The influence of pregnancy upon acute cardiovascular responses to slow and deep breathing.

Abstract

Slow and deep breathing (SDB) is a promising intervention that has provided reductions in blood pressure (BP) in primary hypertension when practised daily and has potential as an intervention to treat women who develop hypertension during pregnancy. Before SDB can be introduced in a clinical setting during pregnancy, it is important to understand whether normal cardiovascular changes that accompany pregnancy influence the acute responses to SDB. Additionally, known structural and mechanical differences in the respiratory systems of men and women may also influence cardiovascular responses to SDB. As most published studies include only male participants this has not been fully investigated. In preparation for a clinical study of SDB with women who develop pregnancy-induced hypertension, this thesis characterised the acute cardiovascular responses to a range of different SDB protocols in three distinct population groups (men, women and pregnant women). Novel analysis techniques were applied to delve deeper into the acute cardiovascular responses, by analysing the inter- and intra-breath phase cardiovascular fluctuations induced by breathing. The results highlight the limitation of using averages to understand the cardiovascular changes induced by SDB. Analysis of within-breath (peak-valley) haemodynamics revealed an increase in the amplitude of oscillations during SDB, whilst the average was unchanged. Respiratory sinus arrythmia tripled during SDB compared with rates during normal breathing across all participant groups. The observed increase of the amplitude of BP oscillations provides clues to potential error signal(s) linking daily practise of SDB to chronic BP reductions. This thesis makes an original contribution to existing knowledge by furthering our understanding of the acute cardiovascular responses to SDB and the need to look more closely at peak-valley haemodynamic oscillations. It provides evidence to support the development of an evidence-based SDB intervention to be used with pregnant women, supporting womencentred care and improving the health and experiences of pregnant women.