Simultaneous registration of rheographic and manometric parameters of the inferior esophageal sphincter in the cat

The aim of the present study was to detect simultaneously hemodynamic parietal events and intraluminal pressure of the Lower Esophageal Sphincter (LES), with particular regards to cyclic changes due to systo-diastolic cardiac activity. A probe for combined Intraluminal Manometric Plethysmography (IMP) and Intraluminal Impedence Plethysmography (IIP) was used. It was a Swan Ganz bipolar pacing catheter, modified by removing the latex balloon from the tip. The exposed side-hole (diameter smaller than 0.5 mm) was utilized as a terminal orifice for an infused manometry system. It was preliminarly essayed in bench tests. A perfusion rate of 1.75 ml/min was chosen as it did not induce significant elevations of the pressure base-line and allowed detection of pressure rise rates up to 300 mm Hg/s. The two metallic rings, originally designed for intracardiac stimulation, were used as low resistance electrodes to record impedence variations. Since very small shifts of recording electrodes induce important artifacts, the present experiments were carried out on curarized cats. In these conditions, artificial ventilation could be temporarily stopped to avoid any artifact due to respiration mechanics. The proposed method seems to be satisfactory enough for simultaneous acquisition of IIP and IMP data at LES level. Recordings of IIP allow to reveal changes in parietal blood content which could chiefly be referred to lamina propria and submucosa districts. On the other hand, IMP cyclic fluctuations would signal variations of total sphincteric tension, likely depending on hemodynamic events in all vascular beds of the wall. In our opinion, a more extensive analysis of IMP and IIP waves, as well as of reciprocal relationships between rheografic and manometric parameters, may provide very useful knowledges on sphincteric physiology.     

Quantifying EGJ morphology and relaxation with high-resolution manometry: a study of 75 asymptomatic volunteers

Our aim was to define normal esophagogastric junction (EGJ) morphology and relaxation characteristics using high-resolution manometry (HRM). To this end, 75 asymptomatic controls underwent HRM with a solid-state manometric assembly incorporating 36 circumferential sensors spaced at 1-cm intervals positioned to record from the hypopharynx to the stomach. Ten 5-ml water swallows were obtained. EGJ relaxation was quantified by 1) nadir pressure, 2) the lowest 3-s mean residual pressure after swallow (E-sleeve), and 3) the transsphincteric gradient 2-6 s after swallowing measured from 2 cm above to 2 cm below the EGJ. A new parameter, integrated relaxation resistance (IRR), was also calculated. The IRR calculation accounted for both the duration of EGJ relaxation and instantaneous E-sleeve-type relaxation pressures during the entire interval of relaxation. The means and ranges (5-95th percentile) for nadir lower esophageal sphincter relaxation pressure (mean: 3.9 mmHg, range: 0-10.1 mmHg) and E-sleeve relaxation pressure (mean: 8.1 mmHg, range: 4.1-15.1 mmHg) were consistent with previously reported values. The mean relaxation interval was 7.95 +/- 0.2 s (mean +/- SE), whereas the median relaxation pressure during that interval was 10.7 +/- 0.5 mmHg (mean +/- SE). Mean IRR was 1.3 mmHg/s (95th percentile: 3.0 mmHg/s). Mean EGJ length was 3.7 cm. In conclusion, HRM provides a seamless dynamic representation of pressure within and across the EGJ. In addition to providing conventional EGJ relaxation parameters, this technology also creates opportunities to quantify more precise measures of EGJ relaxation and morphology.     

The upper esophageal sphincter in the cat: the role of central innervation assessed by transient vagal blockade

