Gas Exchange and Acid-Base Balance of Blood of Pregnant Women with Community-Acquired Pneumonia

Rationale: Pneumonia is the most common non-obstetric infectious cause of maternal death.Mortality rate due to pneumonia in pregnant women reaches 4%, and perinatal mortality ranges from 3 to 12%.The severity of the manifestations of community-acquired pneumonia (CAP) across pregnancy is determined by the compensation of respiratory insufficiency, which is directly related to the gas exchange processes and the acid-base balance (ABB), which maintains the energy balance in the woman's body.We aimed to assess the gas composition and ABB of blood in pregnant women with CAP in the third trimester of pregnancy.Methods: We examined 17 women in the third trimester of pregnancy with a bacterial form of CAP of moderate severity (comparison group: 30 pregnant women with uncomplicated pregnancy).Bacteriological examinations of sputum and a clinical blood test were carried out, the venous blood gases and ABB were determined.The average age of pregnant women was 25.6±2.5 years, the gestational age at the time of the disease was 29.8±2.2weeks.Results:An etiotropic pathogen, Streptococcus pneumoniae, was detected in sputum cultures in 36% of cases, while nonspecific pathogens such as Neisseria and Streptococcus viridians were diagnosed in 45%, and Streptococcus epidermidis -in 18%. 2 pathogens were verified in 45% of cases.The number of erythrocytes, the hemoglobin and its oxygenated form content were significantly lower by 8%, 15% and 3%, respectively, than in the comparison group, the methemoglobin increased by 35%.A statistically significant decrease in oxygen saturation in the blood by 1.2%, partial venous blood oxygen tension by 10% were revealed, which indicated the development of hypoxemia and tissue hypoxia in this group of patients.The state of ABB in the presence of lungs hypoventilation was characterized by the development of signs of hypercapnia, which was resulted in an increase of the partial tension of carbon dioxide by 7%, and a decrease in pH relative to the comparison group.The changes in ABB were of a mixed nature, as evidenced by a 60% decrease in the indices of the buffer bases deficiency.Conclusion: Bacterial CAP of moderate severity in women in the third trimester of pregnancy is characterized by the development of anemia, hypoxemia and tissue hypoxia, mixed acidosis, which is a consequence of impairment not only of the ventilation function of the lungs, but also diffusion and perfusion processes that determine the morbidity and further development of pregnancy complications.