Hypoxemia

While rounding with our newest pediatric pulmonologist:

The seven causes of hypoxemia
1. Low inspiratory partial pressure (fraction) of oxygen: high altitude
2. Alveolar hypoventilation: apnea
3. Impairment of diffusion across blood-gas membrane: pneumonia, interstitial disease
4. Ventilation-perfusion mismatch: asthma
5. Shunt: Arterio-venous malformation, mixing cardiac lesion
6. Reduced mixed venous oxygen content in the context of a shunt: not sure
7. Hemoglobinopathy: carbon monoxide poisoning

Abbreviations: FiO2, a's and b's, a-A gradient, dz, V-Q mismatch, AVM, CO, ddx