Smooth or Stepped? Laboratory Comparison of Enhanced Sonifications for Monitoring Patient Oxygen Saturation

The pulse oximeter (PO) provides anesthesiologists with continuous visual and auditory information about a patient's oxygen saturation (SpO₂). However, anesthesiologists' attention is often diverted from visual displays, and clinicians may inaccurately judge SpO₂ values when relying on conventional PO auditory tones. We tested whether participants could identify SpO₂ value (e.g., "97%") better with acoustic enhancements that identified three discrete clinical ranges by either changing abruptly at two threshold values (stepped-effects) or changing incrementally with each percentage value of SpO₂ (smooth-effects).

In all, 79 nonclinicians participated in a between-subjects experiment that compared performance of participants using the stepped-effects display with those who used the smooth-effects display. In both conditions, participants heard sequences of 72 tones whose pitch directly correlated to SpO₂ value, and whose value could change incrementally. Primary outcome was percentage of responses that correctly identified the absolute SpO₂ percentage, ±1, of the last pulse tone in each sequence.

Participants using the stepped-effects auditory tones identified absolute SpO₂ percentage more accurately (M = 53.7%) than participants using the smooth-effects tones (M = 47.9%, p = .038). Identification of range and detection of transitions between ranges showed even stronger advantages for the stepped-effects display (p < .005).

The stepped-effects display has more pronounced auditory cues at SpO₂ range transitions, from which participants can better infer absolute SpO₂ values. Further development of a smooth-effects display for this purpose is not necessary.