Comparison of forehead and digit oximetry in surgical/trauma patients at risk for decreased peripheral perfusion

Objective

Measurement of pulse oximetry (Spo₂) is often impaired in critically ill patients. Forehead reflectance oximetry, the Max-Fast (Nellcor, Pleasanton, CA), may be less susceptible to poor tissue perfusion and could improve accuracy of oxygen saturation measurement. The objective of this study was to evaluate the use of forehead oximetry measures in critically ill surgical/trauma patients.

Methods

A prospective interventional study of 30 critically ill surgical/trauma patients at risk for decreased peripheral perfusion, as evidenced by need for vasopressor support (24 patients), transfusion of more than 6 unit packed cells in 24 hours (two patients), or an inability to obtain consistent saturation from a digit sensor (four patients), compared forehead and digit-based oximeter Spo₂ readings with co-oximetry (Sao₂) measurements from arterial blood samples. Sao₂ values were converted to functional oxygen saturation (SO₂) measurements for the final comparison. Patients were fitted with forehead (Nellcor Max-Fast) and digit (Nellcor Max A; digit 1) sensors connected to Nellcor OxiMax N-595 oximeters and a digit sensor (Nellcor Max A; digit 2) connected to a multiparameter monitor (Philips CMS [Andover, MA]). Three measurements of Sao₂ were obtained from each subject over a 24-hour time period, and simultaneous measurements of Spo₂ were recorded from the three monitors.

Results

The three Spo₂ measurements (forehead, digit 1, and digit 2) were compared with SO₂ values using the Bland-Altman method to assess agreement. Forehead measurements demonstrated a mean bias of −1.39, whereas digit 1 was −2.61 and digit 2 was −3.84. Pearson correlations (r) for forehead, digit 1, and digit 2 with SO₂ were .834, .433, and .254, respectively. There were fewer unsuccessful measurements with the forehead oximetry technique.

Conclusions

Forehead sensors improve measurement of oxygen saturation in critically ill surgical/trauma patients at risk for decreased peripheral perfusion.