Effect of intracranial pressure on cerebrospinal fluid formation in isolated brain ventricles

The effect of intracranial pressure on cerebrospinal fluid formation has been studied in cats by ventricular perfusion with the aqueduct of Sylvius blocked (isolated ventricular perfusion). It has been found that intracranial pressure has a considerable effect on the rate of cerebrospinal fluid formation, while increases in pressure cause a significant and prolonged decrease in cerebrospinal fluid formation. The effect was observed in animals whether they were initially perfused under lower or under higher intracranial pressure. Cerebrospinal fluid absorption has been studied under the above conditions and it has been noted that the ventricles are capable of significant cerebrospinal fluid absorption, since in isolated ventricles cerebrospinal fluid formation and absorption were in balance at physiological intracranial pressure. In addition, cerebrospinal fluid formation rate within the isolated brain ventricles has been compared with the formation rate in the whole cerebrospinal fluid system. Since only about 30% of the total cerebrospinal fluid formation was observed by isolated ventricular perfusion, it seems that the brain ventricles are not the exclusive site of cerebrospinal fluid formation.     

Effects of lower-body negative pressure on blood flow with applications to the human cardiovascular system

The paper reports a theoretical investigation into the effects of lower-body negative pressure on blood flow through the human cardiovascular system. The human cardiovascular system is modelled as a closed network of arteries, arterioles, capillaries, venules and veins of different lengths and cross-sections. The pumping action is provided by the contraction of the ventricles. The model has been analysed using the finite-element method. The pertinent equations incorporating the effects of lower-body negative pressure for the pressures and flow velocities have been derived, and the quantitative results have been computed. Percentage changes in flow velocities, pressure drops and conductances under the application of lower-body negative pressure in the various segments and organs of the entire cardiovascular system are obtained. The lower-body negative pressure has no effect on the flow rates in carotid, ulnar and coronary arteries, nor on the supply of blood to the upper extremities, kidneys, spleen and liver. The major effects are found in the lower extremities.     

Studies of the cavitational effects of clinical ultrasound by sonoluminescence: 4. The effect of therapeutic ultrasound on cells in monolayer culture in a standing wave field

In previous work the phenomenon of sonoluminescence (SL) has been used to find the conditions in which transient cavitation during exposure to ultrasound is likely to be maximum. This paper reports the effect of therapeutic ultrasound on growth of mouse tumour cells in monolayer culture when the cells are insonated either at a pressure antinode or at a pressure node in a standing wave ultrasound field that is known to produce strong bands of SL at the pressure antinodes. Reduced cell numbers 72 h after insonation were recorded when the cells were insonated at an antinode but not when they were at a node. The possibility that this effect might be an artefact of the experimental system, and further experiments that could elucidate the nature of the damage, are discussed.     

Role of laboratory medicine in medical care--from the point of view of a manager

The Japanese health insurance system has been praised because of the comprehensive coverage of medical costs. The long lifespan of Japanese, the longest in the world, however, because economic conditions are getting worse and medical costs are increasing with the increase of aged people in Japan, the health insurance system is under pressure. The Japanese government is going to start to reduce costs of medical care by applying a system like the DRG/PPS system in the USA, called Diagnosis Procedure Combination(DPC), next year in university hospitals. Under the DPC system, laboratory tests will be non-profit. We have to change the management style of clinical laboratories to cut costs for tests and labor as much as possible, choose tests selectively, respond rapidly to clinical needs, and utilize information technology efficiently for processing of laboratory data. Therefore, corresponding to changes in the medical care system, laboratory medicine has been changing. Commercial clinical laboratories are expanding their pressure in hospitals, and in-hospital laboratories are having a very hard time coping with the pressure. Since laboratory medicine is an essential part of clinical practice, we do not have to be antagonistic.     

