Impact of Oxygenation Status on the Noninvasive Measurement of Hemoglobin

Background: Noninvasive monitoring of hemoglobin (SpHgb) via pulse oximetry has the potential to alert caregivers to blood loss. Previous studies have demonstrated that changes in oxygenation may impact accuracy. Methods: Twenty normal volunteers were monitored using SpHgb at sea level, during ascent to 14,000 feet, at 14,000 feet with 100% oxygen delivery, and again at sea level. Each period consisted of 15 minutes of monitoring. SpHgb measurements were compared to a blood sample using Bland Altman analysis. The loss of the SpHgb signal was also recorded. Results: The mean difference in measured hemoglobin (Hgb) between a venous sample and SpHgb was −2.6 ± 0.96 at 14,000 feet. Ascent to 14,000 feet resulted in a predictable fall in SpO2 and was associated with loss of the SpHgb signal for half the period of observation (7.4 minutes). In the other three conditions, SpHgb signal was missing 1 to 12.6% of the time. The nadir SpO2 was not predictive of the loss of SpHgb signal. Discussion: Changes in...