Studies were performed on four cats to assess the role of extrinsic innervation via the cervical nerve trunks in the control of upper esophageal sphincter function. Transient vagal nerve blockade was accomplished by cooling the cervical vagosympathetic nerve trunks previously isolated in skin loops on each side of the neck. Upper esophageal sphincter pressure was measured using a multilumen oval manometry tube and a rapid pull-through technique. The upper esophageal sphincter response to cervical intraesophageal balloon distention and acid perfusion was assessed. The feline upper esophageal sphincter has a distinct asymmetric pressure profile, whereby anterior pressure greater than posterior pressure greater than left pressure greater than right pressure. Bilateral vagal nerve blockade lowered the mean upper esophageal sphincter pressure from 18.5 +/- 1.5 to 12.0 +/- 2.8 mmHg (1 mmHg = 133.3 Pa) (p less than 0.001), with a significant reduction in pressure in all four quadrants. Intraesophageal balloon distention and acid perfusion both produced a significant increase in upper esophageal sphincter pressure. Bilateral vagal nerve blockade completely abolished the response of the upper esophageal sphincter to balloon distention and acid perfusion. We conclude that normal upper esophageal sphincter tone in the cat is partially mediated by excitatory neural input via the cervical nerve trunks, presumably via the recurrent laryngeal nerves; and cervical intraesophageal balloon distention and acid perfusion produce reflex contraction of the upper esophageal sphincter, which is dependent on neural pathways via the cervical vagal nerve trunks, but the relative contribution of afferent and efferent pathways remains unknown.     

Mechanical function and fatty acid oxidation in the neonatal pig heart with ischemia and reperfusion

We investigated mechanical function and exogenous fatty acid oxidation in neonatal pig hearts subjected to ischemia, followed by reperfusion. Isolated, isovolumically-beating hearts, from pigs 12 h to 2 days of age, were perfused with an erythrocyte-enriched (hematocrit approximately 15%) solution (37 degrees C). All hearts were studied for 30 min. with a perfusion pressure of 60 mmHg (pre-ischemia). One group of hearts (low-flow ischemia, N = 12) was then perfused for 30 min. with a perfusion pressure of approximately 12 mmHg. In the other group (no-flow ischemic arrest, N = 9), the perfusion pressure was zero for 30 min. Following ischemia in both groups, the perfusion pressure was restored to 60 mmHg for 40 min. (reperfusion). Pre-ischemia parameters for all hearts averaged: left ventricular peak systolic pressure, 99.0 +/- 2.0 mmHg; end diastolic pressure, 1.9 +/- 0.2 mmHg; coronary flow, 3.4 +/- 0.1 ml/min per g; myocardial oxygen consumption, 56.6 +/- 1.6 microliter/min per g and fatty acid oxidation, 33.4 +/- 1.4 nmol/min per g. During low-flow ischemia, hearts released lactate, and the corresponding parameters decreased to: 30.7 +/- 0.9 mmHg; 1.2 +/- 0.3 mmHg; 0.8 +/- 0.1 ml/min per g; 26.6 +/- 2.3 microliters/min per g and 12.9 +/- 1.1 nmol/min per g, respectively. Early in reperfusion in both groups, all parameters, except for fatty acid oxidation, exceeded pre-ischemia values, before recovering to near pre-ischemia values. Late in reperfusion, however, rates of fatty acid oxidation exceeded pre-ischemia rates by approximately 60%. Thus, the neonatal pig heart demonstrated similar recovery following 30 min of low-flow ischemia or no-flow ischemic arrest.(ABSTRACT TRUNCATED AT 250 WORDS)     

The relation between pelvic pressure and bladder pressure during pelvic perfusion with standardized flow rates

The aim of this study was to elucidate the relation between pelvic pressure and bladder pressure during pelvic perfusion with standardized flow rates. Anaesthetized Danish Landrace Breed pigs (n = 5) weighing 35-40 kg were studied. Transparenchymally two 6-F catheters were placed in both renal pelves for pressure measurement and perfusion. Transurethrally two catheters were placed in the bladder for pressure measurements and for urine collection and infusion. Bladder filling was done with a constant infusion rate of 45 ml/min during perfusion of both pelves with saline consecutively with the flow rates: 0, 2, 4, 6 and 8 ml/min during continuous measurement of bladder and bilateral pelvic pressure. The baseline diuresis varied from 0.4-1.0 ml/min. Without pelvic perfusion a negative pressure gradient between pelvis and bladder was seen demonstrating the importance of ureteral peristalsis. Pelvic perfusion with 2 ml/min showed that pelvic and bladder pressure were equal demonstrating weakening of ureteral peristalsis. During perfusion with higher flow rates pelvic pressure was higher than bladder pressure, showing that the positive gradient was important for urine transport. In conclusion ureteral peristalsis is important at low flow rates during increasing bladder pressure. At higher flow rates peristalsis weakens and the pressure gradient is the determining factor.     

