Intercrural differences of arterial blood-pressure and blood-flow in new-born infants

Intercrural systolic blood-pressure differences did not exceed 10 mmHg in 22 healthy infants who were term, pre-term or small for their gestational age (three); as measured simultaneously in both legs with 3-cm wide thigh cuffs and mercury-in-silastic strain gauges around the calves. In 13 infants with indwelling umbilical artery catheter and normal angiographic findings in both legs, blood-pressure differences were similarly low in a majority of the infants, but in three of these intercrural differences of 15-20 mmHg were found. Resting and submaximal arterial leg blood-flow, measured with venous occlusion plethysmography, showed larger intercrural differences than blood-pressure, and did not add further information. The results indicate that simultaneous systolic blood-pressure measurements in the legs, with strain gauge plethysmography, is a simple and risk-free noninvasive method, suitable, for example, for diagnosing thromboembolism in infants. An indwelling umbilical artery catheter seems to interfere very little with the arterial circulation in the catheterized leg.     

Arterial blood-pressure change and endogenous circulating substance P in man

Substance P (SP) is a powerful vasodilator and this peptide is today considered to be a chemical messenger. The potential effects on circulating SP of acute changes in arterial blood-pressure was investigated in nine subjects. An increase in arterial mean blood-pressure (+33%, P less than 0.001, n = 9) was obtained by infusion of angiotensin II and a decrease in pressure (-10%, P less than 0.005, n = 6) was obtained by ganglionic blockade. The concentration of SP in plasma, from supine subjects in the normotensive condition, ranged from 3 to 13 pmol/l (with a mean of 5.6 pmol/l). SP was thus within the reference interval: 3-16 pmol/l (n.s.). Plasma SP remained very constant in each subject during the changes in blood-pressure (mean variation in plasma concentration of SP was 0.97 (SD) pmol/l). The results show that acute changes in arterial blood-pressure do not result in any detectable change in plasma SP, this seems to indicate that endogenous circulating SP has no significant role in the vascular tonus controlled by the arterial baroreflex.     

Clinical evaluation of the Copal UA-251 and the Dinamap 1848 automatic blood-pressure monitors

The Copal UA-251 is a small automatic blood-pressure monitor, which relies on a piezo-electric microphone for detection of Korotkoff sounds. The Dinamap 1848 automatic monitor uses the oscillometric method for blood-pressure determination. When compared with the Hawksley random-zero sphygmomanometer, the Copal UA-251 recorded higher systolic blood-pressure, with this discrepancy widening at the upper end of the systolic pressure range. The agreement between these machines was reasonable for diastolic blood-pressure. The Dinamap 1848 had a tendency to consistently over-read systolic and under-read diastolic blood-pressure compared with the Hawksley sphygmomanometer, with median differences of 7 mmHg and -2.5 mmHg respectively.     

两种血压计连续三次测量血压脉搏的比较研究

目的旨在比较电子血压计和水银式血压计的测量效果．方法对１３０人连续三次测量血压和脉搏，测量中基本上无外界干扰．结果发现三次间的血压值有差异，以第一次最高，后逐渐降低，以收缩压更明显，各次血压测量值的均数比较，大部分有极显著性差异，但各次脉率比较无差异结论认为连续重复测量血压值存在着差异，虽有一些内在的因素起作用，其确切的原因尚待进一步研究．     

Capillary filtration coefficient in the forearm of patients with essential hypertension

The capillary filtration coefficient (CFC) in the forearm was followed in patients with essential hypertension and compared with controls, using the method of venous occlusion plethysmography and simultaneous recording of intravenous pressure in the measured segment of the extremity. Arterial blood-pressure was obtained in the contralateral arm by auscultation. The CFC averaged 0.0039 +/- 0.009 ml/100 ml/min/mmHg and 0.0095 +/- 0.0018 ml/100 ml/min/mmHg in hypertensives and controls respectively. The relation between CFC and arterial blood-pressure values was inversely non-linear. The results suggest reduction of the capillary area due to hypertension and possibly functional or structural changes in the microcirculatory bed accompanying systemic blood-pressure increase.     

