The Other Side of Pulse Oximetry
One of the most poorly understood and misused pieces of equipment on an ambulance is the pulse oximeter. From the one-time application to obtain that mythical "room-air sat" for the triage nurse to the EMT who uses it as a litmus test for oxygen therapy rather than as the trending tool it was intended to be, its misapplication is something you can observe in most any EMS system. As a real-time indicator of the effectiveness of ventilation, pulse oximetry places a distant second to waveform capnography.
However, there are a couple of non-traditional uses of pulse oximetry you may find handy in your clinical practice; first, as an aid in palpating blood pressures, and second, as a continuous, real-time assessment of distal circulation.
One easy way to palpate a blood pressure is to place the pulse oximeter probe on a digit in the extremity in which you're taking a blood pressure. Wait for a steady waveform and decent saturation reading, then inflate your BP cuff.
Watch the numbers as the waveform disappears, and when it reappears during deflation. Those numbers are roughly equivalent to the systolic blood pressure reading you'd obtain during conventional palpation of a blood pressure.
It can be done with a manual sphygmanometer and a hand-held pulse oximeter, but it is most easily accomplished using your cardiac monitor with integrated pulse oximetry and NIBP functions. It's not as accurate as direct auscultation, but it’s quick, and far better than simply noting the presence or absence of a distal pulse when circumstances or ambient noise keep you from obtaining anything else.
You can also use your pulse oximeter to continuously evaluate distal circulation in an injured extremity. If you've splinted a fractured limb, or applied a pressure dressing to a laceration, make it a point to place your pulse oximeter probe on a digit in the injured extremity. As long as it gives you a numerical readout and a waveform, you can reasonably assume that distal circulation is adequate.