ARDS & Lung Cancer

Objectives - Identify facts and principles about acute respiratory distress syndrome and lung cancer.

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Acute Respiratory Distress Syndrome

ARDS is acute diffuse inflammatory lung injury leading to increased pulmonary vascular permeability, increased lung weight, and loss of aerated lung tissue. It includes hypoxemia and bilateral radiographic opacities, with increased venous admixture, increased physiologic dead space, and decreased lung compliance.

A syndrome is a combination of symptoms resulting from a single cause or so commonly occurring together that they form a distinct clinical picture.

ARDS Key Components

The source lists these key components:

• Acute onset within 1 week or less
• Chest x-ray or CT showing bilateral opacities consistent with pulmonary edema
• PaO2/FiO2 ratio less than 300 mmHg with 5 cmH2O PEEP or greater
• Not fully explained by cardiac failure or fluid overload
• Objective assessment such as echocardiogram should be performed in most cases when there is no clear cause such as trauma or sepsis

P/F Ratio

The P/F ratio is a quick formula used to identify acute hypoxemic respiratory failure when supplemental oxygen has already been administered and no room air ABG is available.

Criteria for acute hypoxemic respiratory failure:

• PaO2 less than 60 mmHg on room air by ABG
• SpO2 less than 91% on room air by pulse oximetry
• P/F ratio less than 300 while on oxygen

Normal examples from the source:

Normal P/F ratio is greater than 400.

Abnormal examples from the source:

ARDS Pathophysiology

Direct or indirect pulmonary insult causes an inflammatory response that promotes neutrophil accumulation in the lung microcirculation.

These neutrophils migrate across vascular endothelial and alveolar epithelial surfaces, releasing:

• Proteases
• Cytokines
• Reactive oxygen species

This leads to vascular permeability, gaps in the alveolar epithelial barrier, and necrosis of type I and type II alveolar cells.

The result is:

• Pulmonary edema
• Hyaline membrane formation
• Loss of surfactant
• Decreased pulmonary compliance
• Difficult gas exchange

Subsequent fibroblast infiltration can lead to collagen deposition, fibrosis, and worsening disease.

ARDS Causes and Risk Factors

Direct injury causes listed in the source:

• Pneumonia
• Gastric aspiration
• Toxic inhalation
• Near drowning
• Lung contusion from blunt force trauma

ARDS Signs and Symptoms

Signs and symptoms common to ARDS and CHF include:

• Anxiety
• Dyspnea
• Tachypnea
• Reduced lung volumes
• Decreased lung compliance
• Respiratory alkalosis and hypoxemia
• X-ray showing diffuse alveolar and interstitial infiltrates

ARDS vs CHF

ARDS Treatment and Management

Treatment and management listed in the source:

• Mechanical ventilation
• Lung protective strategies
• High-frequency ventilation
• Inverse ratio ventilation
• Pressure control ventilation
• Airway pressure release ventilation

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Lung Cancer

Cancer is a collection of related diseases in which cells divide without stopping and spread into surrounding tissues.

Cancer spreads through:

• Tissue: from where it began into nearby areas
• Lymphatic system: through lymph vessels to other parts of the body
• Blood: through blood vessels to other parts of the body

Lung Cancer Risk

Risks listed in the source include:

• Tobacco smoke exposure, active or passive
• Genetic factors
• Sex
• Diet
• COPD
• Pollution

Lung Cancer Classification

Lung Cancer Pathophysiology

The source sequence:

1. Carcinogen exposure damages genetic material in lung cells.
2. Damaged cells divide out of control.
3. Cancer cells block apoptosis, which recruits macrophages.
4. Macrophages trigger inflammation and angiogenesis.
5. Cancer cells form a tumor using new blood vessels.
6. Cancer cells move to secondary sites through metastasis.

Lung Cancer Signs and Symptoms

Signs and symptoms include:

• Cough
• Dyspnea
• Hemoptysis
• Blood or rusty-colored secretions
• Fatigue
• Unexplained weight loss
• Recurrent respiratory infections
• Hoarseness
• New wheezing

Lung Cancer Diagnosis and Staging

Diagnosis includes:

• Patient history and physical
• Chest x-ray
• CT scan
• PET scan
• Bronchoscopy

Lung cancer stages are indicated by Roman numerals from 0 to IV. The lowest stages indicate cancer limited to the lung. Stage IV is advanced and has spread to other areas of the body.

Lung Cancer Treatment

Non-small cell surgical options include:

• Wedge resection: remove a small section containing the tumor and a margin of healthy tissue
• Segmental resection: remove a larger portion of lung but not an entire lobe
• Lobectomy: remove the entire lobe of one lung
• Pneumonectomy: remove an entire lung

Source survival ranges:

• Non-small cell treatment: 5-year survival 25-60%
• Small cell treatment: 5-year survival 2-19%

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High-Yield Review