Ambulatory blood pressure monitoring is more useful for the diagnosis of various forms of hypertension including white coat and morning surge as well as other conditions that are associated with increased morbidity and mortality such as sleep apnea. Nocturnal changes in blood pressure (BP) can also aid in the diagnosis of various manifestations of blood pressure independent of hypertension known as salt sensitivity (SS) and inverse salt sensitivity (ISS) of blood pressure. SS individuals experience an increase in BP on a high salt diet while ISS individuals experience a paradoxical increase in BP on a low salt diet. SS and ISS phenotypes affect approximately 18% and 15% of normotensives, respectively, which may result in significant morbidity and mortality similar to untreated hypertension. Consuming a personally appropriate salt diet can result in a circadian drop in BP during sleep, and failure to “dip” can lead to significant cardiovascular diseases. Nocturnal dipping is usually recorded using an ambulatory blood pressure monitoring (ABPM) device. Arterial pulse wave measurements using oscillatory photoplethysmography (OP) are minimally invasive when compared to an inflatable cuff, which can disturb sleep and raise blood pressure. We measured nocturnal blood pressure using a ring based photoplethysmograph (SensoGram Technologies, Plano Texas). A UVA Salt Study participant wore their device upon going to bed and then uploaded nocturnal data to the internet each morning. Systolic and diastolic BP is capable of being measured 30 times a minute for approximately 9 hours and providing over 5000 data points each night. Three representative dipping profiles for an individual yielded a dipping reduction of 24% ± 3% for systolic and 40% ± 10% for diastolic (1 - mid-sleeping lowest value/start of evening highest value). This additional data afforded by nocturnal BP measurement is anticipated to improve diagnostic opportunities in the measurement of SS and ISS phenotypes and provide the user with reassurance that nocturnal BP dipping is occurring.
Nocturnal blood pressure dip and morning blood pressure surge: A 24-hour ambulatory blood pressure monitoring study
