Showing papers on "Heart rate variability published in 1983"

Circadian variation of blood pressure in autonomic failure.

Abstract: 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.

Autonomic activity and workload during learning of a simulated aircraft carrier landing task.

Abstract: Heart rate, heart rate variability, and skin conductance responses were continuously recorded from six naive males during learning of a simulated aircraft carrier landing task. There were 30 learning trials spanning more than 1 h. Over trials, heart rate decreased while flight performance increased, indicating that heart rate is sensitive to practice effects. Independent of practice, heart rate and skin conductance amplitude always increased during the last minute of final approach to landing. The results supported the following conclusions: (a) heart rate and skin conductance amplitude are reliable indicators of short-term workload increases as typified by final approach; (b) heart rate is a reliable indicator of longer term workload decreases resulting from practice and increased mastery of the task. Results are discussed within the framework of autonomic activation theory.

Cardiovascular Monitoring in Infants with Respiratory Distress Syndrome

Abstract: Heart rate, short-term heart rate variability, long-term heart rate variability (LTV), mean arterial blood pressure and R-to-pulse time were recorded in 28 infants during the acute phase of respiratory distress syndrome (RDS). The patients were classified by a clinical scoring system into three classes related to the severity of the disease. The LTV was initially significantly (p

Heart rate variability, cardiac mechanics, and subjectively evaluated stress during simulator flight

Abstract: The effects of a simulator flight task on the heart rate variation (HRV) and hemodynamic variables were studied in nine pilots with instrument flight ratings. An electrocardiogram (ECG), phonocardiogram (PCG), and impedance cardiogram (ICG) were recorded continuously during three successive flights. Indices of HRV, power spectra, and autocorrelograms were computed from the R-R interval signal. Stroke volume (SV), cardiac output (CO), and systolic time intervals (STI) were determined by means of the ECG, PCG, and ICG. A scaling method for a subjective evaluation of tiredness, effort, and success during the flight was used. The repeats of the flight task decreased the heart rate (HR), CO, and cardiac index (CI). The different phases of the flight altered the HR (mean 97 min-1, S.E.M. 4 min-1), total HRV (RMSM) (mean 33 ms, S.E.M. 5 ms), and the periodic HRV. Subjectively, the pilots felt only moderate stress. The subjectively evaluated tiredness was significantly associated with the STI. Moderate informative stress in the flight simulator affected the chronotropic parameters of the heart. The inotropic state of the heart was not affected by the different phases of the flight but possibly by the diminishing sympathetic drive with accommodation during the repeats. Language: en

Circadian changes in heart rate in unanesthetized normotensive and spontaneously hypertensive rats.

Abstract: Circadian changes in heart rate and heart rate variability were measured in spontaneously hypertensive (SHR) and normotensive (WKY) rats. Electrocardiograms (ECG) were continuously recorded, over a 24 hour period from freely moving conscious rats via three small metallic subcutaneous electrodes which were positioned a week before the recording period. The findings reported here show: 1/ Mean heart rate calculated over 24 hours were lower in both strains than previously reported. This difference probably reflects the lack of anesthesia and minimal stress in the present study. 2/ The timing of the circadian variations in both strains were the same, suggesting that were both entrained to the light-dark cycle. 3/ The 24 hours mean heart rate variability was significantly higher in SHR than in WKY but in each strain it was similar throughout the 24 hours. This suggests that the vagal tone in SHR was higher by a fairly constant amount throughout the light-dark cycle.

Microprocessor-based long term cardiorespirography. II. Status evaluation in term and premature newborns.

Abstract: In 1965 URBACH et al. and RUDOLPH et al. [35, 39] described a loss of heart rate variability in severely ill neonates. In this study we investigated the correlation between instantaneous heart rate patterns and status diagnosis. We used a microprocessor-based cardiorespirography system. Seventy five newborn infants (51 prematures and 24 term neonates) were studied for about 12 hours each. Twenty nine patients had a second record after the first investigation. Parameters were: Type of frequency and oscillation, long time variability (LTV), short time variability (STV) and the newly introduced P-value (maximal difference between two successive R-peaks in five minutes). We found clear differences between the study groups. With increasing severity of illness mean values ("group mean values") of long time variability, short time variability and P-value decreased. Fixed heart rate became predominant. The most pronounced loss of heart rate variability was seen in infants with severe intracranial bleeding, thus offering a tentative diagnosis. For statistical analysis long time variability and the silent oscillation type have been proved as best parameters for this diagnosis. Severely decreased heart rate variations also have been seen in infants with acute renal failure--possibly because of brain edema--, after application of muscle relaxants, repeated doses of sedatives, and after prolonged anesthesia. Otherwise, the heart rate variability was probably dependent on age and gestational age in prematures and newborn infants without intracranial bleeding. It is possible to use microprocessor-based long time cardiorespirography as a simple screening method for the diagnosis of neonatal intracerebral bleeding. In future experiences transcutaneous measurements of oxygen tension should be included.

A Microcomputer-Based Heart-Rate Variability Monitor

Abstract: A cost-effective method of on-line measurement of beat-to-beat heart-rate variability is presented. Based on a commercial microcomputer, the data is formatted as a histogram covering up to 500 past events in the form of a moving time window. Analysis of the QRS peak detector used in the instrumentation shows the conditions necessary for 1 ms resolution. The system permits the on-line calculation of statistical parameters, which are presented when a hard copy of the histogram is requested.