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At least 1,099 records · Page 61Linked to original sources
PubMed1994

Extradural dead space following cranial bone advancement.

The extradural dead space produced after enlargement of the intracranial space or after reduction of the volume of the intracranial contents persists for an unknown period of time. To investigate this further, an extradural dead space was surgically created by advancement of parietal bones in 9 adult rabbits. By design, there was no connection with the paranasal sinuses. To determine outcome of the dead space, three-dimensional computed tomographic and histological studies were performed. The brain volume decreased in the first 3 months after surgery and remained constant for up to 9 months. The extradural volume increased in the first 4 weeks postoperatively, gradually decreasing in size with time. The brain failed to eliminate the extradural dead space by rearrangement or expansion. An osseous cavity filled with fluid and connective tissue was formed within the dead space. The fluid within it remained, even 9 months after surgery. This could be a potential environment for bacterial invasion if there was a connection with the nasopharynx.

Animals↗
PubMed2000

Dynamic size-change of hand peripersonal space following tool use.

Humans and monkeys share similar sensory integrated processing of tactile and peri-hand visual inputs for coding peripersonal space surrounding the hand. In monkeys, tool use is known to induce a transient elongation of hand-centred peripersonal space along the tool axis. Here we report evidence that, also in humans, the use of a tool can increase the spatial extent of the representation of peri-hand visual space to incorporate the tool. We investigated this phenomenon in patients with tactile extinction, by using a cross-modal paradigm well suited to reveal visual-tactile integration near patients' hand. In the present study cross-modal extinction was assessed far from patients' ipsilesional hand, at the distal edge of a hand-held rake. We found that cross-modal extinction was more severe after patients used the rake to retrieve distant objects with respect to a condition in which the rake was not used. This evidence of an expansion of peri-hand space lasted only a few minutes after tool use. By contrast, peri-hand space expansion was not observed when motor actions towards distant objects did not involve the tool. These findings show that visual peri-hand space has important dynamic properties in humans; it can be expanded and contracted depending upon tool use.

Aged↗
PubMed2001

Microcatheterization of the cervical epidural space via lumbar puncture: technical note.

OBJECTIVE: Deposition of opiates, corticosteroids, or local anesthetics into the epidural space is useful for the management of painful maladies of the cervical and thoracic spine. We describe a novel technique for epidural medication delivery via an angiographic microcatheter inserted at or below the conus and advanced cephalad under fluoroscopic guidance. Unlike commercial kits used by anesthesiologists, this method uses a radiopaque catheter that can be precisely targeted to the levels of interest. The hazards of direct puncture, such as "wet tap" or injury to the cervical cord, are minimized. METHODS: An 18-gauge Tuohy needle is inserted into the lumbar epidural space. A 2.3-French microcatheter and a 0.018-inch steerable guidewire are then introduced through the lumen of the needle. The catheter is fluoroscopically advanced to the cervical epidural space, where Depo-Medrol (Pharmacia & Upjohn, Kalamazoo, MI) is administered. As the catheter is withdrawn, additional corticosteroid can be delivered to the thoracic epidural space, together with long-acting morphine compounds or local anesthetics. Regional pressures within the epidural space and other physiological parameters can be measured, and the local microenvironment can be sampled. RESULTS: To date, we have performed 16 procedures for 13 patients. All patients reported improvement, of varying extent and duration. There have been no complications. CONCLUSION: Our system of accessing the epidural space has many advantages, compared with direct puncture and commercially available kits. It provides a safe means of delivering epidural medication to multiple spinal levels and permits measurement of physiological variables that may be useful in the diagnosis and treatment of cervical and thoracic spine disease.

Angiography↗
PubMed2006

Comparison of 'whoosh' and modified 'swoosh' test for identification of the caudal epidural space in children.

