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Biomedical subjects

M A Frey

Publications and source records attributed to M A Frey.

52 records · Page 3Linked to original sources
PubMed1981

A new ventricular-performance variable using electrocardiogram and carotid pulse contour derivative.

The pre-ejection period (PEP) of systole is a widely used, non-invasive index of ventricular performance. For precise measurements, simultaneous recordings are required from which the Q-wave on the electrocardiogram, second heart sound on the phonocardiogram, and upstroke and incisura of the carotid pulse contour are discretely identifiable and temporally accurate. This is frequently difficult to accomplish. We, therefore, have compared 2 other noninvasive indices of ventricular performance for correlation with PEP in 17 female and 18 male subjects while supine and during head-up tilt. We also examined similarity of these indices to PEP in correlations with heart rate and blood pressure and compared them for ease in monitoring and precision in measurement. The ratio of the peak amplitude of the carotid pulse contour derivative to its total amplitude (DAR) is easier to monitor and more reliably measured than PEP; however, it is poorly correlated with PEP. Time from electrocardiographic Q-wave to peak dD/dt (Q-MAX) is also easier to monitor and somewhat more reliably measured than PEP. Although correlations of PEP and Q-MAZ with subject age are dissimilar, Q-MAX is correlated with PEP in supine and tilted subjects; the 2 variables are similarly correlated with heart rate and arterial pressure; and in 6 subjects both variables were prolonged after intravenous administration of propranolol-hydrochloride. We, therefore, propose Q-MAX as an alternative measure of ventricular performance.

Adolescent↗
PubMed1981

Influence of respiration on stroke volume determined by impedance cardiography.

The conventional method of calculating stroke volume (SV) with impedance has been to measure changes in thoracic impedance for only those beats of the impedance cardiogram (IC) which cross on a specific baseline. This severely limits the number of usable beats since respiration produces oscillation of the IC around this baseline. This study investigated the influence of respiration on SV calculated independent of the baseline in seven women, 20-44 years old, in each of three postures: seated, supine, and standing. SV was determined in three continuous respiratory cycles from the following beats: 1. all; 2. all inspiratory (I); 3. I on baseline; 4. all expiratory (E); 5. E on baseline; 6. all end-E; 7. end-E on baseline (conventional). The absolute values for SV, heart rate (HR), and cardiac output (Q) were posture dependent. SVs did not differ among the respiratory phases in the standing and seated postures; in the supine posture, the smallest SV occurred at end-E on baseline. HR varied with respiration in both the standing and seated postures but not in the supine posture. Despite significant changes in HR in the seated and standing postures, Qs did not differ among the respiratory phases. Supine Qs were significantly smaller during end-E due primarily to a small SV. Consequently, when reporting Q values for supine subjects, it is important to designate the respiratory phase and baseline criteria. Our results indicate that SVs calculated independent of the baseline in general agree with the more conventional method of calculation. Therefore, we recommend the calculation of SV independent of the baseline. The reliability of the data will be increased by increasing the number of observations and SVs can be determined under circumstances where it is difficult to obtain end-E beats on the baseline.

Adult↗
PubMed1980

Cardiovascular response to cooling of limbs determined by noninvasive methods.

Cold, even local exposure to a limited portion of the body, is a stress to man which elevates arterial pressure, thereby intensifying cardiac workload. The sequence of cardiac events following local cooling was noninvasively studied by observation of changes in cardiac interval, left ventricular ejection time, time from A wave of electrocardiogram to the peak of the dD/dt of the carotid pulse wave (which includes pre-ejection period), and amplitude of the pulse wave from a photoelectric cell on the earlobe, along with arterial pressures. Twelve subjects, aged 22--41 years, exposed a hand or foot to cold water for 1 min while seated and while supine (four experiements each). Results indicate that arterial pressure is monotonically elevated throughout the minute of exposure. Cardiac intervals are initially abbreviated, then return towards control. This may include an initial response to the cold, followed by a baroreflex at the heart. Subject posture and limb exposed also affect cardiac responses.

Adult↗
PubMed1980

Effect of a controlled exercise program on serum lipoprotein levels in women on oral contraceptives.

