Diffuse alveolar damage

Diffuse alveolar damage (DAD) is a histologic term used to describe specific changes that occur to the structure of the lungs during injury or disease. Most often DAD is described in association with the early stages of acute respiratory distress syndrome (ARDS). It is important to note that DAD can be seen in situations other than ARDS (such as acute interstitial pneumonia) and that ARDS can occur without DAD. Diffuse alveolar damage (DAD): an acute lung condition with the presence of hyaline membranes. These hyaline membranes are made up of dead cells, surfactant, and proteins. The hyaline membranes deposit along the walls of the alveoli, where gas exchange typically occurs, thereby making gas exchange difficult. Acute respiratory distress syndrome (ARDS): a potentially life-threatening condition where the alveoli are damaged thereby letting fluid leak into the lungs which makes it difficult to exchange gases and oxygenate the blood. It is the general practice of the medical community to use the Berlin criteria to diagnose ARDS. All criteria must be present to make a diagnosis of ARDS. The Berlin Criteria specifies: Timing: onset of respiratory symptoms within one week of an injury/insult. Chest Imaging: either chest x-ray or CT scan, must show bilateral opacities that cannot be fully explained by other conditions such as effusion, lung/lobar collapse, or lung nodules. Origin of Edema: respiratory failure that cannot be fully explained by cardiac failure or fluid overload, this needs objective assessment such as an echocardiogram. Impaired Oxygenation: this can be determined by looking at the ratio of arterial oxygen tension to fraction of inspired oxygen (PaO2/FiO2) that can be obtained based on an arterial blood gas test. Note: all PaO2/FiO2 ratios used in the determination of the severity of ARDS require that the patient be on a ventilator at a setting that includes 5 cm H2O or more of positive end-expiratory pressure (PEEP) or continuous positive airway pressure (CPAP).