Comparison of short-term breathing rate asymmetry of preeclamptic and normotensive women in labor

Abstract Breathing rate asymmetry (BRA) refers to the observed disparities in the acceleration and deceleration phases of human respiration. The techniques employed to assess BRA could also be utilized in exploring hypertensive disorders like pre-eclampsia, which is known to cause autonomic cardiorespiratory changes. This study explores features of complexity, including the asymmetry (time irreversibility) of short-term breath-to-breath breathing rate variability among women with severe and moderate pre-eclampsia features compared to those with normal blood pressure. In our study, we retrospectively analyzed continuous respirogram recordings from women in labor, including those diagnosed with severe pre-eclampsia (SP = 22), moderate pre-eclampsia (P = 19), and normotensive control group (C = 35). Using these data, we calculated 5 min of breath-to-breath (BB) time series to measure Porta's index ( P %), Guzik's index ( G %), and Ehlers' index ( E ), alongside measures of asymmetrical entropy, including the entropy of acceleration runs (HAR), the entropy of deceleration runs (HDR), and total entropy (H). In addition, Fuzzy Entropy (FuzzEn) and Multiscale Fuzzy Entropy (MFE) over timescales 1–20 were calculated from the BB time series. The nonlinearity was assessed by surrogate analysis. The study's results revealed significant differences in short-term BRA; specifically, mean values of G % and E were the lowest in SP compared to C and P. Conversely, mean values of the HDR were higher in the SP group than the C. Higher mean values of MFE and a greater percentage of nonlinearity were observed in the SP group as compared to the C group. Our results suggest that women with severe pre-eclampsia may exhibit a higher short-term BRA characterized by a lower contribution of breathing rate decelerations to short-term variability, higher irregularity and nonlinearity of BB time series, and particularly more irregular behavior of decelerations compared to normotensive women. This may indicate a potential modification in the autonomic control of breathing rate and breathing instability.