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Biomedical subjects

K N Humphries

Publications and source records attributed to K N Humphries.

14 recordsLinked to original sources
PubMed1990

Impact of duplex scanning on carotid endarterectomy.

Duplex ultrasound permits safe and accurate assessment of the extracranial vasculature. This paper reports the change in patterns of referral to a specialized vascular unit following its introduction; increased referrals were seen in all specialties except neurology. A widely available and reliable duplex service has revealed more extracranial vascular disease than was previously recognized, and has increased referrals for carotid endarterectomy, thereby increasing surgical workload.

Adult↗
PubMed1987

Duplex ultrasound monitoring of arterial grafts: prospective evaluation in conjunction with ankle pressure indices after femorodistal bypass.

Duplex scanning and ankle brachial pressure indices have been used to objectively assess 94 femoro-distal bypass grafts 4-8 weeks postoperatively. Twenty grafts were occluded. Of the 74 patent grafts, three distinct groups could be identified on the basis of the non-invasive examination. Group 1. Patent grafts with no evidence of haemodynamically significant disease. Group 2. Patent grafts with localised disease. Group 3. Patent: haemodynamically failed grafts. Ankle brachial pressure indices alone could not differentiate between occluded grafts and grafts that were patent: haemodynamically failed (group 3), or adequately separate between grafts in groups 1 and 2. Duplex scanning when combined with pressure indices identified patent grafts "at risk" due to the presence of haemodynamically significant disease. Life table analysis demonstrated appreciable differences in event free survival between group 1 grafts and "at risk" grafts (groups 2 and 3). Duplex scanning is ideal for regular postoperative surveillance and complements the use of ankle brachial pressure indices in the follow-up of femoro-distal grafts.

Actuarial Analysis↗
PubMed1987

Duplex ultrasound assessment of femorodistal grafts: correlation with angiography.

Fifty-eight grafts have been assessed using duplex scanning and ankle brachial pressure indices. This assessment is compared with the findings by angiography. Eighteen grafts were occluded and 40 patent. Duplex scanning defined graft status with a greater accuracy than pressure indices. Pressure indices alone would not differentiate "satisfactory" grafts from those with localised, haemodynamically significant disease. Only 55% of those grafts with localised stenoses demonstrated a fall of greater than 0.2 in ankle brachial pressure index after exercise. When the information obtained using pressure indices and duplex scanning was combined non-invasive assessment had a sensitivity of 86% and specificity of 94% for detection of localised, haemodynamically significant disease in patent grafts. Haemodynamically significant disease, as defined by angiography, can be detected and localised with duplex scanning complementing the use of pressure indices in graft assessment.

Aged↗
PubMed1985

The role of continuous wave Doppler imaging in a vascular unit.

A continuous wave (CW) Doppler imaging system has been used in the assessment of patients with suspected carotid artery disease. In 137 comparisons with conventional angiography the sensitivity of CW Doppler Imaging was 91% and specificity 93% respectively in the detection of greater than 50% diameter internal carotid stenosis. The main diagnostic criterion for greater than 50% internal carotid stenosis was the presence of a peak internal carotid systolic Doppler shift frequency greater than 4 KHz. An examination protocol is recommended which combines CW Doppler imaging with common carotid waveform changes and the temporal artery compression test.

Arterial Occlusive Diseases↗
PubMed1985

The reliability of Doppler ultrasound techniques in the assessment of carotid disease.

The reliability of continuous wave (CW) Doppler imaging and Duplex scanning in the assessment of carotid artery disease has been evaluated prospectively in comparison with biplanar angiography. Of 130 comparisons the sensitivity of Doppler imaging was 89% and specificity 99% in the detection of greater than or equal to 50% internal carotid stenosis, and 87% and 99% respectively in the diagnosis of internal carotid occlusion. Of 118 comparisons the sensitivity of Duplex scanning was 93% and specificity 98% in the detection of greater than or equal to 50% internal carotid stenosis, and 93% and 99% respectively in the diagnosis of internal carotid occlusion. CW Doppler imaging and Duplex scanning are accurate techniques in the diagnosis and categorisation of internal carotid artery disease. CW Doppler imaging is an effective screening technique for the presence of greater than or equal to 50% internal carotid artery stenosis. Duplex scanning also has the potential for improved detection of early internal carotid artery disease and study of the natural history of atherosclerosis.

