Question

Pathophysiology of respiratory failure secondary to flail chest.

Hint:

Management of flail chest requires stabilization of the chest wall, optimization of ventilation, and management of associated injuries to prevent respiratory failure.

Answer 1

Flail chest is a severe condition resulting from multiple rib fractures, leading to paradoxical chest wall motion. This significantly impairs respiratory mechanics and can result in respiratory failure.
Step 1: Mechanism of Injury:
Flail chest occurs when multiple adjacent ribs are fractured in at least two places, resulting in a free-floating segment of the chest wall. This disrupts the normal integrity of the thoracic cage and impairs ventilation.
Step 2: Paradoxical Chest Wall Motion:
In flail chest, the injured section of the chest wall moves in the opposite direction to the rest of the thoracic cage during breathing. During inspiration, the flail segment is sucked inward while the rest of the chest wall expands. Conversely, during expiration, the flail segment bulges outward while the rest of the chest wall contracts.
Step 3: Impaired Ventilation:
The paradoxical motion prevents effective expansion of the lungs, leading to a reduction in tidal volume and impaired gas exchange. This can result in hypoxemia, hypercapnia, and respiratory acidosis. The compromised ventilation also contributes to atelectasis and a lack of proper airway clearance.
Step 4: Respiratory Failure:
The inability of the lungs to expand adequately due to chest wall instability results in respiratory failure. The body compensates by increasing the respiratory rate and working harder to achieve ventilation, which can eventually lead to fatigue and failure of the respiratory muscles, requiring mechanical ventilation.
Step 5: Associated Injuries:
Flail chest often occurs in conjunction with other serious injuries, including pulmonary contusions, hemothorax, and pneumothorax, which exacerbate respiratory failure. The combined effects of these injuries further complicate management and prognosis.