Acute Respiratory Distress and Mechanical Ventilation

Normal Gas Exchange

• Alveolus Function:
  • Oxygen is inhaled, carbon dioxide is exhaled.
  • Deoxygenated blood is oxygenated and returned to the heart.

Acute Respiratory Failure

• Types of Respiratory Failure:
  • Type 1 (Hypoxemic): Low oxygen in blood due to cardiac/respiratory issues (e.g., ARDS, pneumonia).
  • Type 2 (Hypercapnic): Ventilatory failure (trouble moving air in and out).
  • Mixed Respiratory Failure: Combination of both types.

Signs and Symptoms

• Hypoxemic: Shortness of breath, high respiratory rate, low O2 saturation, altered mental status.
• Hypercapnic: Shortness of breath, tripod position, pursed-lip breathing, decreased reflexes.

Treatment

• Oxygenation: Apply oxygen, manage secretions, use bronchodilators, steroids, and diuretics.
• Maintain Mean Arterial Pressure: Keep >65 mmHg. Ensure adequate nutrition.

VQ Ratio

• Normal VQ Ratio: 0.8 to 1.2.
• Shunting: Perfusion without ventilation (e.g., pneumonia).
• Dead Space: Ventilation without perfusion (e.g., pulmonary embolism).
• Silent Unit: No ventilation or perfusion (e.g., pneumothorax).

Pulmonary Shunting

• Mechanism: Lungs constrict in response to hypoxia, leading to shunting.
• Oxygen Application: Essential for respiratory failure but does not reach lungs in absolute shunting.

ABG Levels

• Normal: PaO2 80-100 mmHg.
• Hypoxemia:
  • Mild: 60-79 mmHg.
  • Moderate: 45-59 mmHg.
  • Severe: <45 mmHg.

Mechanical Ventilation

• Indications: Low PaO2, high CO2, respiratory distress, altered mental status.
• Ventilator Settings:
  • Respiratory Rate: 12-20 breaths/min.
  • Tidal Volume: 6-8 mL/kg.
  • FiO2: Adjusted to keep O2 levels 60-80.
  • PEEP: Usually 5, higher in ARDS.

Ventilator Modes

• Assist Control (CMV): Full ventilatory support.
• SIMV: Allows patient-initiated breaths.

Complications of Mechanical Ventilation

• Barotrauma: Due to high pressures.
• Ventilator Alarms: Low pressure (leaks) vs. high pressure (obstructions).

Suctioning and Basic Care

• Inline Suctioning: Maintain peep.
• Care: Check tube position, lung sounds, and oral care.

ARDS (Acute Respiratory Distress Syndrome)

• Causes: Sepsis, pneumonia, aspiration.
• Phases:
  • Exudative: Fluid leaks into alveoli.
  • Proliferative: Continued inflammation.
  • Fibrotic: Lung fibrosis.

Management of ARDS

• Three P's: Prone, PEEP, Permissive Hypercapnia.
• Medications: Sedation, neuromuscular blockers, antibiotics.

Conclusion

• ARDS Treatment: Focus on reducing inflammation, supporting gas exchange.
• Ventilator Management: Adjust settings to minimize trauma and enhance recovery.