Non-invasive measurement of carboxyhemoglobin (COHb) by new pulse oximeter in human volunteers

Introduction

Carbon monoxide is the most commonly encountered and pervasive poison in our environment. However, conventional pulse oximeters cannot detect the presence of carboxyhemoglobin (COHb) and overestimate arterial oxygenation in patients with severe carbon monoxide poisoning. We developed a new pulse oximeter utilizing three wavelengths which can discriminate three species, oxyhemoglobin (O₂Hb), deoxyhemoglobin (RHb) and COHb. We previously demonstrated that increases in COHb concentration measured by the new pulse oximeter (SpCO) highly correlated with increases in COHb concentration measured by a CO-oximeter (SaCO) in pigs. The present study determined whether COHb was detected by the pulse oximeter with three wavelengths in human.

Methods

The study was approved by the hospital Ethics Committee. Eight human healthy volunteers were tested in this study. They were ventilated with 100% oxygen. Probes of the new three wavelength pulse oximeter were attached to the finger. Then 50 ml of carbon monoxide gas was inhaled by human volunteers. SpCO was non-invasively and continuously measured by the new pulse oximeters. SaCO was also measured by a CO-oximeter after 3 min of inhalation. The same amount of carbon monoxide gas was repeatedly inhaled until SaCO reached 15-20%. Then they were ventilated with 100% oxygen until SaCO reached 5%. SpCO was compared with SaCO.

Results

COHb was non-invasively and continuously detected by the new pulse oximeter. There is a strong correlation between SpCO and SaCO (r = 0.92, P < 0.001).

Conclusion

The results of this study demonstrated that the new pulse oximeter might be useful for non-invasive diagnosis of carbon monoxide poisoning.