It’s an important differential. For emphasis, and in case you need to paste it somewhere, here it is again, in text form.
vasodilatory sepsis anaphylaxis neurogenic obstructive tension pneumothorax cardiac tamponade pulmonary embolism abdominal compartment syndrome (thanks GW) cardiogenic arrhythmia ischemia valvulopathy myopathy
hypovolemic (hemorrhage) chest abdomen retroperitoneum GI tract thigh street hypovolemic (not hemorrhage) vomiting, diarrhea inadequate fluid intake diuresis, hyperglycemia diaphoresis, hyperthermia cirrhosis, pancreatitis, burn
toxicologic calcium channel blocker beta blocker clonidine digoxin opiates sedatives valproic acid TCA phenothiazine CO, CN- metabolic hypoadrenalism hypo/hyperthyroidism spurious (equipment or technique failure)
A few other considerations:
auto-PEEP if intubated