Adolescent↗
PubMed1976

Effects of incubator noise on the cochlea of the newborn.

The possible effects of incubator noise on the hearing of premature babies have long been debated. The type of hearing loss found in 12 low-birthweight children was examined; and the variable noise level in regularly used incubators was measured. This noise, applied to guinea pigs continuously during their second week after birth, was shown histologically to destroy a proportion of the sensory cells in the cochlea. Adult guinea pigs, however, were not vulnerable in this way. The conclusion is that there is definite circumstantial evidence of the damaging effect of many incubators on the hearing of premature infants.

Animals↗
PubMedDate not supplied

The accuracy of duplex scanning in the evaluation of early carotid disease.

The accuracy of duplex scanning in 69 comparisons with biplanar angiography in the detection of early carotid disease has been assessed. The various criteria reported for the categorisation of less than 50% disease have been critically analysed. As part of the study, 50 internal carotid arteries of 25 young, presumed normal medical students of mean age 20 years have been examined. The results suggest that duplex scanning has the ability to grade less than 50% carotid disease into normal, 1-24% and 25-49% stenosis categories. The most sensitive indicator of early disease is obtained from the real-time B-scan. The waveform changes of the maximum frequency envelope were more sensitive than spectral broadening except where full spectral broadening was present. For confident assessment, the real-time B-scan and pulsed Doppler must always be used in conjunction.

Adult↗
PubMedDate not supplied

The validation of duplex scanning and continuous wave Doppler imaging: a comparison with conventional angiography.

Colour-coded continuous wave (CW) Doppler imaging and duplex scanning have been assessed prospectively in comparison with biplanar angiography for their accuracy in detecting significant arterial disease in the extracranial circulation. Of 96 comparisons with biplanar angiography, the sensitivity of Doppler imaging was 90% and specificity 98% in the detection of greater than 50% internal carotid stenosis and 86 and 100%, respectively, in the diagnosis of internal carotid occlusion. Of 85 comparisons with biplanar angiography, the sensitivity of duplex scanning was 93% and specificity 98% in the detection of greater than 50% internal carotid stenosis and 92 and 100%, respectively, in the diagnosis of internal carotid occlusion. The value of the peak systolic Doppler shift frequency of the internal carotid artery signal has proved to be the most reliable indicator of greater than 50% stenosis and is utilised in conjunction with a periorbital examination. It is concluded that both Doppler imaging and duplex scanning are effective screening techniques for the presence of significant (greater than 50%) internal carotid artery disease.

Adolescent↗
PubMedDate not supplied

Characterisation of carotid artery disease: comparison of duplex scanning with histology.

The ability of duplex scanning to characterise the component tissue of atheromatous lesions of the internal carotid artery and to detect ulceration has been examined in a histological study of 42 carotid endarterectomy specimens. The results suggest that the only component of atheromatous lesions of the internal carotid artery which can be characterised from the B-scan is calcification. The presence of ulceration, intraluminal and intramural thrombus, fibrous intimal thickening and necrosis are not related to the echogenic appearance of internal carotid stenoses and may not be detected reliably. B-mode imaging alone cannot reliably grade greater than 50% internal carotid stenoses, but when this is combined with pulsed Doppler in the technique of duplex scanning, accurate results may be obtained.

Arterial Occlusive Diseases↗
PubMedDate not supplied

Extra-tympanic electrocochleography.

A non-invasive technique for recording the cochlear action potential in adults without recourse to sedation or local anaesthesia is presented. This technique has been assessed in two ways: (1) A group of normal subjects was tested to obtain distributions of response amplitude and latency as functions of stimulus intensity. (2) A group of patients with Meniere's disease was tested with trans- and extra-tympanic electrocochleography to compare the intensity amplitude functions and wave-forms obtained from the two methods. On the basis of this study the use of extra-tympanic electrocochleography as a replacement for the trans-tympanic method is discussed.

Acoustic Stimulation↗