BACKGROUND: Caudal analgesia is widely used in pediatric anesthesia practice. The 'whoosh' test which uses air to identify the epidural space, has been recommended as a guide for successful needle placement. However, the use of air may be associated with an incidence of neurological complications. The 'swoosh' test avoids the injection of air and was originally performed using injection of a local anesthetic solution. A comparison was made between the 'whoosh' test and a modified 'swoosh' test using saline to identify the caudal epidural space in children. METHODS: We studied 60 children of either sex in the age group of 2-8 years undergoing inguinal herniotomy. During insertion of the caudal block, a stethoscope was placed over the lower lumbar spine to note the presence or absence of 'whoosh' or 'swoosh', by an independent observer who was blinded to the injection of 1 ml of air or saline which was given simultaneously by the operator into the caudal space. The operator's clinical impression of successful insertion of the needle was also recorded and correlated with the presence or absence of 'whoosh' or 'swoosh'. In addition, the need for supplemental intraoperative analgesia was noted. RESULTS: Overall success rate of caudal block using the 'whoosh' and modified 'swoosh' tests was found to be 96.6% and 93.3%, respectively as judged by the lack of supplementary perioperative analgesia. The sensitivity, specificity and positive predictive value of the 'whoosh' test and clinical predictors of caudal placement was found to be 100% whereas the modified 'swoosh' test had a sensitivity of 93%, specificity of 50% and a positive predictive value of 96%. However, statistically there was no significant difference between the clinical predictors, 'whoosh' and the modified 'swoosh' test for identification of the caudal epidural space. CONCLUSIONS: The modified 'swoosh' test is as reliable as the 'whoosh' test and we recommend it for identification of the caudal epidural space in children as it avoids injection of air into the caudal space.

Air↗
PubMed2005

Prognostic factors for alveolar regeneration: effect of space provision.

OBJECTIVES: The role of space provision as an independent prognostic factor for periodontal regeneration remains to be established. The objective of this study was to evaluate the role of space provision on alveolar bone regeneration in periodontal sites. METHODS: Critical size, supra-alveolar, periodontal defects were created in 11 young adult Beagle dogs. Six animals received a porous ePTFE device to provide for space provision. Five animals received sham surgery. The animals were euthanized at 8 weeks post-surgery. A histometric analysis assessed vertical regeneration of alveolar bone and the width of the alveolar crest at the base of the defect. Because of the correlation of within-dog measurements, a mixed model anova/ancova was used to analyse the data. RESULTS: A significant relationship between the width of the alveolar crest at the base of the defect and bone regeneration was observed with no significant difference between sites receiving the different treatments (p=0.84). Bone regeneration at sites treated with the space-providing device was significantly greater compared with that at sites treated with sham surgery (p=0.0003), and the difference remained significant after adjusting for bone width (p=0.0001). CONCLUSIONS: Space provision has a significant effect on alveolar bone regeneration in periodontal sites. The width of the alveolar bone appears to influence space provision effectively supporting bone regeneration.

Alveolar Bone Loss↗
PubMed1984

A qualitative ultrastructural study of the intercellular spaces between epithelial cells treated in vivo with DMBA.

One of the features of epithelial dysplasia at the histological level is known as "loss of cellular adherence" in which adjacent epithelial cells appear more widely separated from each other than in normal tissues. In this study we examine the effects of the carcinogen DMBA on the epithelium of the hamster cheek-pouch with particular emphasis on the dimensions of the intercellular spaces. DMBA-induced lesions were processed for electron microscopy and assigned to hyperplasia, dysplasia and carcinoma groups, using defined criteria on toluidine blue-stained 1 micron Araldite sections. Untreated pouches were used as a control. At the light-microscopical level, intercellular spaces in hyperplastic epithelium appeared similar to those present in untreated tissue but increased progressively in dysplastic and carcinomatous lesions. Spaces were generally wider between basal and spinous cells than between granular cells, although wide variations were observed between tissue blocks demonstrating similar histological features and also within adjacent areas of the same block. At the ultrastructural level, untreated and hyperplastic tissue showed only occasional focal separations of adjacent plasma membranes; these spaces were more frequent between cells of lower strata. In sections from dysplasias and carcinomas, spaces were always extensive and were occupied by numerous villous or foliate membrane-bound cytoplasmic extensions. These were often attached to each other by desmosomes of apparently normal morphology but of a lower frequency than in untreated epithelium. The increased epithelial separation as indicated by the increased intercellular spaces during chemical carcinogenesis may be a result of any or all of the following factors: desmosomal disruption or their failure to develop; the production of cell-surface molecules which are less adhesive; inflammatory oedema and direct alterations on intercellular junctions and cell-surface components by infiltrating inflammatory cells.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1992

