Arterial Upper Segmental Pressures-Thoracic Outlet

Upper Extremity Pressures

1. Normal

a. <20 mm Hg between right and left brachial pressures

b. Ratio of >1.0 comparing forearm to brachial pressure in a limb (pressure normally remains the same or is slightly increased from upper arm to forearm).  This ratio is abbreviated WBI for wrist/brachial index. 

c. Digit-brachial index (DBI) >0.80.  Digit pressure within 20-30 mmHg of the brachial pressure.  The digit pressure is divided by the higher of the two brachial pressures. 

2. Abnormal

a. >20 mmHg difference between right and left brachial pressures.  Note that the arterial waveforms should be considered when assessing pressures, since there may be bilateral upper extremity disease that can lower pressure relatively equally side-to-side.

b. WBI <1.0 indicates arterial occlusive disease in the vessels between the cuffs 

c. WBI >1.3 suggests underlying arterial calcific disease making vessels non-compressible and pressures falsely elevated. 

d. >30 mmHg difference between radial and ulnar pressures; disease indicated in vessel with the lower pressure

e. Change in WBI of 0.15 on serial studies

Thoracic Outlet Syndrome (TOS)

PPG or PVR waveforms are recorded during performance of functional arm maneuvers.  Duplex ultrasound may also be performed during functional maneuvers.

1. Normal:

a. Waveforms remain unchanged during functional maneuvers or may show slight increase or decrease compared to baseline waveforms

2. Abnormal:

a. Significant decrease in waveforms during functional maneuvers compared to baseline and patient experiences symptoms

b. With duplex, subclavian stenosis (x2 velocity increase with post-stenotic changes) or venous impingement (loss of normal phasic / respiratory patterns) in the thoracic outlet may be detected.