Severity of sleep-disordered breathing improves following parturition

STUDY OBJECTIVE: Changes in sleep-disordered breathing associated with late pregnancy have not previously been systematically investigated; however, a number of case reports indicate exacerbation of obstructive sleep apnea in late pregnancy, often in association with maternal hypertension. We aimed to compare the severity of sleep-disordered breathing and associated maternal blood-pressure responses in late pregnancy with the nonpregnant state. DESIGN: Case-controlled, longitudinal study of sleep-disordered breathing during late pregnancy and postpartum. Study Patients: Ten women referred for suspected sleep-disordered breathing during the third trimester of pregnancy. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: Full overnight polysomnography and continuous systemic blood pressure were measured during the third trimester of pregnancy and 3 months following delivery. Parameters of sleep-disordered breathing, including apnea hypopnea index and minimum overnight arterial oxyhemoglobin saturation, were compared between antenatal and postnatal studies. An improvement in both apnea-hypopnea index and minimum arterial oxyhemoglobin saturation occurred consistently in all subjects postnatally. In non-rapid eye movement sleep, mean apnea-hypopnea index was reduced from 63 +/- 15 per hour antenatally to 18 +/- 4 per hour postnatally (P = .03), and in rapid eye movement sleep, from 64 +/- 11 per hour to 22 +/- 4 per hour (P = .002). Minimum arterial oxyhemoglobin saturation was increased from 86% +/- 2% antenatally to 91% +/- 1% postnatally (P = .01). Arterial blood-pressure responses to apnea peaked at 170 to 180 mm Hg antenatally, while they only peaked at 130 to 140 mm Hg postnatally. CONCLUSION: This study indicates that late pregnancy may be associated with increased severity of sleep-disordered breathing and associated blood-pressure responses.     

A minicomputer system for long-term automatic blood pressure monitoring

An automated system for the indirect measurement of blood pressure on seacted factory workers has been developed and has been in continuous daily operation for nine months. Six industrial workers on a conveyor assembly line are monitored serially. Because of completely automatic operation of this system, blood-pressure data can be collected over a long time period without any experimenter intervention. This system was developed as part of a larger study titled “Effects of Paced Performance on Industrial Productivity, Job Satisfaction and Physiological Stress,” NSF Grant #7718695     

Direct blood-pressure measurements: risks,technological evolution and some current problems

The direct measurement of blood pressure has found widespread use in intensive care units, operating rooms, and in emergency departments. Infection, air embolism and thrombosis are some of the risks to patients associated with both the cannulation procedure and with the apparatus used in the blood-pressure measuring process. Although there is constant revision in an attempt to reduce these risks, they cannot be completely eliminated. The need for direct blood-pressure measurements and the physiological effects of air embolism and thrombosis are reviewed. Infection and problems related to the techniques used to insert the catheters are not discussed.     

Cardiovascular responses to circulating catecholamines in normal pregnancy and in pregnancy-induced hypertension

Patients with pregnancy-induced hypertension (PIH) and healthy pregnant and non-pregnant women were compared with regard to cardiovascular responses to i.v. infusions of noradrenaline (NA) and adrenaline (ADR). This resulted in physiologically relevant concentrations in arterial plasma (maximally 10 nmol/litre for NA and 6 nmol/litre for ADR). Non-pregnant women responded to NA with concentration-dependent increases in blood-pressure, which were caused by peripheral vasoconstriction, as systemic vascular resistance (SVR) was increased by 21%. Cardiac output was reduced by 6%. ADR caused concentration-dependent decreases in SVR (to values 36% below basal) and calf vascular resistance (CVR), as well as increases in cardiac output. Healthy pregnant women responded to NA with similar increases in blood-pressure, but this was due to stroke volume-dependent increases in cardiac output (11%) and not due to vasoconstriction. ADR-induced vasodilatation was attenuated in this group. Cardiac responses to ADR were unaffected by pregnancy. PIH patients demonstrated an enhanced systolic blood-pressure response to NA (19% increase vs 7-8% in the other groups) due to the combined effects of vasoconstriction (11% increase in SVR) and an essentially unchanged cardiac output. ADR-induced decreases in CVR and diastolic blood-pressure were similar to those found in the non-pregnant group. Increases in heart rate were less pronounced, but cardiac output increased as normal. These results indicate that normal pregnancy is associated with attenuated vascular responses to circulating catecholamines. PIH patients do not seem to have undergone this normal adaptation of the vascular system to pregnancy.     

Relationships between short-term blood-pressure fluctuations and heart-rate variability in resting subjects II: a simple model

A simple model of the beat-to-beat properties of the cardiovascular system is used to interpret the results of spectral analysis of blood-pressure and interval data. The model consists of two equations, one representing the fast regulation of interval by the systolic pressure (baroreflex), the other one representing a Windkessel approximation of the systemic arterial system. The model, when applied to interval and blood-pressure data from resting subjects, explains the lack of respiratory variability in the diastolic pressure values. The baroreflex equation seems to describe the data only in the region of respiratory frequencies. The shape of the phase spectrum of systolic pressures against intervals is modelled by difference equations, but no physiological interpretation of these equations is given.     

