Respiratory distress syndrome: Pathology Review

Summary

The script discusses two cases of respiratory distress: Mike, a 55-year-old with pneumonia leading to ARDS, characterized by rapid lung inflammation, hypoxia, and a PF ratio below 300, not caused by heart failure. Donna, a premature infant, develops NRDS due to surfactant deficiency, presenting with respiratory distress and a characteristic chest x-ray pattern. The script explains the pathophysiology, diagnosis criteria, and treatment approaches for both conditions, emphasizing the importance of supportive care and surfactant therapy.

Takeaways

• 💉 Mike, a 55-year-old man, presented with shortness of breath, fever, and cough, which led to a pneumonia diagnosis after a chest x-ray showed a right lower lobe infiltrate.
• 🚑 Despite IV antibiotics, Mike's condition worsened, and he developed septic shock with hypoxemia, requiring intubation, IV fluids, and vasopressors.
• 📉 A repeat x-ray revealed bilateral alveolar opacities, a PF ratio of 109, and heart failure was ruled out by echography, leading to a diagnosis of acute respiratory distress syndrome (ARDS).
• 👶 Donna, an infant born at 36 weeks via C-section, developed respiratory distress hours after birth, presenting with tachypnea, chest retractions, and nasal flaring.
• 🩻 Donna’s chest x-ray showed a diffuse reticulogranular ground glass appearance with air bronchograms, confirming neonatal respiratory distress syndrome due to surfactant deficiency.
• 🫁 Type 2 pneumocytes are responsible for producing surfactant, which prevents alveolar collapse. Damage to these cells contributes to both ARDS and neonatal respiratory distress syndrome.
• 🔥 ARDS is characterized by alveolar damage caused by conditions like sepsis, leading to fluid accumulation in the alveoli, pulmonary edema, and impaired gas exchange.
• 🩸 Diagnosis of ARDS involves acute onset (within 1 week), bilateral lung opacities on imaging, a PF ratio below 300, and ruling out cardiac causes.
• 🛠️ Treatment of ARDS focuses on supportive care, such as mechanical ventilation with positive end-expiratory pressure (PEEP) and low tidal volumes to prevent further lung damage.
• 👶 Neonatal respiratory distress syndrome is often linked to premature birth, maternal diabetes, or C-section delivery. It is treated with continuous positive airway pressure (CPAP) or surfactant therapy.

Q & A

What led to Mike's diagnosis of pneumonia?

Mike's diagnosis of pneumonia was based on his presentation of shortness of breath, high fever, and cough, along with a chest x-ray showing a right lower lobe infiltrate.

What complications did Mike experience after being treated for pneumonia?

Despite treatment, Mike developed hypoxia and hypotension, eventually progressing to septic shock. A repeat x-ray showed bilateral alveolar opacities, indicating acute respiratory distress syndrome (ARDS).

What are the four criteria used to diagnose acute respiratory distress syndrome (ARDS)?

The four criteria for diagnosing ARDS are: (1) acute onset within one week, (2) bilateral opacities on chest imaging, (3) a PF ratio below 300 mmHg, and (4) respiratory failure not due to cardiac causes like heart failure.

What role do type 2 pneumocytes play in lung function and injury response?

Type 2 pneumocytes produce surfactant, which reduces surface tension in the alveoli, preventing their collapse. They also proliferate in response to lung injury and can differentiate into type 1 and type 2 cells.

What is the mechanism behind the development of pulmonary edema in ARDS?

In ARDS, the alveolar-capillary membrane becomes more permeable due to inflammation, allowing fluid to leak into the alveoli, leading to pulmonary edema. This impairs gas exchange and worsens respiratory function.

What findings on Mike's arterial blood gas analysis supported his ARDS diagnosis?

Mike's arterial blood gas analysis revealed a PF ratio of 109 mmHg, which is significantly below the threshold for ARDS, indicating severely impaired gas exchange.

What are the risk factors for neonatal respiratory distress syndrome (NRDS) in Donna's case?

Donna's risk factors for neonatal respiratory distress syndrome include her premature delivery at 36 weeks gestational age and being delivered by C-section, which can reduce the stress-induced glucocorticoid surge needed for surfactant production.

What are the characteristic findings of neonatal respiratory distress syndrome on chest x-ray?

The characteristic chest x-ray findings for neonatal respiratory distress syndrome include diffuse reticulogranular ground glass appearance with air bronchograms.

What are the key differences between ARDS and neonatal respiratory distress syndrome (NRDS)?

ARDS is caused by widespread lung inflammation in response to various triggers, such as sepsis or trauma, while NRDS is caused by a deficiency of surfactant in newborns, often due to prematurity. ARDS affects older individuals, while NRDS primarily affects preterm infants.

What treatment options are available for neonatal respiratory distress syndrome (NRDS)?

Initial treatment for NRDS includes nasal continuous positive airway pressure (CPAP) to keep the alveoli open. If this fails, endotracheal intubation and intratracheal surfactant therapy are used. Antenatal corticosteroids are also given to mothers at risk of preterm delivery to reduce the severity of NRDS.