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- Borges, João Batista, et al.
(author)
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Zero expiratory pressure and low oxygen concentration promote heterogeneity of regional ventilation and lung densities
- 2016
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In: Acta Anaesthesiologica Scandinavica. - : Wiley. - 0001-5172 .- 1399-6576. ; 60:7, s. 958-968
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Journal article (peer-reviewed)abstract
- BackgroundIt is not well known what is the main mechanism causing lung heterogeneity in healthy lungs under mechanical ventilation. We aimed to investigate the mechanisms causing heterogeneity of regional ventilation and parenchymal densities in healthy lungs under anesthesia and mechanical ventilation. MethodsIn a small animal model, synchrotron imaging was used to measure lung aeration and regional-specific ventilation (sV.). Heterogeneity of ventilation was calculated as the coefficient of variation in sV. (CVsV.). The coefficient of variation in lung densities (CVD) was calculated for all lung tissue, and within hyperinflated, normally and poorly aerated areas. Three conditions were studied: zero end-expiratory pressure (ZEEP) and FIO2 0.21; ZEEP and FIO2 1.0; PEEP 12 cmH(2)O and F(I)O(2)1.0 (Open Lung-PEEP = OLP). ResultsThe mean tissue density at OLP was lower than ZEEP-1.0 and ZEEP-0.21. There were larger subregions with low sV. and poor aeration at ZEEP-0.21 than at OLP: 12.9 9.0 vs. 0.6 +/- 0.4% in the non-dependent level, and 17.5 +/- 8.2 vs. 0.4 +/- 0.1% in the dependent one (P = 0.041). The CVsV. of the total imaged lung at PEEP 12 cmH(2)O was significantly lower than on ZEEP, regardless of FIO2, indicating more heterogeneity of ventilation during ZEEP (0.23 +/- 0.03 vs. 0.54 +/- 0.37, P = 0.049). CVD changed over the different mechanical ventilation settings (P = 0.011); predominantly, CVD increased during ZEEP. The spatial distribution of the CVD calculated for the poorly aerated density category changed with the mechanical ventilation settings, increasing in the dependent level during ZEEP. ConclusionZEEP together with low FIO2 promoted heterogeneity of ventilation and lung tissue densities, fostering a greater amount of airway closure and ventilation inhomogeneities in poorly aerated regions.
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| 2. |
- Karbing, D. S., et al.
(author)
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Journal of Clinical Monitoring and Computing 2017 end of year summary : respiration
- 2018
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In: Journal of clinical monitoring and computing. - : Springer Science and Business Media LLC. - 1387-1307 .- 1573-2614. ; 32:2, s. 197-205
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Research review (peer-reviewed)abstract
- This paper reviews 32 papers or commentaries published in Journal of Clinical Monitoring and Computing in 2016, within the field of respiration. Papers were published covering airway management, ventilation and respiratory rate monitoring, lung mechanics and gas exchange monitoring, in vitro monitoring of lung mechanics, CO2 monitoring, and respiratory and metabolic monitoring techniques.
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| 4. |
- Pellegrini, Mariangela, et al.
(author)
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Expiratory Diaphragm Activity Reduces Atelectasis Formation
- 2016
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Conference paper (peer-reviewed)abstract
- Rationale. If the diaphragm, known as the major inspiratory muscle, is active also during expiration, it will limit closure of the smallairways as well as cyclic opening and closing of airways and alveoli. We investigated the expiratory role of the diaphragm in conditionsthat promote lung collapse. Methods. Acute lung injury was induced in 8 anesthetized, tracheostomized pigs by repeated lung lavages, targeting a PaO2/FiO2 of 250mmHg. After stabilization, the animals were switched to spontaneous breathing (SB) and underwent a decremental continuous positiveend-expiratory pressure (PEEP) trial of 15, 12, 9, 6, 3 and 0 cmH2O. During steady state conditions, para-diaphragmatic dynamic-CT scans(dCTs) were obtained together with measurements of respiratory variables. In 4 pigs, the same protocol was repeated during mechanicalpressure control ventilation (PCV) in fully muscle-paralyzed animals. The electrical diaphragmatic activity was continuously recordedduring the expiration (EAdiexp) and during apnea (EAdimin). The EAdiexp recording from end-inspiration to end-expiration was dividedinto 4 quartiles (Q1, Q2, Q3, Q4) and the mean value for each of them was expressed as percentage of the EAdi peak. During SB and PCV,the dCT scans collected at end-expiration and half-expiration were identified and the amount of collapse (atelectasis) in that cut wascalculated. The atelectatic tissue was defined as the sum of voxels with a density between -100 and +100 Hounsfield Units. Results. When, during spontaneous breathing, PEEP was lowered from 15 to 6 cmH2O, the EAdiexp increased significantly in all 4quartiles of the expiratory curve (see Figure, left panel). The EAdimin increased when PEEP was reduced from 12 to 0 cmH2O. However,atelectasis did not increase in size until PEEP was below 9 cmH2O. Larger atelectasis was seen during PCV (with no measurable EAdi) thanduring SB at PEEP levels from 9 to 0 cmH2O. This was seen not only at end-expiration, but already half way down the expiration (seeFigure, right panels). Conclusions. The increasing diaphragm activity with decreasing airway pressure during the expiration will protect against atelectasisformation. The effects of the diaphragmatic activity are visible already half way down the expiration. These findings have potentialimplications how to design ventilatory support strategies in a wide range of pathological lung conditions, from chronic obstructivepulmonary disease to acute lung injury.
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