Feasibility and accuracy of nasal alar pulse oximetry

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The nasal ala is an attractive site for pulse oximetry because of perfusion by branches of the external and internal carotid arteries. We evaluated the accuracy of a novel pulse oximetry sensor custom designed for the nasal ala.


After IRB approval, healthy non-smoking subjects [n=12; aged 28 (23–41) yr; 6M/6F] breathed hypoxic mixtures of fresh gas by a facemask to achieve oxyhaemoglobin saturations of 70–100% measured by traditional co-oximetry from radial artery samples. Concurrent alar and finger pulse oximetry values were measured using probes designed for these sites. Data were analysed using the Bland–Altman method for multiple observations per subject.


Bias, precision, and accuracy root mean square error (ARMS) over a range of 70–100% were significantly better for the alar probe compared with a standard finger probe. The mean bias for the alar and finger probes was 0.73% and 1.90% (P<0.001), respectively, with corresponding precision values of 1.65 and 1.83 (P=0.015) and ARMS values of 1.78% and 2.72% (P=0.047). The coefficients of determination were 0.96 and 0.96 for the alar and finger probes, respectively. The within/between-subject variation for the alar and finger probes were 1.14/1.57% and 1.87/1.47%, respectively. The limits of agreement were 3.96/−2.50% and 5.48/−1.68% for the alar and finger probes, respectively.


Nasal alar pulse oximetry is feasible and demonstrates accurate pulse oximetry values over a range of 70–100%. The alar probe demonstrated greater accuracy compared with a conventional finger pulse oximeter.

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