Assessment of PEEP-induced reopening of collapsed lung regions in acute lung injury: are one or three CT sections representative of the entire lung?

Qin, Lu; Malbouisson, Luíz Marcelo Sá; Mourgeon, Eric; Goldstein, Ivan; Coriat, Pierre; Rouby, Jean‐Jacques

doi:10.1007/s001340101049

Cited by 63 publications

(44 citation statements)

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“…Of peculiar importance is the requirement for assessing alveolar recruitment on the whole lung. It has been clearly shown that assessing alveolar recruitment on 1 or 3 CT sections may result in a gross overestimation or underestimation of alveolar recruitment of the whole lung [40]. As reported in supine patients with ARDS, alveolar recruitment resulting from PEEP predominates in nondependent and cephalic lung regions, is rather limited in the diaphragmatic region and can even be negative (alveolar derecruitment) caudally to the diaphragmatic cupola [36,41].…”

Section: Measurement Of Alveolar Recruitment and Lung Overinflationmentioning

confidence: 98%

“…As a consequence, assessing alveolar recruitment on a single juxta-diaphragmatic CT section often underestimates recruitment of the whole lung. In contrast, because apical and juxta-hilar CT sections are more representative of upper lobes than of lower lobes, assessing alveolar recruitment on 3 CT sections often overestimates recruitment of the whole lung [40].…”

Section: Measurement Of Alveolar Recruitment and Lung Overinflationmentioning

confidence: 99%

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Pressure/volume curves and lung computed tomography in acute respiratory distress syndrome

Rouby¹,

Lü²,

Vieira³

2003

European Respiratory Journal

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Pressure/volume curves and lung computed tomography in acute respiratory distress syndrome. J-J. Rouby, Q. Lu, S. Vieira. #ERS Journals Ltd 2003. ABSTRACT: Pressure/volume (P/V) curves can be measured by static methods, constant or sinusoidal flow methods and the dynostatic method that allows a breath-tobreath determination of P/V curves. Recent ventilators are equipped with specific flow generators and software aimed at obtaining P/V curves without disconnecting the patient from the ventilator.The most recent generation of computed tomography scanners allows the quantitative determination of lung aeration, lung volumes (gas and tissue), alveolar recruitment and lung overinflation of the whole lung. In the supine position, the acute respiratory distress syndrome (ARDS) lung is characterised by an increase in lung tissue that predominates in upper lobes and a massive loss of aeration that predominates in lower lobes.In a minority of ARDS patients, the loss of aeration is homogeneously distributed. The overall lung volume of upper lobes is preserved suggesting an alveolar floodinginduced loss of aeration. In contrast, the overall lung volume of lower lobes is reduced because the heart and the abdomen exert an external compression that contributes to the loss of aeration. The P/V curve is a lung recruitment curve and the chord compliance indicates the potential for recruitment. In such patients, alveolar recruitment resulting from positive end-expiratory pressure is not accompanied by lung overinflation.In a majority of acute respiratory distress syndrome patients, upper lobes remain partially or totally aerated despite a marked regional increase in lung tissue. The upper lobes9 overall lung volume is either normal or increased, suggesting that the lung does not collapse under its own weight as generally believed. In lower lobes, the overall lung volume is reduced because the heart and the abdomen exert an external compression that contributes to the loss of aeration. The pressure/volume curve is influenced by the recruitment of poorly and nonaerated lung regions and by the mechanical properties of the part of the lung remaining aerated. In such patients, alveolar recruitment resulting from positive end-expiratory pressure w10 cmH 2 O is preceded and accompanied by lung overinflation. Eur Respir J 2003; 22: Suppl. 42, 27s- Respiratory pressure/volume (P/V) curves can be easily obtained at the bedside in critically ill patients whose lungs are mechanically ventilated. Many ventilators are now equipped with flow generators and software that allow the obtention and the analysis of the P/V curve without disconnecting the patient from mechanical ventilation. Hypothesis and concepts serving for interpreting the P/V curves of patients with acute respiratory distress syndrome (ARDS) have been deeply modified during the past 15 yrs. Initially believed to reflect the mechanical properties of the "baby" lung [1], the P/V curve is now rather considered as a lung recruitment curve [2] which is markedly influenced by the regiona...

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Section: Measurement Of Alveolar Recruitment and Lung Overinflationmentioning

confidence: 98%

Section: Measurement Of Alveolar Recruitment and Lung Overinflationmentioning

confidence: 99%

Pressure/volume curves and lung computed tomography in acute respiratory distress syndrome

Rouby¹,

Lü²,

Vieira³

2003

European Respiratory Journal

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“…Calculations based on density measurements, in contrast, are more robust because average density is less sensitive to small errors in boundary registration. Several important studies have highlighted the potential errors associated with undersampling or single-slice analysis (32,33). Alternatively, whole lung or lobar analysis permits the use of conservation of mass principles to measure changes in absolute air or tissue volumes.…”

