Elevation gradient of intrathoracic pressure

1961 ◽  
Vol 16 (3) ◽  
pp. 465-468 ◽  
Author(s):  
John J. Krueger ◽  
Thomas Bain ◽  
John L. Patterson
Keyword(s):  
Pressure Gradient ◽  
Lung Tissue ◽  
Regional Differences ◽  
Work Of Breathing ◽  
Elevation Gradient ◽  
Intrathoracic Pressure ◽  
Vertical Gradient ◽  
Vertical Position ◽  
Horizontal Position ◽  
The Mean

Intrathoracic (intrapleural) pressure was measured in 15 anesthetized mongrel dogs held in the vertical position. A small balloon attached to a polyethylene catheter was inserted, without admission of air, into the chest through the 3rd intercostal space, or above the first rib, and passed down to the costophrenic sulcus. Along the lateral, anterolateral, and posterolateral aspects of the lung surface a vertical gradient of pressure was found, amounting to an increase of +0.21 cm H2O/cm descent, which was absent when the animal was in the horizontal position. This pressure gradient agrees closely with the gradient predicted on the basis of the mean density of lung tissue at end expiration in these animals. Among the implications of these findings is the possible existence of regional differences in the elastic work of breathing, based on differences in vertical distance between parts of the lung. Submitted on May 2, 1960

Regional differences in pleural lymphatic albumin concentration in sheep

1987 ◽  
Vol 252 (1) ◽  
pp. H64-H70 ◽  
Author(s):  
K. H. Albertine ◽  
E. L. Schultz ◽  
J. P. Wiener-Kronish ◽  
N. C. Staub
Keyword(s):  
Hydrostatic Pressure ◽  
Regional Differences ◽  
Left Lung ◽  
Vertical Gradient ◽  
Dark Field ◽  
Vertical Position ◽  
Albumin Concentration ◽  
The Difference ◽  
Field Reflectance ◽  
Vertical Height

We used quantitative reflectance autoradiography to compare the concentration of albumin in visceral pleural lymphatics at the cranial and caudal ends of the sheep's lung in the vertical (60 degrees head-up) and horizontal (supine) positions. Twelve to fourteen hours after injecting 125I-albumin intravenously we placed four anesthetized sheep in the vertical position to establish a microvascular hydrostatic pressure gradient along the vertical height of the lung. We placed two anesthetized sheep in the horizontal position. Four hours later, we fixed the left lung and removed visceral pleural tissue blocks from the cranial and caudal ends, separated by a 15-cm distance, along the costovertebral margin. We measured the silver grain density in the pleural lymphatic autoradiograms by dark-field reflectance microspectrophotometry. In the vertical position, the lymph albumin concentration at the cranial end (top) of the lung averaged 2.5 +/- 0.4 g/dl compared with the caudal end (bottom), which averaged 1.8 +/- 0.3 g/dl. The difference (42% greater at the top than the bottom) is significant (P less than 0.05). The computed gradient in perimicrovascular interstitial albumin osmotic pressure was 0.26 +/- 0.13 cmH2O/cm lung height. There were no differences between the cranial and caudal lymphatic groups in the two horizontal sheep. We conclude that in the sheep lung there is a gradient in perimicrovascular albumin concentration due to the vertical gradient in microvascular hydrostatic pressure.

A description of a vertical floating collimator; and an account of its application to astronomical observations with a circle and with a zenith telescope

1833 ◽  
Vol 2 ◽  
pp. 340-342
Keyword(s):  
Focal Length ◽  
Vertical Position ◽  
Circular Aperture ◽  
Plane Mirror ◽  
Horizontal Position ◽  
Astronomical Observations ◽  
The Subject ◽  
The Mean ◽  
Bull's Eye ◽  
Exact Point

