Are there different types of respiratory failure?
Some clinicians divide respiratory failure into two categories. The hypoxemic type is generally caused by mismatch of ventilation and perfusion in the lung. Hypoxemic respiratory failure from mismatch of ventilation to perfusion is often associated with normal or low P co 2 . Other patients with respiratory failure have an overall decrease in alveolar ventilation that is usually the result of upper airway obstruction, neuromuscular disease, thoracic trauma, or muscle fatigue. These patients have increases in P co 2 and relatively proportional decreases in P o 2 . The physiology in most children with respiratory failure is a combination of these two types, because one type often leads to the other. For instance, an infant with bronchiolitis initially may have hypoxemia from atelectasis and ventilation-perfusion mismatch, but may progress to inadequate alveolar ventilation when airway resistance is high and respiratory muscle fatigue supervenes.