Surgery – Truss – Pad
Patent
1996-03-08
1998-02-10
Bahr, Jennifer
Surgery
Truss
Pad
128687, A61B 502
Patent
active
057158266
DESCRIPTION:
BRIEF SUMMARY
This application claims benefit of international application PCT/GB94/01997, filed Sep. 14, 1994.
INTRODUCTION
The present invention relates generally to vascular investigation and more specifically to a method and device for use in assessing the state of blood vessels within the human or animal body.
PRIOR ART
Vascular diseases involving sclerosis, stenoses or occlusions can be very difficult to diagnose before their effects strike. Progressive narrowing of arteries, if not identified and treated, can lead to total occlusion. Depending on the site, this may lead to the loss of a leg, or cause a heart attack or stroke. If a stenosis can be detected at an early stage, remedial measures may be taken, such as arterial reconstruction and/or angioplasty. Monitoring of haemodynamic characteristics, such as blood pressure, as an aid in indicating or assessing vascular disease, is unreliable. It is estimated that a vessel has to be occluded by more than 50% of cross sectional area before a drop in peak pressure across a stenosed segment is perceptible.
At present there are a number of methods available to physicians to aid in the detection of vascular disease. Some are invasive methods, such as that of introducing a catheter into an artery under investigation and thereby examining directly or indirectly the internal state of the vessel, be it by use of direct pressure monitoring techniques, ultrasound, camera techniques, or otherwise. Such methods are clearly not without their dangers.
There are also a number of non-invasive techniques widely used in such investigations, such as a variety of imaging techniques. Colour flow duplex ultra-sonography is one such technique, but this involves expensive equipment and requires an operator highly skilled in the interpretation of the results. Angiography is an alternative technique, in which radio-opaque contrast is introduced into the vascular system and X-ray methods are used to image the arterial lumen to enable identification and location of stenoses and occlusions. This is a relatively straightforward technique but is still highly operator-dependent in terms of the skill and experience needed to interpret the results. A 3-dimensional, or at least biplanar, approach must be taken to successfully apply the above imaging technique, as a stenosis perceptible in one image plane may not be perceptible in another. A further disadvantage exists in these known diagnostic techniques, in that they are not readily applicable to all parts of the body's vascular system. For example, in the iliac segment of the human body, a high-risk region where stenoses leading to occlusions and critical ischaemia can occur, the anatomical region of interest is at least partially acoustically shielded by the abdominal organs. Ultrasonic methods are therefore very difficult to apply in this region.
From the above it is clear that there exists a need for a non-invasive technique for use in the prediction or the diagnosis of vascular disease which is simple, effective and cheap to employ such as to be appropriate for the screening of subjects.
The background to the present invention also includes the study of pulse volume recordings (PVRs). PVRs are used to give information about the dynamics of vascular pulsatile flow at sites in the human body and are generally studied as waveforms measured by means of a plethysmography cuff located at the site of interest, the waveform representing the pulsatile vascular pressure. PVRs are not intended to provide absolute blood pressures, but the shape of the waveform produced can give useful qualitative clinical information about the vascular system. Work involving the use of PVRs in vascular investigation is described, for example, in an article in The Journal of Vascular Surgery, Volume 13, Number 2, February 1991, pages 284 to 293, entitled "Impedance analysis to identify the at risk femorodistal graft", by M. G. Wyatt et al.
PVR analysis is available as a feature of a commercially available machine, the PVL-50 portable vascular laboratory available from
REFERENCES:
patent: 5050613 (1991-09-01), Newman et al.
patent: 5101828 (1992-04-01), Welkowitz et al.
patent: 5265011 (1993-11-01), O'Rourke
Wyatt et al: "Impedance analysis to identify the at risk femorodistal graft", Journal of Vascular Surgery, vol. 13, No. 2, Feb. 1991, pp. 284-293, cited in the application, see p. 285, left column, line 14-line 46, see figure 1.
Horrocks Michael
Skidmore Robert
Bahr Jennifer
British Technology Group Limited
Yarnell Bryan K.
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