Use of pulse oximetry as a noninvasive indicator of intravascular volume status

The use of pulse oximetry as a noninvasive method to assess intravascular volume status is described. Pulse oximeters providing a continuous display of the pulse waveform offer a new method of estimating relative volume status during positive-pressure ventilation. Like intraarterial pressure tracings, the peaks of the pulse waveform demonstrate increased variation in response to positive-pressure ventilation when a patient becomes hypovolemic. Pulse oximeter waveform tracings were compared with central venous pressure and intraarterial pressure tracings in 12 patients undergoing major operative procedures. A significant correlation (r = 0.61) was seen between pulse waveform variation and systolic pressure variation, which has previously been shown to be a sensitive indicator of hypovolemia. When data from individual patients were analyzed separately, the correlation between pulse waveform variation and systolic pressure variation was as high as 0.88.