Myocardial blood volume and coronary resistance during and after coronary angioplasty

Animal experiments have shown that the coronary circulation is pressure distensible, i.e., myocardial blood volume (MBV) increases with perfusion pressure. In humans, however, corresponding measurements are lacking so far. We sought to quantify parameters reflecting coronary distensibility such as MBV and coronary resistance (CR) during and after coronary angioplasty. Thirty patients with stable coronary artery disease underwent simultaneous coronary perfusion pressure assessment and myocardial contrast echocardiography (MCE) of 37 coronary arteries and their territories during and after angioplasty. MCE yielded MBV and myocardial blood flow (MBF; in ml · min(-1) · g(-1)). Complete data sets were obtained in 32 coronary arteries and their territories from 26 patients. During angioplasty, perfusion pressure, i.e., coronary occlusive pressure, and MBV varied between 9 and 57 mmHg (26.9 ± 11.9 mmHg) and between 1.2 and 14.5 ml/100 g (6.7 ± 3.7 ml/100 g), respectively. After successful angioplasty, perfusion pressure and MBV increased significantly (P < 0.001 for both) and varied between 64 and 118 mmHg (93.5 ± 12.8 mmHg) and between 3.7 and 17.3 ml/100 g (9.8 ± 3.4 ml/100 g), respectively. Mean MBF increased from 31 ± 20 ml · min(-1) · g(-1) during coronary occlusion, reflecting collateral flow, to 121 ± 33 ml · min(-1) · g(-1) (P < 0.01), whereas mean CR, i.e., the ratio of perfusion pressure and MBF, decreased by 20% (P < 0.001). In conclusion, the human coronary circulation is pressure distensible. MCE allows for the quantification of CR and MBV in humans.     

Deglutitive upper esophageal sphincter relaxation: a study of 75 volunteer subjects using solid-state high-resolution manometry

This study aimed to use a novel high-resolution manometry (HRM) system to establish normative values for deglutitive upper esophageal sphincter (UES) relaxation. Seventy-five asymptomatic controls were studied. A solid-state HRM assembly with 36 circumferential sensors spaced 1 cm apart was positioned to record from the hypopharynx to the stomach. Subjects performed ten 5-ml water swallows and one each of 1-, 10-, and 20-ml volume swallows. Pressure profiles across the UES were analyzed using customized computational algorithms that measured 1) the relaxation interval (RI), 2) the median intrabolus pressure (mIBP) during the RI, and 3) the deglutitive sphincter resistance (DSR) defined as mIBP/RI. The automated analysis succeeded in confirming bolus volume modulation of both the RI and the mIBP with the mean RI ranging from 0.32 to 0.50 s and mIBP ranging from 5.93 to 13.80 mmHg for 1- and 20-ml swallows, respectively. DSR was relatively independent of bolus volume. Peak pharyngeal contraction during the return to the resting state postswallow was almost 300 mmHg, again independent of bolus volume. We performed a detailed analysis of deglutitive UES relaxation with a novel HRM system and customized software. The enhanced spatial resolution of HRM allows for the accurate, automated assessment of UES relaxation and intrabolus pressure characteristics, in both cases confirming the volume-dependent effects and absolute values of these parameters previously demonstrated by detailed analysis of concurrent manometry/fluoroscopy data. Normative values were established to aid in future clinical and investigative studies.     

Chinese medicinal herbs Muh-Shiang Bin-Lang-Wan increases the motility of sphincter of Oddi in anesthetized rabbits through activation of M1 muscarinic receptors

The sphincter of Oddi (SO) plays an important role in regulating the bile flow into the duodenum. This study was designed to investigate the effect of Chinese Medicinal Herbs Muh-Shiang-Bin-Lang-Wan (MSBLW) and their mechanism of action on regulating the motility of SO in rabbits. The activity of SO in anesthetized rabbits was measured by using a continuously perfused open-tip manometric method. The rabbits were administered with different doses of MSBLW through naso-gastric tubes. The SO motility before and after the administration of MSBLW were recorded, and analyzed with a computer equipped with an off line analysis software. The results showed that the SO activity, in terms of tonic pressure and phasic contraction pressure, were significantly changed. A significant lower tonic pressure and a higher phasic contraction pressure were noticed 40-60 min after administration of MSBLW with a peak response at 0.5-1.0 gm range. The responses were blocked by pretreatment of muscarinic receptors (M1) antagonist, pirenzepine (10 mg/kg, orally). We conclude that MSBLW is effective in increasing the SO motility in rabbits through activation of M1 muscarinic receptors. However, potential application of MSBLW in the treatment of human biliary disorders needs further evaluation.     

