USMLE Step 1 Question Bank – Acute respiratory distress Syndrome

Hello Students, I am discussing in this video tutorial  about ARDS or Acute Respiratory distress syndrome for PG Medical Entrance Exams and USMLE preparation. If you want to cover this topic for MCQ type exams, you must first listen to  tutorial and then read these points and then if you study the topic from some standard textbook of Medicine, you will find it very interesting and easy to understand.


ARDS is characterized by

—Breathlessness, —Decreased PO2 — Hypoxaemia and  Diffuse pulmonary infiltrates

—We can also found Low Tidal Volume and  non cardiogenic —Pulmonary edema in ARDS.

In addition, Acute respiratory distress syndrome is also characterized by —Increase in Respiratory rate and leading to CO2 washout and resulting in hypocapnea. ARDS can lead to —Stiff lung with reduced compliance

Etiology: ARDS has varied etiology and following points must be remembered as etiological factors for ARDS

—Sepsis and Multiorgan Failure




—Multiple blood transfusions

—Gastric aspiration

—Toxic gas inhalation

—Lung contusion

—Narcotic overdose

Phases: ARDS has following 3 phases.

Exudative Phase- Edema-7 days

Proliferative phase- Interstitial inflammation-8-21 days

Fibrotic phase- Fibrosis-After 3 weeks


—ARDS: PaO2/FIO2 <200 mmHg

—ALI    : PaO2/FIO2  200-300 mmHg

—Bilateral alveolar or interstitial infiltrates

PCWP <18 mmHg


—Treatment of underlying medical condition

—DVT prophylaxis

—Infection control

—Hydration and Nutrition

—Low Tidal volume mechanical ventilation, Prone positioning, minimize left atrial filing pressures

—No definitive role of glucocorticoids

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