What is ARDS anyway?

Pathophysiology:
ARDS stands for Acute Respiratory Distress Syndrome.This occurs when fluid fills up the alveoli in the lungs. This makes it harder for oxygen to enter the bloodstream, which may lead to organ dysfunction. ARDS generally occurs secondary to a prior injury or disease. About 90% of the cells that make up the alveoli are called Type i epithelial cells. This is where Oxygen and Carbon dioxide gas exchange takes place when we breathe. It is normally very easy for Oxygen to diffuse through this layer of cells into the capillaries where it binds with the hemoglobin in the red blood cells. The alveolar cells normally form a very tight barrier around the alveolar space, which prevents fluid from entering and disrupting gas exchange. In ARDS, the alveolar epithelial barrier breaks, allowing flooding of the alveolar space making it difficult or impossible for oxygen to diffuse into the capillaries.

ARDS is associated with diffuse alveolar damage (DAD) and lung capillary endothelial injury. The pathophysiology of ARDS can be seen in figure A. Figure B shows the difference between a normal alveolus compared to one affected by ARDS. 

 Figure A https://www.pinterest.com/pin/34480753371721180/



Figure B https://www.youtube.com/watch?v=IOj-4oH9ROY

Etiology:
Causes of ARDS: There are various risk factors for ARDS. For nearly 20% of patients, the cause is unknown. ARDS risk factors include:

•     Bacteremia
•     Sepsis
•     Trauma, with or without pulmonary contusion
•     Fractures, particularly multiple fractures and long bone fractures
•     Burns
•     Massive transfusion
•     Pneumonia
•     Aspiration 

To learn more about causes, visit this link: http://www.mayoclinic.org/diseases-conditions/ards/basics/causes/con-20030070

Epidemiology:
ARDS affects approximately 150,000 people in the United States annually, with a very high risk of mortality/morbidity rate with 30-35% of patients dying from complications associated with ARDS. Factors that contribute to high mortality/morbidity rates include: limitations in lung function, severe muscle weakness, decrease in ability to think and recall, and psychological effects such as anxiety, depression, and post-traumatic stress disorder.

For further information, read the following article: http://www.thoracic.org/patients/lung-disease-week/2011/ards-week/general-info.php

References: https://www.nhlbi.nih.gov/health/health-topics/topics/ards/, http://www.mayoclinic.org/diseases-conditions/ards/basics/causes/con-20030070, http://www.thoracic.org/patients/lung-disease-week/2011/ards-week/general-info.php,

http://www.healthcommunities.com/ards/pathophysiology.shtml#sthash.bxFOlXVx.dpuf