The construction of the instrument which forms the subject of this paper, is a material improvement on that of the horizontal floating collimator, of which an account was given by the author in the Philosophical Transactions for 1825. Its superiority is derived from its adaptation to the vertical instead of the horizontal position, by which the sources of error arising from the necessity of transferring the instrument to different sides of the observatory, and of taking the float out of the mercury and replacing it, at each observation, are wholly obviated. The vertical floating collimator has the further advantage of being adapted for use, not only with a circle, but also with a telescope, either of the refracting or reflecting kind. Such a telescope, furnished with a wire micrometer, and directed to the zenith, becomes a zenith telescope, free from all the objections to which the zenith sector, and the zenith telescope, with a plumb line, are liable. The instrument itself is supported on a square mahogany stand, which slides on two parallel beams fixed at the upper part of the observatory in the direction of the meridian, and which has a circular aperture in the centre, having at its edge a projecting rim of iron to admit of the passage of the telescope. The telescope, of which the focal length is 8 inches, is supported in the vertical position by a bridge connecting it with a circular iron ring, 10 inches and 6/10 ths in diameter, which floats in mercury. The mercury is contained in a circular iron trough, the central aperture of which is sufficiently large to allow of its turning freely round the rim, which rises from the margin of the aperture of the stand. The object-glass of the telescope is placed at its lowest end, and its focus is occupied by a diaphragm, composed of two brass plates, each cut so as to form an angle of 135°, and placed opposite to each other, so that the angular points are brought to an accurate coincidence; thus leaving on each side intervening spaces, which form vertical angles of 45° each. The telescope below, whether belonging to a circle or a zenith telescope, is to be directed so that the image of these angles shall be bisected by the micrometer wire; for which purpose the diaphragm of the collimator is illuminated by a bull’s-eye lantern, placed at a convenient distance upon one of the beams crossing the observatory, the light being reflected downwards by a plane mirror placed on a screen with a suitable aperture immediately above the collimator. The collimator is then to be turned half round in azimuth, the motion being facilitated by rollers, and limited, as to extent, by two catches which receive a projecting wire fixed to the outer circle of the trough. When in this situation, the observation of the diaphragm by the telescope, and the bisection of its angles, are to be repeated, and the mean of the two positions will indicate the exact point of the zenith.

Stress distribution in gudgeon pins

1997 ◽  
Vol 32 (5) ◽  
pp. 375-386 ◽  
Author(s):  
H Fessler ◽  
T H Hyde
Keyword(s):  
Shear Stress ◽  
Cross Section ◽  
Vertical Position ◽  
Shear Stresses ◽  
Horizontal Position ◽  
Connecting Rod ◽  
Compressive Stresses ◽  
The Mean ◽  
Hoop Stresses ◽  
Realistic Shape

Frozen stress photoelastic tests were carried out on four shapes of gudgeon pins, loaded in a piston of realistic shape by a realistic connecting rod. The results showed that the greatest stresses occurred in the gaps between the piston and connecting rod at the horizontal position in the bore. Measured compressive hoop stresses and calculated shear stresses there were up to 2 1/2 times the mean shear stress. Thick ring calculations slightly overpredicted the compressive stresses and the tensile hoop stresses at the vertical position, i.e. they are 'safe’. The greatest axial stresses were smaller than the above. Measured pin deflections between the piston bosses were less than the results of simple beam calculations, which ignored the restraints exerted by the piston. Ovalization of the cross-section was largest in the middle.

Regional lung volume trajectories during expiratory flow in dogs

1996 ◽  
Vol 80 (4) ◽  
pp. 1144-1148 ◽  
Author(s):  
T. A. Wilson ◽  
M. J. Hill ◽  
R. D. Hubmayr
Keyword(s):  
Three Dimensional ◽  
Quadratic Function ◽  
Vertical Gradient ◽  
Small Scale ◽  
Vertical Position ◽  
Lung Capacity ◽  
Total Variability ◽  
Anesthetized Dogs ◽  
The Mean ◽  
Highly Correlated

