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Biomedical subjects

B T Engel

Publications and source records attributed to B T Engel.

At least 19 recordsLinked to original sources
PubMed1992

Overnight increases in haematocrit: additional evidence for a nocturnal fall in plasma volume.

Our previously published studies with monkeys describe a characteristic nocturnal haemodynamic pattern consisting of a monotonic decline in cardiac output and central venous pressure, and a concomitant rise in total peripheral resistance. These findings led us to hypothesize that there is a reduction in total plasma volume during the night. Since a fall in plasma volume should cause an increase in haemoglobin and plasma protein concentration, we designed this experiment to test the hypothesis that haematocrit levels would be significantly greater in the morning than in the evening. In a study of five monkeys, the levels of haematocrit were measured at 1700 h and at 0900 h the next morning for 14 days. The average morning haematocrit levels were 6.5% higher than the average evening values. Lower plasma volume and possibly greater blood viscosity could contribute to the pathophysiology of the morning increase in the incidence of 'silent' ischaemia and catastrophic vascular events such as sudden cardiac death, myocardial infarctions and strokes in man.

Animals↗
PubMed1992

Effect of nocturnal atrial demand cardiac pacing on diurnal hemodynamic patterns.

Heart rate (HR), stroke volume (SV), intra-arterial blood pressure, and central venous pressure were recorded on a beat-to-beat basis, 18 h/day (1800-1200 h the following day), for approximately 2 mo in four monkeys (Macaca mulatta). Cardiac output, left ventricular work, and total peripheral resistance were derived from these primary measurements. During the 1st mo we measured these parameters under control conditions, and during the 2nd mo the animals were studied while HR was paced by atrial demand pacing sufficient to prevent the normal nocturnal fall in HR (approximately 10 beats/min above the fastest hourly average rate recorded during the control condition). The main hypothesis of this study was that when HR is prevented from falling, SV, which normally does not fall overnight, would fall; this hypothesis was confirmed. In addition, we observed that, during the period of pacing, relative to the control period, SV was approximately 14% greater during the early evening and 4% lower during the early morning; total peripheral resistance was similar during the early evening but was 13% higher by morning. Throughout the night, systolic pressure was approximately 4% greater, diastolic pressure was 17% higher, central venous pressure was 43% greater, and left ventricular work was 27% higher. These findings show that when HR is prevented from falling overnight by atrial demand pacing, even to a relatively modest degree, there can be very significant sustained changes in cardiovascular function.

Animals↗
PubMed1992

Systematic nocturnal atrial demand pacing results in high-output heart failure.

Beat-to-beat parameters of heart rate (HR), intra-arterial blood pressure (BP), central venous pressure, and derived indexes of cardiac output and total peripheral resistance were recorded 18 h/day (from 1800 to 1200 h the following day) in four monkeys (Macaca mulatta) during 20 control days followed by 20 days of atrial demand pacing. The pacing rate was set at approximately 10 beats/min above the fastest hourly average HR recorded during the control period, i.e., sufficient to prevent the normal nocturnal fall in HR. Nocturnal pacing resulted in progressive weekly increases in central venous BP and arterial BP. Analyses of levels and diurnal trends in hemodynamic parameters and cardiac function curves across consecutive 5-day periods of nocturnal pacing revealed a hemodynamic pattern characteristic of high-output heart failure, which progressively increased (week by week) during the early morning hours (0500-0700). Sustained elevated left ventricular work resulting from the prevention of a nocturnal fall in HR may have been responsible for the reduction in cardiac function seen in this experimental model.

Animals↗
PubMed1992

Responses of sympathetic nerves innervating blood vessels in interscapular, brown adipose tissue and skin during cold stimulation in anesthetized C57BL/6J mice.

The effect of cold stimulation on the activity of sympathetic nerves running along blood vessels in interscapular, brown adipose tissues (IBAT) and skin overlying IBAT was examined in 15, urethane-anesthetized, artificially ventilated, C57BL/6J mice. Cold stimulation was applied caudal to the pelvic area using a plastic bag containing iced water. The stimulation of 14-16 min duration reduced core temperature measured at the esophagus or muscle near the esophagus by approximately 4 degrees C from a control temperature of about 38 degrees C. The stimulation decreased the activity of the nerve branches to IBAT, while it increased the activity of the nerve branches to skin. Blood flow in the IBAT increased significantly following the stimulation; however, this effect was abolished by the denervation. These findings suggest that the sympathetic innervation of the blood vessels in the IBAT plays a major role in thermoregulation against cold by decreasing the vascular tone and thus increasing the IBAT blood flow. An increase in the IBAT blood flow would facilitate the dissipation of heat from the IBAT to various organs as well as the supply of energy stuffs to the IBAT.

Adipose Tissue, Brown↗
PubMed1992

Urinary incontinence: an augmented prompted void approach.

Continence improves from 44.7% dryness at baseline to 54.7% at the end of treatment, an improvement of 22%, or about one incontinent episode per day. Urinary incontinence is improved in cognitively impaired residents by augmenting the prompted voiding procedure with a bellpad. Bladder behavior changes with behavioral treatment strategies, because the volume voided into an appropriate receptacle increased an average of 26 mL per 2 hours. Reimbursement policies should not exclude treatment of the severely cognitively impaired nor the immobile in nursing homes.

