| 1. |
- Buehler, Sarah, et al.
(författare)
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Simultaneous monitoring of intratidal compliance and resistance in mechanically ventilated piglets : A feasibility study in two different study groups
- 2015
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Ingår i: Respiratory Physiology & Neurobiology. - : Elsevier BV. - 1569-9048 .- 1878-1519. ; 219, s. 36-42
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Tidskriftsartikel (refereegranskat)abstract
- Compliance measures the force counteracting parenchymal lung distension. In mechanical ventilation, intratidal compliance-volume (C(V))-profiles therefore change depending on PEEP, tidal volume (V-T), and underlying mechanical lung properties. Resistance counteracts gas flow through the airways. Due to anatomical linking between parenchyma and airways, intratidal resistance-volume (R(V))-profiles are hypothesised to change in a non-linear way as well. We analysed respiratory system mechanics in fifteen piglets with lavage-induced lung injury and nine healthy piglets ventilated at different PEEP/V-T-settings. In healthy lungs, R(V)-profiles remained mostly constant and linear at all PEEP-settings whereas the shape of the C(V)-profiles showed an increase toward a maximum followed by a decrease (small PEEP) or volume-dependent decrease (large PEEP). In the lavage group, a large drop in resistance at small volumes and slow decrease toward larger volumes was found for small PEEP/V-T-settings where C(V)-profiles revealed a volume-dependent increase (small PEEP) or a decrease (large PEEP and large VT). R(V)-profiles depend characteristically on PEEP, V-T, and possibly whether lungs are healthy or not. Curved R(V)-profiles might indicate pathological changes in the underlying mechanical lung properties and/or might be a sign of derecruitment.
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| 2. |
- Fernandez-Ayala, Victor Nan, et al.
(författare)
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DESIGN OF A HALE UAV FOR ATMOSPHERIC IMAGING
- 2022
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Ingår i: 33rd Congress of the International Council of the Aeronautical Sciences, ICAS 2022. - : International Council of the Aeronautical Sciences. ; , s. 1078-1087
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Konferensbidrag (refereegranskat)abstract
- Optical phenomena in the upper atmosphere, such as northern lights, airglow, noctilucent clouds and thunderstorm-related transient luminous phenomena reveal the complex processes coupling different layers of the atmosphere and the near earth space. Bad weather and lighting conditions, as well as geographical constraints, limit the possibilities of ground based imaging. Therefore, an autonomous high altitude long endurance (HALE) fixed-wing unmanned aerial vehicle (UAV) is proposed for atmospheric imaging, as a joint student-driven research project between the Aeronautics and Vehicle Engineering- and the Space and Plasma Physics departments at KTH Royal Institute of Technology. The Autonomous Light Platform for High Altitude atmospheric imaging (ALPHA) is specifically designed for operations in the environmentally harsh conditions found in Arctic nighttime. This paper presents the conceptual design phase of the aircraft, as well as the initial manufacturing and flight testing methodology of a half-scale prototype.
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| 3. |
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| 4. |
- Kawati, Rafael, et al.
(författare)
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Change in expiratory flow detects partial endotracheal tube obstruction in pressure-controlled ventilation
- 2006
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Ingår i: Anesthesia and Analgesia. - : Ovid Technologies (Wolters Kluwer Health). - 0003-2999 .- 1526-7598. ; 103:3, s. 650-657
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Tidskriftsartikel (refereegranskat)abstract
- Only extreme degrees of endotracheal tube (ETT) narrowing can be detected with monitoring of tidal volume (V-T) during pressure-controlled ventilation (PCV). To assess the degree of ETT obstruction in PCV and to compare it to V,, monitoring, we produced 3 levels of partial ETT obstruction in 11 healthy anesthetized piglets using ETTs of 4 different inner diameters (IDs 9.0, 8.0, 7.0, and 6.0 mm). An expiratory flow over volume (<(V)over dot >(e)-V) curve was plotted and the time constant (tau(e)) at 15% of expiration time (T-e) was calculated. We also calculated the fractional volume expired during the first 15% of T-e (V-ex (fract, 15)) and compared those variables to full expiratory V, for each of the 3 obstructions. V-T monitoring failed to detect ETT narrowing. By contrast, V-ex (fract,15) decreased and tau(e)e increased significantly with increasing ETT narrowing (for IDs 9.0, 8.0, 7.0, and 6.0, mean V-ex (fract,15) was 195, 180, 146, and 134 mL respectively and mean tau(e) was 380, 491, 635, 794 ms for IDs 9.0, 8.0, 7.0, and 6.0 respectively). We conclude that when the elastic recoil that drives <(V)over dot >(e) is appropriately considered, analysis of <(V)over dot >(e) and V-ex (fract,15) detects partial ETT obstruction during PCV.
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| 5. |
- Sándor, János, et al.
