacological treatment to prevent progression of the generalized vascular disorder. Ongoing trials will show whether revascularization has added, long-term effects on blood pressure, renal function, and cardiovascular prognosis.

Incidental renal artery stenosis is an independent predictor of mortality in patients with peripheral vascular disease.

In patients with peripheral vascular disease (PVD), mortality is high and renal artery stenosis (RAS) is a frequent incidental finding. RAS carries a high risk for mortality, but whether incidentally discovered RAS is a risk factor for mortality is unknown. The prognostic impact of incidental RAS for mortality was studied in 550 consecutive patients who underwent intra-arterial digital subtraction angiography for PVD in a single center between 1997 and 2000. In 491 patients (336 men, 155 women; mean follow-up 3.8 +/- 1.9 yr), the renal arteries were visualized and follow-up data were available. RAS (diameter reduction > 50%) was present in 26% of the patients. Mortality in the RAS group was 59 versus 28% in the non-RAS group (odds ratio 3.8; 95% confidence interval 2.5 to 5.7; P < 0.0001). Diabetes, previous myocardial infarction, history of PVD, stroke, and hypertension were more frequent in the RAS group; age was higher and GFR was lower in the RAS group. Therefore, RAS was associated with elevated mortality and increased prevalence of cardiovascular risk factors. Cox regression analysis showed that RAS was an independent predictor for mortality (P = 0.005), along with age, diabetes, smoking, previous myocardial infarction, history of PVD, and stroke. In patients who were evaluated for PVD by digital subtraction angiography, mortality was high. Incidental RAS was a frequent finding and an independent predictor for mortality. Whether RAS is a marker for or, alternatively, a mediator of the poor prognosis and whether prognosis can be improved by specific intervention should be the subject of future prospective studies.