Adult↗
PubMed1991

Autonomic blockade does not prevent learned heart rate attenuation during exercise.

Each of three monkeys was operantly conditioned to slow its heart, to exercise (lift weights) and to attenuate the tachycardia of exercise by combining these two skills. Each was further tested during beta-adrenergic blockade (atenolol), combined alpha-adrenergic blockade (prazosin) and beta-adrenergic blockade, or cholinergic blockade (methylatropine). During all experiments heart rate, stroke volume, intraarterial blood pressure, O2 consumption, and CO2 production were recorded on a beat-to-beat basis. Each animal was able to attenuate the tachycardia of exercise under each of the drug conditions, indicating that "central command" is not the expression of fixed, cardiovascular and pulmonary reflexes elicited by somato-motor commands, but rather is an adaptive behavior, determined by environmental contingencies and mediated by cardiovascular and pulmonary as well as somato-motor commands. The ability of the animals to perform with greater cardiac efficiency during the combined exercise and heart rate slowing task relative to the exercise-only task was not affected by sympathetic blockade; however, parasympathetic blockade did reduce cardiac efficiency.

Animals↗
PubMed1991

Cold tolerance and metabolic heat production in male C57BL/6J mice at different times of day.

Nine-month-old male C57BL/6J mice were subjected to three-hour cold stress tests (partial restraint at 6 degrees C) at 9:00 a.m. or at 1:00 p.m. Tests were repeated three times at two-week intervals at the same time of day. Body temperature was measured by colonic thermoprobe, and metabolic heat production was measured by indirect calorimetry during each test. All mice showed habituation to repeated cold exposures (an improvement of cold tolerance across tests) due to an increase in metabolic heat production. The levels of metabolic heat production were similar during morning and afternoon testing; however, mice tested in the afternoon had consistently poorer cold tolerance, which indicated increased heat loss. Increased heat loss in mice of similar body weight and presumably similar body composition, suggests that there is less effective cold-induced skin vasoconstriction during the afternoon. We hypothesize that the compromised skin vasomotor response during the afternoon cold exposure results from competing effects of vasodilation due to local autoregulation stimulated by a circadian reduction of cardiac output during the sleep phase, and vasoconstriction due to the cold stress.

Animals↗
PubMed1991

Prevalence, incidence and correlates of urinary incontinence in healthy, middle-aged women.

The prevalence, incidence and correlates of urinary incontinence were studied in a community-based sample of 541 healthy, middle-aged women 42 to 50 years old. Participants were evaluated on 2 occasions approximately 3 years apart. Of the participants 58% reported urine loss at some time and 30.7% reported incontinence on a regular basis at least once per month. During 3 years the cumulative incidence of regular incontinence in previously continent women was 8.0%. Among those with regular incontinence 64.9% said the volume of loss was 1 or 2 drops, while 35.1% reported that they needed to change their garments. Only 25.5% of the patients had sought treatment. Continence status was significantly related to body mass index and race but not to patient age, parity, caffeine or alcohol intake, smoking, physical activity, prior gynecological surgery or several psychological variables. The results indicate that urinary incontinence is common among middle-aged women. That few seek treatment suggests a need for more information about women's attitudes toward incontinence and more attention to this problem by health care providers.

Adult↗
PubMed1991

Normative patterns of diurnal urination across 6 age decades.

The patterns and frequency of diurnal urination were studied in 412 male and 244 female participants in the Baltimore Longitudinal Study of Aging. Men urinated less often (mean 4.8 voids per day) than women (mean 5.6 voids per day). There was no main effect for age decade. However, an age by sex interaction showed that voiding in men increased across the decades and in women it decreased. The highest frequency was found in women in their 30s (mean 6.2) and the lowest was in men in their 30s (mean 4.3). Men and women in the 70 and older age group had the same voiding frequency (mean 5.0). In men frequency of urination was related to benign prostatic enlargement and 2 of 4 symptoms of urinary obstruction (change in the force of the urinary stream and having to urinate again shortly after voiding). In women frequency was related negatively to a history of pregnancy complications but not to parity. In both sexes frequency was unrelated to the reported daily ingestion of coffee, tea or diuretics, and no relationships were found with a history of an anxiety disorder.

Adult↗
PubMed1991

Hemodynamic and respiratory concomitants of learned heart rate control during exercise.

Each of three monkeys was trained to slow its heart, to exercise (lift weights), and to attenuate the tachycardia of exercise by combining these two skills. During all experiments, heart rate, stroke volume, intra-arterial blood pressure, O2 consumption, and CO2 production were recorded on a beat-to-beat basis. All animals reliably attenuated the tachycardia of exercise, indicating that this expression of central command is, at least in part, a learned motor skill. Double-product (heart rate X systolic pressure) was attenuated during combined sessions relative to exercise only sessions, and heart rate was always lower at similar levels of cardiac output, indicating that under the combined conditions, animals were performing with better cardiac efficiency at comparable levels of mechanical effort. Analyses of O2 consumption, CO2 production, and respiratory quotient (the ratio of CO2 production to O2 consumption) suggested that the animals also might have been delivering more O2 to their working muscles during combined sessions.

