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Biomedical subjects

P Aspinall

Publications and source records attributed to P Aspinall.

10 recordsLinked to original sources
PubMed1997

Color Doppler imaging in untreated high- and normal-pressure open-angle glaucoma.

PURPOSE: To evaluate ocular blood flow velocity indices in untreated primary open-angle glaucoma (POAG) and normal pressure glaucoma (NPG). METHODS: Twenty-five untreated patients with NPG, 23 untreated patients with POAG, and 26 age-matched normal control subjects underwent color Doppler imaging for the measurement of blood flow velocity in the central retinal and ophthalmic arteries. Neither the patients nor the control subjects were using systemic beta-blockers or calcium channel blockers. After log transformation of non-normal data, group differences were compared with a one-way analysis of variance followed by unpaired t-test with the Bonferroni correction. Statistical significance was set at P < 0.05. RESULTS: The central retinal artery end diastolic velocity was significantly lower in patients with POAG than in normal subjects. The ophthalmic artery peak systolic velocity (PSV) was significantly greater in patients with POAG than in those with NPG and normal subjects. The resistance index (RI) of both the ophthalmic and central retinal arteries was significantly greater in patients with POAG than in normal subjects, and the central retinal artery RI was significantly greater in those with NPG than in normal subjects. Systemic pulse pressure and systolic blood pressure were significantly greater in patients with POAG compared with normal subjects. Multiple regression analysis showed a significant relation between ophthalmic artery PSV and intraocular pressure (but not with any of the cardiovascular parameters) in the POAG group. Chi-square analysis found significantly more systemic vascular disease in patients with NPG and POAG compared with that of normal subjects. CONCLUSIONS: There was an increased resistance to blood flow in the central retinal artery of untreated patients with NPG and POAG and also in the ophthalmic artery of patients with POAG. The ophthalmic artery peak systolic velocity was elevated in untreated patients with POAG. Altered ocular circulation (with different patterns of presentation) appears to be common to patients with NPG and patients with POAG.

Aged↗
PubMed1995

Measurement of ocular blood flow velocity using colour Doppler imaging in low tension glaucoma.

The purpose of this study was to compare the velocity of blood flow and vascular resistance measured by colour Doppler imaging in the ophthalmic and central retinal arteries in 34 eyes of 34 patients (mean age 68.1 years) with low tension glaucoma (LTG) and 17 eyes of 17 age-matched normal controls (mean age 65.2 years). The Acuson 128 machine (using a 7.5 MHz probe) was used to measure peak systolic velocity (PSV), end-diastolic velocity (EDV) and resistive index (RI). The EDV of the ophthalmic artery (OA) in the LTG was significantly (p = 0.04) less than in the normal control group. There was a significant (p = 0.02) increase in the vascular RI of both the OA and central retinal artery in the LTG group compared with the normal controls. The OA RI increased with age (r = 0.61, p = 0.0001), and the OA EDV decreased with age (r = -0.50, p = 0.003), in the LTG group but not in the normal control group. The results suggest an increased resistance to blood flow in the ophthalmic and central retinal arteries of LTG patients.

Aged↗
PubMed1994

When a vulnerable patient absconds.

This case-study examines the nurse's role when a patient at risk absconds. It highlights possible weaknesses in the system for dealing with absconding patients who are so cognitively and emotionally impaired, that they may present a danger to themselves. The issues of patient identification and stigmatization are raised along with the possible conflict this may cause in psychiatric nurses. Recommendations for care at ward level are made, including asking the vulnerable patient to wear an identity bracelet and the instigation of a prepared action plan which involves engaging the help of outside agencies should a patient abscond.

Aged↗
PubMed1992

Low contrast visual acuity changes in human immuno-deficiency virus (HIV) infection.

A pilot study of low contrast visual acuity testing using Regan Charts has been undertaken in 34 patients seropositive for Human Immuno-Deficiency Virus and 20 normal control subjects. Low contrast visual acuities of the HIV (+) patients both with and without HIV retinopathy were found to be significantly lower than the age-matched controls (p < 0.01). This finding is probably attributable to pathology related to HIV in the visual pathways/Central Nervous System. Lowest contrast Chart (Chart C) was found to be a useful diagnostic tool for HIV retinopathy and presumed neuropathy.

Adult↗
PubMed1992

The effect of anticonvulsants on cognitive functioning following a probable encephalitic illness.

A 54-year-old man developed an acute encephalitic illness and subsequently suffered from marked memory difficulties. Considerable improvement with anticonvulsant therapy was demonstrated using a ward-based observation programme and serial neuropsychological assessments. The case report highlights the prominent role played by epileptic activity in determining the severity of the patient's amnesia.

Carbamazepine↗
PubMed1984

Clinical inferences and decisions--II. Decision trees, receiver operator curves and subjective probability.

In patient management, clinical decisions follow a logical sequence which can be formally expressed as a decision tree in which the uncertainties associated with each alternative outcome may be made explicit using Bayes' theorem. Where test data is used in the formulation of a decision, the uncertainty associated with the information it conveys may be modified by changing the pass/fail criterion to alter the false positive and false negative error rate. Classical procedures based on information theory are described to illustrate how this may be achieved for any test. When hard data is not available to permit such an approach, the clinician must rely on his own past experience or that of a colleague. Several methods are available for quantifying such experience by estimating subjective probabilities associated with an action or test result. Two simple methods are described for deriving subjective probabilities for subsequent use within a Bayesian decision model.

Bayes Theorem↗
PubMed1983

Clinical inferences and decisions--I. Diagnosis and Bayes' theorem.

Clinical decisions are based upon inferences derived from test evidence where data is collected as a means of hypothesis testing. In medicine, the initial expectation of a clinical state is rarely expressed in the classical scientific language of a null hypothesis where alternative outcomes are assumed to be equally probable, because clinical experience reinforces the maxim that common events occur commonly. The collection of test evidence in clinical practice, therefore, is directed towards overturning prior likelihoods for a clinically pathological state which are far from mere chance expectations. The extent to which any test evidence can modify such prior expectations not only depends on its relevance to the clinical state in question (i.e. the hypothesis) but also is largely influenced by the inherent error rates in the test itself. Clinical decision models should reflect these facts. Using examples from the field of ophthalmology, this paper presents a normative model using Bayes' theorem of conditional probabilities which provides a rational framework upon which to base or appraise clinical decisions. Parts II and III of the series will expand this clinical application of decision theory to show how it may be used in the absence of hard test evidence and also where a different emphasis or utility may be placed on false positive or false negative errors.

Bayes Theorem↗