Change in posture during sleep causes errors in non-invasive automatic blood pressure recordings.

Area of Science:

• Cardiovascular physiology
• Biomedical engineering
• Sleep medicine

Background:

• Automatic non-invasive blood pressure monitors are widely used for sleep studies.
• Blood pressure readings can be affected by hydrostatic pressure differences due to body position.
• Variations in blood pressure during sleep are common but their causes require further investigation.

Purpose of the Study:

• To investigate the influence of posture changes on blood pressure fluctuations during sleep.
• To compare blood pressure variations during sleep with those induced by posture changes in recumbent positions.
• To determine the extent to which posture changes contribute to night-time blood pressure variability.

Main Methods:

• Blood pressure was measured non-invasively every 20 minutes overnight in 20 men.
• Consecutive blood pressure differences and maximum differences were calculated.
• Blood pressure changes were compared between four standardized recumbent postures in 20 volunteers.

Main Results:

• Mean difference between consecutive overnight blood pressure recordings was 7.6 mmHg.
• Maximum blood pressure difference during sleep ranged from 7-32 mmHg systolic and 6-26 mmHg diastolic.
• Posture changes in recumbent volunteers induced average blood pressure differences of 9 mmHg and maximum differences up to 27 mmHg systolic.

Conclusions:

• Changes in body posture significantly contribute to blood pressure variations recorded by non-invasive devices during sleep.
• The magnitude of blood pressure variation due to posture changes is comparable to that observed during overnight monitoring.
• Posture-induced hydrostatic effects are a primary driver of apparent blood pressure fluctuations during sleep.