Thursday, February 18, 2010

Respiratory failure

Dead space ventilation versus shunt: A shunt does not respond to 100% oxygen administration.

There are two types of respiratory failure: (1) Hypoxemia without hypercapnia; (2) Hypoxemia with hypercapnia

Type 1 respiratory failure is characterized by low PaO2, normal or low PaCO2, and increased arterial-alveolar gradient. This caused by perfusion, ventilation, or diffusion defect, or right-to-left shunt (i.e. Tetralogy of Fallot).

Type 2 respiratory failure is characterized by low PaO2, hypercapnia, and normal arterial-alveolar gradient. This can be caused by hypoventilation due to drugs (for example, barbiturates depress respiratory center in medulla), upper airway obstruction (epiglottitis, croup), chest bellows dysfunction (polio, ALS, Guillain-Barre), or skeletal deformities (kyphoscoliosis, pectus excavatum).

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