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Biomedical subjects

R Skidmore

Publications and source records attributed to R Skidmore.

At least 55 records · Page 3Linked to original sources
PubMed1981

The role of pulsatility index in the clinical assessment of lower limb ischaemia.

The routine clinical use of pulsatility index (PI) in the quantitative assessment of Doppler blood velocity/time waveforms, was assessed in normals and in patients with leg ischaemia. Two thousand and five hundred common femoral artery waveforms were studied in 57 subjects (38 males, 19 females). PI values showed a mean variability of 17% in subjects in normal sinus rhythm (NSR) (range 4.1-13.2). In 17 patients in atrial fibrillation (AF) but with no clinical arterial disease, PI varied 26%. Variability was reduced, using a ten beat average, to 7.5% in NSR and 9% in AF. Rise in PI correlated well with increase in peripheral resistance (R = 0.82) but PI was poorly related to arterial stiffness (R = 0.50). Although PI was able to identify patients with proximal arterial narrowing it was unable to distinguish the severity of disease as assessed arteriographically minimum diameters (R = 0.30). From our observations we conclude that while PI has an established place in the assessment of peripheral arterial disease it must be applied with caution and averaging from ten heart beats is an essential manoeuvre. PI may prove to be a more reliable index for assessing distal rather than proximal disease.

Adult↗
PubMed1980

Upstream stenosis. Its diagnosis by Doppler signals from the femoral artery.

Transcutaneous femoral artery Doppler signals were measured with a 10-MHz pencil probe in 263 lower limbs of 135 patients. The Doppler waveforms were compared with arteriograms in 125 limbs with lower-limb ischemia and in 138 controls in the detection of minor (< 50%) and major (> 50%) iliac-artery stenosis. Doppler maximum velocity-time waveforms were obtained using a maximum frequency follower, and the wave-form shape was analyzed using a Laplace transform (LT) to produce a coefficient, the LT damping. Pulsatility index (PI) was also calculated. In 62 limbs with minor artery disease, mean LT damping was significantly greater than normal (0.5 +/- 0.15 vs 0.33 +/- 0.06; P < .001). In 63 limbs with major iliac stenosis, mean LT damping was higher still (0.78 +/- 0.16; P < .02). The LT damping was not affected by increased distal impedance and there was a good correlation with iliac stenosis in 65 limbs with an occluded superficial femoral artery (r = -0.73). The results with PI were inferior at every grade of severity of iliac disease when assessed by receiver-operator characteristic curves. These results suggest that LT damping is a sensitive method of analyzing femoral Doppler signals in the noninvasive detection of iliac artery stenosis.

Arterial Occlusive Diseases↗
PubMed1979

Pulsed Doppler angiography in lower limb arterial ischemia.

A 30-channel pulsed Doppler vessel imaging system (MAVIS, GEC Medical, Middlesex, England), was used to obtain images and maximal Doppler velocity time waveforms in the diagnosis of stenosis of the origin of the profunda femoris artery (PFA) and in the detection of structural changes within Dacron arterial grafts. In PFA scans of 33 limbs in 22 patients (mean age, 52 years), PFA stenosis of more than 50% at operation was invariably associated with a damping factor of the maximal Doppler velocity-time waveform of greater than 1.5 (eight limbs). In 12 limbs with a normal PFA at operation, the damping factor was always less than 1.4, and in 13 limbs of normal patients without arterial disease, the damping factor was always less than 1.34. In studies of 10 mm arterial grafts, the internal diameter of 14 iliopopliteal grafts scanned just above the popliteal anastomosis was strikingly reduced as compared with the femoral anastomosis of 14 aortoiliofemoral grafts and seven axillobifemoral grafts. These preliminary results suggest that MAVIS studies can be used noninvasively to detect PFA stenosis and to identify luminal narrowing of iliopopliteal grafts.

Angiography↗
PubMed1977

Tumour detection by ultrasonic Doppler blood-flow signals.

Ultrasonic Doppler blood-flow signals which seem to be associated with malignant tumour neovascularization have been detected in the female breast. No such signals have been detected from cysts. This discovery may lead to the development of a highspeed ultrasonic Doppler scanner which might make breast screening for cancer practicable.

Adenofibroma↗
PubMed1977

The concept and measurement of bladder work.

The methodology for the calculation of bladder work from pressure volume traces has been described. Bladder work values have been calculated from the urodynamic data of 50 male patients. When bladder work values were related to the micturition time and the volume passed, a highly significant correlation was demonstrated with urethral resistance. Bladder work values may be a useful index in the diagnosis of bladder outflow obstruction.