The effects of a 10-wk individualized bicycle ergometer interval training program were investigated in a group of 13 sedentary women on a specific oral contraceptive (50 micrograms mestranol, 1 mg norethisterone) to determine if, like men on physical training, their high-density lipoprotein cholesterol levels would increase. Six additional women on the oral contraceptive served as a nonexercising control group. All subjects were between 18 and 30 yr and were nonsmokers. Diet and alcohol intake were stable throughout the study period, and were monitored throughout. The interval training program was three times per week, 30-min exercise per session, at 70% maximum heart rate reserve (resting heart rate + 0.7 x [maximum heart rate-resting heart rate]). Training produced increases (p < 0.05) in maximum oxygen uptake. Body weight was unchanged. However, unlike similar training programs with males, there were no significant changes in plasma high-density lipoprotein cholesterol or triglycerides. In women receiving estrogen progestin oral contraceptives, consistent exercise programs may fail to elevate high density lipoprotein cholesterol levels, consistent with an interaction of sex hormone-exercise effects and/or with the less marked effect of exercise on high-density lipoprotein cholesterol in women.

Adult↗
PubMed1980

Reflex cardiovascular responses to cold exposure of the face or foot.

Six subjects performed a breathholding maneuver during facial cooling and immersed their foot in cold water, without drugs and after the intravenous administration of propranolol plus atropine (P + A). Cardiac interval (INT), mean interval for longest consecutive 5 cycles (L5INT/5); systolic time intervals including electromechanical systole (EMS), left ventricular ejection time (LVET), pre-ejection period (PEP), and PEP/LVET; and systolic (SP) and diastolic pressures (DP) were monitored during supine rest, during apnea with a plastic bag of ice water on the face, and from 16-30th and 46-60th sec of 1-min periods of foot immersion in 4 degrees C water. P+A administration induced reduction in INT, L5INT/5, and LVET and increase in PEP, PEP/LVET, and DP. INT, L5INT/5, PEP, SP, and DP increased during facial cooling without drugs. Only the increases in INT and L5INT/5 were abolished by P+A and thus considered to result from reflexes mediated by vagal or sympathetic outflow to the heart. Reductions in INT, L5INT/5, EMS, PEP, and PEP/LVET at 16-30 sec of foot immersion without drugs were not observed after P+A; 46-60 sec responses neared resting values, however, with and without P+A. These results indicate an initial cardiac reflex response to foot immersion may be overpowered by the ventricular afterload and the foot immersion may be overpowered by the ventricular afterload and the baroreceptor response due to the increased arterial pressure.

Adult↗
PubMed1979

Systolic time intervals during combined hand cooling and head-up tilt.

Cardiac effects initiated by hand cooling and head-up tilt, separately and in combination, were studied in human subjects. Systolic and diastolic arterial pressures, heart rate, pre-ejection period (PEP), and left ventricular ejection time (LVET) were measured while subjects were resting supine, supine with hand immersed in 10 degrees C water, tilted 70 degrees head up, and hand immersed during head-up tilt. Hand immersion and head-up tilt individually increased diastolic blood pressure and concomitantly increased the duration of PEP. During the combined maneuver, the increase in diastolic pressure was greater than observed during either separate maneuver; however, the combined maneuver had no comparable summative effect on PEP prolongation. An interaction appears to occur during the combined maneuver which counteracts the Frank/Starling effect on PEP due to decreased venous return during head-up tilt.

Adult↗
PubMed1979

Cardiac response to whole-body heating.

Changes in ventricular function, as described by systolic time interval analysis, have been studied during heat stress and the time course of these changes, as well as changes in heart rate, have been investigated. Seven male and female subjects, 22-35 years of age, immersed their lower legs in water 42-44 degrees C for 30 min; their trunks and upper legs were enclosed in nonpermeable plastic to prevent evaporative heat loss. Total beat interval (R-R), left ventricular ejection time (LVET), pre-ejection period (PEP), arterial blood pressure, and oral temperature were monitored periodically during heating and recovery (post-hearing) periods. The stress induced significant (p less than 0.05) decreases in R-R and LVET by 5 min of heating which continued decreasing throughout the 30-min heating period. Heart rate accelerated from 72 up to 97 beats/min. LVET's during heat stress were shorter than those at similar resting heart rates. R-R and LVET were increased significantly by 1-min recovery but had not returned to preheating levels at 15 min. PEP, on the other hand, was not reduced until 15 min of heating, and did not start to recover until 3 min post-heating, after which it reached values exceeding control. A small increase in systolic blood pressure was maintained throughout heating and remained at 15 min recovery. Oral temperature increased approximately 1 degree C during the heating procedure; 50% of this was dissipated by 15 min recovery. Results are consistent with a two-stage cardiac response to heat-vagal withdrawal followed by a strong sympathetic outflow to the heart affecting both inotropic and chronotropic characteristics.

