Study of Blood Pressure during Controlled Respiration

Abstract

It is well known that respiration can have significant effects on blood pressure and other physiological features. However, little is known about the stability and patterns of respiration during controlled studies. In this research we compared blood pressure, heart rate, respiration and respiration patterns during normal breathing and breathing associated with relaxation and meditation. Continuous respiration patterns were recorded with ethical permission from normal subjects while seated, over 30-minute periods, with their blood pressure measured at the start and end of each recording period using an automated non-invasive cuff device. The same device was used for all measurements to avoid any device bias. The first set of recordings were made with no instruction on breathing technique. The subjects were then invited to an open lecture on meditation techniques, and given some additional instruction before a second similar 30-minute study period, but with no further instruction or feedback during the recording. Comparing respiration during normal breathing with that during meditation, the average number of full respiratory cycles over the 30-minute periods fell significantly from 355±44 (mean±SD) to 197±80 (p=0.012). There were no significant differences between sequential 10-minute sub-periods in either of the two study periods. The pattern of the respiration waveform during meditation was less skew (0.18±0.20 compared with 0.42±0.24, p=0.004). During normal breathing, systolic and diastolic blood pressure and heart rate fell over the 30-minute period in all subjects, but not significantly. During controlled breathing there were no consistent changes. It is possible that the expected fall in blood pressure and heart rate during meditation was offset by the slower respiration, with the consequent depth of respiration being deeper.