Lecture Notes: Respiratory Distress Syndromes

Case Study 1: Mike

• Patient: Mike, 55-year-old male
• Symptoms: Shortness of breath, high fever, cough
• Diagnosis:
  • Chest x-ray: Right lower lobe infiltrate suggestive of pneumonia
  • Treatment began with IV antibiotics
  • Developed hypoxemia and hypotension (septic shock)
  • Further symptoms: Bilateral alveolar opacities detected in a repeat chest x-ray, PF ratio of 109 mmHg
  • Diagnosis: Acute Respiratory Distress Syndrome (ARDS)

Case Study 2: Donna

• Patient: Donna, infant delivered by cesarean section at 36 weeks
• Initial Condition: APGAR score of 9
• Symptoms after birth: Tachypnea, chest wall retractions, nasal flaring, tachycardia
• Diagnosis:
  • Chest x-ray: Diffuse reticulogranular ground glass appearance with air bronchograms
  • Diagnosis: Neonatal Respiratory Distress Syndrome (NRDS)

Physiology of Respiratory Distress

Alveoli and Pneumocytes

• Type 1 Pneumocytes: Thin, large surface area for gas exchange
• Type 2 Pneumocytes: Produce surfactant, proliferate in response to lung injury, act as stem cells
• Surfactant: Decreases alveolar surface tension, absence leads to alveolar collapse

Acute Respiratory Distress Syndrome (ARDS)

• Characteristics: Rapid onset of widespread lung inflammation, triggered by sepsis, aspiration, trauma
• Pathophysiology:
  • Cytokines (TNF-alpha, interleukin-1) released causing neutrophil recruitment
  • Neutrophils release reactive oxygen species and proteases
  • Damage to alveolar capillary membrane causing pulmonary edema and alveolar collapse

Symptoms and Diagnosis

• Fever, shortness of breath, tachypnea, chest pain, hypotension, hypoxia
• Diagnosis Criteria:
  1. Acute onset (within one week)
  2. Chest x-ray showing bilateral opacities
  3. PF ratio < 300 mmHg
  4. Not due to cardiac causes

Treatment

• Supportive care with supplemental oxygen or mechanical ventilation
• Maintain positive end-expiratory pressure
• Monitor for pulmonary hypertension and reduced cardiac output

Neonatal Respiratory Distress Syndrome (NRDS)

• Cause: Surfactant deficiency, frequently due to prematurity or specific birth conditions (e.g., C-section)
• Risk Factors: Prematurity, maternal diabetes, cesarean delivery

Symptoms and Diagnosis

• Initial symptoms: Dyspnea, tachypnea, tachycardia
• Diagnosis via chest x-ray: Low lung volume, reticulogranular ground glass appearance
• Tests for Lung Maturity: Amniocentesis to measure lecithin-sphingomyelin ratio

Treatment

• Antenatal corticosteroids for at-risk pregnancies
• Nasal continuous positive airway pressure
• If necessary: Endotracheal intubation and surfactant therapy

Summary

• ARDS: Inflammation and pulmonary edema due to alveolar injury, requires urgent treatment
• NRDS: Surfactant deficiency leading to respiratory distress in newborns, manage with oxygen therapy and surfactant replacement

Final Recap

• Mike's symptoms and history confirm ARDS
• Donna's premature birth and symptoms suggest NRDS