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Biomedical subjects

G A Harshfield

Publications and source records attributed to G A Harshfield.

47 records · Page 3Linked to original sources
PubMed1983

Foil electret transducer for blood pressure monitoring.

A foil electret microphone for use under the cuff of an automatic blood pressure monitoring system is described. The transducer is designed to operate with relatively flat sensitivity over a static pressure range of 40 to 250 mm Hg (5.33 X 10(4) to 3.33 X 10(5) dyn/cm2). The new electret microphone differs from conventional microphones used for airborne sound reception in two ways: (1) the diaphragm thickness is 50 micron rather than the typical 12.5 or 25 micron, and (2) the backplate contains a set of annular ridges spaced at 4 mm rather than the typical 7-10 mm. This microphone offers three advantages over the piezoelectric microphone now in use: (1) greater tolerance in positioning the microphone over the brachial artery, (2) nearly 20-dB higher sensitivity and signal-to-noise ratio, and (3) the ability to obtain measurements with the microphone placed midway between the elbow and shoulder. Tests of the new foil electret microphone in conjunction with the automatic blood pressure monitoring system indicate that the automatic and conventional measurements of systolic and diastolic blood pressure agree to within 5 mm Hg at least 90% of the time. In addition, the electret microphone is able to obtain automatic measurements on subjects with a wider range of ages and sizes.

Acoustics↗
PubMed1982

Blood pressure during normal daily activities, sleep, and exercise. Comparison of values in normal and hypertensive subjects.

Blood pressure (BP) readings were taken every 15 minutes using a noninvasive ambulatory BP recorder during 24 hours in 25 subjects with normal BP, 25 with borderline hypertension, and 25 with established essential hypertension. Readings were analyzed for four situations: (1) physician's office, (2) work, (3) at home, and (4) asleep. Treadmill exercise tests were also performed on a separate occasion with the Bruce protocol. The 24-hour recording in all three groups showed the highest BPs at work and the lowest during sleep. The situational BP changes were generally similar, but both hypertensive groups differed from normal subjects in that they showed consistently higher BPs in the physician's office than at home, whereas normal subjects showed a similar rise of systolic pressure to that of normal subjects. Pressures recorded in the physician's office gave good predictions of the average 24-hour pressure in normal and established hypertensive subjects, but not in the borderline group; in such patients, 24-hour monitoring may be of particular value in establishing the need for treatment.

Adult↗
PubMed1982

Situational variations of blood pressure in ambulatory hypertensive patients.

Blood pressure and heart rate were recorded at 15-min intervals for 24 hr in 60 untreated patients with uncomplicated mild essential hypertension using a new automatic noninvasive portable recorder. During the recording, the patients went about their normal daily routine, of which they kept a detailed record. The data were analyzed for five different recording situations: in the clinic, at work, at home, asleep, and average of the entire 24-hr period. Twenty-four hour readings were also compared with previously obtained casual readings. Clinic readings were correlated with the average 24-hr values, but for individual patients clinic pressures were relatively poor predictors of 24-hr pressures. Pressures recorded in the clinic were also greater than average 24-hr values. Similar degrees of correlation were found between clinic, home, work, and sleep pressures. Pressures recorded in the clinic were similar to pressures at work but higher than at home or asleep. In contrast, heart rate was similar in all conditions except during sleep, when it was lower. Previously measured casual pressures were also correlated with the clinic readings, with systolic values being similar, but diastolic values higher in the clinic during the 24-hr recording. For patients with clinic diastolic pressures in the range 90-104 mm Hg, 24-hr pressures varied from 75 to 100 mm Hg. We conclude that pressures measured casually in the clinic do not accurately reflect average 24-hr pressures and that ambulatory recording is helpful in the evaluation of mildly hypertensive patients.

Adult↗
PubMed1982

Ambulatory monitoring in the evaluation of blood pressure in patients with borderline hypertension and the role of the defense reflex.

The differences between blood pressure (BP) readings taken in the clinic and during normal daily activities were assessed in two studies using a noninvasive ambulatory BP monitor (Avionics). In the first study 30 untreated hypertensive patients (17 with borderline pressures, average diastolic less than or equal to 95, and 13 established hypertensives, diastolics above 95) and 5 normotensive subjects had 30 readings taken in the physician's office and 30 while at home. Conventional sphygmomanometer BPs were also recorded in the office. In the borderline group home BPs were significantly lower than clinic BPs, whereas this difference was less marked for the established and normotensive group. In the second study BP was measured every 15 minutes for 24 hours in 25 normal subjects, 25 borderline and 25 established hypertensives, and readings categorized according to four recording situations: physician's office, work, at home, and sleep. BPs in all groups were highest at work and lowest asleep, and directional changes were similar. Both hypertensive groups showed higher BPs in the physician's office than at home, while normal subjects showed no difference. BPs recorded in the physician's office were good predictors of 24 hour average BP in normal and established hypertensive subjects, but not in the borderline group: in such patients 24 hour monitoring may be of particular value in evaluating the need for treatment.

Adolescent↗
PubMed1979

Development of individual differences of cardiovascular regulation in the Bailey recombinant inbred mice.

