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Biomedical subjects

D G Altman

Publications and source records attributed to D G Altman.

At least 253 records · Page 14Linked to original sources
PubMed1985

Blood pressure variability in health, hypertension and autonomic failure.

24h intra-arterial pressure monitoring was used to examine blood pressure variability in 5 normal volunteers, 137 subjects with suspected or established essential hypertension and 9 subjects with autonomic failure. Subjects with autonomic failure showed increased short-term blood pressure variability while active but reduced values at rest. Heart rate variability was low at all times. 24h recordings were reduced to hourly mean values and two indices of variability derived - day-night difference and average hourly change. For blood pressure, subjects with autonomic failure showed negative values of the former but high values of the latter; both indices of heart rate variability were low. In the remaining group, the relationship of these indices to constitutional factors, mean blood pressure and indices of physical activity during the study was explored. Day-night difference in systolic pressure was negatively correlated with mean pressure and average hourly change positively related to age. No other relationship was significant.

Adult↗
PubMed1984

A fair trial?

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Clinical Trials as Topic↗
PubMed1983

Effect on intra-arterial blood pressure of slow release metoprolol combined with placebo or chlorthalidone.

Thirty patients with essential hypertension participated in a double blind crossover trial in which they were randomly allocated to treatment with either once daily slow release metoprolol (200 mg) with placebo or once daily slow release metoprolol (200 mg) with chlorthalidone (25 mg). Ambulatory intra-arterial blood pressure was recorded continuously for 24-48 hours before treatment and two months after each change in regimen. The response of blood pressure and pulse rate to a standard exercise protocol that included supine rest and tilt, isometric, and dynamic bicycle exercise was measured during the same recording periods. Both treatments appreciably reduced blood pressure and pulse rate; mean daytime intra-arterial blood pressure was reduced from 174/95 mm Hg to 158/85 mm Hg by metoprolol plus placebo and to 143/78 mm Hg by metoprolol plus chlorthalidone. This reduction with the combined treatment was significantly greater than with metoprolol and placebo (p systolic = 0.001, p diastolic = 0.004). Mean night time pressures were reduced from 148/78 mm Hg to 139/75 mm Hg by metoprolol plus placebo and to 116/61 mm Hg by metoprolol plus chlorthalidone. Again the reduction in blood pressure was significantly greater with combined treatment (p less than 0.001) than with metoprolol plus placebo. Once daily slow release metoprolol is effective in controlling blood pressure, but this effect is greatly enhanced by the addition of a diuretic.

Adult↗
PubMed1983

Is the statistical assessment of papers submitted to the "British Medical Journal" effective?

A study was performed to judge the effectiveness of the statistical assessment scheme for papers submitted to the "British Medical Journal." Statistical criticism of the content of 200 submitted papers which had already been seen by a subject referee led directly or indirectly to 73 (37%) being rejected for publication. In most cases (53 out of 73) serious problems requiring more than minor revision were identified. A comparison of reports on subsequently unpublished and published papers showed that adverse statistical assessments--suggesting major problems--were more common in the papers that were not accepted for publication. Moderate, or less, revision was recommended for 63% of published papers but 39% of the remainder. A checklist of relevant questions was used in making a detailed comparison of 12 published papers, six of which had been statistically assessed and six of which had not. This comparison yielded little evidence that the papers that had been assessed were statistically more acceptable than those that had not been assessed but re-emphasised the subjectivity of refereeing and assessment.

Periodicals as Topic↗
PubMed1983

The effects of oxprenolol on ambulatory intra-arterial blood pressure in essential hypertension.

Continuous intra-arterial blood pressure recording using the "Oxford" technique has been used to study the antihypertensive effects of oxprenolol taken three times daily in fully ambulatory patients with essential hypertension, outside hospital. During the first 24 h of treatment there was a reduction in daytime heart rate and a small reduction in daytime blood pressure. After 10 weeks treatment there was a more substantial fall in daytime blood pressure from the hour of waking, but no effect on sleeping nighttime blood pressure or heart rate. Twenty-four hour variation, as assessed by the amplitude of a fitted regression curve, showed a reduction in heart rate but not blood pressure variation. In 4 patients restudied after 11 weeks treatment with oxprenolol (tid) and cyclopenthiazide at 9 a.m. there was some evidence of an antihypertensive effect occurring during both the daytime and nighttime.

