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. 2019 Oct 27;16(21):4138.
doi: 10.3390/ijerph16214138.

Phenomenological and Thermodynamic Model of Gas Exchanges in the Placenta during Pregnancy: A Case Study of Intoxication of Carbon Monoxide

Juliana Rangel Cenzi  1 , Cyro Albuquerque  2 , Carlos Eduardo Keutenedjian Mady  1
Affiliations

Phenomenological and Thermodynamic Model of Gas Exchanges in the Placenta during Pregnancy: A Case Study of Intoxication of Carbon Monoxide

Juliana Rangel Cenzi et al. Int J Environ Res Public Health. .

Abstract

The present work simulates the transport of oxygen, carbon dioxide, and carbon monoxide between a fetus's circulatory system and the mother's. The organ responsible for this exchange is the placenta. Carbon monoxide is a common air pollutant, and it impacts the physiological conditions even in low concentration. The impacts of carbon monoxide are especially dangerous for pregnant women, fetuses, and newborn babies. A model of carbon monoxide transport, from the literature, is modified to simulate a pregnant woman (original model was a male), therefore changing some parameters to express the adjusted respiratory system. It was considered the gas exchange in the placenta, to evaluate the concentration of these different gases in the fetus arterial and venous blood. Three methods of the exergy analysis are implemented for both mother and fetus respiratory systems, aiming at the comparison with the respiratory system of a male adult. The destroyed exergy of the literature did not have the same trend as the models proposed in this article, taking into consideration the hemoglobin reactions. In contrast, the entropy generation associated only with the diffusion transport phenomena was one order of magnitude lower than the other methods. The placenta destroyed exergy rate is significantly higher compared to the irreversibilities of the mother's respiratory system. One possible explanation is the fact that the placenta has other physiological functions than gas transportation.

Keywords: carbon monoxide intoxication; exergy analysis; placenta; respiratory system.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Figures

Figure 1
Figure 1
Gas exchange model for pregnancy indicating the mother respiratory system obtained in [20] and the gas exchanges in the placenta proposed in the present analysis.
Figure 2
Figure 2
Placenta with the stream of the mother and fetus arterial and venus blood.
Figure 3
Figure 3
CO2 partial pressure in maternal blood. The conversion of CO in ppm to kg/m3 is to divide by 0.001.
Figure 4
Figure 4
Maternal respiratory system exergy efficiency. The conversion of CO in ppm to kg/m3 is to divide by 0.001.
Figure 5
Figure 5
Maternal respiratory system destroyed exergy rate as a function of carbon monoxide intoxication in ppm. The conversion of CO in ppm to kg/m3 is to divide by 0.001.
Figure 6
Figure 6
Maternal respiratory system destroyed exergy rate per oxyhemoglobin (saturation of O2 in the blood), which is a function of carbon monoxide poisoning.
Figure 7
Figure 7
O2 partial pressure in maternal and fetal blood as a function of carbon monoxide intoxication in ppm. The conversion of CO in ppm to kg/m3 is to divide by 0.001.
Figure 8
Figure 8
Fetal hemoglobin saturation with oxygen as a function of carbon monoxide intoxication in ppm. The conversion of CO in ppm to kg/m3 is to divide by 0.001.
Figure 9
Figure 9
Hemoglobin saturation with carbon monoxide in maternal and fetal blood as a function of carbon monoxide intoxication in ppm. The conversion of CO in ppm to kg/m3 is to divide by 0.001.
Figure 10
Figure 10
Placenta’s exergy efficiency as a function of carbon monoxide intoxication in ppm. The conversion of CO in ppm to kg/m3 is to divide by 0.001.
Figure 11
Figure 11
Placenta’s exergy destruction rate as a function of carbon monoxide intoxication in ppm. The conversion of CO in ppm to kg/m3 is to divide by 0.001.
Figure 12
Figure 12
Fetal respiratory system destroyed exergy rate per oxyhemoglobin (saturation of oxygen), which is a function of carbon monoxide poisoning.
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