Sleep disordered breathing and the cardiovascular system

Davies, Robert J.O (1993) Sleep disordered breathing and the cardiovascular system. University of Southampton, Doctoral Thesis.

Abstract

Ambulatory blood pressure, sleeping beat to beat blood pressure, left ventricular anatomy, lipid and insulin levels were compared in nineteen obstructive sleep apnoea patients, nineteen snorers, and controls matched for age, sex, obesity, tobacco and alcohol intake. In the snorers, none of the end points differed from control. In the sleep apnoea patients, daytime blood pressure was not raised and did not change after a treatment. Nighttime blood pressure was raised on both the ambulatory and beat to beat recordings, and this resolved with treatment. The other end points were similar in the patients and their controls. These results suggest that daytime high blood pressure in sleep apnoea patients is due to associated obesity. Nighttime blood pressure is independently raised, and this corrects with sleep apnoea treatment.

The systolic blood pressure falls with inspiration, and rises with arousal from sleep. The ability of these changes to identify sleep disordered breathing has been examined. Computer algorithms identifying these changes were applied to recordings from twenty-one subjects having polysomnography for possible sleep apnoea. In half these subjects, a respiratory cause for the disturbance was identified from the size of the respiratory blood pressure falls. 80% of all the subjects studied could be defined as either normal, or clearly abnormal from their blood pressure profile alone. Screening the blood pressure profile could reduce the need for more detailed sleep studies.

Arousal from sleep raises the blood pressure. To assess whether transient arousal alone could explain the nighttime blood pressure rises of sleep apnoea, the haemodynamic response to induced arousal was studied in nine normal volunteers.

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