Parenchymal markers were placed in the left caudal lobes of anesthetized dogs, and the three-dimensional positions of the markers were tracked by biplane videofluoroscopy during expiration from total lung capacity (TLC) to approximately 30% TLC at steady expiratory flows of 0.3-7% TLC/s. Regional volumes of samples of parenchyma with volumes at TLC of 1-5 cm3 were obtained by computing the volumes of tetrahedral defined by taking the markers, four at a time, as apices of the tetrahedra, Regional volume (Vr), as a fraction of volume at TLC, was plotted against average volume (VL), as a fraction of volume at TLC, and Vr was fit by a quadratic function of VL. The initial slopes of the plots, dVr/dVL at VL = 1, varied by +/- 26% from the mean slope of 1. The curvatures were highly correlated with the slopes, and the Vr vs. VL plots formed a nest of “onion skins”. The initial slopes were weakly correlated with the vertical position of the centroid of the tetrahedron, with the slope increasing by approximately 20%/cm, on average, in the dorsal direction in the supine dog. The vertical gradient in Vr accounted for approximately 30% of the total variability; small-scale heterogeneity contributed the remaining 70%. These results confirm earlier quasistatic measurements of nonuniform Vr and provide the first data on curvature of Vr trajectories. The mechanisms that cause the nongravitational component of Vr variability and the curvatures of the trajectories are unknown.

scholarly journals Use and success evaluation of percutaneous aortic balloon valvuloplasty in different hemodynamic entities of severe aortic stenosis in the TAVR era

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
K Piayda ◽  
A Wimmer ◽  
H Sievert ◽  
K Hellhammer ◽  
S Afzal ◽  
...  
Keyword(s):  
Heart Failure ◽  
Aortic Valve ◽  
Aortic Stenosis ◽  
Aortic Valve Replacement ◽  
Pressure Gradient ◽  
Severe Aortic Stenosis ◽  
Primary Treatment ◽  
Low Flow ◽  
Mean Pressure ◽  
The Mean

Abstract Background In the era of transcatheter aortic valve replacement (TAVR), there is renewed interest in percutaneous balloon aortic valvuloplasty (BAV), which may qualify as the primary treatment option of choice in special clinical situations. Success of BAV is commonly defined as a significant mean pressure gradient reduction after the procedure. Purpose To evaluate the correlation of the mean pressure gradient reduction and increase in the aortic valve area (AVA) in different flow and gradient patterns of severe aortic stenosis (AS). Methods Consecutive patients from 01/2010 to 03/2018 undergoing BAV were divided into normal-flow high-gradient (NFHG), low-flow low-gradient (LFLG) and paradoxical low-flow low-gradient (pLFLG) AS. Baseline characteristics, hemodynamic and clinical information were collected and compared. Additionally, the clinical pathway of patients (BAV as a stand-alone procedure or BAV as a bridge to aortic valve replacement) was followed-up. Results One-hundred-fifty-six patients were grouped into NFHG (n=68, 43.5%), LFLG (n=68, 43.5%) and pLFLG (n=20, 12.8%) AS. Underlying reasons for BAV and not TAVR/SAVR as the primary treatment option are displayed in Figure 1. Spearman correlation revealed that the mean pressure gradient reduction had a moderate correlation with the increase in the AVA in patients with NFHG AS (r: 0.529, p<0.001) but showed no association in patients with LFLG (r: 0.145, p=0.239) and pLFLG (r: 0.030, p=0.889) AS. Underlying reasons for patients to undergo BAV and not TAVR/SAVR varied between groups, however cardiogenic shock or refractory heart failure (overall 46.8%) were the most common ones. After the procedure, independent of the hemodynamic AS entity, patients showed a functional improvement, represented by substantially lower NYHA class levels (p<0.001), lower NT-pro BNP levels (p=0.003) and a numerical but non-significant improvement in other echocardiographic parameters like the left ventricular ejection fraction (p=0.163) and tricuspid annular plane systolic excursion (TAPSE, p=0.066). An unplanned cardiac re-admission due to heart failure was necessary in 23.7% patients. Less than half of the patients (44.2%) received BAV as a bridge to TAVR/SAVR (median time to bridge 64 days). Survival was significantly increased in patients having BAV as a staged procedure (log-rank p<0.001). Conclusion In daily clinical practice, the mean pressure gradient reduction might be an adequate surrogate of BAV success in patients with NFHG AS but is not suitable for patients with other hemodynamic entities of AS. In those patients, TTE should be directly performed in the catheter laboratory to correctly assess the increase of the AVA. BAV as a staged procedure in selected clinical scenarios increases survival and is a considerable option in all flow states of severe AS. (NCT04053192) Figure 1 Funding Acknowledgement Type of funding source: None