Utilizing intraluminal pressure differences to predict esophageal bolus flow dynamics

Successful esophageal emptying depends on the generation of a sustained intrabolus pressure (IBP) sufficient to overcome esophagogastric junction (EGJ) obstruction. Our aim was to develop a manometric analysis paradigm that describes the bolus driving pressure difference and the flow permissive time for esophageal bolus transit. Twenty normal subjects were studied with a 36-channel manometry assembly (1-cm spacing) during two 5- and one 10-ml barium swallows and concurrent fluoroscopy. Bolus domain pressure plots were generated by plotting bolus domain pressure (BDP) and EGJ relaxation pressure. BDP was defined as the pressure midway between the peristaltic ramp-up and the proximal margin of the EGJ. The flow permissive time was defined as the period where the BDP was > or = EGJ relaxation pressure. The mean BDP was 11.7 +/- 1.0 mmHg (SE), and the mean flow permissive time was 3.9 +/- 0.4 s for 5-ml swallows in normal controls. The mean BDP difference during flow was 4.0 +/- 1.0 mmHg. There was no significant difference in the fluoroscopic transit time and the flow permissive time calculated from the BDP plots (5 ml: fluoroscopy 3.4 +/- 0.2 s; BDP 3.9 +/- 0.4 s, P > 0.05). BDP plots provide a reliable measurement of IBP and its relationship with EGJ relaxation. The time available for flow can be readily delineated from this analysis, and the driving pressure responsible for flow can be accurately described and quantified. This may help predict abnormal bolus transit and the underlying mechanical properties of the EGJ.     

Temporal relationships between wall motion, intraluminal pressure, and flow in the isolated rabbit small intestine

Intraluminal manometry is a tool commonly used to record motility in the human digestive tract. The recorded signal results from a combination of factors, including the hydrodynamic pressure transmitted through the intestinal contents due to contraction of the gut wall and the force of the gut wall acting on the sensors in regions of a luminal occlusion. However, the actual relationships between small bowel wall contraction, the measured intraluminal pressure, and the resultant flow have not been directly addressed. Video recording and high-resolution fiber-optic manometry were used to create spatiotemporal video maps of diameter and intraluminal pressure from isolated segments of rabbit small intestine. In the unstimulated gut, longitudinal muscle contractions were the only detectable motor pattern; circular muscle contractions were elicited by distension or erythromycin (1 μM). Longitudinal muscle contractions were not lumen-occlusive, although they caused measurable low-amplitude changes in pressure. Localized nonpropagating circular muscle contractions caused small localized, nonpropagating peaks of intraluminal pressure. Propagating contractions of circular muscle evoked larger, propagating pressure changes that were associated with outflow. Propagating circular muscle contractions often caused dilation of aboral receiving segments, corresponding to "common cavities"; these were propulsive, despite their low intraluminal pressure. The highest-amplitude pressure events were caused by lumen-occlusive circular muscle contractions that squeezed directly against the catheter. These data allow us to define the complex relationships between wall motion, intraluminal pressure, and flow. A strong correlation between circular and longitudinal muscle contraction and intraluminal pressure was demonstrated. Common-cavity pressure events, caused by propulsion of content by circular muscle contractions into a receptive segment, were often of low amplitude but were highly propulsive. Studies of wall motion in isolated preparations, combined with manometry, can assist in interpretation of pressure recordings in vivo.     

