Physiological Etiology

‣ (Alveolar Blood Gas)	Additional S/S	‣	Cause	Treatment
Normal	‣, Hypoventilation (low RR)		Not breathing (‣ )	Ventilation devices
Normal			Decreased FiO2 in the air (high altitude, unhooked oxygen supply)	O2
High	Low‣	responsive	Low diffusion at membrane (e.g. ‣ )	O2
High	‣	Non-responsive	‣ (low O2sat exacerbate it)
High	hyperventilation (high RR) → functional lung unit help ensure globally normal PCO2	responsive	‣ (reduced V) *Most Common	O2

Clinical Pearl

PCO2 respond to hyperventilation, but PO2 does not → because HbSat is already high in the well-perfused regions.
Diffusion problem commonly don’t affect PCO2, but PO2, as CO2 is very diffusible