Effects of Intermittent Sequential Compression in Venous Hypertensive Microangiopathy

1994 ◽  
Vol 9 (3) ◽  
pp. 99-103 ◽  
Author(s):  
G. V. Belcaro ◽  
A. N. Nicolaides
Keyword(s):  
Venous Insufficiency ◽  
Marked Change ◽  
Venous Hypertension ◽  
Horizontal Position ◽  
Acute Effects ◽  
Doppler Flowmetry ◽  
Vasomotor Activity ◽  
The Mean ◽  
Intermittent Sequential Compression ◽  
Normal Controls

Objective: To investigate the acute effects of sequential compression on the microcirculation in limbs with chronic venous hypertension causing venous microangiopathy. Design: One group of patients with venous hypertension and a group of normal, comparable subjects were treated with intermittent sequential pneumatic compression applied for 30 min. Skin blood flow was measured by laser Doppler flowmetry at the perimalleolar region at rest (horizontal position) and on standing. The measurements were repeated at 0, 30 and 60 min after cessation of the compression. As criteria of inclusion, only limbs with high perimalleolar skin flux and decreased venoarteriolar response were included. Setting: St Mary's Hospital, London (teaching hospital). Patients, participants: Sixteen limbs in 16 patients with chronic venous hypertension and 12 limbs of comparable healthy volunteers were studied. Results: At rest, in the normal controls, the mean (SD) flux was 0.56 (0.3) units; it decreased on average by 35% on standing (venoarteriolar response). There was normal vasomotor activity. In patients, the mean flux was 1.45 (0.8) ( p < 0.025) and the median venoarticular response only 7%. There was very limited vasomotor activity. Vasomotor activity started 10 min after the commencement of compression. At the end of the compression period there was a marked change towards normality. Resting flux was 0.90 (0.5) (significantly decreased) and the venoarteriolar response had increased to 23% ( p < 0.025) with an improvement in vasomotor activity. These changes persisted at 30 and 60 min. Conclusions: The findings offer an explanation of the effect of sequential compression on the healing of leg ulcers in chronic venous insufficiency.

scholarly journals Monitoring Vegetation Greenness in Response to Climate Variation along the Elevation Gradient in the Three-River Source Region of China

2021 ◽  
Vol 10 (3) ◽  
pp. 193
Author(s):  
Zhaoqi Wang ◽  
Xiang Liu ◽  
Hao Wang ◽  
Kai Zheng ◽  
Honglin Li ◽  
...  
Keyword(s):  
Vegetation Index ◽  
Source Region ◽  
Elevation Gradient ◽  
Climate Variation ◽  
Mean Annual Precipitation ◽  
Near Infrared Reflectance ◽  
Area Index ◽  
Vegetation Greenness ◽  
The Mean ◽  
The Impact