A method for producing regional hypoglycemia in blood perfused tissue

Numerous studies have focused on the metabolic contributions of glucose and other substrates in isolated tissue preparations by examining the effects of eliminating glucose from the physiologic perfusate or bath solution. To date, however, an effective method of glucose removal from the blood supply to selected tissue in the whole animal model has not been available. We have developed a method for blood glucose removal by continuous flow dialysis. This method was used to generate isolated coronary hypoglycemia for an investigation of myocardial metabolic substrate selection during hypoperfusion in open-chest, anesthetized dogs. Arterial blood was passed through the dialysis system against an isotonic and physiologic dialysate solution prior to controlled coronary perfusion. During normal perfusion pressure (100 mmHg), with a coronary blood flow of 32 ± 4 ml/min, arterial blood glucose was reduced from 3.26 ± 0.31 to 0.54 ± 0.14 mM. When blood flow was reduced to 12 ± 3 ml/min with lower perfusion pressure (40 mmHg), dialysis reduced arterial glucose from 3.53 ± 0.36 to 0.15 ± 0.03 mM. We conclude that this is an effective method for producing regional hypoglycemia.     

Physiology of the esophageal pressure transition zone: separate contraction waves above and below

Manometrically measured peristaltic pressure amplitude displays a well-defined trough in the upper esophagus. Whereas this manometric "transition zone" (TZ) has been associated with striated-to-smooth muscle fiber transition, the underlying physiology of the TZ and its role in bolus transport are unclear. A computer model study of bolus retention in the TZ showed discoordinated distinct contraction waves above and below. Our aim was to test the hypothesis that distinct upper/lower contraction waves above/below the manometric TZ are normal physiology and to quantify space-time coordination between tone and bolus transport through the TZ. Eighteen normal barium swallows were analyzed in 6 subjects with concurrent 21-channel high-resolution manometry and digital fluoroscopy. From manometry, the TZ center (nadir pressure amplitude) and the upper/lower margins of the pressure trough were objectively quantified. Using fluoroscopy, we quantified space-time trajectories of the bolus tail and bolus tail pressures and maximum intraluminal pressures proximal to the tail with their space-time trajectories. In every swallow, the bolus tail followed distinct trajectories above/below the TZ, separated by a well-defined spatial "jump" that terminated an upper contraction wave and initiated a lower contraction wave (3.32 +/- 1.63 cm, P = 0.0004). An "indentation wave" always formed within the TZ distal to the upper wave, increasing in amplitude until the lower wave was initiated. As the upper contraction wave tail entered the TZ, it slowed and the tail pressure reduced rapidly, while indentation wave pressure increased to normal tail pressure values at the initiation of the lower wave. The TZ was a special zone of segmental contraction. The TZ is, physiologically, the transition from an upper contraction wave originating in the proximal striated esophagus to a lower contraction wave that moves into the distal smooth muscle esophagus. Complete bolus transport requires coordination of upper/lower waves and sufficient segmental squeeze to fully clear the bolus from the TZ during the transition period.     

Study of intestinal flow by combined videofluoroscopy, manometry, and multiple intraluminal impedance

Assessment of patterns of flow in the small bowel is difficult. Multiple intraluminal impedance has been recently used for study of flow dynamics in the esophagus. Our aims were 1) to validate multiple intraluminal impedance by correlating impedance events with intestinal flow as detected by fluoroscopy and 2) to determine intestinal flow patterns in the fasting and postprandial period and their correspondence with manometry. First, six healthy subjects underwent simultaneous video-fluoroscopic, manometric, and impedance recording from the duodenum. Videofluoroscopy was used to validate impedance patterns corresponding with barium flow in the fasting and postprandial periods. Next, 16 healthy subjects underwent prolonged simultaneous recording of impedance and manometry in both periods. Most flow events were short (10 cm or less), with antegrade flow being the most common. Correspondence between impedance and videofluoroscopy increased with increasing length of barium flow. Impedance corresponded better with flow, at any distance, than manometry. However, impedance and manometric events, when analyzed separately as index events, always corresponded with fluoroscopic flow. The fasting and postprandial periods showed comparable patterns of flow, with frequent, highly propulsive manometric and impedance sequences. Motility index was positively and significantly associated with length of impedance events. Phase 3 of the migrating motor complex could be easily recognized by impedance. Multiple intraluminal impedance can detect intestinal flow events and corresponds better with fluoroscopic flow than manometry.     

