Development and validation of eco-friendly designed heat and moisture exchange filters for the safeguard of the respiratory tract and of the environment

Abstract

For many years, Heat and Moisture Exchange (HME) filters have been used for the safeguard of hospitalized patients subjected to long-term mechanical ventilation, anaesthesia, or intensive care. These devices, also namely “artificial noses”, are essential to maintain normal levels of humidity, warmth, and decontamination of the trachea when the upper airways are bypassed and in general when patients are subjected to ventilation with technical gases. Their function is to retain and reuse part of the heat and the moisture captured from the exhaled air, to precondition the inhaled technical gas. The currently used HME devices still have some limitations concerning above all the costs of raw materials and processes as well as their environmental impact. Further, this study aims to develop and validate eco-friendly and biodegradable HME filters developed through a green manufacturing process and reusing raw materials deriving from food waste to reduce their environmental impact. In detail, an extremely porous aerogel has been developed by exploiting the chemical advantages offered by biopolymers, like gelatin and chitosan, and designed with a view of attempt selection of raw materials and of process parameters for the obtaining of highly efficient devices, but while maintaining a low costs attractive to the market of disposable devices such as HME. Between the process parameters, freeze-drying and cross-linking steps were managed to achieve the target of low cost and time savings, making the process more easily scalable at industrial level, and improving the HME efficiency. Pressure drops, moisture and heat transfer, microbial filtration efficiency and bacteriostatic capacity of the HME filters were validated, both in vitro and in a hospital environment, also highlighting the device's ability to capture bacterial and inhibit their proliferation, a key feature for the preservation of patent health and of clinical instruments as well as for the possibility of being marketed. Further, it was achieved a proof of concept on the inclusion of a diagnostic tool in the HME structure. It can provoke the colour changing of the device in the presence of bacteria. This would make it easier to de-hospitalize patients, reducing healthcare costs but keeping their health status constantly monitored outside the hospital.