scholarly journals Assessment at Different Airway Pressures of Vertical Gradient of Pleural Pressure in a Swine Model of Obesity

2020 ◽  
Author(s):  
L. Grassi ◽  
R. Santiago De Santis ◽  
C. Lima ◽  
G.C. Alcala ◽  
M.B.P. Amato ◽  
...  
Keyword(s):  
Vertical Gradient ◽  
Pleural Pressure ◽  
Swine Model ◽  
Airway Pressures

Inhomogeneity during deflation of excised canine lungs. I. Alveolar pressures

1988 ◽  
Vol 65 (4) ◽  
pp. 1757-1765 ◽  
Author(s):  
D. O. Warner ◽  
R. E. Hyatt ◽  
K. Rehder
Keyword(s):  
Pressure Gradient ◽  
Vertical Gradient ◽  
Pleural Pressure ◽  
Alveolar Pressure ◽  
Limiting Value

Factors both intrinsic and extrinsic to the lung may cause inhomogeneity of alveolar pressures during deflation. Wilson et al. (J. Appl. Physiol. 59: 1924-1928, 1985) predicted that any such inhomogeneity would be limited by interdependence of regional expiratory flows. To test this hypothesis and to explore how the pleural pressure gradient might affect inhomogeneity of alveolar pressures, we deflated at submaximal flows excised canine lobes that first were suspended in air and then were immersed in foams that simulated the vertical gradient of pleural pressure. Interregional inhomogeneity of regional transpulmonary pressures was measured with use of an alveolar capsule technique. Flow-dependent inhomogeneity of alveolar pressures was present, with differences in alveolar pressure quickly relaxing to a constant limiting value at each flow. Foam immersion increased inhomogeneity at a given flow. We conclude that factors intrinsic to the lung cause significant inhomogeneity of alveolar pressures at submaximal expiratory flows and that this inhomogeneity is enhanced by the extrinsic gradient of pleural pressure. These observations are consistent with the interdependence of flow proposed by Wilson et al.

Pressure outside the extrapulmonary airway in dogs

1978 ◽  
Vol 45 (3) ◽  
pp. 437-441 ◽  
Author(s):  
S. G. Spiro ◽  
B. H. Culver ◽  
J. Butler
Keyword(s):  
Lung Volume ◽  
Standing Position ◽  
Pleural Pressure ◽  
Positive Pressure ◽  
Anterior Surface ◽  
Lung Inflation ◽  
Airway Narrowing ◽  
Thin Fluid ◽  
Airway Pressures ◽  
Anesthetized Dogs

We have measured the static and dynamic transmural pressures of extrapulmonary airways during positive pressure lung inflation in anesthetized dogs suspended in the standing position. Thin, fluid-filled catheters measured pressures within and on the anterior surface of the airways in the mediastinum and neck. The change from mediastinal to cervical static extra-airway pressures (Pea) was not abrupt but occurred through the thoracic outlet and the root of the neck. The static Pea in the mediastinum was more positive than pleural pressure when lung volume was increased with positive pressures. During forced deflation equal pressure points (EPP) were in labor bronchi from which airway narrowing extended towards the mouth. Under these conditions, the dynamic mediastinal Pea mouthward of the EPP remained close to pleural pressures even at high volumes. This suggested that forces of restitution generated in the surrounding tissues by the narrowing of the airways did have a small effect in reducing the pressure affecting their anterior surface.

Liquid thickness vs. vertical pressure gradient in a model of the pleural space

1987 ◽  
Vol 62 (4) ◽  
pp. 1747-1754 ◽  
Author(s):  
S. J. Lai-Fook ◽  
D. C. Price ◽  
N. C. Staub
Keyword(s):  
Body Position ◽  
Vertical Gradient ◽  
Radioactive Tracer ◽  
Pleural Space ◽  
Pleural Pressure ◽  
Cylindrical Shape ◽  
Liquid Pressure ◽  
Rubber Balloon ◽  
Plastic Cylinder ◽  
Pleural Liquid Pressure