Digital infrared thermographic imaging for remote assessment of traumatic injury

The purpose of this study was to test the hypotheses that digital infrared thermographic imaging (DITI) during simulated uncontrolled hemorrhage will reveal 1) respiratory rate and 2) changes of skin temperature that track reductions of stroke volume. In 45 healthy volunteers (25 men and 20 women), we recorded the ECG, finger photoplethysmographic arterial pressure, respiratory rate (pneumobelt and DITI of the nose), cardiac output (inert rebreathing), and skin temperature of the forehead during lower body negative pressure (LBNP) at three continuous decompression rates; slow (-3 mmHg/min), medium (-6 mmHg/min), and fast (-12 mmHg/min) to an ending pressure of -60 mmHg. Respiratory rates calculated from the pneumobelt (14.7 ± 0.9 breaths/min) and DITI (14.9 ± 1.2 breaths/min) were not different (P = 0.21). LBNP induced an average stroke volume reduction of 1.3 ml/mmHg regardless of decompression speed. Maximal reductions of stroke volume and forehead temperature were -100 ± 12 ml and -0.32 ± 0.12°C (slow), -86 ± 12 ml and -0.74 ± 0.27°C (medium), and -78 ± 5 ml and -0.17 ± 0.02°C (fast). Changes of forehead temperature as a function of changes of stroke volume were best described by a quadratic fit to the data (slow R(2) = 0.95; medium R(2) = 0.89; and fast R(2) = 0.99).Our results suggest that a thermographic camera may prove useful for the remote assessment of traumatically injured patients. Life sign detection may be determined by verifying respiratory rate. Determining the magnitude and rate of hemorrhage may also be possible based on future algorithms derived from associations between skin temperature and stroke volume.     

NO在胆道加压引起的反射活动中的作用

向胆道加压至 4kPa ,可同时引起血压降低和Oddi括约肌 (SO)肌电活动减弱或消失 ,这总称为胆道加压反射 ,其中前者称为胆道 血压反射 ,后者称为胆道 SO反射。本实验应用 3 2只家兔观察一氧化氮 (NO)对胆道加压反射活动的影响。在静脉滴注去甲肾上腺素 4 μg/(kg·min)引起血压升高和SO肌电振幅增大的基础上 ,再行胆道加压至 4kPa ,仍同时引起血压降低和Oddi括约肌 (SO)肌电活动减弱 ;而在静脉注射NO合酶抑制剂NG 硝基 L 精氨酸 (L NNA) 10mg/kg引起血压升高和SO肌电振幅增大的基础上 ,再行胆道加压至 4kPa,全部动物胆道 血压反射受到完全抑制 ,即未出现血压降低反应 ;少数 ( 3 /8)动物胆道 SO反射受到完全抑制 ,多数 ( 5 /8)动物该反射受到明显抑制 (P <0 0 1)。向SO局部灌注L NNA ,只引起SO肌电振幅增大而不影响血压 ,在此基础上行胆道加压 ,对胆道 SO反射的影响与全身用药相似 ,对胆道 血压反射却无影响。这提示 ,这两种反射活动是相对独立的 ,是经不同传出途径和效应器实现的 ;且这两种反射都主要是通过NO介导的     

Bronchial collateral vessel micropuncture pressure in postobstructive pulmonary vasculopathy.

Postobstructive pulmonary vasculopathy, produced by chronic ligation of one pulmonary artery, markedly increases bronchial blood flow. Previously, using arterial and venous occlusion, we determined that bronchial collaterals enter the pulmonary circuit at the distal end of the arterial segment. In this study, we tested the hypothesis that pressure in bronchial collaterals (Pbr) closely approximates that at the downstream end of the arterial segment (Pao). We pump perfused [111 +/- 10 (SE) ml/min] left lower lobes of seven open-chest live dogs 3-15 mo after ligation of the left main pulmonary artery. Bronchial blood flow was 122 +/- 16 ml/min. We measured pulmonary arterial and venous pressures and, by arterial and venous occlusion, respectively, Pao and the pressure at the upstream end of the venous segment (Pvo). Pbr was obtained by micropuncture of 34 pleural surface bronchial vessels 201 +/- 16 microns in diameter. We found that Pbr (14.4 +/- 1.0 mmHg) was similar to Pao (15.0 +/- 0.8 mmHg) but differed significantly (P < 0.01) from Pvo (11.3 +/- 0.5 mmHg). In addition, Pbr was independent of systemic arterial pressure and bronchial vessel diameter. Light and electron microscopy revealed that, in the lobes with the ligated pulmonary artery, the new bronchial collaterals entered the thickened pleura from the parenchyma via either bronchovascular bundles or interlobular septa and had sparsely muscularized walls. We conclude that, in postobstructive pulmonary vasculopathy, bronchial collateral pressure measured by micropuncture is very close to the pressure in precapillary pulmonary arteries and that most of the pressure drop in the bronchial collaterals occurs in vessels > 350 microns in diameter.     