(författare)
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A subduralis vérzés miatt kezelt betegek halálozását befolyásoló tényezók : [Predictors of lethal outcome in subdural haemorrhage]
- 2003
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Ingår i: Ideggyogyaszati Szemle. - : Literatura Medica Kiado. - 0019-1442 .- 2498-6208. ; 56:11-12, s. 386-395
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Tidskriftsartikel (refereegranskat)abstract
- Background: Subdural haemorrhage (SDH) is of high public health importance because of its frequency, high case fatality ratio (CFR) and the young age of affected population. Despite the fact that the effectivity of guideline based treatment has been improved in the last decade, the Hungarian praxis shows variable compliance for recommendations.Objectives: The study aimed to describe the heterogeneity of the treatment effectivity (by geographically identifying the populations provided with appropriate or non-optimal level care), to determine the relationship between the institutional proxies quality and the results of treatment for SDH by linking the proxies properties to the patients' records.Methods: The institutions' protocols were assessed by a self-completed questionnaire in 1997. The participating hospitals treated 79% of the Hungarian patients with SDH. The Hungarian hospital discharge data in 1997-1999 were the source of patient specific data. The risk factors of lethal outcome were investigated by logistic regression analysis.Results: High proportion of patients had been treated in hospital with low compliance for guidelines. The non-permanent access to neurosurgical service and CT facility, the lack of intracranial pressure monitoring and the respiration support provided out of intensive care units worsened the survival of subjects. It was quantified that the full compliance could have diminished the case fatality ratio by 15-20%. The ratio of extreme county level CFRs exceeded 2.36 and extrapolating the effectivity observed in the county with lowest lethality, the Hungarian CFR would have been reduced by 21% among patients with SDH main diagnosis. (The interpretation of findings is limited by the lack of differentiation between acute and chronic cases and of direct categorisation of severity for subdural haemorrhage in the official hospital discharge records).Discussion: The study results urge the increase of compliance for evidence based guidelines, since despite of some validity issues, it was demonstrated that the deviation from recommended practice is reflected in the disadvantageous outcome.
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| 6. |
- Schumann, Stefan, et al.
(författare)
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Analysis of Dynamic Intratidal Compliance in a Lung Collapse Model
- 2011
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Ingår i: Anesthesiology. - 0003-3022 .- 1528-1175. ; 114:5, s. 1111-1117
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Tidskriftsartikel (refereegranskat)abstract
- Background: For mechanical ventilation to be lung-protective, an accepted suggestion is to place the tidal volume (V-T) between the lower and upper inflection point of the airway pressure-volume relation. The drawback of this approach is, however, that the pressure-volume relation is assessed under quasistatic, no-flow conditions, which the lungs never experience during ventilation. Intratidal nonlinearity must be assessed under real (i.e., dynamic) conditions. With the dynamic gliding-SLICE technique that generates a high-resolution description of intratidal mechanics, the current study analyzed the profile of the compliance of the respiratory system (C-RS). Methods: In 12 anesthetized piglets with lung collapse, the pressure-volume relation was acquired at different levels of positive end-expiratory pressure (PEEP: 0, 5, 10, and 15 cm H2O). Lung collapse was assessed by computed tomography and the intratidal course of C-RS using the gliding-SLICE method. Results: Depending on PEEP, C-RS showed characteristic profiles. With low PEEP, C-RS increased up to 20% above the compliance at early inspiration, suggesting intratidal recruitment; whereas a profile of decreasing C-RS, signaling overdistension, occurred with V-T > 5 ml/kg and high PEEP levels. At the highest volume range, C-RS was up to 60% less than the maximum. With PEEP 10 cm H2O, C-RS was high and did not decrease before 5 ml/kg V-T was delivered. Conclusions: The profile of dynamic C-RS reflects nonlinear intratidal mechanics of the respiratory system. The SLICE analysis has the potential to detect intratidal recruitment and overdistension. This might help in finding a combination of PEEP and V-T level that is protective from a lung-mechanics perspective.
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| 7. |
- Schumann, S., et al.
(författare)
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Cardiogenic oscillations to detect intratidal derecruitment and overdistension in a porcine model of healthy and atelectatic lungs
- 2018
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Ingår i: British Journal of Anaesthesia. - : Elsevier BV. - 0007-0912 .- 1471-6771. ; 121:4, s. 928-935
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Tidskriftsartikel (refereegranskat)abstract
- Background: Low positive end-expiratory pressure (PEEP) can result in alveolar derecruitment, and high PEEP or high tidal volume (V-T) in lung overdistension. We investigated cardiogenic oscillations (COS) in the airway pressure signal to investigate whether these oscillations can assess unfavourable intratidal events. COS induce short instantaneous compliance increases within the pressure-volume curve, and consequently in the compliance-volume curve. We hypothesised that increases in COS-induced compliance reflect non-linear intratidal respiratory system mechanics. Methods: In mechanically ventilated anaesthetised pigs with healthy (n = 13) or atelectatic (n = 12) lungs, pressure-volume relationships and the ECG were acquired at a PEEP of 0, 5, 10, and 15 cm H2O. During inspiration, the peak compliance of successive COS (C-COS) was compared with intratidal respiratory system compliance (C-RS) within incremental volume steps up to the full V-T of 12 ml kg(-1). We analysed whether C-COS variation corresponded with systolic arterial pressure variation. Results: C-COS-volume curves showed characteristic intratidal patterns depending on the PEEP level and on atelectasis. Increasing C-RS- or C-COS-volume patterns were associated with intratidal derecruitment with low PEEP, and decreasing patterns above 6 ml kg(-1) and high PEEP showed overdistension. C-COS was not associated with systolic arterial pressure variations. Conclusions: Heartbeat-induced oscillations within the course of the inspiratory pressure-volume curve reflect nonlinear intratidal respiratory system mechanics. The analysis of these cardiogenic oscillations can be used to detect intratidal derecruitment and overdistension and, hence, to guide PEEP and V-T settings that are optimal for respiratory system mechanics.
