Applied respiratory physiology

Respiratory failure, hypoxia with or without hypercarbia, is common in infants and children. Knowledge of the underlying abnormal physiology facilitates diagnosis and therapy. Isolated hypoxia can result from ventilation perfusion mismatch, intra- and extrapulmonary shunting and impaired diffusion. Intra- and extrapulmonary shunting can be distinguished from the other conditions by a poor response to supplementary oxygen. Hypercarbia indicates an inadequate minute ventilation which can result from upper or lower airway obstruction, reduced respiratory system compliance or conditions adversely affecting the respiratory pump.