Air change rates and infection risk in school environments: Monitoring naturally ventilated classrooms in a northern Italian urban context.

The importance of building ventilation in avoiding long-distance airborne transmission has been highlighted with the advent of the COVID-19 pandemics. Among others, school environments, in particular classrooms, present criticalities in the implementation of ventilation strategies and their impact on indoor air quality and risk of contagion. In this work, three naturally ventilated school buildings located in northern Italy have undergone monitoring at the end of the heating season. Environmental parameters, such as CO2 concentration and indoor/outdoor air temperature, have been recorded together with the window opening configurations to develop a two-fold analysis: i) the estimation of real air change rates through the transient mass balance equation method, and ii) the individual infection risk via the Wells-Riley equation. A strong statistical correlation has been found between the air change rates and the windows opening configuration by means of a window-to-volume ratio between the total opening area and the volume of the classroom, which has been used to estimate the individual infection risk. Results show that the European Standard recommendation for air renewal could be achieved by a window opening area of at least 1.5 m2, in the most prevailing Italian classrooms. Furthermore, scenarios in which the infector agent is a teacher show higher individual infection risk than those in which the infector is a student. In addition, the outcomes serve school staff as a reference to ensure adequate ventilation in classrooms and keep the risk of infection under control based on the number of the students and the volume of the classroom.

Prospective evaluation of a double-lumen subclavian dialysis catheter for acute vascular access.

The safety and efficacy of a parallel, double-lumen hemodialysis catheter used to achieve acute, temporary vascular access were evaluated prospectively in 134 hospitalized adult patients in whom 162 catheters were placed. The arterial flow rates and venous resistance were such that 84 per cent of the catheters provided satisfactory access for dialysis. Minor manipulations of the catheter were frequently required to maximize function. Three serious complications occurred, including one instance each of pneumothorax, hemorrhage, and nonfatal pericardial tamponade.