Adult↗
PubMed1983

Serum immunoglobulin concentrations in preschool children measured by laser nephelometry: reference ranges for IgG, IgA, IgM.

Serum immunoglobulin concentrations were determined on sera from 298 healthy children aged six months to six years using the Hyland laser nephelometer PDQ system. Age-specific 95% reference ranges for serum IgG, IgA and IgM are presented; considerable care has been taken to ensure statistical validity of the reference ranges. The wide range of values in children under two years suggest that measuring immunoglobulin concentrations in this age group is of little value in diagnosing immunodeficiency.

Aging↗
PubMed1983

Circadian variation of blood pressure in autonomic failure.

We have monitored ambulant intra-arterial blood pressure with the Oxford system in six subjects with autonomic failure who exhibited postural hypotension. Plotting pooled hourly mean values we have demonstrated a consistent circadian trend in blood pressure that was the inverse of the normal pattern, with the highest pressures at night and the lowest in the morning. In four subjects, confinement to bed did not substantially alter this pattern. Heart rate variability was much reduced in four of the subjects, but relatively normal in two in whom blood pressure variation was also less abnormal. There was a correlation of the nadir of the blood pressure measurements with the reported time of peak incidence of orthostatic symptoms. These findings are of importance in both the management and physiologic testing of patients with this condition.

Adult↗
PubMed1982

Assessment of the accuracy and role of self-recorded blood pressures in the management of hypertension.

Self-recording of the blood pressure by patients away from hospital or office ("home blood pressure") has been advocated as providing a better estimate of "true" blood pressure. The reliability of home blood-pressure recording has been assessed only by standard indirect methods which themselves are subject to considerable error and variability. The accuracy of self-recorded blood pressures was therefore assessed in 57 patients with essential hypertension by comparison with simultaneous measurements of clinic blood pressures and with intra-arterial blood pressures recorded at home and at hospital. Home systolic blood pressures showed good agreement with clinic and intra-arterial pressures, but home diastolic blood pressures overestimated intra-arterial pressures, as did clinic diastolic pressures. The clinic and home diastolic pressures showed good agreement. There was considerable variability in individual differences comparing the indirect and intra-arterial methods, though the two indirect methods showed much closer agreement. This study suggests that home blood pressures are as accurate as clinic readings but may be recorded more frequently and thus provide more useful information. Neither is likely to approximate the intra-arterial blood pressure.

Adult↗
PubMed1981

Can placebo therapy influence arterial blood pressure?

1. With standard sphygmomanometric techniques used in conjunction with continuous intra-arterial monitoring the antihypertensive effect of placebo was examined in a group of patients participating in a controlled clinical trial. 2. Twelve of the 20 patients entered completed all stages of a randomized double-blind controlled trial of placebo and indoramin. Clinic blood pressure in patients receiving placebo showed reductions which were highly significant (P less than 0.001). Simultaneous intra-arterial monitoring showed no reduction of the blood pressure over the 24 h studied. 3. The clinic pressures showed minimal reduction of blood pressure in response to indoramin therapy whereas intra-arterial pressures showed a significant fall (P less than 0.01). 4. The response of the blood pressure to placebo appears to be an artifact of the indirect sphygmomanometric method and its use as a control in this study led to under-estimation of the efficacy of indoramin.

Double-Blind Method↗
PubMed1981

The effect of genital mycoplasmas on human fetal growth.

The relation between maternal genital colonization by mycoplasmas and fetal growth was examined in a study of 195 women. Swabs were taken from the endocervix on three occasions during pregnancy and once post partum. Ureaplasma urealyticum organisms (ureaplasmas) were recovered from 42.7 per cent of Caucasian women and from 34.6 per cent of Asian women at their first antenatal visit. These isolation rates remained similar throughout pregnancy, although there was a decrease in isolation after delivery. Mycoplasma hominis was recovered from 6.5 per cent of Caucasians and from 11.5 per cent of Asians at their first antenatal visit and these rates remained fairly constant during pregnancy and after delivery. Caucasian women colonized by ureaplasmas had a longer mean length of gestation (p less than 0.025) than non-colonized women. Furthermore, the colonized women gave birth to infants who had a statistically significant greater mean birth weight and a greater mean birth weight-for-dates than those of the non-colonized Caucasians. There was no correlation between gestational length, birth weight, or birth weight-for-dates and genital colonization of Asian mothers by ureaplasmas or M. hominis. It is clear the ureaplasmas are not associated with low birth weight in our population.

Asia↗