Placement of finger oximeter on the ear: comparison with oxygen saturation values taken from the finger

Pulse oximetry is widely used to assess oxygen saturation (SpO₂) in order to guide patient care and monitor the response to treatment. However, inappropriate oximeter probe placement has been shown to affect the measured oximetry values in healthy and normoxic outpatients. This study evaluated how treatment decisions might be impacted by SpO₂ values obtained using a finger probe placed on the pinna of the ear in a cohort of 46 patients receiving non-invasive ventilation compared with values obtained from a probe on the finger and the results of arterial blood gas (ABG) (SaO₂) analysis. Bland-Altman analysis was performed to evaluate agreement between the methods. Finger probe saturation was not statistically different from SaO₂, with a mean difference of -0.66% (P>0.05). Saturation from the ear was significantly different (-4.29%; P<0.001). Subgroup analysis in hypoxic patients (SaO₂<90%) showed a significant difference between ABG SaO₂, and finger and ear SpO₂. The study provides evidence that placement of a finger probe on the ear is unsafe clinical practice, potentially leading to patient mismanagement.