An in vitro study of a microbubble contrast agent using a clinical ultrasound imaging system

Optimal insonation settings for contrast imaging are yet to be specified, mainly due to the lack of good understanding of the behaviour of the microbubbles. A satisfactory model that explains the behaviour of individual contrast agent scatterers has not yet been reported in the literature. An in vitro system based on a commercial scanner (ATL HDI3000) has been developed to investigate the backscatter of such agents. Suspensions of Definity were introduced in an anechoic tank. The frequency of transmitted ultrasound varied from 1 to 5 MHz, pulse period from 2 to 10 periods and peak negative acoustic pressure from 0.08 to 1.7 MPa. The backscatter at the fundamental and second harmonic frequency windows from the agent was normalized in terms of the corresponding components of backscatter from a blood mimicking fluid suspension. The agent provided a dominant resonance effect at 1.6 MHz transmit frequency. Second harmonic normalized backscatter averaged around 9 dB higher than the fundamental. The normalized fundamental backscatter intensity was linear with peak negative pressure. The second harmonic at resonance peaked at 0.5 MPa suggestive of bubble disruption above such pressure. The system proved capable of illustrating the ultrasonic behaviour of Definity in vitro, and the investigation suggested particular insonation conditions for optimal image enhancement using Definity.     

美国国家压疮咨询委员会2016年压力性损伤的定义和分期解读

压疮是临床常见的慢性难愈性创面,由于其发病率和患病率较高,治疗周期长,治疗花费高,压疮的防治一直受到广泛关注。针对压疮,目前已经发布了两版国际性的指南,在2016年,美国国家压疮咨询委员会(NPUAP)对压疮的定义和分期重新做了更新,笔者在此做以简要阐述和解读。     

Simulation of steady cardiovascular flow in the presence of stenosis using a finite element method

Stenosis could affect one or more segments of the human cardiovascular system. It is a problem capable of causing grave effects. In the present study, the finite element method has been utilised to construct a computer simulation model for the human cardiovascular system in which one or more blood carrying elastic segments are affected by stenosis. Computational effects on the effects of stenosis in aorta arch, carotid, and coronary arteries on parameters of steady flow through the system are presented. It is found that when the total flow rate through the heart is maintained constant, the most notable effect is a very marked increase in pressure drop occurring over the length of the vessel affected with stenosis. Pressure drop in many other segments also increases but by a much smaller extent. On the other hand, when the pressure at the inlet of the ascending aorta and the outlet of the vena cava are maintained constant, the most marked effect is a decrease of flow rate through the stenosed vessel. Stenosis not only causes a pressure drop in the affected segments but it also changes pressures at points distal from the site of stenosis. It also causes a redistribution of flow through the cardiovascular system.     

Acute and chronic servo-control of renal perfusion pressure

We describe a servo-control system for acute and chronic regulation of renal perfusion pressure or pressures in other parts of the circulation. The system employs a Dacron-reinforced inflatable silastic occluder of sufficient strength and durability to produce large pressure gradients for long periods of time (at least 10 days) in the abdominal aortas of large dogs. The occluder is inflated with an inexpensive, bidirectional DC motor syringe pump that is controlled by a comparator feedback circuit connected to the output of a driver amplifier of a Grass polygraph or any other suitable recorder. The system has a rapid response time for precise control and has been used to maintain a constant renal perfusion pressure in experiments lasting as long as 10 days. The system has diverse applications in studies of acute or chronic regulation of renal hemodynamics as well as the hemodynamics of other organ systems. The main advantages of this system, besides its durability and precision of control, are that it is very inexpensive (total cost including the syringe pump is less than $150), easy to construct, and can be used in chronic studies for servo-controlling renal perfusion pressure or pressures in other parts of the circulation.     

A sympathetic view of the sympathetic nervous system and human blood pressure regulation

New ideas about the relative importance of the autonomic nervous system (and especially its sympathetic arm) in long-term blood pressure regulation are emerging. It is well known that mean arterial blood pressure is normally regulated in a fairly narrow range at rest and that blood pressure is also able to rise and fall 'appropriately' to meet the demands of various forms of mental, emotional and physical stress. By contrast, blood pressure varies widely when the autonomic nervous system is absent or when key mechanisms that govern it are destroyed. However, 24 h mean arterial pressure is still surprisingly normal under these conditions. Thus, the dominant idea has been that the kidney is the main long-term regulator of blood pressure and the autonomic nervous system is important in short-term regulation. However, this 'renocentric' scheme can be challenged by observations in humans showing that there is a high degree of individual variability in elements of the autonomic nervous system. Along these lines, the level of sympathetic outflow, the adrenergic responsiveness of blood vessels and individual haemodynamic patterns appear to exist in a complex, but appropriate, balance in normotension. Furthermore, evidence from animals and humans has now clearly shown that the sympathetic nervous system can play an important role in longer term blood pressure regulation in both normotension and hypertension. Finally, humans with high baseline sympathetic traffic might be at increased risk for hypertension if the 'balance' among factors deteriorates or is lost. In this context, the goal of this review is to encourage a comprehensive rethinking of the complexities related to long-term blood pressure regulation in humans and promote finer appreciation of physiological relationships among the autonomic nervous system, vascular function, ageing, metabolism and blood pressure.     

