Physiologic and Other Effects of Silicone Mask Respirator N99 in the Coronavirus 2019 Outbreaks

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Yutthana Apichatbutr


Introduction: The coronavirus outbreak which has spread across the world resulting in a significant shortage of the N 95 type of medical mask. For this reason, the University of Navamindradhiraj jointly developed a medical mask made from silicone type N 99 (Silicone Mask Respirator N 99) that filters more than 99% of bacteria and viruses. This research shows the study of respiratory physiology and the impact of using N 99 silicone mask in general volunteers.

Methods: A prospective study was carried out by 20 volunteers breathing through a HEPA filter fitted with a silicone N 99 mask doing routine work and testing for breathing through volumetric capnography every 1 hour until at the end of 3-hours. The required measurements were measured dead space volume (Vd), dead space volume / tidal volume (Vd / Vt), end- tidal CO2 (EtCO2), alveolar CO2, oxygen saturation, airway resistance and a satisfaction questionnaire after all studies were performed.

Results: Total 20 subjects were eight males and twelve females, mean age was 31 years (SD), mean body mass index was 21.60 ± 2.23 kg / m2 and no underlying disease. Volumetric capnography was used to calculate the respiratory parameters. With silicone N 99, the average dead space volume increased 27.57 ± 7.57 ml( p=0.001). The mean proportion of dead space volume / tidal volume before and after wearing the N 99 silicone mask was 0.22 ± 0.03 and 0.25 ± 0.03 respectively, with 0.03 increments (p = 0.011). End- tidal CO2 measurements before and after wearing the N 99 silicone mask were found to be 35.35 ± 2.32 mmHg and 36.71 ± 2.25 mmHg (p = 0.054). When calculating alveolar CO2 before and after wearing silicone N 99 was 32.94 ± 3.06 mmHg and 34.52 ± 2.64 mmHg respectively (p = 0.085). Respiratory resistance measurements before and after wearing the N 99 silicone mask was 2.53 ± 0.37 cmH2O/L/sec and 4.14 ± 0.8 cmH2O/L/sec increased by 1.53 ± 0.72 cmH2O/L/sec (p <0.001). The oxygenation value before and after using the mask is normal (p = 0.355). According to the user satisfaction questionnaire, there was no headache in the volunteers. Respiration heat and stinging, irritation, sweating, odor, scores were 1-2 points (not at all uncomfortable to a little uncomfortable), and masked communication and mask tightening were scored 2-3 points range (a little uncomfortable to moderately uncomfortable).

Conclusion: When the silicone mask N 99 was continuously used for while it has shown that respiratory dead space and resistance were increased statistically significant but results of oxygenation and carbon dioxide levels were typical throughout use. It is therefore safe to use the N 99 silicone mask.


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