Effect of somatostatin on lower esophageal sphincter (les) pressure and serum gastrin in normal and achalasic subjects

Serum gastrin and lower esophageal sphincter (LES) responses to somatostatin infusion were evaluated in ten normal subjects and in nine achalasic patients in order to determine evidence of hormonal (presumably gastrin)control of LES pressure. After somatostatin infusion, a significant decrease of serum gastrin was observed in normal subjects at 30 min (81.6 +/- 3.2 versus 40.0 +/- 4.7 pg/ml; p less than 0.01) and a rapid increase of LES pressure was also observed (26.0 +/- 1.3 versus 34.1 +/- 1.6 mmHg; p less than 0.01). In achalasia no change was observed in serum gastrin concentration after somatostatin infusion. LES pressure at 20 min however significantly decreased (45.8 +/- 7.6 versus 31.6 +/- 2.3 mmHg; p less than 0.05). Endogenous gastrin is not a major control factor for LES pressure in either normal or achalasic subjects.     

A two-stage regulatory system for pressure-constant perfusion of coronary vessels

This paper describes a double-loop servo-controlled pump system for the constant-pressure perfusion of a coronary artery. Due to the transient nature of changes in coronary vasomotor tone, such a perfusion system must have a fast regulatory response. In the first stage, a servo-controlled pump primes a windkessel having a volume of 35 ml with blood. The pumping rate is electronically controlled to maintain a constant pressure within the windkessel max. 700 mmHg. The maximal flow rate is 300 ml/min. To reduce the high pressure in the windkessel to the desired coronary perfusion pressure, a variable flow resistance, comprising a clamped thin-walled silicone tube, is provided in the output line of the system. A fast servo-motor drives the clamp and is controlled by an electronic regulator, using a second feedback loop from the pressure signal measured at the tip of the perfusion cannula. The system stabilizes the coronary perfusion pressure within 300 ms. An additional modulation of the setpoint signal in synchrony with the cardiac cycle improves the phasic pattern of the blood flow, and thus prevents changes in transmural blood flow distribution. The dead volume of the overall system is about 60 ml. Hemolysis caused by this system during five hours of perfusion in vivo is negligible.     

21毫米人造心脏瓣膜泵的设计及研制

为了研究能够长期置入主动脉瓣环的左心室辅助装置,研制出直径21毫米重27克可植入的主动脉瓣膜泵.装置包括一个转子和一个定子.转子由驱动磁钢和叶轮组成;定子装有带铁心的电机线圈和出口导叶.装置被置於主动脉瓣位置,所以不占用额外的解剖空间.血泵能像自然心脏一样直接将血液由心室输送到主动脉,不需要连接管道和旁路,因此对自然生理循环的干扰可以减到最低.血泵流量由最大到零周期变化.血液动力学测试表明,当血泵转速为17500转/分钟时,可以产生流量5升/分钟、压力增益50毫米汞柱的血流;同一转速下,当流量为零时,血泵能保持主动脉舒张压为80毫米汞柱.     

Measurement of small-intestinal motor activity in the preterm infant

The development of motor activity within the small intestine of preterm human infants is very poorly understood. Using a miniaturized multilumen continuous perfusion manometric technique the motor activity of the small intestine was followed longitudinally in a group of preterm infants. The system performed well at very low perfusion rates and clearly showed increases in both the magnitude and organization of motor activity with increasing gestational age.