Animals↗
PubMed1991

Diurnal variations in central venous pressure.

We analysed the haemodynamic patterns of seven monkeys (Macaca mulatta) during a one-month period during which we monitored beat-to-beat levels of heart rate, stroke volume, intra-arterial pressure and central venous pressure 7 days/week, 18 h/day. We replicated an earlier finding that cardiac output falls and total peripheral resistance rises throughout the night: the fall in cardiac output was mediated by a fall in heart rate since stroke volume did not change; and the rise in peripheral resistance reflected a homeostatic adjustment to the fall in cardiac output since blood pressure was stable throughout the night although it fell early in the evening. In addition, we have shown for the first time that central venous pressure also falls throughout the night; this occurs even in the presence of alpha- and beta-adrenergic sympathetic blockade. Since stroke volume does not change overnight this indicates that the nocturnal fall in cardiac output is not due to a shift of blood volume into the venous compartment. These findings support our hypothesis that there is a nocturnal decline in plasma volume.

Animals↗
PubMed1991

Assessing toileting skills and habits in an adult day care center.

In a structured assessment of mobility and toileting skills, all the continent clients but only 46.2% of incontinent clients were able to toilet themselves, even with verbal and physical guidance. Unobtrusive observation of toileting habits indicated that incontinent clients used the toilet less often than continent clients and used more staff assistance to do so. On mental status examination, incontinent clients scored significantly lower than continent clients. Incontinence in this population is a multidimensional disorder in which physical disability is a predominant factor.

Aged↗
PubMed1991

Cardiovascular responses as behavior.

Exercise is a ubiquitous, biologically and clinically significant behavior. Although the somatomotor responses are generally regarded as "behavior," the cardiovascular adjustments that accompany these responses are generally considered to be reflexes that are elicited by neurally mediated stimuli and metabolites arising from working muscles. We report experimental evidence that monkeys can be trained to exercise, to slow heart rate, and to combine these two skills. Furthermore, some animals will emit more physical work at slower heart rates (at comparable levels of cardiac output) and lower left ventricular work during the combined condition relative to an exercise-only condition. Thus, these findings show that the cardiovascular and somatomotor responses of exercise can be dissociated and that both sets of responses should be considered behaviors. Also included are results that show these animals can perform these behaviors during sympathetic or vagal blockade. These findings are further evidence that the cardiovascular adjustments to exercise are, in part, learned behaviors because they show that the behavior--attenuation of the tachycardia of exercise--is not a reflex that is specifically tied to any neuroeffector system; rather, this behavior is emitted to achieve a contingent reward, and the nervous system will use whatever mechanisms are available to attain that consequence.

Animals↗
PubMed1990

Nocturnal hemodynamic patterns in dogs.

Several species which have a single daily wake-sleep cycle show a progressive fall in cardiac output and rise in total peripheral resistance during sleep, a cardiovascular response which may reflect a progressive decrease in plasma volume. The present study showed that no such progressive overnight changes in cardiac output or total peripheral resistance occur in the dog, a carnivore which tends to be awake and to drink intermittently during the night. Progressive overnight bradycardia (-12.7 +/- 3.1%) and compensatory increase in stroke volume (14.8 +/- 6.0%) were observed in this species, however. These findings are consistent with the view that differences between primates and carnivores in overnight hemodynamic function are related to species differences in sleep and ingestive behavior.

Animals↗
PubMed1990

Cost-effectiveness of treating incontinence in severely mobility-impaired long term care residents.

Severely mobility-impaired residents in long term care facilities are usually incontinent. The incontinence and immobility predispose this group to decubitus ulcers and urinary tract infections that have been described as adding to the "consequence costs of incontinence" of $80 million per year. In this quasi-experimental study of ten subjects, a mechanical lift (Clinilift) was used with a two-hour schedule to improve incontinence. Subjects showed improvement in not only dryness but also volume of urine voided and the frequency of decubitus ulcers and UTIs. Because this incontinence treatment is labor intensive, the costs of treating incontinence increased by $2.90 over the cost of providing incontinent care. When the costs of decubitus ulcers and urinary tract infections are considered, however, the treatment savings were $13.38 per patient per day.

Activities of Daily Living↗
PubMed1990

A descriptive analysis of nursing staff behaviors in a teaching nursing home: differences among NAs, LPNs, and RNs.

Various staff behaviors in a nursing home were sampled seven times a day, 5 days a week over 37 months and were coded separately for LPNs, RNs, and NAs. The behavior most frequently observed was patient care, which occurred during 56.9% of the samples. We observed staff interacting with patients during 10.7% and with other staff during 19.5% of the samples. The LPNs displayed significantly more patient care behaviors and NAs significantly more nonwork behaviors than other nursing staff. RNs displayed the least nonwork behavior. We conclude that nursing staff devote most of their time to patient needs and relatively little time to nonproductive activities.

Behavior↗