plasma norepinephnne levels in a group of healthy subjects of varying age. The interrelationships between these measurements, age, and blood pressure were examined. In addition, age, plasma norepinephrine levels, baroreflex sensitivity and blood pressure were correlated with each other with partial correlation analysis to hold individual variables constant to investigate possible causal relationships between these parameters. MethodsFifty-four healthy unmedicated volunteers (35 males and 19 females) ranging in age from 14 to 77 years (49 ± 18 years, mean ± SD) were studied All subjects had a normal cardiovascular (including blood pressure) and respiratory history, electrocardiogram, and chest x-ray; results of physical examination and a fasting blood glucose level also were normal. All subjects had a blood pressure of less than 150/90 mm Hg after supine rest for 30 minutes. Consent for performing all studies was obtained from each subjectThe studies were performed the morning after an overnight fast. The subjects lay supine, and a 19-gauge butterfly needle was inserted into one antecubital vein. After subjects had been supine for at least 30 minutes, blood pressure was measured with a standard cuff method. Blood samples, 10 ml, were then collected in prechilled tubes containing ethylenediaminetetraacetic acid for the determination of basal plasma norepinephrine levels. After immediate centrifugation at 4°C, the plasma was separated and frozen at -80°C for analysis at a later time.The Valsalva maneuver was performed with the subjects supine. The brachial artery was cannulated percutaneously. A polygraph recorded intra-arterial blood pressure, electrocardiogram (lead V 3 ), and air temperature of the nasal cavity (to monitor respiration) The Valsalva maneuver was conducted by blowing into a rubber tube connected to a mercury column and maintaining a pressure of 40 mm Hg for 15 seconds with glottis open The subjects practiced the maneuver until reproducible hemodynamic responses were obtained. When measurements were made, the recording was earned out at a paper speed of 100 mm/sec.Baroreflex sensitivity during Valsalva's maneuver was obtained according to the methods of Palmero and co-workers" and Goldstein and colleagues 12 as follows. During a later period in phase 4, following the release of the Valsalva maneuver, the increase in blood pressure accompanied a progressive slowing of the heart rate. Here, linear regressions were obtained between systolic blood pressure and R-R intervals with a one-beat delay. In all subjects studied, the correlation coefficients (r) were statistically significant, and the r value was always greater than 0.80. The baroreflex sensitivity index was defined as the slope of this linear regression line.Norepinephnne concentrations were assayed by high-performance liquid chromatography with fluorometric detection. 13 Interassay variability was ± 6 % .
Inter-relationship between age, systolic blood pressure and baroreflex sensitivity index derived from the Valsalva manoeuvre was investigated in either combined or separated groups of normal and hypertensive subjects. Both in the total population as a whole and in each blood pressure subgroup, the baroreflex sensitivity index was significantly inversely related to age and to systolic blood pressure. Furthermore, age was significantly related to systolic blood pressure except in the hypertensive group. Partial correlation analysis showed that, in the total and hypertensive population, the baroreflex sensitivity index was significantly related to age and systolic blood pressure independently of each other variable. In the normal group, however, the baroreflex sensitivity index was not related to systolic blood pressure after adjusting for the effect of age, but remained significantly related to age independently of systolic blood pressure. The estimates of relative effects of the two variables on baroreflex sensitivity by multiple regression analysis were consistent with these results. Thus a prevailing concept of the inhibitory effect of blood pressure on baroreflex function may be accurate exclusively in hypertensive patients, and baroreflex function appears to be more sensitive to age-related changes in this system than to those related to blood pressure level, particularly in non-hypertensive normal subjects.
Summary: The purpose of this study was twofold: to establish an ECG respiration monitoring system, and to evaluate the clinical usefulness of this system. Our purpose was to determine how many patients with cardiovascular disorders may have unrecognized sleep apnea and whether such apneic episodes are an important cause of cardiac arrhythmias. The study group included 81 patients, age range 40-95 years, and 13 healthy males, age range 52-72 years. The 24-h ECG respiration recordings were obtained with the two-channel Holter recorder. Airflow at the nose using a nasal thermister or chest wall movement by impedance pneumography was recorded as respiration record on the second channel. Sleep apnea was observed 69% and 77-100% in the control subjects and patients with cardiovascular disorders, respectively. Episodes of sleep apnea were most frequent in the patients with old myocardial infarction. Grading of apneas was defined according to the length of apnea. Short duration apneas were observed only in the control subjects, but longer apneic episodes were observed in patients with cardiovascular disorders. Bradyarrhythmias observed were to be relative to apneic episodes longer than 20 s, while ventricular arrhythmias were observed only in the patients with old myocardial infarction, coincident with apneas lasting longer than 40 s. Atrioventricular conduction disturbances were also observed to be related to the occurrence of sleep apnea. These results suggest that 24-h ECG respiration monitoring is useful not only for the observation of sleep apneic episodes, but also in clarifying the relationship between cardiac arrhythmias and apneic episodes.
