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

When performing work equivalent to routine bedside nursing with N95-masks, non-pregnant subjects have been previously reported to maintain their V E compared with controls, with non-significant changes in the TV and BF [26] . Other studies in both non-pregnant and pregnant subjects have shown, on the contrary, an increase or decrease in BF but the TV and V E were not measured in these trials [17, 27, 28] . In contrast, our pregnant subjects were unable to proportionately increase both TV and BF to maintain their V E during rest and in response to exercise while breathing through N95-masks materials. A significant 26 % reduction in V E, with a 23 % reduction in mean TV was noted during exercise, possibly due to diaphragmatic splinting. This decrease in V E led to a corresponding decrease in VO 2 (13.8 %) and VCO 2 (17.7 %) (Fig. 7) . The decrease in FeO 2 and increase in FeCO 2 are likely due to a stimulation of the respiratory drive resulting in greater efforts required to breathe through the N95 mask materials and a concomitant greater extraction of O 2 for aerobic metabolism. These results also suggest that the N95 mask may impede gaseous exchange resulting in hypoventilation. Although the subjects appeared to adapt to the increased workload with no changes in the other maternal and fetal physiological parameters with no evidence of hypoxia found on finger-tip capillary oxygen saturation nor increased lactic acid production to suggest a shift toward anaerobic respiration, our results suggest that performing physical work with the N95-mask appears to stress the aerobic metabolism and increase the CO 2 load within the circulation.