Respiratory Failure and Intensive Care
Core concepts
Respiratory failure is classified as type I hypoxemic or type II hypercapnic. Pediatric acute respiratory distress syndrome requires acute onset within 7 days, hypoxemia, positive-pressure ventilation with positive end-expiratory pressure of at least 5, and chest imaging not fully explained by cardiac failure. Severe asthma is treated with oxygen, short-acting beta-agonists, systemic corticosteroids, and magnesium. Signs of impending failure include a silent chest, exhaustion, altered mental status, and rising carbon dioxide; a normal or rising carbon dioxide in a tiring asthmatic is ominous. Lung-protective ventilation uses low tidal volumes of about 4–8 mL/kg predicted body weight, adequate positive end-expiratory pressure, and permissive hypercapnia except when intracranial pressure is elevated. High-flow nasal cannula and noninvasive ventilation are used for selected patients. Foreign body aspiration and epiglottitis are airway emergencies.
Traps
Do not rely on pulse oximetry alone in poor perfusion. A “normal” carbon dioxide level is not reassuring in severe asthma. High tidal volumes worsen lung injury in pediatric acute respiratory distress syndrome. Delaying intubation in an exhausted child is dangerous.
Worked example and rule of thumb
A child in status asthmaticus with drowsiness and carbon dioxide 55 mmHg after maximal therapy needs intubation and mechanical ventilation, not more nebulizers alone. Rule of thumb: in acute severe asthma, a rising carbon dioxide level signals fatigue and impending respiratory failure.