In recent studies using relatively noninvasive techniques, the vertical gradient in pleural liquid pressure was 0.2–0.5 cmH2O/cm ht, depending on body position, and pleural liquid pressure closely approximated lung recoil (J. Appl. Physiol. 59: 597–602, 1985). We built a model to discover why the vertical gradient in pleural pressure is less than hydrostatic (1 cmH2O/cm). A long rubber balloon of cylindrical shape was inflated in a plastic cylinder. The “pleural” space between the balloon and cylinder was filled with blue-dyed water. With the cylinder vertical, we measured pleural pressure by a transducer through side taps at 2-cm intervals up the cylinder. The pressure was measured with different amounts of water in the pleural space. With a clear separation between the balloon and the container, the vertical gradient in pleural liquid pressure was hydrostatic. As water was withdrawn from the pleural space, the balloon approached the wall of the container. Over an 8-cm-long midregion of the model where the balloon diameter matched the cylinder diameter, the vertical gradient was not hydrostatic and was virtually absent. In this region, the pleural liquid pressure was uniform and equal to the recoil of the balloon. In this section we could not see any pleural space. By scintillation imaging using 99mTc-diethylenetriamine pentaacetic acid in the water, we estimated the thickness of this flat “costal” pleural space to be approximately 20 microns. Radioactive tracer injected at the top of the pleural space appeared by 24 h at the bottom, which indicated a slow drainage of liquid by gravity.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Continuous negative abdominal pressure: mechanism of action and comparison with prone position

2018 ◽  
Vol 125 (1) ◽  
pp. 107-116 ◽  
Author(s):  
Takeshi Yoshida ◽  
Doreen Engelberts ◽  
Gail Otulakowski ◽  
Bhushan Katira ◽  
Niall D. Ferguson ◽  
...  
Keyword(s):  
Lung Injury ◽  
Prone Position ◽  
Mechanism Of Action ◽  
Respir Crit ◽  
Vertical Gradient ◽  
Lung Compliance ◽  
Pleural Pressure ◽  
Abdominal Pressure ◽  
Prone Positioning ◽  
Positive End Expiratory Pressure

We recently reported that continuous negative abdominal pressure (CNAP) could recruit dorsal atelectasis in experimental lung injury and that oxygenation improved at different transpulmonary pressure values compared with increases in airway pressure (Yoshida T, Engelberts D, Otulakowski G, Katira BH, Post M, Ferguson ND, Brochard L, Amato MBP, Kavanagh BP. Am J Respir Crit Care Med 197: 534–537, 2018). The mechanism of recruitment with CNAP is uncertain, and its impact compared with a commonly proposed alternative approach to recruitment, prone positioning, is not known. We hypothesized that CNAP recruits lung by decreasing the vertical pleural pressure (Ppl) gradient (i.e., difference between dependent and nondependent Ppl), thought to be one mechanism of action of prone positioning. An established porcine model of lung injury (surfactant depletion followed by ventilator-induced lung injury) was used. CNAP was applied using a plexiglass chamber that completely enclosed the abdomen at a constant negative pressure (−5 cmH2O). Lungs were recruited to maximal positive end-expiratory pressure (PEEP; 25 cmH2O) and deflated in steps of PEEP (2 cmH2O, 10 min each). CNAP lowered the Ppl in dependent but not in nondependent lung, and therefore, in contrast to PEEP, it narrowed the vertical Ppl gradient. CNAP increased respiratory system compliance and oxygenation and appeared to selectively displace the posterior diaphragm caudad (computerized tomography images). Compared with prone position without CNAP, CNAP in the supine position was associated with higher arterial partial pressure of oxygen and compliance, as well as greater homogeneity of ventilation. The mechanism of action of CNAP appears to be via selective narrowing of the vertical gradient of Ppl. CNAP appears to offer physiological advantages over prone positioning. NEW & NOTEWORTHY Continuous negative abdominal pressure reduces the vertical gradient in (dependent vs. nondependent) pleural pressure and increases oxygenation and lung compliance; it is more effective than prone positioning at comparable levels of positive end-expiratory pressure.

scholarly journals Esophageal pressures in acute lung injury: do they represent artifact or useful information about transpulmonary pressure, chest wall mechanics, and lung stress?

2010 ◽  
Vol 108 (3) ◽  
pp. 515-522 ◽  
Author(s):  
Stephen H. Loring ◽  
Carl R. O'Donnell ◽  
Negin Behazin ◽  
Atul Malhotra ◽  
Todd Sarge ◽  
...  
Keyword(s):  
Acute Lung Injury ◽  
Lung Injury ◽  
Critically Ill ◽  
Chest Wall ◽  
Critically Ill Patients ◽  
Transpulmonary Pressure ◽  
Pleural Pressure ◽  
Lung Inflation ◽  
Airway Pressures ◽  
Gravitational Gradients