Humans↗
PubMed1976

The measurement of urethral resistance and mural tension using simple programmable modules.

The theory of urethral resistance and the derivation or mural tension have been discussed. A method for the continuous calculation and presentation of these parameters has been described. Urethral resistance and mural tensions are altered by the presence of bladder outflow obstruction and have been shown to return to normality after the obstruction is removed.

Humans↗
PubMedDate not supplied

Physiological interpretation of Doppler shift waveforms: the femorodistal segment in combined disease.

A new method is presented for assessing the femorodistal segment in multisegmental arterial disease, using the Laplace transform technique of Doppler waveform analysis. Blood velocity/time waveforms were obtained at femoral and ankle levels in three groups of limbs--50 without arterial disease, 12 with isolated aortoiliac stenoses, and 32 with femoropopliteal occlusions, with and without proximal disease. The waveforms were analysed for Laplace transform and pulsatility index values. The omega 0 coefficients of the Laplace transform analysis at femoral and ankle levels were compared in each subject, as the omega 0 gradient (femoral/ankle omega 0): and pulsatility index damping factor (femoral/ankle P1) was also calculated. The omega 0 gradient was shown to detect femoropopliteal occlusion in the presence of multisegmental arterial disease and to give some indication of its haemodynamic significance. The diagnostic accuracy of the omega 0 gradient was superior to that of pulsatility index damping factor. When combined with its existing ability to detect aortoiliac stenosis, this new application of the Laplace transform method offers the possibility both of a system for complete localisation of significant arterial lesions, and potential for follow-up of vascular surgical procedures in the lower limb, from two simple Doppler recordings.

Aortic Valve Stenosis↗
PubMedDate not supplied

Variability and reproducibility of arterial Doppler waveforms.

The variability and reproducibility of arterial Doppler waveforms are influenced by factors such as operator experience, physiological changes in the patient, and the type of Doppler processing system. Some aspects of these were studied using Laplace transform analysis of waveforms from the femoral and posterior tibial arteries of normal subjects and arteriopaths. Five consecutive waveforms were obtained from the femoral and posterior tibial arteries of normal subjects during about 1 hr of supine rest. Group 1 (n = 20) was studied 9 months before Group 2 (n = 11), early in the operator's experience of waveform recording. Variability (root mean square) of femoral and posterior Laplace delta decreased from 16.9 to 12.5%, and 23.3 to 17.9% respectively (P less than 0.05 in each case). In arteriopaths (n = 8) there was a trend to more variable results at femoral level (only significant in the case of Laplace omega 0 - P less than 0.05), while posterior tibial results tended to be less variable. Normal subjects examined in the longer term (n = 4), with a mean interval of 28 days between recordings, did not show significantly greater variability than those examined over 1 hr. There was no significant difference in variability of results in normal subjects (n = 30) using instantaneous average Doppler processing compared with maximum frequency processing, except in the case of posterior tibial Laplace omega 0 (maximum frequency more variable - P less than 0.05).

Adult↗
PubMedDate not supplied

Doppler developments in the last quinquennium.

The major advances which have taken place during the last five years in the development of ultrasonic Doppler devices and methods of Doppler signal analysis are reviewed. The following aspects of instrumentation are considered: crossed beam Doppler systems, range measuring Doppler systems, duplex systems, flow mapping systems, transducers and measurements of system performance. Analytical methods are discussed in the following categories: waveform analysis, including the extraction of single-value waveforms and their applications to the diagnosis of vascular disease; spectral analysis, including the derivation of frequency spectra and their application in the study of blood flow; and volume flow estimation. It is concluded that it is likely to be in the study of the information in Doppler frequency spectra, two-dimensional real-time Doppler images and in the measurement of blood flow volume that most progress will be made.

Blood Volume Determination↗
PubMedDate not supplied

Giant congenital melanocytic nevus with underlying hypoplasia of the subcutaneous fat.

A 17-week-old boy with a giant congenital melanocytic nevus (GCMN) of the left lower extremity was noted to have a reduction in circumference of the left lower extremity relative to the contralateral side. The skin overlying the GCMN was persistently warm when compared with the surrounding and contralateral skin. Comparative plain radiography, ultrasonography, and magnetic resonance imaging showed fat hypoplasia of the left lower extremity, with bone and muscle appearing unaffected. The possible role of cytokines produced by the nevus in fat hypoplasia in GCMN is discussed.

Adipose Tissue↗