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 non-pregnant subjects, it has been shown that use of N95-respirators can increase CO 2 levels within the masks by 1.8-3 %, suggesting that the increase in expired CO 2 concentration could also be due to the accumulation of expired CO 2 trapped in the dead space of the N95 mask [29, 30] . Our results do not support such a view because FiCO 2 did not increase even with the use of N95 materials and total CO 2 intake was reduced due to the corresponding decrease in V E . These results further affirm that the increase in expired CO 2 mainly arose from increased rate of aerobic metabolism. The higher circulating CO 2 concentration observed in our study was in agreement with increase in transcutaneous CO 2 observed in pregnant and non-pregnant women after a 20-minute exercise wearing a respirator as compared to not wearing the respirator [17] . It must be borne in mind that CO 2 levels in the blood of pregnant women are usually lower due to physiological hyperventilation. An increase in forced expired CO 2 which reflects a rise in blood CO 2 levels hence contributes to impair elimination of fetal CO 2 as arterial CO 2 is normally reduced in pregnancy to allow for a steeper diffusion gradient of CO 2 from fetal blood across to the mother.