Automatic control of blood pressures with multiple drug inputs

Control of arterial blood pressure has been successfully achieved by infusing a single vasoactive drug. However, in clinical practice, blood pressures are frequently controlled using multiple drug infusions. This paper presents a computer based adaptive control algorithm for simultaneous infusions of both an inotropic agent and a vasoactive agent to maintain the blood pressures at desired levels. We present the dynamics of the system with a bilinear two-input, two-output model. A least-squares parameter estimation algorithm has been employed using an output error method. Results of computer simulations of an electrical analog model of the heart and circulatory system are presented.     

无创性静脉测压仪的研制

我们研制了无创性静脉测压仪 ,并探讨了无创性静脉测压的可行性与准确性。无创性静脉测压仪构造包括 1气路部分 ,2气敏探头 ,3电路部分和数据处理部分 ,4压力控制手柄。采用配对设计对体外血管模型和实验动物犬肠系膜上静脉、门静脉和腔静脉进行穿刺测压与贴壁测压比较研究。结果表明 :体外血管模型实验发现无创性贴壁测压值与穿刺测压值有极好的直线相关关系 (r=0 .99,p<0 .0 0 0 5 ) ,动物实验无创性贴壁测压值与穿刺测压值也有良好的直线相关关系 (r=0 .97,p<0 .0 0 5 )。说明是无创性静脉测压仪能准确测定口径较大静脉的血管内压。     

Pressure measurements during injection of corticosteroids:in vivo studies

Intralesional injection of corticosteroids is an effective treatment for capillary hemangiomas. Complications include embolisation of corticosteroid particles into the ocular circulation resulting in permanent loss of vision. This research is aimed at developing an injection cannula and monitoring system to prevent such inadvertent embolisation. A cannula has been designed to simultaneously estimate the pressure at its tip and the flow rate during injection. The estimation technique has previously been validated using an in vitro model. In this study, the cannula was tested in vivo with canine liver at injection flow rates of 2.5 to 21 ml min-1. The pressure generated in the tissue during injection was calculated using the technique developed. This was compared with direct in situ pressure measurements made with a coaxial outer cannula. The mean calculated pressure was seen to be linearly related to the mean measured pressure with a slope of 0.97, correlation coefficient of 0.99 and standard error of 2.74 mmHg. Similar trends were observed between the maximum calculated and maximum measured injection pressure: slope = 1.0, r = 0.99 and standard error = 5.54 mmHg. The estimation of the mean and maximum pressure from the cannula and monitoring system was accurate in canine liver. High pressures close to 250 mmHg were generated in tissues during injection.     

Automatic calibration of the inlet pressure sensor for the implantable continuous-flow ventricular assist device

Significant progress in the development of implantable ventricular assist devices using continuous-flow blood pumps has been made recently. However, a control method has not been established. The blood pressure in the inflow cannula (inlet pressure) is one of the candidates for performing an adequate control. This could also provide important information about ventricle sucking. However, no calibration method for an inlet pressure sensor exists. In this study, an automatic calibration algorithm of the inlet pressure sensor from the pressure waveform at the condition of ventricle sucking was proposed. The calibration algorithm was constructed based on the consideration that intrathoracic pressure could be substituted for atmospheric pressure because the lung is open to air. We assumed that the inlet pressure at the releasing point of the sucking would represent the intrathoracic pressure, because the atrial pressure would be low owing to the sucking condition. A special mock circulation system that can reproduce ventricle sucking was developed to validate the calibration algorithm. The calibration algorithm worked well with a maximum SD of 2.1 mmHg for 3-min measurement in the mock circulation system. While the deviation was slightly large for an elaborate calibration, it would still be useful as a primitive calibration. The influence of the respiratory change and other factors as well as the reliability of the calibration value should be investigated with an animal experiment as a next step.     

