Estimating the Dead Space Volume Between a Headform and N95 Filtering Facepiece Respirator Using Microsoft Kinect

Abstract

N95 filtering facepiece respirator (FFR) dead space is an important factor for respirator design. The dead space refers to the cavity between the internal surface of the FFR and the wearer's facial surface. This article presents a novel method to estimate the dead space volume of FFRs and experimental validation. In this study, six FFRs and five headforms (small, medium, large, long/narrow, and short/wide) are used for various FFR and headform combinations. Microsoft Kinect Sensors (Microsoft Corporation, Redmond, WA) are used to scan the headforms without respirators and then scan the headforms with the FFRs donned. The FFR dead space is formed through geometric modeling software, and finally the volume is obtained through LS-DYNA (Livermore Software Technology Corporation, Livermore, CA). In the experimental validation, water is used to measure the dead space. The simulation and experimental dead space volumes are 107.5-167.5 mL and 98.4-165.7 mL, respectively. Linear regression analysis is conducted to correlate the results from Kinect and water, and R(2) = 0.85.

Is a Mask That Covers the Mouth and Nose Free from Undesirable Side Effects in Everyday Use and Free of Potential Hazards?

“…The respiratory physiology and gas exchange play a key role in maintaining a health-sustaining balance in the human body [136,153]. According to the studies we found, a dead space volume that is almost doubled by wearing a mask and a more than doubled breathing resistance (Figure 3) [59][60][61] lead to a rebreathing of carbon dioxide with every breathing cycle [16][17][18]39,83] with-in healthy people mostly-a subthreshold but, in sick people, a partly pathological increase in the carbon dioxide partial pressure (PaCO 2 ) in the blood [25,34,58]. According to the primary studies found, these changes contribute reflexively to an increase in respiratory frequency and depth [21,23,34,36] with a corresponding increase in the work of the respiratory muscles via physiological feedback mechanisms [31,36].…”

“…We were able to demonstrate a statistically significant correlation of the observed adverse effect of hypoxia and the symptom of fatigue with p < 0.05 in the quantitative evaluation of the primary studies. Our review of the literature shows that both healthy and sick people can experience Mask-Induced Exhaustion Syndrome (MIES), with typical changes and symptoms that are often observed in combination, such as an increase in breathing dead space volume [22,24,58,59], increase in breathing resistance [31,35,60,61], increase in blood carbon dioxide [13,15,17,19,[21][22][23][24][25][26][27][28][29][30]35], decrease in blood oxygen saturation [18,19,21,23,[28][29][30][31][32][33][34], increase in heart rate [23,29,30,35], increase in blood pressure [25,35], decrease in cardiopulmonary capacity [31], increase in respiratory rate [15,21,23,…”

“…The average dead space volume during breathing in adults is approximately 150-180 mL and is significantly increased when wearing a mask covering the mouth and nose [58]. With an N95 mask, for example, the dead space volume of approximately 98-168 mL was determined in an experimental study [59]. This corresponds to a mask-related dead space increase of approximately 65 to 112% for adults and, thus, almost a doubling.…”

A highly efficient cloth facemask

“…The mask internal volume is about 0.5 L. This is similar to the tidal volume associated with normal breathing [Hallett et al, 2020], but about half that for singing [Binazzi et al, 2006]. The mask internal volume is about 3-5 times larger than that for N95 respirators [Xu et al, 2015]. Given the limited deflection of the mask material this implies substantial exchange of air, which will help to alleviate any buildup of CO2 or depletion of O2 (see Section 3.5).…”

A Sew-Free Origami Mask for Improvised Respiratory Protection

“…This places the mask below the range of 100 - 165 ml that is estimated for N95 masks. 41 Some physiological effects have been noted associated with prolonged use of N95 masks such as increased CO 2 retention and inhalation from expired breath. 42 This might be an important consideration for individuals with respiratory or heart impairments.…”