Effect of road traffic accident contaminants on pulse oximetry among normoxaemic volunteers

Introduction Pulse oximetry is a simple and reliable non-invasive method used widely in emergency care. Signal strength is usually easy to interpret in most monitors and is used as a simple validation tool for the reliability of the readings. However it is known from the literature that in certain circumstances the oxygen saturation readings could be false in spite of a deceptively normal signal. The aim of this study was to compare the pulse oximetry readings on fingers contaminated with natural contaminants which might appear in a road traffic accident (RTA) scenario. Methods 50 healthy volunteers were included. Beside the control fingers, the others were contaminated by (1) dried blood (B), (2) soil (S), (3) oil grease (O) and (4) green extract from natural leaves (G). Results The average control reading was 99.1% (SD 1.11). The average readings on the contaminated fingers were as follows: B: 98.6% (SD 1.27); S: 98.7% (SD 1.17); O: 98.5% (SD 1.09); G: 98.7% (SD 1.06). There was a statistically different decrease in the readings between the B and O groups compared to control. Conclusion Pulse oximetry could give unreliable readings despite a normal signal when a patient's fingers are contaminated - especially with dried blood or black oil grease which are both common in road traffic accidents. Cleaning the fingers before pulse oximetry therefore should be considered.