Respiratory and cardiovascular actions of orexin-A in mice

Ample evidence has been reported to show a probable contribution of orexin in the central cardiovascular regulation. Although cardiovascular and respiratory centers in the brain are located close to each other and are interconnected, the possible participation of orexin in respiratory regulation has not been fully documented. Here we examined the effects of intracerebroventricular administration of orexin-A on respiratory and cardiovascular parameters in urethane-anesthetized mice. Respiratory frequency and tidal volume were recorded simultaneously with blood pressure and heart rate. Orexin-A (0.003-3 nmol in 2 microL) or vehicle was administered into the lateral ventricle or cisterna magna. Lateral ventricular administration induced a rise in respiratory frequency (by 11% at the highest dose), tidal volume (76%), blood pressure (13%) and heart rate (6%) in a dose-dependent manner. With intracisternal administration, however, respiratory frequency did not change while a similar increase in tidal volume (75%) was observed. A relatively larger cardiovascular response was elicited with intracisternal administration (blood pressure 26%, heart rate 9%). On the other hand, with either administration route, orexin-A did not affect reflex increases in respiratory frequency and tidal volume in response to hypoxia and hypercapnia. These results show possible participation of orexin-A not only in the cardiovascular regulation but also in the respiratory control system. Moreover, orexin can affect the cardiorespiratory control system at multiple sites in different ways. Orexin-A seems not to be involved in respiratory reflex regulation in mice at least under anesthetized condition.     

Patterns of laryngeal electromyography and the activity of the respiratory system during spontaneous laughter

Laryngeal muscle electromyography (EMG) and measures of the behavior of the respiratory system have been made during spontaneous laughter in two groups of subjects. The smaller group also had a direct measure of tracheal pressure during this behavior. Laryngeal adductors such as the thyroarytenoid (TA) and lateral cricoarytenoid (LCA) exhibited brief high-amplitude bursts of activity, at a rate of approximately 5 Hz, which were usually associated on a 1 : 1 basis with the sound bursts (ha ha ha) of laughter. The laryngeal abductor, posterior cricoarytenoid (PCA), also showed bursts of activity that were out of phase with TA and LCA. The cricothyroid (CT) was only weakly, if at all, modulated during the bursting activity of the other laryngeal muscles. Tracheal pressure usually exhibited positive pressure pulses during laughter that were often, but not always, temporally correlated to the bursts of laryngeal adductor EMG activity. Such pressure modulations appeared to precisely determine when-and if-phonation was produced during the laugh. During laughter, laryngeal EMG is highly stereotyped both within and between subjects. In most instances, this activity appears to be supported by coordinated pulses of tracheal pressure. The periaqueductal gray (PAG) has been shown in animal studies to produce emotionally indicative vocalizations, in which the laryngeal and respiratory system are coordinated. Therefore, it is suggested that the PAG is involved with the production of laughter.     

Pressure measurements during injection of corticosteroids:in vivo studies

Intralesional injection of corticosteroids is an effective treatment for capillary hemangiomas. Complications include embolisation of corticosteroid particles into the ocular circulation resulting in permanent loss of vision. This research is aimed at developing an injection cannula and monitoring system to prevent such inadvertent embolisation. A cannula has been designed to simultaneously estimate the pressure at its tip and the flow rate during injection. The estimation technique has previously been validated using an in vitro model. In this study, the cannula was tested in vivo with canine liver at injection flow rates of 2.5 to 21 ml min⁻¹. The pressure generated in the tissue during injection was calculated using the technique developed. This was compared with direct in situ pressure measurements made with a coaxial outer cannula. The mean calculated pressure was seen to be linearly related to the mean measured pressure with a slope of 0.97, correlation coefficient of 0.99 and standard error of 2.74 mmHg. Similar trends were observed between the maximum calculated and maximum measured injection pressure: slope=1.0, r=0.99 and standard error=5.54 mmHg. The estimation of the mean and maximum pressure from the cannula and monitoring system was accurate in canine liver. High pressures close to 250 mmHg were generated in tissues during injection.     