Acute lung injury can be worsened by inappropriate mechanical ventilation, and numerous experimental studies suggest that ventilator-induced lung injury is increased by excessive lung inflation at end inspiration or inadequate lung inflation at end expiration. Lung inflation depends not only on airway pressures from the ventilator but, also, pleural pressure within the chest wall. Although esophageal pressure (Pes) measurements are often used to estimate pleural pressures in healthy subjects and patients, they are widely mistrusted and rarely used in critical illness. To assess the credibility of Pes as an estimate of pleural pressure in critically ill patients, we compared Pes measurements in 48 patients with acute lung injury with simultaneously measured gastric and bladder pressures (Pga and Pblad). End-expiratory Pes, Pga, and Pblad were high and varied widely among patients, averaging 18.6 ± 4.7, 18.4 ± 5.6, and 19.3 ± 7.8 cmH2O, respectively (mean ± SD). End-expiratory Pes was correlated with Pga ( P = 0.0004) and Pblad ( P = 0.0104) and unrelated to chest wall compliance. Pes-Pga differences were consistent with expected gravitational pressure gradients and transdiaphragmatic pressures. Transpulmonary pressure (airway pressure − Pes) was −2.8 ± 4.9 cmH2O at end exhalation and 8.3 ± 6.2 cmH2O at end inflation, values consistent with effects of mediastinal weight, gravitational gradients in pleural pressure, and airway closure at end exhalation. Lung parenchymal stress measured directly as end-inspiratory transpulmonary pressure was much less than stress inferred from the plateau airway pressures and lung and chest wall compliances. We suggest that Pes can be used to estimate transpulmonary pressures that are consistent with known physiology and can provide meaningful information, otherwise unavailable, in critically ill patients.

Inhomogeneity during deflation of excised canine lungs. III. Single-breath O2 tests

1988 ◽  
Vol 65 (4) ◽  
pp. 1775-1781
Author(s):  
D. O. Warner ◽  
R. E. Hyatt ◽  
K. Rehder
Keyword(s):  
Dead Space ◽  
Vertical Gradient ◽  
Pleural Pressure ◽  
Phase Iii ◽  
Flow Limitation ◽  
Single Breath ◽  
Expired Gas ◽  
Expiratory Flow ◽  
Phase Iv

Both interregional and intraregional mechanisms may cause changes in N2 concentration of expired gas during the phases of the single-breath O2 test (SBO2) that follow dead-space washout. To evaluate the possible importance of each mechanism, we performed the SBO2 in excised canine lungs that were first suspended in air and then immersed in stable foams that simulated the vertical gradient of pleural pressure. The lungs were deflated at constant submaximal flows. The slope of phase III diminished with increasing expiratory flow and increased with foam immersion. The onset of phase IV depended on flow, and a terminal decrease in N2 concentration (phase V) was often observed. Simultaneously measured estimates of regional flows and volumes (J. Appl. Physiol. 65: 1764-1774, 1988) were used to further interpret these results. The onset of phase IV at flows greater than quasi-static signified the onset of flow limitation of dependent regions. The onset of phase V corresponded to flow limitation of nondependent regions.

scholarly journals Comparison of pleural and esophageal pressure in supine and prone positions in a porcine model of acute respiratory distress syndrome

2020 ◽  
Vol 128 (6) ◽  
pp. 1617-1625 ◽  
Author(s):  
N. Terzi ◽  
S. Bayat ◽  
N. Noury ◽  
E. Turbil ◽  
W. Habre ◽  
...  
Keyword(s):  
Acute Respiratory Distress Syndrome ◽  
Respiratory Distress Syndrome ◽  
Respiratory Distress ◽  
Prone Position ◽  
Distress Syndrome ◽  
Porcine Model ◽  
Vertical Gradient ◽  
Esophageal Pressure ◽  
Pleural Pressure ◽  
Positive End Expiratory Pressure

In a porcine model of acute respiratory distress syndrome, we found that static end-expiratory esophageal pressure did not change significantly in prone position compared with supine position at any positive end-expiratory pressure (PEEP) tested between 5 and 20 cmH2O. Prone position was associated with an increased ventral pleural pressure and reduced end-expiratory dorsal-to-ventral pleural pressure (Ppl) vertical gradient, likely due to a more even distribution of mechanical forces over the chest wall.

Environmental elements for revitalization of entomophages in theforest plantations of the arid zone

2019 ◽  
pp. 55-70
Author(s):  
И.Р. Грибуст
Keyword(s):  
Woody Plants ◽  
Arid Zone ◽  
Cumulative Effect ◽  
Vertical Gradient ◽  
Steppe Zone ◽  
Maximum Effect ◽  
Forest Belt ◽  
Scientific Center ◽  
Biotic Potential ◽  
Estimation Of Distribution

