Validity of ear oximetry in clinical exercise testing.

Because of suspicion that the ear oximeter might measure the oxyhemoglobin saturation of arterial blood inaccurately during heavy exercise, we made concurrent ear oximetric and blood measurements on 14 consecutive patients with arterial catheters during clinical exercise tests. After correcting for carboxyhemoglobin, the estimated and measured values for the oxyhemoglobin saturation of the blood agreed well, as did resting ear and blood values; however, during heavy exercise, ear oximetric values were falsely elevated in two patients with interstitial pulmonary disease and were falsely depressed in five patients with cardiovascular limitation to exercise. In another patient, ear oximetric values declined during heavy exercise despite mild hyperoxia, suggesting hypoperfusion of the ear. Considering the clinical and physiologic importance of oxyhemoglobin saturation, ear oximetric values during heavy exercise should be cautiously interpreted.