Effects of daily activities and social behavior on blood-pressure elevation

This study examined the effects of daily activities and social behavior on the blood-pressure elevation in 21 normotensives, 20 borderline hypertensives, and 20 sustained essential hypertensives. Blood pressures were recorded over a 24-hr period using an ambulatory monitor while subjects recorded their daily activities and social involvement at each cuff inflation. Results indicated that only a moderate proportion of the blood pressure readings of the two clinical groups exceeded 140/90 mm Hg. Results also suggested that the blood pressures of normotensives were more responsive to changes in physical activity, while the blood pressures of sustained hypertensives were more responsive to social involvement. When group differences emerged on mean blood-pressure elevation, analyses indicated that the two hypertensive groups frequently differed from the normotensive group but rarely from each other. The results suggest that differences in blood-pressure elevation cannot be fully understood without considering behavior and support its continued inclusion in the study of blood pressure.This research was supported in part by National Institutes of Health Grant HL 29795 to Janis H. Crowther and Mary Ann P. Stephens.     

A laser Doppler technique for measuring distal blood-pressure: a comparison with conventional strain-gauge technique

Twenty-five patients with peripheral circulatory disorders were examined by laser Doppler and strain-gauge techniques to compare these methods of measuring distal systolic blood-pressure. The correlation coefficients for simultaneous measurement of toe and ankle systolic blood-pressures were high, 0.98 and 0.99 respectively. The correlation coefficient for successive measurements of toe pressure was lower, 0.83, probably because of a variation in blood-pressure with time. The laser Doppler method seems to be more sensitive than the strain-gauge method in the low-pressure range. The laser Doppler probe is easy to attach to most skin surfaces and the laser Doppler technique may be, therefore, an alternative and a complement to the strain-gauge method when the strain-gauge is difficult to use on damaged or ulcerous toes and feet.     

Cardiovascular responses and plasma catecholamines in old age

Plasma catecholamines and haemodynamic responses to isometric handgrip, orthostatic body position and dynamic cycle exercise were studied in 10 healthy old men (mean age 71 years) and 10 healthy young men (mean age 26 years). At rest, plasma noradrenaline (NA) was significantly higher in the old age group. During handgrip there were greater increases in heart rate and blood-pressure in the young rather than in the old men, while forearm blood-flow increase was similar in the two age groups, and there was no increase in NA in either groups. In the orthostatic position heart rate increased in the young men only, and forearm blood-flow decreased more in the young than in the old men. NA concentration increased similarly in both age groups. During dynamic exercise the increases in both the heart rate and the blood-pressure, at similar relative submaximal as well as maximal loads, were smaller in the old men. At maximal work NA and adrenaline (A) concentrations were higher in the young men, while at the lowest load, NA concentration was higher in the old men. Similar increases in exercise heart rate, blood-pressure or rate of perceived exertion corresponded to lower increases in NA in the old men. It can be concluded that old men, compared with young men, have a reduced maximal capacity to release NA and A upon provocation. In addition, the sensitivity for catecholamines in the target organ is reduced with age, as suggested by the smaller increases in heart rate and blood-pressure for a given increase in NA during exercise. The higher basal NA level and the higher NA level, during moderate provocation, may suggest a compensatory increase in activity.     

Highly flexible capacitive strain gauge for continuous long-term blood pressure monitoring

An innovative procedure for measuring blood pressure, with none of the disadvantages of current procedures, is proposed. A highly-flexible capacitive strain gauge has been designed to measure changes in the diameter of a blood vessel; such changes are indicative of blood pressure. The sensor is implanted and wrapped around an arterial blood vessel during the normal course of a surgical procedure. In vivo tests, demonstrating the feasibility of this concept, are reported, along with in vitro tests and notes on sensor design and fabrication. These continuous blood pressure monitoring sensors may be used for a continuous long-term monitoring of blood pressure and pulse. They may also be combined with a real-time nerve stimulation technique or a course of medication to create a closed-loop system for blood-pressure control.     

The use of successive blood-pressure measurements to estimate blood-pressure variability

Multiple daily, self-determined blood-pressure measurements were obtained from 254 hypertensive patients for 1 month. In an effort to establish a practical and reliable technique for estimating blood-pressure variability, standard deviations from three (at one time of day) or nine (throughout the day) successive self-determinations were compared with a reference value, taken to be the standard deviation for the entire month (252 determinations per subject). Neither the standard deviation of three measures taken on one occasion nor that of nine measures taken throughout the day correlated well with the reference value (average R₃=.21 for SBP, .20 for DBP; average R₉=.39 for SBP, .38 for DBP). However, when a sample consisting of 12 measures (taken three at a time, at the same time of day, weekly for 4 weeks) was used, the average correlation rose to .60 for SBP and .54 for DBP. Thus, it appears that 12 samples taken in this way provide a reliable estimate of the standard deviation for an entire month, and it is suggested that this sampling technique also would enhance the reliability of conclusions drawn from assessments of the prognostic value of blood-pressure variability.     

