- As illustrated below, if the cuff is inflated only to the initial disappearance of the sound, the actual SBP maybe underestimated.
- Cause is a mystery.
- Avoided by palpating the disappearance of the pulse by inflation of cuff before using stethoscope to estimate the SBP. Cuff should be inflated 20-30 mmHg higher than the estimated SBP.
Level of arm
- Should be at the level of heart
- Too high: the readings will be lower
- Too lower: the readings will be higher
- Due to hydrostatic effect
Blood pressure deficits between left and right arm
- Normal is <10 mmHg, >20 mmHg is abnormal
– Subclavian steal syndrome
– Aortic dissection
BP deficits between arms and legs
- Chronic ischemia of lower extremities
- Coarctation of aorta (aorto-femoral delay in pulse)
- 500 mL of blood shifts to lower body on standing up.
- Defined as drop in SBP >20 mmHg or drop in DBP >10 mmHg
- Orthostatic hypotension happens when:
– Excessive loss of fluid
– Lack of compensatory mechanism (autonomic dysfunction)
- Evidence showed that
– Finding of postural drop in SBP has no proven value
– The better findings are postural increment of pulse >30/min OR dizziness on standing up
Blood pressure and impaired consciousness
- Cushing reflex – normally due to increased ICP (structural lesions)
- Cushing triad: 3B: Blood pressure increases, Bradycardia, Breathing irregular
Pathogenesis of Cushing Reflex
Steven McGee, Evidence Based Physical Diagnosis, pg 153-160