Epidemiological blood pressure (BP) surveys suggest that BP determinations are often subject to considerable within-visit variation. For this reason, a memorandum from a WHO/ISH meeting published in 1983 1 stressed that BP should be measured at least three times over a period of at least 3 minutes at each visit and the lowest reading should be recorded. The same committee has now recommended that two or more measurements should be taken over the same interval and the mean value should be used.2 The scientific basis for this slight change in the recommendation has not been fully explained. The present study was performed to obtain information on the magnitude and time course of the variability in casual BP measurements recorded for individual patients during routine clinical practice that would be useful in determining the desirable number of BP readings in outpatient clinic settings.Patients with a history of hypertension (systolic BP> 160mmHgordiastolic BP>90mmHg, or both) were recruited consecutively from our outpatient clinic. The study subjects consisted of 63 patients (38 men and 25 women) aged 63 ± 11 (SD) years, 46 of whom were undergoing antihypertensive therapy. Seventyeight percent of patients had end-organ damage, as evidenced by Grade II and HI retinopathy or left ventricular hypertrophy, or both.BP and heart rate (HR) were recorded in the sitting position by nurses using an automatic blood pressure recorder (Model BP103-N; Nippon Kohrin, Komaki, Japan) throughout to eliminate observer error.3 This device determines the systolic, mean, and diastolic BPs based on an orderly sequence of oscillations in cuff pressure. 4 The device was set to inflate automatically every minute. Each patient had four consecutive BP measurements at each visit, and the examination was repeated four times in an identical manner at 2-or 4-week intervals. Figure 1 shows the mean differences between the individual values and the average of four serial readings at each visit for a total of 252 (63 patients X 4 visits) BP and HR measurements. They were significantly different from each other when tested by oneway analysis of variance (p<0.0001). As seen in Figure 1, systolic, mean, and diastolic BP levels progressively decreased during multiple readings. The mean value of the fourth reading was lower than that of the first by 4.3, 2.3, and 1.9 mm Hg, respectively. The differences between the mean values of the first two readings and those of the last two readings were statistically significant, while the differences between each of the last two readings were not significant. For systolic and mean, but not diastolic, BP the differences between each of the first two readings were also insignificant. Finally, the HR obtained in the first reading was significantly higher than that of successive readings. The mean value of the second reading was lower than that of the first one by 2.5 beats/min.Thus, we may conclude that at least three, rather than two, BP readings over a short interval in an outpatient clinic practice are desirable,...
The present study was performed to obtain basic information as to the influences of two fundamental variables, age and blood pressure, on the circulatory responses during the Valsalva maneuver. Although a positive linear relationship between age and resting systolic blood pressure was present in the study population of 90 normal and uncomplicated hypertensive subjects, the pressure overshoot and the change in R-R intervals during phase 4 in the Valsalva maneuver were significantly inversely related to age or resting systolic blood pressure independently of each other variable. Furthermore, age was related negatively to the maximum R-R interval in phase 4 and positively to the decline of blood pressure post-Valsalva release in phase 3 even after adjusting for the effect of blood pressure, but age-independent relationships between these two indexes and resting systolic blood pressure were not statistically significant. The data indicate that changes in circulatory responses to the Valsalva maneuver occur with aging and high blood pressure, suggesting that the sympathetic vasoregulation and the baroreflex control of heart rate in the maneuver are impaired by these two variables. Such alterations appear to be more strongly related to age than to blood pressure level.
The magnitude of the change in heart rate in Valsalva maneuver (Tachycardia ratio) was also depressed in hypertensives. The increase in heart ratee was also inhibited in normotensive and hypertensive elderly subjects on atropine, cold pressor and tilting tests. The ratio of the increase in heart rate to increase in plasma norepinephrine on tilting was reduced with aging the both groups. In normotensives, aging caused an increase in plasma norepinephrine at rest and a decrease in response of plasma renin activity on tilting. Neither affinity nor capacity of binding sites in lymphocytes for radio-labeled pindolol was affected by age and hypertension. These results suggest that parasympathetic and sympathetic regluation of heart rate are altered with aging and that hypertension has additive effects on these changes. These dysfunctions may be caused at least in part, by the reduced baroreflex sensitivity as well as the decreased sympathetic responsiveness of hearts, apparently due to a postreceptor defect.Valsalva maneuver, baroreflex sensitivity (Jpn J Geriat 22: [1][2][3][4][5][6][7][8][9][10][11][12] 1985)
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