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| 8. |
- Schumann, S., et al.
(författare)
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Determination of respiratory system mechanics during inspiration and expiration by FLow-controlled EXpiration (FLEX) : a pilot study in anesthetized pigs
- 2014
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Ingår i: Minerva Anestesiologica. - 0375-9393 .- 1827-1596. ; 80:1, s. 19-28
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Tidskriftsartikel (refereegranskat)abstract
- Background. Differences between inspiratory and expiratory lung mechanics result in the hysteresis of the pressure volume-loop. While hysteresis area is a global parameter describing the difference between inspiration and expiration in mechanics under quasi-static conditions, a detailed analysis of this difference under the dynamic conditions of mechanical ventilation is feasible once inspiratory and expiratory compliance (C-in/C-ex) are determined separately. This requires uncoupling of expiratory flow rate and volume (V). Methods. Five piglets were mechanically ventilated at positive end-expiratory pressure (PEEP) levels ranging from 0 to 15 cmH(2)O. Expiratory flow rate was linearized by a computer-controlled resistor (flow-controlled expiration). The volume-dependent C-in(V) and C-ex(V) profiles were calculated from the tracheal pressure volume-loops. Results. The intratidal curve-progression of C-ex(V) was altogether higher with a steeper slope compared to C-in(V). With increasing positive end-expiratory pressure (PEEP) dynamic hysteresis area decreased and C-ex(V) tended to run more parallel to C-in(V), Conclusion. The relation between inspiratory and expiratory compliance profiles is associated with the hysteresis area and behaves PEEP dependent. Analysing the C-in-C-ex-relation might therefore potentially offer a new approach to titrate PEEP and tidal volume.
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| 9. |
- Schumann, S., et al.
(författare)
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Dynamic Hysteresis Behaviour of Respiratory System Mechanics
- 2013
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Ingår i: Biomedizinische Technik (Berlin. Zeitschrift). - : Walter de Gruyter GmbH. - 1862-278X .- 0013-5585. ; 58
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Tidskriftsartikel (refereegranskat)abstract
- The static pressure-volume (PV) curve of the respiratory system is characterized by hysteresis behaviour. Determination of separate inspiratory and expiratory compliance is required to analyse this phenomenon during the dynamic situation of mechanical ventilation. In five piglets expiratory flow was linearized (flow-controlled expiration, FLEX) to allow for compliance estimation separately for inspiration and expiration. Expiratory compliance was higher than inspiratory compliance along the entire intratidal course, converging at higher volumes. At higher PEEP levels expiratory and inspiratory compliance tended to run more in parallel. We conclude that the analysis of the separate inspiratory and expiratory compliance profiles allows for indicating unfavourable mechanical ventilation settings.
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| 10. |
- Vimláti, László, 1971-
(författare)
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Benefits of Spontaneous Breathing : Compared with Mechanical Ventilation
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- When spontaneous breathing (SB) is allowed during mechanical ventilation (MV), atelectatic lung areas are recruited and oxygenation improves thereby. Whether unsupported SB at its natural pattern (without PEEP and at low pressure/small tidal volume) equally recruits and improves oxygenation, and if so by which mechanism, has not been studied.A porcine lung collapse model was designed to study this question. The cardiac output dependency of the pulmonary shunt was investigated with healthy lungs and with major shunt (during one-lung ventilation) and with SB, MV and continuous positive airway pressure (CPAP). The hypoxic pulmonary vasoconstriction (HPV) was blocked with sodium nitroprusside (SNP) to see whether HPV is the only mechanism available for ventilation/perfusion (VA/Q) matching during MV and SB. In all experiments, respiratory rate and tidal volume during MV were matched to SB. Oxygenation was assessed by serial blood gas measurements, recruitment by thoracic CTs; pulmonary shunt was assessed by multiple inert gas elimination or venous admixture.SB attained better oxygenation and lower pulmonary shunt compared with MV, although it did not recruit collapsed lung. Pulmonary shunt did not correlate with cardiac output during SB, whereas a correlation was found during MV and CPAP. With blocked HPV, pulmonary shunt was considerably lower during SB than MV.In conclusion, SB improves VA/Q matching as compared with MV, even when no recruitment occurs. In contrast to MV and CPAP, cardiac output has no major effect on pulmonary shunt during SB. The improved VA/Q matching during SB despite a blocked HPV might indicate the presence of a SB-specific mechanism that improves pulmonary blood flow redistribution towards ventilated lung regions independent of or supplementary to HPV.
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