Changes in Ventilation Inhomogeneity and Respiratory Function Following Elective Caesarean Section Under Regional Anaesthesia: a Prospective Observational Study

Pregnancy is associated with physiological changes affecting the cardiorespiratory system as a consequence of an increase in both cardiac output and intra-abdominal pressure. These alterations lead to a ventilation/perfusion mismatch which is potentiated by a decrease in functional residual capacity (FRC). These effects explain why pregnant women are more prone to the occurrence of hypoxemia, particularly in the third trimester of their pregnancy. The importance of the ventilation inhomogeneity can be estimated from the lung clearance index (LCI) measured by the non-invasive nitrogen multiple breath washout (N2 MBW) technique. Moreover the loss in lung volume is associated with reduction in respiratory system compliance, which can also be assessed non-invasively by the forced oscillation technique (FOT).

To our knowledge, there is no existing data on LCI or FRC using the aforementioned techniques in pregnant women. Furthermore, existing data on respiratory function in pregnant women is largely restricted to spirometric and body plethysmographic measurements taken primarily in the 1970s-1980s. As such, the important roles of lung ventilation inhomogeneity as well as the potential changes following birth after caesarean section have yet to be completely characterised.