  Background: At the beginning of 2020, a high number of COVID-19 cases
affected Italy in a short period, causing a difficult supply of medical
equipment. To deal with the problem, many healthcare operators readapted
different masks to medical devices, but no experiment was conducted to evaluate
their performance. The aims of our study were: to assess the performances of
three masks and a CPAP helmet in their original configuration and after
modifications, in the maintenance of mean pressure and half-amplitude
variations using different PEEP valves and to analyse the impact of
antibacterial (AB) or antibacterial-viral (ABV) pre-valve PEEP filters on the
effective PEEP delivered to the patients. Four pressure ports were installed on
each mask (three on helmet), mean values and half amplitudes of pressure were
recorded. Tests were performed with any, AB, ABV filter before the PEEP valve.
CPAP helmet was the most efficient interface producing more stable mean
pressure and less prominent half-amplitude variations but the non-medical
masks, especially after the modifications, maintained a stable mean pressure
value with only a moderate increase of half-amplitude. The use of AB and ABV
filters, produced respectively an increase of 2,23% and 16.5% in mean pressure,
compared to no filter condition. CPAP helmet is the most reliable interface in
terms of detected performance, but readapted masks can assure almost a similar
performance. The use of ABV filters before the PEEP valve significantly
increases the detected mean pressure while the AB filters have almost a neutral
effect.
