Blood pressure varies continually throughout the day, making a single or even a few readings unrepresentative, either through the circumstance of the individual or through errors obtained in the measurement of the blood pressure. An accurate baseline pressure is often difficult to obtain due to presence of various stimuli.
Variations in blood pressure can be contributed to race, age, sex, time of day, activity, emotion, posture, etc. (MacGillivray et al., 1969). Within-patient variation can be due to systemic variation, e.g. women have a lower blood pressure than men after the age of 45 (Kannel, 1974); circadian rhythm — blood pressure will be lower during sleep than wakefulness, especially during the first two hours of sleep (Coccagna et al., 1971) [attenuation and reversal of the diurnal variation have been described in pre-eclampsia (Dame et al., 1977; Halligan et al., 1996; Murnaghan et al., 1980; Redman et al., 1976; Sawyer et al., 1981; Seligman, 1971)]; diastolic pressure will increase on standing; dynamic exercise increases the systolic pressure while cessation of prolonged exercise will cause a decrease (Kenney and Seals, 1993), etc. Smoking (Cellina et al., 1975; Mann et al., 1991) or drinking coffee (Jeong and Dimsdale, 1990; Smits et al., 1985) will also cause a rise in blood pressure and many daily activities such as micturition, defecation, eating and drinking can have significant effects on the blood pressure. These random variations of blood pressure will most likely result in sampling errors.
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Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...