Acute Respiratory Distress Syndrome (ARDS) Pathophysiology and Etiology

15 Questions

What is the primary pathophysiologic mechanism leading to impaired gas exchange in Acute Respiratory Distress Syndrome?

Increased permeability of the alveolar-capillary membrane

Which of the following is a risk factor for developing Acute Respiratory Distress Syndrome?

Chronic alcohol abuse

What is the characteristic radiographic finding in Acute Respiratory Distress Syndrome?

Acute onset, bilateral opacities on CXR/CT

Which of the following is an example of indirect lung injury leading to Acute Respiratory Distress Syndrome?

Sepsis

What is the characteristic laboratory finding in Acute Respiratory Distress Syndrome?

Hypoxemia refractory to oxygen therapy

In childhood, which gender is more likely to develop asthma?

Male

What is a common allergen exposure that can trigger asthma?

Tobacco smoke

Which diagnostic test is used to identify specific allergens?

Skin test

What does blood eosinophilia indicate in asthma patients?

Severe forms of asthma

What is the purpose of pulmonary function tests (PFTs) in asthma diagnosis?

To assess severity of disease

What does spirometry measure during a pulmonary function test?

Air volume and flow rate

Which factor is a trigger for asthma exacerbations?

All of the above

What is the purpose of a chest radiograph (CXR) in asthma diagnosis?

To visualize air tapering in severe cases

What is the term for the measurement of oxygen and carbon dioxide levels in the blood?

Blood gas analysis

Which of the following is NOT a host factor that contributes to asthma risk?

Age

Study Notes

Acute Respiratory Distress Syndrome (ARDS)

Major cause of respiratory failure in critically ill patients

Pathophysiology

Diffuse alveolar damage leads to increased permeability
Increased permeability causes protein-rich edema
Protein-rich edema impairs gas exchange

Etiology

Direct Lung Injury:
- Pneumonia (bacterial, viral, aspiration)
- Pulmonary contusion
- Gastric aspiration
- Inhalational injury (smoke, toxins)
Indirect Lung Injury:
- Sepsis
- Severe trauma (multiple fractures, burns)
- Acute pancreatitis
- Drug overdose/toxicity

Risk Factors

Age > 65 years
Chronic alcohol abuse
Obesity
Chemotherapy (bleomycin)
Diabetes mellitus

Clinical Presentations

Progressive dyspnea
Acute onset, bilateral opacities on CXR/CT
Hypoxemia refractory to O2 (P/F ratio)

Risk Factors of Asthma

Host factors include genetics, with a higher risk of asthma in males during childhood and females during adulthood
Environmental factors that contribute to asthma include allergen exposure, respiratory infections, pollution, smoking, and occupational factors

Triggers of Asthma

Respiratory infections
Physical activity
Hormonal fluctuations
Medications such as non-selective beta-blockers, aspirin, and other NSAIDs
Inhaled irritants like tobacco smoke, pollution, cold dry air, and hot humid air
Inhaled allergens

Diagnosis of Asthma

Allergen testing through skin test to identify specific allergens
Complete Blood Count (CBC) to check for total and differential leucocytic count
Blood eosinophilia may indicate severe forms of asthma
Sputum examination to check for cellular content or pathogens
Chest Radiograph (CXR) to show air tapering in severe cases
Blood Gas Analysis to monitor oxygen and carbon dioxide levels
Pulmonary function tests (PFTs) to assess severity of the disease and monitor its course and treatment

Pulmonary Function Tests (PFTs)

Spirometry measures lung volume by recording the amount and rate of air breathed in and out over a specified time
Primary PFTs used in asthma diagnosis include forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC)
FEV1 is the volume of air forcefully exhaled in one second, approximately 3-4 L
FEV1 percentages:
- 80% or above: normal
- 60-80% predicted: mild
- 50-60% predicted: moderate