The finger systolic pressure (FSP) can be used to monitor a patient with Raynaud's phenomenon during controlled cooling of a finger.
Method (see Figure 1, page 768, Nielsen 1978):
(1) A cuff with 2 outlets connected to a chilled water supply is placed around the middle phalanx of the finger being evaluated. Cooling to each temperature is done for 5 minutes before the systolic blood pressures are recorded.
(2) An occlusive cuff is placed on the proximal phalanx of the finger being evaluated.
(3) A strain gauge is placed on the distal phalanx to measure the systolic pressure in the finger being evaluated.
(4) The control finger is on the same hand as the finger being evaluated.
(5) An occlusive gauge is placed on the middle phalanx of the control finger.
(6) A strain gauge on the distal phalanx of the control finger is used to measure the systolic pressure at the same time as the systolic pressure in the test system.
Measurements:
(1) finger systolic pressure (FSP) of control finger while the test finger is at 30°C
(2) FSP of test finger at 30°C
(3) FSP of control finger while the test finger is cooled to 20°C
(4) FSP of test finger at 20°C
(5) FSP of control finger while the test finger is cooled to 15°C
(6) FSP of test finger at 15°C
(7) FSP of control finger while the test finger is cooled to 10°C
(8) FSP of test finger at 10°C
FSP in percent for 20°C =
= (FSP of test finger at 20°C) / ((FSP of test finger at 30°C) - ((FSP of control finger at 30°C) - (FSP of control finger at 20°C))) * 100%
FSP in percent for 15°C =
= (FSP of test finger at 15°C) / ((FSP of test finger at 30°C) - ((FSP of control finger at 30°C) - (FSP of control finger at 15°C))) * 100%
FSP in percent for 10°C =
= (FSP of test finger at 10°C) / ((FSP of test finger at 30°C) - ((FSP of control finger at 30°C) - (FSP of control finger at 10°C))) * 100%
Interpretation:
• Patients with Raynaud's phenomenon show an increased arterial tone at a higher temperature than people without Raynaud's phenomenon, resulting in the arterial closure.
