We evaluated a new device, the BTI Biox II Ear Oximeter, for intermittent and continuous measurement of arterial oxygen saturation (SaO2). The oximeter calculates SaO2 as a function of light transmittance through an arterialized earlobe. In 183 patients, SaO2 values from the ear oximeter were compared with values obtained simultaneously from direct arterial blood samples, which were analyzed by the Instrumentation Laboratory 282 CO-Oximeter. The coefficient of correlation (r) between the ear oximeter reading and the actual SaO2 in all patients was 0.829. The range of SaO2 studied was 61 to 99%. When the sum of arterial carbon monoxide saturation (SaCO) and SaO2, analyzed by the CO-Oximeter, was compared with the ear oximeter reading, r was 0.914. The highest correlation (r = 0.932) was obtained when the ear oximeter reading was compared with measured SaO2 in only the 129 patients with an SaCO value of 3% or less. We found that the BTI Biox II Ear Oximeter provided accurate, continuous measurement of a patient's oxygenation status in the absence of elevated carboxyhemoglobin levels in the blood. It is relatively insensitive to variations in skin pigmentation and peripheral perfusion, and the instrument's compact design and light weight add to its usefulness in a variety of clinical situations. Additional benefits include patient comfort, ease of operation, cost efficiency, and reliability of instrumentation.
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