The Three-River Source Region (TRSR) is vital to the ecological security of China. However, the impact of global warming on the dynamics of vegetation along the elevation gradient in the TRSR remains unclear. Accordingly, we used multi-source remote sensing vegetation indices (VIs) (GIMMS (Global Inventory Modeling and Mapping Studies) LAI (Leaf Area Index), GIMMS NDVI (Normalized Difference Vegetation Index), GLOBMAP (Global Mapping) LAI, MODIS (Moderate Resolution Imaging Spectroradiometer) EVI (Enhanced Vegetation Index), MODIS NDVI, and MODIS NIRv (near-infrared reflectance of vegetation)) and digital elevation model data to study the changes of VGEG (Vegetation Greenness along the Elevation Gradient) in the TRSR from 2001 to 2016. Results showed that the areas with a positive correlation of vegetation greenness and elevation accounted for 36.34 ± 5.82% of the study areas. The interannual variations of VGEG showed that the significantly changed regions were mainly observed in the elevation gradient of 4–5 km. The VGEG was strongest in the elevation gradient of 4–5 km and weakest in the elevation gradient of >5 km. Correlation analysis showed that the mean annual temperature was positively correlated with VIs, and the effect of the mean annual precipitation on VIs was more obvious at low altitude than in high altitude. This study contributes to our understanding of the VGEG variation in the TRSR under global climate variation and also helps in the prediction of future carbon cycle patterns.

Cross-sectoral Analysis of 1.4 Million AOK-insured Patients with Back Pain in Baden-Württemberg – What Influence does Outpatient Specialist Care Have?

2021 ◽  
Author(s):  
Tom R. Jansen ◽  
Heinz Endres ◽  
Lina Barnewold ◽  
Petra Kaufmann-Kolle ◽  
Sabine Knapstein ◽  
...  
Keyword(s):  
Primary Care ◽  
Back Pain ◽  
Surgical Procedures ◽  
Regional Differences ◽  
Pain Medication ◽  
Hospital Treatment ◽  
Specialist Care ◽  
Billing Data ◽  
Primary Care Clinics ◽  
The Mean

Abstract Background Back pain is one of the leading causes of disability globally and the most common musculoskeletal pain in Germany. The lifetime prevalence of back pain ranges from 74% to 85%, and the point prevalence ranges from 32% to 49%. One in five individuals with statutory health insurance visits a doctor at least once a year for back pain, and 1 in 20 individuals is on sick leave at least once a year. The question as to what extent can different outpatient care concepts substantially contribute to improving care and avoiding inpatient hospital treatment has repeatedly been the subject of controversial political discussions. This study aimed to present a description of the reality of care in Baden-Württemberg (BW), Germany, based on claims data. Material and Methods Anonymised routine billing data of AOK Baden-Württemberg were analysed in compliance with data protection regulations. The billing data cover the outpatient and inpatient care sectors. All AOK patients in BW who received at least one ICD10 diagnosis from their physician in the first half of 2015 were considered for the analysis. Patients with at least one diagnosis of back pain were evaluated as patients with back pain, whereby the assignment to the diagnosis group of specific or non-specific back pain was made based on the code. Results In the first half of 2015, nearly 988 925 patients with back pain were registered in the 6696 primary care clinics in BW, approximately 302 524 patients in 1172 orthopaedic clinics and 17 043 patients in 89 neurosurgical clinics. Primary care clinics reported back pain diagnosis in 34.6%, orthopaedic clinics in 51.9% and neurosurgical clinics in 78.6% of cases. Primary care clinics diagnosed a specific cause in approximately one-third of patients with back pain, orthopaedic clinics in approximately 40% of their patients and neurosurgery clinics in one in two cases. Overall, approximately 1.2% of 1.3 million patients with back pain (January to December 2015 in BW) were hospitalised. Inpatient therapy consisted of surgical therapy and conservative therapy. Nucleotomy, decompression and spondylodesis were the three most common surgical procedures performed. Pain medication and remedy prescriptions decreased pain after spinal surgery. There are significant regional differences in referral and surgery rates. The mean inpatient referral rate was 535 of 100 000 AOK insurants, and the median was 536 of 100 000 AOK insurants. The mean surgery rate among all admitted patients with back pain was 49.9%, and the median was 49.8%. Conclusion The vast majority of patients with back pain are treated as outpatients. Only approximately 1.2% of all patients with back pain were treated as inpatients in 2015. Of these, approximately half underwent surgery. Spinal surgeries led to a decrease in pain medication and remedy prescription postoperatively. The three most frequent surgical procedures were ‘decompression’, ‘excision of disc tissue’ and ‘spondylodesis’. There were significant regional differences.

