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Biomedical subjects

R C Hermida

Publications and source records attributed to R C Hermida.

78 records · Page 5Linked to original sources
PubMedDate not supplied

Biomedical pattern discrimination of neonatal cardiovascular risk.

Genetic risk is a primary contributing factor to the predisposition of a newborn child to elevated blood pressure later in life. An index for this factor is needed to assess in the neonate the success or failure of preventive interventions instituted for the pregnant woman. This index could be based on characteristics describing the variability of blood pressure and heart rate during the first days after birth. In the search for such an index, the systolic and diastolic blood pressures and heart rates of 150 newborn babies were automatically monitored at about 30-minute intervals for 48h with a Nippon Colin device, starting early after birth. On the basis of questionnaires given to the parents, the neonates were assigned to a group of either a negative or positive family history of high blood pressure, according to the absence or presence of high blood pressure and/or related cardiovascular disease in two generations (those of the newborn's parents and grandparents). Circadian characteristics and descriptive statistics for the three circulatory variables were used for classification by a so-called "monotest", an all-subsets variable selection technique for biomedical discriminant analysis. For a particular combination of variables, the "monotest" performs as many steps of separate analyses as the total number of subjects, each subject's data being compared as a set with those of all others ("leave-one-out" approach). When the circadian amplitude of systolic blood pressure was used as classifier, the "monotest" yielded a 63% classification equivalent to prior criteria, the latter being based on a negative or a positive family history of high blood pressure. The "monotest" complements rhythmometric procedures and defines a set of individualized criteria for risk assessment. The combined use of automatic hardware for time-specified sampling with proper software for signal processing and discriminant analysis allows to recognize parameters of blood pressure circadian variability as a source of information for neonatal classification according to cardiovascular disease risk.

Blood Pressure↗
PubMedDate not supplied

Hardware-software approach for neonatal cardiovascular risk estimation.

Genetic risk is a primary contributing factor to the predisposition of a newborn child to elevated blood pressure later in life. To determine whether there is a correlation between potential genetic risk as established by family history and measured physiologic variables in the neonate, the systolic and diastolic blood pressures and heart rates of 150 newborn babies were automatically monitored at about 30-minute intervals for 48 hours with a Nippon Colin device, starting early after birth. Circadian parameters (obtained by the linear least-squares fit of a 24-hour cosine curve to each individual series) and descriptive statistics for the three circulatory variables were used in a multiple-regression analysis to compute a linear prediction function for a neonatal cardiovascular risk score. This score was obtained for each neonate on the basis of the presence or absence of overt cardiovascular disease, elevated blood pressure, or obesity across two generations, those of the newborn's parents and grandparents. Results from multiple regression indicate that the best model for prediction of the risk score includes the circadian amplitudes of systolic and diastolic blood pressure, the circadian range of heart rate, and the 90% range and standard deviation of diastolic blood pressure. The multiple correlation coefficient between the predicted and the computed risk scales is 0.666, a value that, although statistically significant (p < 0.001), is still low for a generalized practical use of the model in predicting risk.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiovascular Diseases↗
PubMedDate not supplied

Time-specified reference limits for ambulatorily monitored blood pressure in clinical health.

For the study of blood pressure, the use of automatic fully ambulatory recording systems greatly facilitates data collection and, in combination with proper software, the interpretation of results. Hardware for automatic long-term measurement is here wedded to a set of software modules to assess the circadian variability of human blood pressure. To evaluate changes in blood pressure within a day, the authors analyzed 150 series of systolic and diastolic blood pressures and heart rates automatically monitored every 30 minutes for at least 48 hours. Subjects were clinically healthy men and women 19-23 years of age. Individual circadian-rhythm parameters computed for each time series by least-squares rhythmometry were used to assess rhythm characteristics of all subjects and for each gender separately. Those individual parameters were also used for the computation of a so-called paradesm, a (here 90%) time-specified prediction region for the amplitude-acrophase pair. The limits thus obtained for the circadian amplitude (an index of within-day variability) of blood pressure were exceeded in cases of amplitude-hypertension. Additionally, the original data were used to compute time-specified prediction limits for blood pressure and heart rate in clinical health. Such reference limits may serve for an objective and positive definition of health, for the screening and diagnosis of disease, and for gauging a subject's response to treatment. The combined hardware-software method for the establishment of time-qualified reference limits presented allows the assessment of the extent and timing of rhythmic change and can be used for the interpretation of single values obtained at specified times.