Section: Assumptions and Limitationsmentioning

confidence: 99%

Computed Tomography Studies of Lung Mechanics

Simon

Christensen²,

Low³

et al. 2005

Proceedings of the American Thoracic Society

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The study of lung mechanics has progressed from global descriptions of lung pressure and volume relationships to the highresolution, three-dimensional, quantitative measurement of dynamic regional mechanical properties and displacements. X-ray computed tomography (CT) imaging is ideally suited to the study of regional lung mechanics in intact subjects because of its high spatial and temporal resolution, correlation of functional data with anatomic detail, increasing volumetric data acquisition, and the unique relationship between CT density and lung air content. This review presents an overview of CT measurement principles and limitations for the study of regional mechanics, reviews some of the early work that set the stage for modern imaging approaches and impacted the understanding and management of patients with acute lung injury, and presents evolving novel approaches for the analysis and application of dynamic volumetric lung image data. Keywords: computed tomography; mathematical modeling; physiologyThe phenomena covered by the word "respiration" are very diverse. When a person is seen to breathe, what is observed is a movement of the chest and abdomen by which air is alternately drawn into his lungs and again expelled. This constitutes the mechanical aspect of respiration.-August Krogh, 1941 In the 60-odd years since A. Krogh (1) opened his treatise on the comparative physiology of respiration with these words, an enormous amount of work has explored the relationship between lung expansion or deformation and the forces that drive such changes. Most recently, advances in imaging techniques have extended the study of lung mechanical behavior to the regional level, and currently evolving technologies permit the threedimensional characterization of dynamic lung volume changes in intact subjects. X-ray computed tomography (CT), because of its speed, widespread availability, high-resolution anatomic visualization, and unique ability to quantify regional air and tissue volumes, provides a particularly powerful tool for the noninvasive measurement of lung mechanics in experimental models as well as human subjects. This review presents relevant CT measurement principles for regional mechanics, presents examples of static and dynamic approaches to lung mechanics, and emphasizes some exciting and promising new high-resolution, vol-

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“…Thus the quantitative analysis is very laborious and time consuming, which precludes its use in the daily patient management [35,37,38]. In order to expand the possibility to use the quantitative analysis to estimate lung recruitment, Lu et al studied only one or three lung CT images instead of the whole lung CT scan, which required a significantly lower time [7]. However, the agreement was poor because of the inhomogeneous distribution of the disease in the lung parenchyma [7,21].…”

Section: Discussionmentioning

confidence: 99%

“…Owing to its simplicity the multiple pressure-volume curve has been proposed as an adequate surrogate for the estimation of lung recruitment [5,6]. However, it may underestimate lung recruitment in patients with focal aeration loss [7]. Electrical impedance tomography provides noninvasive real-time imaging of pulmonary inflation which could predict the lung recruitability [8], but it computes only a small fraction of the lung and is affected by the movements of intrathoracic blood due to the application of PEEP.…”

Section: Introductionmentioning

confidence: 99%

Visual anatomical lung CT scan assessment of lung recruitability

et al. 2012

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Purpose: The computation of lung recruitability in acute respiratory distress syndrome (ARDS) is advocated to set positive end-expiratory pressure (PEEP) for preventing lung collapse. The quantitative lung CT scan, obtained by manual image processing, is the reference method but it is time consuming. The aim of this study was to evaluate the accuracy of a visual anatomical analysis compared with a quantitative lung CT scan analysis in assessing lung recruitability. Methods: Fifty sets of two complete lung CT scans of ALI/ARDS patients computing lung recruitment were analyzed. Lung recruitability computed at an airway pressure of 5 and 45 cmH 2 O was defined as the percentage decrease in the collapsed/ consolidated lung parenchyma assessed by two expert radiologists using a visual anatomical analysis and as the decrease in not aerated lung regions using a quantitative analysis computed by dedicated software.Results: Lung recruitability was 11.3 % (interquartile range 7.39-16.41) and 15.5 % (interquartile range 8.18-21.43) with the visual anatomical and quantitative analysis, respectively. In the Bland-Altman analysis, the bias and agreement bands between the visual anatomical and quantitative analysis were -2.9 % (-11.8 to ?5.9 %). The ROC curve showed that the optimal cutoff values for the visual anatomical analysis in predicting high versus low lung recruitability was 8.9 % (area under the ROC curve 0.9248, 95 % CI 0.8550-0.9946). Considering this cutoff, the sensitivity, specificity, and diagnostic accuracy were 0.96, 0.76, and 0.86, respectively. Conclusions: Visual anatomical analysis can classify patients into those with high and low lung recruitability allowing more intensivists to get access to lung recruitability assessment.

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Assessment of PEEP-induced reopening of collapsed lung regions in acute lung injury: are one or three CT sections representative of the entire lung?

Cited by 63 publications

References 0 publications

Pressure/volume curves and lung computed tomography in acute respiratory distress syndrome

Pressure/volume curves and lung computed tomography in acute respiratory distress syndrome

Computed Tomography Studies of Lung Mechanics

Visual anatomical lung CT scan assessment of lung recruitability

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