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That Ominous Decrescendo
By Nana Dadzie Ghansah
A pulse oximeter is an indispensable tool for the anesthesiologist, intensivist, and emergency room physician. It not only gives a readout of the oxygen saturation but also shows the pulse. Several of the high-grade ones emit a sound with each pulse. Even more impressive, the tone and pitch of that pulse oximeter sound changes if the oxygen saturation changes. Now imagine something happens to a patient that acutely affects oxygenation, making the oxygen content in the blood decrease. As the measured saturation drops, one can hear the emitted sound change into a low, ominous pitch, and tone.
No situation is more noticeable than when one is in the process of securing a difficult airway either before surgery or in a patient in extremis. In the time that one goes through the process of intubation, the patient is not receiving any oxygen. In most cases, intubation takes less than a minute. A change is hardly seen in oxygenation if the patient is not in extremis. If the intubation is challenging and takes longer than a minute, one will hear the sound change in pitch and tone with each pulse:
Beep — beeep — beeeep — beeeeep…
This unnerving decrescendo adds a particular urgency to the situation that no amount of training and experience can wholly take away. It is like hearing a clock tick…