Studies of Blood-pressure Regulation III. Dynamics of Arterial Blood Pressure on Carotid-sinus Nerve Stimulation

Öberg , P. Å. and U. Sjöstrand , Studies of blood-pressure regulation. III. Dynamics of arterial blood pressure on carotid-sinus nerve stimulation. Acta physiol. scand. 1971. 81. 96–109. An analysis of the properties of the blood pressure regulatory system has been made by means of carotid-sinus nerve stimulation. The method used involves analog simulation of the nonlinear properties of this reflex. The analysis gives the gain-frequency and the gain-phase shift curves characterizing the system under study. A resonance frequency for the system is mostly found in the frequency range 0.03–0.06 Hz. Modulation of the control signal decreases the systemic bandwidth. Non-linear simulation indicates that the mammalian blood pressure regulating system has some of the characteristics of a sampled regulatory system. The afferent information in the carotid-sinus baroreceptor reflex stabilizes the systemic blood pressure by means of its pulsating nature. Transfer functions characterizing the system under study are given. The data presented are relevant to the functional characteristics of baropacer systems.     

The effect of atmospheric pressure on ventricular assist device output

The effect of cabin pressure change on the respiratory system during flight is well documented in the literature, but how the change in atmospheric pressure affects ventricular assist device (VAD) output flow has not been studied yet. The purpose of our study was to evaluate the change in VAD output using a mock circulatory system in a low-pressure chamber mimicking high altitude. Changes in output and driving pressure were measured during decompression from 1.0 to 0.7 atm and pressurization from 0.7 to 1.0 atm. Two driving systems were evaluated: the VCT system and the Mobart system. In the VCT system, output and driving pressure remained the same during decompression and pressurization. In the Mobart system, the output decreased as the atmospheric pressure dropped and recovered during pressurization. The lowest output was observed at 0.7 atm, which was 80% of the baseline driven by the Mobart system. Under a practical cabin pressure of 0.8 atm, the output driven by the Mobart system was 90% of the baseline. In the Mobart system, the output decreased as the atmospheric pressure dropped, and recovered during pressurization. However, the decrease in output was slight. In an environment where the atmospheric pressure changes, it is necessary to monitor the diaphragmatic motion of the blood pump and the driving air pressure, and to adjust the systolic:diastolic ratio as well as the positive and negative pressures in a VAD system.     

Power spectral analysis of heart rate and blood pressure variability in anaesthetized dogs.

Short-term oscillation of heart rate and blood pressure are mainly regulated by the automatic nervous system. It has been proposed that non-neural factors, such as changes in intrathoracic pressure, can strongly modulate this rhythmicity. Our aim was to evaluate the effect of changing intrathoracic pressure and central autonomic nervous activity on heart rate and blood pressure variability. Evaluation was performed by using spectral analysis techniques with autoregressive modelling. The variability in heart rate and blood pressure remained in animals with open chest or paralysed respiratory muscles. After vagotomy, the variability in heart rate decreased, but not that of blood pressure. Total spinal anaesthesia elicited a decrease in the variability in blood pressure. The pharmacological blockade of alpha- and beta-receptors further decreased both variabilities. It was concluded that in anaesthetized dogs heart rate and blood pressure variability are mainly of central origin and non-neural factors have only minor effect on these central rhythms. High (> 0.15 Hz), medium (0.07-0.15 Hz) and, obviously low (0.00-0.07 Hz) frequency variations in heart rate are mostly mediated vagally. In blood pressure, medium and obviously low frequency variations are modulated by sympathetic nervous system, whereas high frequency variations are secondary to the heart rate variation.     

Dispositif de controle automatique des aspirations chirurgicales en chirurgie cardiaque

At attempt has been made by the authors to automate the aspiration of blood in cardiac surgery under extra-corporal circulation. The presence of blood at the end of tubing can be detected by means of a system based upon the blood's property of conductivity. The motor of the aspiration pump is halted when there is no blood. The motor is triggered when blood appears. Another detector has been designed to prevent the suction effect when the extremity of the tube is applied against a wall. This suction is accompanied by depression inside the tube which persists even if the pump is stopped. This depression is picked up by a vacuometer. An electronic system detects a limit level of negative pressure and stops the pump motor. To oppose the persistence of this suction blood arrives through a calibrated aperture at the level of the aspiration tubing from a reservoir in which there is at mospheric pressure; this enables the cannula to detach itself from the tissue. The pump will start again when the pressure in the tube is equal to atmospheric pressure and if there is blood at the end of the cannula. These two detectors have been linked in such a way as to form an automatic aspiration unit.