Nutrition in space: evidence from the U.S. and the U.S.S.R.

Space flight exposes humans to a hostile, stressful environment as well as to the weightlessness associated with microgravity. The stresses of space travel affect nutritional balance, as evidenced by interrelated changes in body composition, energy utilization, and endocrine function. The limited data gathered thus far suggest that space flight incurs acute decreases in fluid mass and chronic, ongoing changes in muscle and bone mass. Concurrent with these changes is an increase in energy used per unit body mass. Other preliminary data suggest that bed rest and space flight may incur increased sensitivity to insulin. Further research is needed to determine the human energy and protein requirements for space, as well as a means of quantifying changes in body composition during extended-duration space flight.

Body Composition↗
PubMed1968

Fluid transport and tubular intercellular spaces in reptilian kidneys.

Renal tubules of crocodiles, lizards, snakes, and turtles have intercellular spaces similar in type to those observed in the mammalian gall bladder, but different from those of mammalian renal tubules. The fluid movements across renal tubules of reptiles are correlated with the width of the tubular intercellular spaces. In the proximal tubules, where transport is always isosmotic, the spaces are open whenever the tubular epithelium is tranporting, but closed when no transport is taking place. In distal tubules, intercellular spaces are wide open when the osmolality of the urine is close to that of the blood, that is, when the fluid resorbed is almost isosmotic to the tubular fluid. The apical two-thirds of the intercellular spaces are closed when the urine is hypoosmotic. They are also closed when the tubules are not transporting, as in collapsed tubules or tubules poisoned with ouabain. Thus, as in the gall bladder, the open intercellular spaces appear to be found whenever there is fluid transport across the epithelium.

Animals↗
PubMed2005

Contribution of folate biosynthesis to Ralstonia solanacearum proliferation in intercellular spaces.

The vigorous proliferation of Ralstonia solanacearum OE1-1 in host intercellular spaces after the invasion of host plants is necessary for the virulence of this bacterium. A folate auxotroph, RM, in which a mini-Tn5 transposon was inserted into pabB encoding para-aminobenzoate synthase component I, lost its ability to vigorously proliferate in intercellular spaces along with its systemic infectivity and virulence after inoculation into roots and infiltration into leaves of tobacco plants. Complementation of RM with the pabB gene allowed the mutant to multiply in intercellular spaces and to cause disease. In tobacco plants that were pretreated with folate, RM was able to vigorously proliferate in the intercellular spaces and cause disease. Interestingly, when it was inoculated through cut stems, the mutant multiplied in the plants and was virulent. Moreover, the mutant multiplied well in stem fluids but not in intercellular fluids, suggesting that the folate concentration within intercellular spaces may be a limiting factor for bacterial proliferation. Therefore, folate biosynthesis contributes to the vigorous proliferation of bacteria in intercellular spaces and leads to systemic infectivity resulting in virulence.

DNA Transposable Elements↗
PubMed2003

Coding of auditory space.

Behavioral, anatomical, and physiological approaches can be integrated in the study of sound localization in barn owls. Space representation in owls provides a useful example for discussion of place and ensemble coding. Selectivity for space is broad and ambiguous in low-order neurons. Parallel pathways for binaural cues and for different frequency bands converge on high-order space-specific neurons, which encode space more precisely. An ensemble of broadly tuned place-coding neurons may converge on a single high-order neuron to create an improved labeled line. Thus, the two coding schemes are not alternate methods. Owls can localize sounds by using either the isomorphic map of auditory space in the midbrain or forebrain neural networks in which space is not mapped.

