Pre-eclampsia is associated with sleep-disordered breathing and endothelial dysfunction

Abstract

Pre-eclamptic toxaemia (PET) may be associated with both endothelial dysfunction (ED) and sleep-disordered breathing (SDB). It was hypothesised that females with PET would demonstrate both SDB and ED, and that a correlation between these two would suggest a potential causative association. A total of 17 females with PET and 25 matched females with uncomplicated pregnancy were studied. They underwent a nocturnal ambulatory sleep study (using Watch_PAT100) and noninvasive evaluation of endothelial function utilising the reactive hyperaemia test (using Endo_PAT 2000). A higher ratio of post- to pre-occlusion pulse-wave amplitude (endothelial function index (EFI)) indicated better endothelial function. Females with PET had a significantly higher respiratory disturbance index (RDI) and lower EFI than controls (18.4+/-8.4 versus 8.3+/-1.3.h(-1), and 1.5+/-0.1 versus 1.8+/-0.1, respectively). Blood pressure significantly correlated with RDI and with EFI. EFI tended to correlate with RDI. In conclusion, these results suggest that both sleep-disordered breathing and endothelial dysfunction are more likely to occur in females with pre-eclamptic toxaemia than in females with uncomplicated pregnancies. The current authors speculate that respiratory disturbances contribute to the functional abnormality of the blood vessels seen in females with pre-eclamptic toxaemia, although causality cannot be determined based on this study.

Figures

FIGURE 1

Endothelial dysfunction (ED) evaluation by the reactive hyperaemia test. Four channels are presented as follows: raw data of the occluded finger (probe 1); raw data of the unoccluded finger (probe 2); moving time average of the occluded finger (trend 1); and moving time average of the unoccluded finger (trend 2). a) shows an individual with ED (there is a lack of vasodilatation in post-obstruction period), whereas b) shows a normal endothelial response (there is a marked increase in pulse-wave amplitude indicating vasodilation shortly following the removal of the obstruction). In both cases, there is no systemic response as indicated by the stable signal in the nonoccluded arm.

FIGURE 2

Respiratory disturbance index (RDI) of pre-eclamptic toxaemia (PET) and controls. The RDI of the PET group was significantly higher than in the control group. #: p=0.03.

FIGURE 3

The endothelial dysfunction (ED) score of the two groups is presented, indicating the averages (■) and the individual data (●). The ED score of the pre-eclamptic toxaemia (PET) group was significantly lower than in the control group. Most females with PET had an ED score below the threshold of normality (······=1.67), whereas most controls were above it. #: p=0.03.

FIGURE 4

An example of normal endothelial function, with vasoconstrictive systemic response. In this example, the post-occlusion pulse-wave amplitude (PWA) in the occluded arm (occlusion duration 5.2 min, probe 1) is similar to the pre-occluded values, which could have been misinterpreted as abnormal endothelial function. However, looking at this individual systemic response (assessed in the control arm, probe 2), it can be seen that this individual had a vasoconstrictive (stress) response with the cuff inflation (arrow), and, therefore, the “unchanged” PWA seen in the tested arm actually results from local vasodilatation, indicating a normal endothelial function (endothelial dysfunction score 2.16). This example emphasises the advantage of monitoring systemic response during the reactive hyperaemia test.