AssessmentsAcute respiratory distress syndrome
Acute respiratory distress syndrome
USMLE® Step 1 style questions USMLE
USMLE® Step 2 style questions USMLE
A 45-year-old woman is brought to the emergency department because of upper abdominal pain. She has nausea, vomiting, and anorexia. Medical history is contributory for gallstones. Patient's BMI is 39 kg/m2. Her temperature is 38°C (100.4°F), pulse is 107/min, respirations are 31/min, and blood pressure is 85/65 mm Hg. Physical examination shows an ecchymotic discoloration over the flanks. Alkaline phosphatase and serum lipase are both elevated. Which of the following is most likely an associated complication of this patient's condition?
Content Reviewers:Vincent Waldman, PhD
Acute Respiratory Distress Syndrome, or ARDS, is exactly what it sounds like.
‘Acute’ means that it happens rapidly.
‘Respiratory distress’ means that a person becomes unable to breathe and oxygenate their blood, and ‘syndrome’ means that it is a group of symptoms that may be caused by any number of underlying conditions.
Air enters the lungs through a series of airways that branch and narrow until they end in clusters of alveoli, which look kinda like a bunch of grapes.
These cell layers are fused to one another by the basement membrane and surrounding the alveoli and blood vessels is connective tissue made up of mostly proteins and water - in a space called the interstitial space.
The alveolar epithelial cells—called pneumocytes—come in two types.
The vast majority are type I pneumocytes, which are thin and have a large surface area, a shape that allows oxygen and carbon dioxide to pass through them easily.
The alveoli are so tiny that their walls end up being really close together.
The process of ARDS gets started when inflammatory molecules arrive in the lungs.
More specifically, these are cytokines like TNF-alpha and interleukin 1, that come through the bloodstream due to a systemic illness like a massive infection, or get released locally by alveolar macrophages in response to a lung injury.
Whatever the source, these cytokines cause capillary endothelial cells to secrete inflammatory molecules, and express adhesion molecules on their surface that help circulating immune cells to adhere or stick to them.
These neutrophils launch into inflammatory mode, releasing proteases, enzymes that digest protein, reactive oxygen molecules, that cause free radical damage, and cytokines, which perpetuate the cycle of inflammation.
As a result of this inflammation, a few important things happen. First, some inflammatory molecules are pro-coagulant, meaning they make the blood more likely to clot.
- "Robbins Basic Pathology" Elsevier (2017)
- "Functional Food and Diseases" Centurion University of Technology and Management (2021)
- "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
- "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
- "Acute Respiratory Distress Syndrome" JAMA (2012)