Animals↗
PubMed1998

Tissue spaces in rat heart, liver, and skeletal muscle in vivo.

Tissue spaces were determined in rat heart, liver, and skeletal muscle in vivo using isotopically labeled [14C]inulin. Tracer was injected into the jugular vein of pentobarbital-anesthetized male Sprague-Dawley rats. After a 30-min equilibration period, a blood sample was taken, and heart, liver, and gastrocnemius muscle were excised and immediately freeze clamped at liquid nitrogen temperatures. The extracellular inulin space was 0.209 +/- 0.006 (n = 13), 0.203 +/- 0.080 (n = 7), and 0.124 +/- 0.006 (SE) ml/g wet wt tissue (n = 8) for heart, liver, and skeletal muscle, respectively. Total tissue water was 0.791 +/- 0.005 (n = 9), 0.732 +/- 0.002 (n = 9), and 0.755 +/- 0.005 ml/g wet wt tissue (n = 10) for heart, liver, and skeletal muscle, respectively. Expressed as a percentage of total tissue water, the intracellular space was 73.6, 72.2, and 83. 7% for heart, liver, and skeletal muscle, respectively. With use of 2,3-diphospho-D-glyceric acid as a vascular marker, the interstitial space was calculated by subtracting the counts in tissue due to whole blood from total tissue counts and dividing by plasma counts. The interstitial space was 18.8, 22.4, and 14.5% of total tissue water, with accompanying plasma spaces of 7.7, 5.3, and 1.8% for heart, liver, and gastrocnemius muscle, respectively. The tracer method used in this study provides a quantitative assessment of water distribution in tissues of nonnephrectomized rats that has applications for calculation of tissue ion and metabolite concentrations, gradients, and fluxes under normal and pathophysiological conditions.

Animals↗
PubMed1985

Error due to dead-space admixture in single-breath method for estimation of pulmonary blood flow.

The single-breath method of Kim et al. (J. Appl. Physiol. 21: 1338-1344, 1966) for the estimation of pulmonary blood flow is based on a single-alveolus lung model for which an analytical relationship has been established between the kinetic behavior of the alveolar O2 and CO2 tensions and the pulmonary blood flow. The analysis is based on the assumption that the dead-space contribution to the expirate is negligible after expiration of a predefined volume. We have examined the influence of this assumption on the estimation of pulmonary blood flow by computer simulation in a lung model that incorporates deadspace contribution to the expirate. Data on the fractional contribution of the dead space to the expired gas were obtained from Tsunoda et al.'s study (J. Appl. Physiol. 32: 644-649, 1972) on the emptying pattern of normal adult lungs. The results show that failure to take account of the dead-space contribution can cause an underestimation in the pulmonary blood flow of greater than 30%. The error can be reduced by ignoring the first part of the expiration but only at the cost of an increase in the sensitivity of the single-breath method to measurement noise. This property of the system is demonstrated experimentally. The error due to dead-space admixture depends on the total volume of dead-space gas, the measurement noise, the pulmonary blood flow, and the emptying characteristics of the dead-space compartment during expiration. In normal subjects it is possible to optimize the experimental design so that the systematic error is less than 5% and the coefficient of variation is less than 10%.(ABSTRACT TRUNCATED AT 250 WORDS)

Computers↗
PubMed1986

Physiological dead space and effective parabronchial ventilation in ducks.

