Hypoxia and Hypoxemia - Overview
Hypoxia - insufficient oxygen delivered to tissues to meet demands
Hypoxemia - low oxygen in the blood (most common type of hypoxia)
PIO2 - atmospheric oxygen (how much O2 is inspired)
PAO2 - alveolar oxygen (how much O2 reaches the alveoli)
PaO2 - oxygen dissolved in arterial blood (measured on ABG)
SaO2 - percent saturation of hemoglobin in arterial blood
CaO2 - oxygen content of arterial blood (dissolved & Hb bound)
HYPOXEMIC HYPOXIA
 - Insufficient oxygen in the blood (the most common type of hypoxia)
 - Low PaO2
ISCHEMIC HYPOXIA
 - Insufficient blood flow to tissues, also called stagnant hypoxia (e.g low cardiac output)
 - Low SvO2 → Low PaO2
ANEMIC HYPOXIA
 - Insufficient O2 carrying capacity (e.g. severe blood loss) or abnormal hemoglobin (e.g. COHb, MetHb)
 - Low CaO2 → Low SvO2 → Low PaO2
CYTOPATHIC HYPOXIA
 - Cells cannot use oxygen (e.g. cyanide toxicity, maybe sepsis)
 - High PaO2, High SvO2

Dr. Nick Mark MD @nickmmark

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