Pulse Oximeter Failure Thresholds in Hypotension and Vasoconstriction

The degree of systolic hypotension causing failure and recovery were tested simultaneously with three oximeters (CSI 504US, Nellcor N-200, and Ohmeda 3740), in nine normal male volunteers. Failure of pulse oximeters on fingers occurs at pressures too low for adequate tissue perfusion except when vasoconstriction is present. There are minor threshold differences between instruments, but efforts to increase sensitivity may not be justified in view of the local arterial desaturation evident at current thresholds during normoxia