Gas exchange in avian lungs is described by a cross-current model that has several differences from the alevolar model of mammalian gas exchange [e.g., end-expired PCO2 greater than arterial PCO2 (PaCO2)]. Consequently the methods available for estimating effective ventilation and physiological dead space (VDphys) in alveolar lungs are not suitable for an analysis of gas exchange in birds. We tested a method for measuring VDphys in birds that is functionally equivalent to the conventional alveolar VDphys. A cross-current O2-CO2 diagram was used to define the ideal expired point (PEi) and VDphys was calculated as from the equation, VDphys = [(PEiCO2--PECO2)/PEiCO2]. VT, where VT is tidal volume. In seven Pekin ducks VDphys was 13.8 ml greater than anatomic dead space and measured changes in the instrument dead space volume. VDphys also reflected changes in ventilation-perfusion inequality induced by temporary unilateral pulmonary arterial occlusion. Bohr dead space, calculated by substituting end-expired PCO2 for PEiCO2, was insensitive to such inhomogeneity. Enghoff dead space, calculated by substituting PaCO2 for PEiCO2, is theoretically incorrect for cross-current gas exchange and was often less than anatomic dead space. We conclude that VDphys is a useful index of avian gas exchange and propose a standard definition for effective parabronchial ventilation (VP) analogous to alveolar ventilation (i.e., VP = VE--VDphys, where VE is total ventilation).

Animals↗
PubMed1990

Effect of common dead space on VA/Q distribution in the dog.

Several previous studies have shown worsening ventilation-perfusion (VA/Q) relationships in humans during heavy exercise at sea level. However, the mechanism of this deterioration remains unclear because of the correlation with ventilatory and circulatory variables. Our hypothesis was that the decrease in the series dead space-to-tidal volume ratio during exercise might be partly responsible because mixing in the common dead space can reduce apparent inequality. We tested this notion in 10 resting anesthetized normocapnic dogs passively hyperventilated by increase tidal volume and a) inspired CO2 or b) external dead space. We predicted less apparent VA/Q inequality in condition b because of mixing in the added dead space. After base-line measurements, conditions a and b were randomly assigned, and after a second set of base-line measurements they were repeated in the reverse order in each dog. VA/Q inequality was measured by the multiple inert gas elimination technique. Comparison of conditions a and b demonstrated that additional external dead space improved (P less than 0.001) the blood flow distributions as hypothesized [log standard deviation of perfusion = 0.49 +/- 0.02 (SE) in condition b and 0.61 +/- 0.03 in condition a with respect to 0.52 +/- 0.03 at base line]. This study suggests that the increased tidal volume during exercise could uncover VA/Q inequality not evident at rest because of the higher ratio of common dead space to tidal volume at rest.

Animals↗
PubMed1994

Pulmonary dead space and airway dimensions in dogs at different levels of lung inflation.

The quasi-stationary front that separates inspired gas from mixed alveolar gas is largely determined by the balance between diffusive and convective forces of gas transport. To investigate parameters influencing this balance, a study was performed on eight anesthetized ventilated beagle dogs. Measurements were made of the volume of pulmonary dead space corresponding to four end-inspiratory lung volumes. Aerosol recovery techniques were used to determine airway sizes at lung depths corresponding to those respective dead space volumes as well as at fixed volumetric depths between 70 and 250 ml. Mean dead space volumes as measured by a single inhalation of He (and SF6) were 112 +/- 15 (SD) ml (127 +/- 15 ml), 120 +/- 18 ml (137 +/- 20 ml), 127 +/- 18 ml (145 +/- 20 ml), and 133 +/- 19 ml (155 +/- 21 ml) at end-inspiratory lung volumes of 64, 71, 79, and 86%, respectively, of total lung capacity. At fixed lung depths the airway diameters increased with higher levels of lung inflation. However, airway diameters "at the end of the dead space" did not change significantly. They were approximately 0.5 mm for SF6 dead space and approximately 0.75 mm for He dead space. These findings support the theoretical prediction that the position of the diffusion front during breathing is strongly dependent on airway geometry and much less dependent on parameters of the breathing maneuver.

Animals↗
PubMed2001

Historical aspects of the early Soviet/Russian manned space program.