Adult↗
PubMedDate not supplied

Computation of time-specified tolerance intervals for ambulatorily monitored blood pressure.

Hypertension is an important risk factor for strokes, heart attacks, and other vascular diseases. Pharmacologic treatment of high blood pressure reduces the incidence of these complications and prolongs life, so there is a strong incentive to identify and treat individuals with high blood pressure. The development of automatic instrumentation for noninvasive and ambulatory blood pressure monitoring makes it possible to follow the time course of blood pressure variations continuously in healthy peer groups to be used as a reference standard as well as in potentially hypertensive subjects. For clinical applications, tolerance intervals should be substituted, whenever possible for prediction limits. When only hybrid data (time series of data collected from a group of subjects) are available, such a tolerance interval can be difficult to determine following a parametric approach similar to the procedure used for the computation of prediction intervals when consideration of both within-subject and among-subjects variances is wanted. The authors have developed a nonparametric method for the computation of such tolerance intervals. Because the method is based on bootstrap techniques, it does not require the assumption of normality or symmetry in the data and is thus more appropriate when dealing with small samples. The method was used to establish time-qualified reference limits for series of blood pressure and heart rate values monitored automatically in healthy individuals of both genders. The use of these tolerance intervals may eliminate many false-positive and false-negative diagnoses that might be obtained when relying on time-unspecified single samples. These limits can serve as a reference for comparisons of a given subject's blood pressure series over time, yielding nonparametric measures of extent and timing of any blood pressure excess or deficit. Such indices can then be used for an objective and positive definition of health, for the screening and diagnosis of disease, and for gauging responses to treatment.

Adult↗
PubMedDate not supplied

Computer-based medical system for the computation of blood pressure excess in the diagnosis of hypertension.

A computer-based system for assessing hypertension was designed by combining hardware for automatic, long-term blood pressure (BP) measurement with a set of software modules for computing time-specified tolerance intervals and evaluating measures of BP excess. BP is so variable that the identification and proper definition of hypertension are highly ambiguous when based on single measurements. One first step in dealing with such variability is to replace the constant limits for BP frequently used in the assessment of hypertension by a time-specified reference interval. Once such a threshold is available, a hyperbaric index can be computed by numerical integration as the total area (within one cycle) of any given patient's BP above the threshold. In order to examine the extent of normal physiologic excess, a series of 266 systolic and diastolic BP and heart rate (HR) measurements were automatically monitored every 30 minutes for at least 48 hours from clinically healthy subjects, aged 19 to 25 years. Original data were used to obtain 90% tolerance intervals for each gender separately. The hyperbaric index was then computed for each individual BP profile. The distribution of the maximum hyperbaric index (maximum of the values computed for systolic, mean arterial, and diastolic BP levels shows a highest value of 14.839 mmHg x hr for the men and of 10.229 mmHg x hr for the women. These values represent a testable threshold for assessing hypertension based on the proposed approach. The tolerance intervals obtained from the reference population were also used to compute hyperbaric indices for a series of 175 BP measurements sampled from clinically healthy people, as well as a series of 60 measurements sampled from patients with mild hypertension. Sensitivity and specificity in the diagnosis of hypertension based on the hyperbaric index were both 100%, as opposed to values obtained from computing the BP load, the average of the BP series, or the circadian amplitude, all of which provided a much poorer diagnostic test. The software system developed for automatically establishing time-qualified tolerance limits from a reference population and assessing the extent and timing of BP elevation for a test subject may help to establish a prognosis and diagnosis, with a correspondingly better assessment of health status, to initiate treatment if needed, to time treatment when it is most desirable and least harmful in terms of undesired effects, and to gauge the patient's response to treatment.

Adult↗