Peripheral representation of antennal orientation by the scapal hair plate of the cockroach Periplaneta americana

2001 ◽  
Vol 204 (24) ◽  
pp. 4301-4309 ◽  
Author(s):  
J. Okada ◽  
Y. Toh
Keyword(s):  
Single Unit ◽  
Periplaneta Americana ◽  
Vertical Component ◽  
Horizontal Component ◽  
Vertical Position ◽  
Horizontal Position ◽  
Joint Movement ◽  
Basal Segment ◽  
Dynamic Phase ◽  
Hair Sensilla

SUMMARY Arthropods have hair plates that are clusters of mechanosensitive hairs, usually positioned close to joints, which function as proprioceptors for joint movement. We investigated how angular movements of the antenna of the cockroach (Periplaneta americana) are coded by antennal hair plates. A particular hair plate on the basal segment of the antenna, the scapal hair plate, can be divided into three subgroups: dorsal, lateral and medial. The dorsal group is adapted to encode the vertical component of antennal direction, while the lateral and medial groups are specialized for encoding the horizontal component. Of the three subgroups of hair sensilla, those of the lateral scapal hair plate may provide the most reliable information about the horizontal position of the antenna, irrespective of its vertical position. Extracellular recordings from representative sensilla of each scapal hair plate subgroup revealed the form of the single-unit impulses in response to hair deflection. The mechanoreceptors were characterized as typically phasic-tonic. The tonic discharge was sustained indefinitely (&gt;20 min) as long as the hair was kept deflected. The spike frequency in the transient (dynamic) phase was both velocity- and displacement-dependent, while that in the sustained (steady) phase was displacement-dependent.

The structure of a highly decelerated axisymmetric turbulent boundary layer

2021 ◽  
Vol 929 ◽  
Author(s):  
N. Agastya Balantrapu ◽  
Christopher Hickling ◽  
W. Nathan Alexander ◽  
William Devenport
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Shear Layer ◽  
Layer Thickness ◽  
Boundary Layer Thickness ◽  
Large Scale ◽  
Convection Velocity ◽  
Mean Flow ◽  
Mean Velocity ◽  
The Mean

Experiments were performed over a body of revolution at a length-based Reynolds number of 1.9 million. While the lateral curvature parameters are moderate ( $\delta /r_s < 2, r_s^+>500$ , where $\delta$ is the boundary layer thickness and r s is the radius of curvature), the pressure gradient is increasingly adverse ( $\beta _{C} \in [5 \text {--} 18]$ where $\beta_{C}$ is Clauser’s pressure gradient parameter), representative of vehicle-relevant conditions. The mean flow in the outer regions of this fully attached boundary layer displays some properties of a free-shear layer, with the mean-velocity and turbulence intensity profiles attaining self-similarity with the ‘embedded shear layer’ scaling (Schatzman & Thomas, J. Fluid Mech., vol. 815, 2017, pp. 592–642). Spectral analysis of the streamwise turbulence revealed that, as the mean flow decelerates, the large-scale motions energize across the boundary layer, growing proportionally with the boundary layer thickness. When scaled with the shear layer parameters, the distribution of the energy in the low-frequency region is approximately self-similar, emphasizing the role of the embedded shear layer in the large-scale motions. The correlation structure of the boundary layer is discussed at length to supply information towards the development of turbulence and aeroacoustic models. One major finding is that the estimation of integral turbulence length scales from single-point measurements, via Taylor's hypothesis, requires significant corrections to the convection velocity in the inner 50 % of the boundary layer. The apparent convection velocity (estimated from the ratio of integral length scale to the time scale), is approximately 40 % greater than the local mean velocity, suggesting the turbulence is convected much faster than previously thought. Closer to the wall even higher corrections are required.

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