[Reliability of pulsatile saturometry in patients with shock. Digital standard sensors are not reliable for facial measurement!].

INTRODUCTION

Non-invasive monitoring of oxygen saturation by pulse oxymetry (SpO(2)) is sometimes perturbed on fingers during shock states. Other sites are possible (toes, forehead, nose, ear). Self-adhesive standard digital sensors are commonly used off-label in these sites. We have assessed their reliability for all of these sites.

METHODS

We have studied patients presenting a stabilized shock state and receiving vasoconstrictive catecholamines. When an arterial blood gas was ordered, six SpO(2) were measured quasi-simultaneously (self-adhesive standard sensors): right and left index, toe, forehead, nose and ear. SpO(2) at "finger", "toe", "forehead", "nose" and "ear" were compared to the arterial oxygen saturation (SaO(2)) by using the Bland and Altman method. The plethysmographic curve was assessed as "correct" or "unsatisfactory".

RESULTS

Hundred and ten patients were included (63 ± 15 years, SAPSII 46 ± 16, catecholamines: 0.6 ± 0.5 μg/kg/min). Plethysmographic curves are more often of "correct" quality for fingers (90%) than for the other locations (50 to 70%). Bias are low for all the locations (-0.1 to +1.5%). Limits of agreement are around ±5% for fingers and toes, but as high as ±15% for the face locations. When the analysis is restricted to plethysmographic curves of "good" quality, the limits of agreement are unchanged for fingers and toes, but improved (between ±5 to ±10%) for face locations.

CONCLUSION

In patients with a shock receiving vasoconstrictive catecholamines, the reliability of SpO(2) measurements with standard sensors appears better for fingers than for toes and face locations. These standard sensors should be discouraged for facial measurement because of their low reliability, even when the plethysmographic curve seems correct. Sensors specifically designed for each facial site exist, and their reliability should be estimated in patients receiving vasoconstrictive catecholamines.