Fig. 1.
The predicted maternal and fetal [HbCO] when a mother breaths 50 ppm CO for 16 h, followed by an 8 h period in which no CO was inspired. The level of CO exposure is equivalent to smoking about 1–1.5 packs of cigarettes per day, followed by an 8 h sleep period. Figure modified by Longo (1977) based on the mathematical model by Hill et al. (1977).