Previous research has demonstrated that the cardiovascular system (CVS) is not completely developed in the rat until 20 days of age. Prior to this age the sympathetic nervous system (SNS) is dominant during resting conditions and the stress response is vagally mediated, which is the opposite of most adult rats. In the present research, using the Bailey recombinant inbred strains and their progenitor strains (C57BL/6By and BALB/cBy), we determined the developmental period for the CVS in mice. The CVS was controlled by a high SNS tone and the stress response was vagally mediated at 8 days of age. By 12 days of age, the mice had much slower baseline heart rates which were vagally controlled. Significant strain differences were also found with a polygenic model accounting for these differences. The stress response of the 12-day-old mice was not interpretable because of individual differences in the adult coping strategies. These differences were accounted for by a different polygenic model than was found in the baseline condition.

Analysis of Variance↗
PubMedDate not supplied

Psychologic differences between high-, normal-, and low-renin hypertensives.

Sixty-one male subjects with mild untreated essential hypertension were classified by renin-sodium profiling as high renin (HR--13 Subjects), normal renin (NR--33 Subjects), or low renin (LR--15 Subjects). The HR subjects reported significantly more symptoms of sensitivity, depression, anxiety, hostility, paranoia, and psychotic thought than LR subjects on the Symptom Checklist (SCL-90). The NR subjects also reported more symptomatology than LR subjects. Similar differences between HR and LR subjects were found with the Cattell 16 Personality Factor Questionnaire (16PF).

Adult↗
PubMedDate not supplied

The influence of happiness, anger, and anxiety on the blood pressure of borderline hypertensives.

Differences in blood pressure associated with reported happiness, anger, and anxiety are examined among 90 borderline hypertensives during 24-hr blood pressure monitoring. There were 1152 individual ambulatory blood pressure readings for which subjects classified their emotional state as happy (n = 628), angry (n = 67), or anxious (n = 457) on scales from one (low) to ten (high). Pressures were transformed to z-scores using the subject's 24-hr mean and standard deviation to assess relative elevation during reported emotional arousal. The results show that emotional arousal significantly increases systolic and diastolic pressure (p less than 0.00001), an effect independent of posture and location of subject during measurement (at work, home, or elsewhere). On average, pressures during reported angry or anxious states were higher than those during a happy state (p less than 0.01). Examination of arousal intensity showed that scores on the happiness scale were inversely related to systolic pressure (p less than 0.01) whereas the degree of anxiety was positively associated with diastolic pressure (p less than 0.02). Emotional effects were also related to the degree of individual daily pressure variation such that the greater the variability, the larger the blood pressure change associated with the emotions. The results suggest that happiness, anger, and anxiety increase blood pressure to differing degrees and that emotional effects may be greater in individuals with more labile blood pressure.

Adolescent↗
PubMedDate not supplied

What is the value of home blood pressure measurement in patients with mild hypertension?

To investigate the value of home blood pressure (BP) measurements, the BP was recorded daily by the patient at home and compared with recordings in the physician's office and with a 24-hour BP recording taken with a noninvasive ambulatory BP recorder in a group of 93 patients with mild untreated hypertension. Office BPs (mean 148/94 mm Hg) were higher than either home (138/89 mm Hg) or average 24-hour BPs (131/89 mm Hg). For systolic BP, home and office measurements gave similar correlations with 24-hour BP (0.67 and 0.55). For diastolic BP, however, home readings were lower and more accurate (0.76 vs 0.36). Thus, our findings indicate that home readings reflect the overall level of BP more reliably than office readings, and if due consideration is given to the fact that they are usually lower than office readings, they may be used as an alternative and cost-effective means of evaluating patients with mild hypertension.

Adolescent↗
PubMedDate not supplied

What is the role of ambulatory blood pressure monitoring in the management of hypertensive patients?

Noninvasive ambulatory blood pressure (BP) recording is now clinically available for the evaluation of hypertensive patients. It is well known that pressures measured in the office or clinic are unreliable and that repeated measurements are better at predicting outcome than are single measurements. Several studies have compared the correlation between target organ damage and different measures of BP, and in every instance ambulatory BP measurements have given better correlations than clinic readings. In one prospective study the ambulatory BP readings were more predictive of BP-related morbidity than were clinic readings. Data are now being obtained that will establish normal ranges of BP during ambulatory monitoring, against which values from patients being evaluated for hypertension can be compared. It is concluded that ambulatory BP monitoring is of clinical value for the evaluation of patients with mild hypertension.

Adult↗
PubMedDate not supplied

Racial differences in ambulatory blood pressure monitoring-derived 24 h patterns of blood pressure in adolescents.

BACKGROUND: Many pathologic conditions are characterized by a blunted nocturnal decline in blood pressure. OBJECTIVE: To review the evidence that African Americans display a similar pattern and examine factors associated with the pattern. METHOD: We reviewed published racial comparisons of patterns of ambulatory blood pressure in adults and youths. RESULTS: Authors of 15 studies reported finding blunted nocturnal declines in African Americans and authors of two studies did not. Authors of studies of Africans in Africa and of blacks from other countries reported normal nocturnal declines. Both intake of sodium and indexes of body size have been related to nocturnal blood pressure in African-American youths. This pattern is related to greater than normal target-organ changes. CONCLUSION: ; We conclude that the race of a patient should be considered when evaluating a 24h pattern of blood pressure in an adolescent; and the blunted nocturnal decline displayed by many African-American adolescents is the result of a gene-environment interaction and therefore is susceptible to modification through changes in diet, level of activity, and other environmental factors.

Adolescent↗