Введение. Лесомелиоративное обустройство территорий малолесных регионов коренным образом преобразует ранее пустынные пространства. Позитивные изменения влажностнотеплового, почвенного, гидрологического режимов, обогащение аборигенной дендрофлоры новыми видами влечет за собой также и трансформацию животного мира, в том числе населения насекомых. Энтомосообщества формируются за счет представителей степной группы, обитателей естественных ценозов, а также группы лесных насекомых, в числе которых виды, являющиеся опасными вредителями и их энтомофаги. Цель работы анализ изменения разнообразия насекомыхэнтомофагов в насаждениях засушливой зоны различных параметров и состояния. Объекты исследований насекомыеэнтомофаги, обитающие в энтомокомплексах защитных насаждениях различного дендрологического состава ФНЦ агроэкологии РАН на территории Волгоградской области (кадастр. 34:34:000000:122 34:08:000000:6). Материалы и методика. Сбор материала проводили в насаждениях различного хозяйственного значения. Объектами исследования являлись полезные насекомые. Отбор проб проводили посредством окашивания крон энтомологическим сачком, визуальным осмотром модельных ветвей и ручным сбором хищников и паразитированных видов филлофагов с последующим выведением имаго в лабораторных условиях. Результаты и обсуждение. В сообществе полезных насекомых защитных лесных насаждений сухостепной зоны зафиксирован 221 вид энтомофагов, относящихся к 7 отрядам и 32 семействам. Различия экологических условий, ассортимент древесных растений в каждой из посадок, характер и интенсивность негативного внешнего влияния определяют особенности фаунистического населения, в т. ч. энтомофагов. Оценка распределения количественного обилия паразитов и хищников показала, что в лесных полосах хищников в среднем в три раза больше паразитических насекомых. Отчетливо прослеживаются вариации изменения разнообразия энтомофагов в насаждениях разного класса жизнеспособности. Конструктивные особенности, флористическая обедненность и сформировавшийся микроклимат существенно ограничивает жизнедеятельность энтомофагов в малорядных (23 ряда) насаждениях, численность которых здесь снижается в среднем в 2,5 раза по сравнению с многорядными посадками. В вертикальном градиенте посадок по мощности накопления биотического потенциала полезных насекомых выделяется травянистый ярус, наличие которого в лесополосе обусловливает увеличение числа особей энтомофагов в сообществе в 1,32,7 раза. Наименьшую роль в накоплении полезной группы насекомых играет наличие развитого подлеска. Заключение. Наличие в насаждениях энтомофильных древесных растений и развитого травостоя важнейшие экологические факторы для накопления биотического потенциала энтомофагов. Максимальный эффект обеспечивает совокупное влияние определяющих экологоструктурных элементов в многорядных посадках. Introduction. Forest reclamation area developmentpoor regions is radically transforms the previously desolate space. Positive changes in moistureheat, soil, hydrological regimes, enrichment of native dendroflora with new species also entails the transformation of the animal world, including the insect population. Entomologiste formed by the representatives of the steppe group of the inhabitants of the natural coenoses, and the group of forest insects, including species that are dangerous pests and their entomophages. The purpose of the analysis of changes in the diversity of insect entomophages in the plantations of the arid zone of different parameters and conditions. The objects of research insectsentomophages living in entomocomplexes protective plantation of different dendrological composition of the Federal scientific center for Agroecology wounds on the territory of the Volgograd region (the cadaster number is 34:34:000000:122 34:08:000000:6). Materials and methods. Collection of material was carried out in plantations of various economic importance. The objects of study were useful insects. Samples were collected by hilling crowns entomological net, by visual inspection of the model branches and handcollection of predators and parasitism species of phyllophagous with subsequent excretion of adults in the laboratory. Results and discussion. 221 species of entomophages belonging to 7 groups and 32 families were recorded in the community of useful insects of protective forest plantations of the dry steppe zone. Differences in environmental conditions, the range of woody plants in each of the plantings, the nature and intensity of the negative external influence determine the characteristics of the faunal population, including entomophages The estimation of distribution of quantitative abundance of parasites and predators showed that in forest bands of predators on average three times more parasitic insects. Variations in the diversity of entomophages in plantings of different classes of viability are clearly observed. Design features, floristic depletion and formed microclimate significantly limits the life activity of entomophages in smallrow (23 rows) plantations, the number of which is reduced by an average of 2.5 times compared to multirow planting. In the vertical gradient of plantings on the power of accumulation of biotic potential of useful insects, a grassy tier is allocated, the presence of which in the forest belt causes an increase in the number of entomophages in the community by 1.32.7 times. The least role in the accumulation of a useful group of insects is played by the presence of developed undergrowth. Conclusion. The presence of entomophilic woody plants and developed herbage in the plantations are the most important environmental factors for the accumulation of the entomophage biotic potential. The maximum effect provides a cumulative effect of determining ecological and structural elements in multirow landings.

Sign in / Sign up

Export Citation Format

Share Document