Human spaceflight was one of the great physiological and engineering triumphs of the 20th century. Although the history of the United States manned space program is well known, the Soviet program was shrouded in secrecy until recently. Konstantin Edvardovich Tsiolkovsky (1857-1935) was an extraordinary Russian visionary who made remarkable predictions about space travel in the late 19th century. Sergei Pavlovich Korolev (1907-1966) was the brilliant "Chief Designer" who was responsible for many of the Soviet firsts, including the first artificial satellite and the first human being in space. The dramatic flight of Sputnik 1 was followed within a month by the launch of the dog Laika, the first living creature in space. Remarkably, the engineering work for this payload was all done in less than 4 wk. Korolev's greatest triumph was the flight of Yuri Alekseyevich Gagarin (1934-1968) on April 12, 1961. Another extraordinary feat was the first extravehicular activity by Aleksei Arkhipovich Leonov (1934-) using a flexible airlock that emphasized the entrepreneurial attitude of the Soviet engineers. By the mid-1960s, the Soviet program was overtaken by the United States program and attempts to launch a manned mission to the Moon failed. However, the early Soviet manned space program has a preeminent place in the history of space physiology.

Astronauts↗
PubMed1997

Dead space and slope indices from the expiratory carbon dioxide tension-volume curve.

The slope of phase 3 and three noninvasively determined dead space estimates derived from the expiratory carbon dioxide tension (PCO2) versus volume curve, including the Bohr dead space (VD,Bohr), the Fowler dead space (VD,Fowler) and pre-interface expirate (PIE), were investigated in 28 healthy control subjects, 12 asthma and 29 emphysema patients (20 severely obstructed and nine moderately obstructed) with the aim to establish diagnostic value. Because breath volume and frequency are closely related to CO2 elimination, the recording procedures included varying breath volumes in all subjects during self-chosen/natural breathing frequency, and fixed frequencies of 10, 15 and 20 breaths x min(-1) with varying breath volumes only in the healthy controls. From the relationships of the variables with tidal volume (VT), the values at 1 L were estimated to compare the groups. The slopes of phase 3 and VD,Bohr at 1 L VT showed the most significant difference between controls and patients with asthma or emphysema, compared to the other two dead space estimates, and were related to the degree of airways obstruction. Discrimination between no-emphysema (asthma and controls) and emphysema patients was possible on the basis of a plot of intercept and slope of the relationship between VD,Bohr and VT. A combination of both the slope of phase 3 and VD,Bohr of a breath of 1 L was equally discriminating. The influence of fixed frequencies in the controls did not change the results. The conclusion is that Bohr dead space in relation to tidal volume seems to have diagnostic properties separating patients with asthma from patients with emphysema with the same degree of airways obstruction. Equally discriminating was a combination of both phase 3 and Bohr dead space of a breath of 1 L. The different pathophysiological mechanisms in asthma and emphysema leading to airways obstruction are probably responsible for these results.

Adult↗
PubMed2003

Clinical results with the acoustic puncture assist device, a new acoustic device to identify the epidural space.

UNLABELLED: Sixty patients scheduled for lumbar epidural anesthesia were included in a study in which we evaluated the efficacy of localizing the epidural space by means of an acoustic signal. A prototype of an acoustic puncture assist device, connected to the epidural needle by an extension tube, generated the pressure needed to perform the epidural puncture and translated this pressure into corresponding acoustic and visible signals. The device frees the anesthesiologist to handle the epidural needle with both hands and to detect the epidural space by means of these signals. In all 60 patients (100%), the epidural space was successfully located by using the acoustic signal. In all cases, this was confirmed by the pressure measurement, which proved to be a reliable indicator for correct identification of the epidural space. We conclude that it is possible to locate the epidural space by means of the acoustic puncture assist device. The method proved to be reliable, safe, and simple in this study. The benefits of this new epidural puncture technique include better needle control, teaching, control of correct catheter placement, and documentation. The last can be an important adjunct to anesthesia practice. IMPLICATIONS: The authors demonstrate that it is possible to identify the epidural space by an acoustic and visible signal. An experimental setup constructed for this purpose makes the epidural puncture procedure audible and visible.

Acoustic Stimulation↗