The Finapres is a non-invasive continuous finger arterial blood pressure monitor, based on the vascular unloading technique, described by the Czech physiologist Jan Peñáz and the physiological criteria invented by Karel Wesseling.
Finapres is the acronym for Finger arterial pressure, the quantity that is measured continuously by the Finapres. With the volume-clamp method of Peñáz, the finger arteries are clamped at a fixed diameter, although intra-arterial pressure changes continuously, by applying an external pulsating pressure via an inflatable bladder mounted in a finger cuff and a fast-acting servo system. Finapres uses the criteria of Wesseling for determination of the setpoint. The diameter at which the finger arteries are clamped is determined from an infrared plethysmograph mounted in the finger cuff, such that transmural pressure is zero and intra-arterial and cuff pressures are equal, both in shape and in level at all times.
Portapres is an ambulatory non-invasive finger arterial blood pressure monitor.
This battery-operated, lightweight device is worn in a waist belt. A height correction unit is used to compensate hydrostatic blood pressure changes in the finger. The measurement is performed in two (adjacent) fingers alternately at selectable intervals and is fully automatic.
A measurement is automatically suspended after an operational error and the measurement is automatically restarted after a waiting period. The data are stored on a built-in memory card that allows more than 24-hour finger arterial pressure waveform storage and can be downloaded to a PC for a full beat-to-beat analysis.
Special Portapres systems have been developed for various space agencies.
Finometer is a non-invasive haemodynamic cardiovascular monitor based on the measurement of finger blood pressure providing:
- Non-invasive continuous monitoring of the finger arterial pressure
- Brachial pressure waveform and level reconstruction from finger arterial pressure
- Cardiac output, stroke volume and peripheral resistance computation
[i] A consensus view on the technique of ambulatory blood pressure monitoring
Staessen JA, Fagard R, Thijs L, Amery A.
Hypertension 1995; 26: 912-8
ii] Why use Finapres or Portapres rather than intra-arterial or intermittent non-invasive techniques of blood pressure measurement?
Langewouters GJ, Settels JJ, Roelandt R, Wesseling KH.
J Med Eng Technol 1998; 22: 37-43