Mineralocorticoid-induced hypertension in patients with orthostatic hypotension.

The mechanism of recumbent hypertension induced by fludrocortisone was studied in seven patients with orthostatic hypotension. All showed increases in blood pressure in the recumbent and standing positions, and hypertensive levels were achieved on recumbency in four of them. Hypertensive retinopathy developed in two patients and cardiomegaly in one. Initial blood-pressure elevations were associated with sodium retention and plasma-volume expansion. However, with long-term treatment, plasma volume decreased to control levels despite further blood-pressure increases. Treatment did not affect plasma levels of catecholamines but did enhance pressor responsiveness to infused norepinephrine in some subjects. Hemodynamic studies indicated that hypertension in the recumbent position was related to increases in total peripheral-vascular resistance and not to changes in cardiac output. Clinically, hypertension in the recumbent position is an important risk of fludrocortisone treatment in patients with orthostatic hypotension. This unusual model of chronic mineralocorticoid-induced hypertension is not volume dependent but is related to increased peripheral-vascular resistance.     

Über die Wirkung von 3-Methylcholanthren auf den Drosselungshochdruck bei Ratten

Zusammenfassung Ratten, bei denen ein Drosselungshochdruck nach Goldblatt gesetzt worden war, entwickelten keinen Hochdruck, wenn ihnen kurz nach der Operation 3-Methylcholanthren injiziert wurde. Ihr Blutdruck war sogar niedriger als der der Kontrolltiere.Ratten, die nicht operiert worden waren und nur 3-Methylcholanthren erhalten hatten, wiesen noch sehr viel geringere Blutdruckwerte auf.Es kann angenommen werden, daß 3-Methylcholanthren zu einer erheblichen Schädigung im Bereich des Vasomotorenzentrums geführt hat. Diese Schädigung war auch bei Tieren nachweisbar, bei denen noch keine Tumoren aufgetreten waren. Nach Auftreten der Tumoren war der Blutdruckabfall noch erheblich stärker.

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Summary Rats with renoprival hypertension (Goldblatt) did not develop hypertension if 3-methylcholanthren was injected shortly after surgery. Their blood-pressure was even lower than the pressure of the control group.Rats, receiving only 3-methylcholanthren and without surgery, showed even lower blood-pressure levels.It can be assumed that 3-methylcholanthren affected and damaged the vasomotoric centre. This effect was even found in those animals that had not as yet developed turmours. The blood-pressure dropped to even lower levels after the tumours appeared.

     

The relationship between vessel-wall elasticity and Korotkoff-sound frequency

An experimental investigation of the effect of vessel elasticity on Korotkoff-sound frequency has been conducted. A model was constructed to simulate conditions in the upper arm during blood-pressure determination. The experiment was performed using both cylindrical rubber tubes and fresh canine arteries. The modulus of elasticity of the specimens was measured using an apparatus for determining the pressure-volume relationship of distensible tubes. Sound waves produced by the specimens were recorded with an oscilloscope. Logarithmic plots of the data show that, as the modulus of elasticity increased, the sound frequency decreased. The data presented in this paper provides additional support for the hypothesis that the elastic characteristics of the artery do not play an important part in the genesis of the frequency of the Korotkoff sounds.     

Die Wirkung von Desoxycorticosteron auf den Blutdruck bei der Ratte nach vorheriger Behandlung mit 3-Methyl-cholanthren

Zusamenfassung Bei Ratten, die mit 3-Methylcholanthren injiziert worden waren, ist ein Absinken des Blutdrucks eingetreten.Bei Ratten, die sechs Wochen nach der 3-Methylcholanthren-Injektion einseitig nephrektomiert und mit Desoxycorticosteron behandelt wurden, trat eine Blutdrucksteigerung auf, die der der DOC-Kontrollen entsprach.Gleichzeitig wurde bei den männlichen Tieren eine Verzögerung des Tumorwachstums, in einzelnen Fällen Rückbildung und Verschwinden der Tumoren beobachtet. Bei den weiblichen Tieren nahm die Tumorrate ab — 10% statt 50%. Das Tumorwachstum ist ebenfalls verzögert.

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Summary Lower blood-pressure levels were found in rats injected with 3-methylcholanthren.Elevated blood-pressure levels were found in rats which were unilaterally nephrectomized and treated with desoxycorticosteron 6 weeks following injection of 3-methylcholanthren. The blood-pressure levels were unchanged as compared to the DOC control group.Simultaneously, retardation of tumour growth was found in male rats, in isolated cases regression and disappearance of the tumours was observed. The tumour rate declined in female rats — 10% instead of 50%. Tumour growth was likewise retarded.