Respiratory consequences of N95-type Mask usage in pregnant healthcare workers—a controlled clinical study

Tong, Pearl Shuang Ye; Kale, Anita Sugam; Ng, Kailyn; Loke, Amelia Peiwen; Choolani, Mahesh Arjandas; Lim, Chin Leong; Chan, Yiong Huak; Chong, Yap Seng; Tambyah, Paul Anantharajah; Yong, Eu-Leong

In both phases, the participants wore a tight fitting mask (Hans Rudolph) that was attached to the metabolic cart through an air sampling tube. Inspired ambient air and expired air were channeled through a pneumotachometer that was attached to the front of the mask which calculated air volume by the rate of rotation of a rotor turbine located within it. The turbine had zero resistance to air flow and the rate of rotation of the turbine, sensed by infrared light within the pneumotachometer, corresponds directly to inspired and expired air volume for each breath. Multiple air samples from each expired-breath was drawn into the metabolic carts through a sampling line for the measurement of oxygen and carbon dioxide content by the respective gas sensors within the metabolic carts. From this data, the following parameters were calculated: volumes of oxygen (VO 2 ) and carbon dioxide (VCO 2 ) exchanged, breathing frequency (BF), tidal volume (TV), minute ventilation (VE), forced expired O 2 (FeO 2 ), forced expired CO 2 (FeCO 2 ), forced inspired end-tidal O 2 and CO 2 concentrations (Fi et O 2 , Fi et CO 2 ).