Identifying patients with ARDS: time for a different approach

Schuster, Daniel P.

doi:10.1007/s001340050486

Cited by 52 publications

(18 citation statements)

References 49 publications

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“…high-permeability lung edema, in its definition, as previously suggested. 30 In fact, it is surprising that in about half of the patients currently considered as affects by ALI/ ARDS, as defined by the American-European Consensus Conference, the amount of collapsed lung tissue, which is strictly related to the formation of gravity-dependent lung edema, is almost negligible, and, even more, very similar to that observed in patients with unilateral pneumonia, which, by definition, are not included into the ALI/ARDS definition.…”

Section: Ct-scanning and Ards Definitionmentioning

confidence: 99%

Lung imaging during acute respiratory distress syndrome: CT- and PET-scanning

Bellani

Caironi

2011

Trends in Anaesthesia and Critical Care

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s u m m a r yIn this article we review some of the main findings obtained by Computed Tomography (CT) and Positron Emission Tomography (PET) concerning the pathophysiology of Acute Respiratory Distress Syndrome (ARDS). CT is based on the detection of physical densities, allowing measurement of regional aeration. Beginning from the revolutionary concept of the "baby lung", CT findings later led to a further evolution of the ARDS lung model, showing that the lungs behave as a wet "sponge", with the dependent regions collapsing under the superimposed weight. More recently, CT scan has been used to quantify the potential for lung recruitment, showing that this is extremely heterogeneous among ARDS patient and tightly linked to mortality. PET (possibly combined with CT) is a functional imaging technique, based on the detection of a labeled molecule administered to a subject. Based on which molecule is used, different functions can be imaged. In the course of experimental ARDS injection of [ 13 N]N 2 À labeled saline has been used to image regional gas exchange. Administration of [18 F]FDG allows the image of cellular metabolic activity, reflecting neutrophils activation during inflammation. This technique has been applied in experimental ARDS and, more recently, in patients showing, for example, that inflammatory activity of the lungs is markedly increased also in "normally aerated" regions and, in some cases, even higher than in the non-aerated ones. We will present here some of the findings obtained by the two techniques in the clinical setting of ARDS, also discussing some of their possible future applications.

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Section: Ct-scanning and Ards Definitionmentioning

confidence: 99%

Lung imaging during acute respiratory distress syndrome: CT- and PET-scanning

Bellani

Caironi

2011

Trends in Anaesthesia and Critical Care

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“…The detection of acute lung injury (ALI), especially for the purpose of identifying appropriate patients for clinical trials of novel treatments, remains a controversial and important problem [1,2,3,4,5]. At present the diagnosis of ALI (or the putatively more severe form of the acute respiratory distress syndrome, ARDS) depends entirely on a set of readily obtained but clearly nonspecific clinical criteria, collectively known as the AmericanEuropean Consensus Conference (AECC) criteria [6].…”

Section: Introductionmentioning

confidence: 99%

“…At present the diagnosis of ALI (or the putatively more severe form of the acute respiratory distress syndrome, ARDS) depends entirely on a set of readily obtained but clearly nonspecific clinical criteria, collectively known as the AmericanEuropean Consensus Conference (AECC) criteria [6]. The value of these criteria has been challenged [2,3,4,5], but in the absence of some evidence-based alternative the AECC criteria continue to be used, almost universally, to establish inclusion criteria for ALI/ARDS clinical trials.…”

Section: Introductionmentioning

confidence: 99%

Detecting lung injury in patients with pulmonary edema

et al. 2002

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“…If the ARDS is defined as the condition detected in patients who have higher lung recruitability, the extraordinary potential of CT analysis in defining ARDS is immediately apparent. The notion that lung edema or lung capillary permeability should be a cornerstone of the definition of ARDS is not novel [24,25], but, unfortunately, it has been ignored for long time, probably because of the technical difficulties associated with its assessment. The authors believe that two CT scans are required for ARDS diagnosis, one taken at end-expiration at low pressure level, and one taken at end-inspiration at a higher pressure level.…”

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confidence: 99%

The Role of CT-scan Studies for the Diagnosis and Therapy of Acute Respiratory Distress Syndrome

Gattinoni

Caironi

Valenza

et al. 2006

Clinics in Chest Medicine

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The radiologic assessment of lung infiltrates by conventional anterior-posterior chest radiographs has been embedded in the concept of acute respiratory distress syndrome (ARDS) since its original description by Ashbaugh and colleagues [1]. In fact, the presence of bilateral lung infiltrates as detected by chest radiograph, in association with ''refractory'' hypoxemia and impaired mechanics of the respiratory system (stiff lung), was one of the mandatory criteria for ARDS diagnosis. In the mid-1980s, however, the first reports describing ARDS by using CT scanning changed the view of the syndrome [2][3][4]: the ARDS lung appeared to be affected by the disease process nonhomogeneously, with the CT densities distributed mainly in the dependent lung regions. The quantitative analysis of CT scanning gave new insights concerning the pathophysiology of the syndrome and provided a firm rationale for modifying the mechanical ventilation in use at that time [5][6][7]. This article discusses in some detail what the authors believe is or should be the role of the CT scanning in the diagnosis and therapy of ARDS. Quantitative analysis of CT scanningBecause the authors believe that the quantitative analysis of CT scanning is of paramount importance for ARDS diagnosis and for a rational setting of mechanical ventilation, a brief description of the technique and its limits is necessary. (A more detailed description of the quantitative analysis may be found elsewhere [7,8]). Physical principles of CT scanningThe digital image produced by the CT scan is based on the measure of the attenuation coefficient (m) (ie, the reduction of the radiation intensity upon passage through matter). Traversing from one side of the patient to the other, the X-ray beam is attenuated by all the voxels (volume elements of the tissue) through which passes. The intensity of the emerging X-ray is described by the Lambert law of absorption, that is,where I is the intensity of the emerging X-ray beam, and I 0 is the intensity of the X-ray beam at the source. By measuring the intensity I and I 0 , the CT calculates the integral over the function m of the attenuation coefficient along the X-ray beam. Then, through a different mathematical algorithm (usually filtered back projection), a given attenuation number m is assigned to each voxel (m voxel ). This attenuation number primarily represents the density of the voxel (ie, the ratio of mass to the volume) and is expressed as the CT number [9], which relates to the density of the water (m water ):CT ¼ 1000 Â m voxel À m water m waterConventionally a CT number equal to zero Hounsfield units (HU) indicates that density equals

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Identifying patients with ARDS: time for a different approach

Cited by 52 publications

References 49 publications

Lung imaging during acute respiratory distress syndrome: CT- and PET-scanning

Lung imaging during acute respiratory distress syndrome: CT- and PET-scanning

Detecting lung injury in patients with pulmonary edema

The Role of CT-scan Studies for the Diagnosis and Therapy of Acute Respiratory Distress Syndrome

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