Adult↗
PubMed1979

Systolic time intervals and other cardiovascular changes following leg elevation.

Cardiovascular responses were noninvasively monitored as the legs of 16 supine human subjects were passively elevated to increase return of blood to the heart. Forearm vasodilation occurred promptly as previously observed by Roddie and Shepard (7). Arterial pressure and heart rate were unchanged. Ventricular performance, monitored by systolic-time-interval analysis, was enhanced after a delay of approximately 6 s, an effect which lasted throughout the 40-s leg-elevation period. All affected variables returned to control levels after the legs were lowered. This delayed response could result reflexly from stimulation of receptors in the left atrial region causing an increase in sympathetically mediated contractility or directly from the Frank-Starling mechanism in response to increased left ventricular filling.

Adult↗
PubMed1977

Changes in left ventricular activity during apnea and face immersion.

Apneic face immersion in water has been analyzed with respect to its effects upon heart rate and ventricular function in a group of highly trained teenaged swimmers of both sexes. Both parameters have been studied on a beat-by-beat basis throughout the maneuvers and analysis of the systolic time intervals has provided a noninvasive tool for studying changes in ventricular function. It was observed that the pre-ejection period of systole is lengthened, while left ventricular ejection time shows little change with apnea, face wetting (27 degrees C), or a combination of these. This decrease in ventricular function, however, lags behind the previously well-recognized decrease in heart rate, a difference which is particularly obvious when face immersion is performed in the postexercise state. This suggests ventricular function changes are regulated separately from heart rate changes and thus may be a secondary effect. Analysis of the face immersion reflex on a beat-by-beat basis has also revealed a more rapid development of bradycardia with colder (15 degrees C) water. A model has been developed to describe the face immersion reflex in the light of these findings and previous information.

Adolescent↗
PubMed1976

Semiautomated processing of systolic time intervals.

Systolic time intervals are commonly used to identify changes in ventricular function. The method described facilitates measurement and calculation of many such intervals. This method utilizes a printed polygraph recording of electrocardiogram, phonocardiogram, and carotid pulse contour; a digitizing device for reading the necessary coordinates from the record; and a minicomputer for calculation of the intervals and for data analysis. Intervals related to approximately 100 pulse beats can be read, calculated, printed in chart and graph form, and subjected to some analyses in about an hour.

Automation↗
PubMedDate not supplied

Assessing and teaching self-care to youths with diabetes mellitus.

PURPOSE: To investigate the nature of diabetes (health deviation) self-care in youths with IDDM and to relate diabetes self-care to metabolic control, perceived health status, and general (universal) self-care. METHOD: Thirty seven youths with IDDM between the ages of 11-19 completed the Diabetes Self-Care Practices Instrument, Denyes Self-Care Practice Instrument, and Denyes Health Status Instrument. Metabolic control was measured by glycosylated hemoglobin. Data were analyzed by correlational analysis. RESULTS: Diabetes self-care was positively related to general (universal) self-care, health status, and metabolic control. CONCLUSIONS: Results of the study provide clear direction for ongoing assessment and teaching of diabetes self-care in youths with IDDM.

Adolescent↗
PubMedDate not supplied

Blood pressure, electrolytes, and body size: their relationships in young relatives of men with essential hypertension.

In 154 white chldren aged 8 to 18 years from four large kindreds, relationships among blood pressure (BP), age, sex, body size, and electrolyte excretion were studied. Each kindred was ascertained through one male aged 35-58 years with essential hypertension, namely, a diastolic blood pressure (DBP) over 95 mm Hg. Weight, relative weight (relative to NCHS median for age, sex, and stature), subcutaneous fatfolds, various indices of obesity, and other measures of body size were significantly correlated with systolic blood pressure (SBP) and DBP in each sex (r = 0.3 to 0.7). Sodium and potassium excretion in 24-hour urine was also positively correlated with some measures of body size, and tended to increase with body size at a slightly more rapid rate in boys than in girls. In addition, there was a strong correlation between electrolyte excretion and BP in boys (r = 0.2 to 0.6); however, when the effects of age, body size and fatness were statistically removed, the correlations between BP and electrolyte excretion were not significant, except for 4th phase diastolic pressure (DBP4). These data, therefore, while not strongly supporting a relationship between sodium excretion and BP in children, do not rule out such a relationship, especially in families with a history of hypertension. In addition, these data provide further evidence of a very strong association between BP and body size and fatness in boys and girls.

Adolescent↗