Breathing for Two: Unraveling the Complex Interplay of Pregnancy and Respiratory Physiology

][4] However, noticeable alterations take place in lung volumes during pregnancy, including a gradual decline in end-expiratory lung volume in the latter half of gestation, resulting in an 8-40% reduction at term.This decrease is primarily attributed to a 7-22% reduction in residual volume.FRC subsequently experiences a decrease of 9.5-25%, while inspiratory capacity rises at an equivalent rate to maintain a constant total lung capacity.These changes represent the adaptive adjustments within the respiratory IntroductIonThe respiratory system experiences unique changes in gynecologic and obstetric conditions, and pregnancy, that can increase susceptibility to diseases.This review discusses the normal physiological alterations that occur during pregnancy, as well as the pathologic disorders and diseases that can arise. BIologIcal VarIatIons that EnsuE d u r I n g a typIcal prEgnancyDuring a healthy pregnancy, significant alterations in respiratory and cardiovascular function occur to support the mother and fetus.These changes can exacerbate preexisting disorders and make it difficult to interpret laboratory and imaging studies.For example, upper airway edema is common during pregnancy, often resulting in nasal congestion, which can lead to nosebleeds during nasal intubation.The configuration of the chest wall also changes, with an increase in coastal angle lower chest wall circumference, and elevation of the diaphragmatic position.However, muscle strength remains unchanged, allowing for increased minute ventilation (MV) and delivery stresses. 1ung function and volume are also affected during pregnancy, with a reduction in functional residual capacity (FRC) due to the elevation of the diaphragm and increased pulmonary blood volume.This can lead to rapid desaturation during hypopnea, making endotracheal intubation more hazardous.Airway function is largely unchanged, although respiratory drive and MV significantly increase, and carbon dioxide production increases in the third trimester.These changes result in primary respiratory alkalosis, with arterial blood gas measurements showing a pH range of 7.40-7.47and partial pressure of carbon dioxide (PCO 2 ) reaching as low as 28-32 mm Hg.The tidal volume also increases by 30-35%, while the respiratory rate remains relatively unchanged.