Influence of sensor site location on pulse oximetry kinetics in children.

A pulse oximeter sensor is used to monitor changes in arterial hemoglobin oxygen saturation (SpO2) in anesthetized pediatric patients. The authors compared the kinetics of desaturation and resaturation measured by sensors placed over central (tongue, cheek) and peripheral (finger, toe) vascular beds in children with congenital heart disease. Desaturation time was defined as the time which elapsed between the onset of apnea and a 4% decrease in SpO2 from baseline. The desaturation times averaged 24 +/- 12 s, 56 +/- 34 s, and 58 +/- 28 s for the cheek, finger, and toe, respectively (n = 40; P < 0.0001 for cheek versus finger or toe). Resaturation time was defined as the interval between the resumption of ventilation and a 4% increase in SpO2 above the nadir. Resaturation times averaged 12 +/- 8 s for the cheek, 40 +/- 36 s for the finger, and 47 +/- 25 s for the toe (n = 40; P < 0.0001 for cheek versus finger or toe). A comparison of the kinetics at two central sensor sites, cheek and tongue, respectively, revealed no significant differences in desaturation times (20 +/- 10 s vs 21 +/- 9 s) or resaturation times (10 +/- 6 s vs 7 +/- 3 s) (n = 13). The authors conclude that both desaturation and resaturation are detected earlier by centrally placed sensors.