106 - Comparing Pulse Oximetry/Blood Pressure Measurements Based on Sensor Location

Background: The use of sedation or general anesthesia as advanced behavior management techniques is sometimes warranted for rendition of safe dental treatment in pediatric dentistry. Proper monitoring is necessary to ensure patient safety during these procedures. Two monitors included in the standard armamentarium are pulse oximeters, measuring oxygen saturation (SpO2), and non-invasive blood pressure (NIBP) cuffs, for assessment of cardiovascular function. A variety of factors exist that have led to blood pressure cuffs interchangeably placed on either the upper arm or lower calf, and pulse oximeters placed on the finger or toe, especially in children. Studies reporting on data of NIBP measurements taken from upper arm and lower calf in children are contradicting. To our knowledge, there are no other studies comparing oxygen saturation of pulse oximeters placed on index finger and second toe in children. This study aims to: (1) evaluate if location of pulse oximeter (index finger versus second toe) leads to statistically significant variances in recorded measurement and (2) evaluate if location of blood pressure cuff (upper arm versus lower calf) results in statistically significant differences in blood pressure values.

Design: IRB approval was received (11255) for this study. 50 children aged 3-9 defined as ASA Class I or II receiving comprehensive dental treatment in the operating room under general anesthesia in the Riley Hospital Outpatient Surgery Center, Indianapolis, IN were included. NIBP cuffs placed on upper arm and ipsilateral lower calf, just superior to the ankle bone. Pulse oximeters placed on index finger and ipsilateral second toe. Following induction of general anesthesia, measurements were simultaneously recorded every five minutes for a total range of 30 to 55 minutes. Agreement between locations was evaluated using intraclass correlation coefficients (ICCs) and Bland-Altman plots. Comparisons for mean differences between the two locations were made using mixed-model ANOVA to incorporate correlations among measurements within the same subject. A two-sided 5% significance level was used for all tests. Analyses were performed using SAS version 9.4 (SAS Institute, Inc., Cary, NC, USA).

Results: Agreement between arm/calf and finger/toe measurements were low, based on both the mean differences and the relatively large differences between the measurements – limits of agreement (difference +/- 2 standard deviations) are approximately -15mmHg to +20mmHg for systolic NIBP, up to approximately -10mmHg to +20mmHg for diastolic NIBP, and approximately -2% to +3% for SpO2. On average, arm systolic and diastolic NIBPs were significantly lower than calf BPs and finger SpO2 were significantly lower than second toe SpO2 (p <.001).

Conclusion: (1) Lower systolic and diastolic measurements of the arm were noted when compared to lower calf and (2) oxygen saturation was lower when obtained via pulse oximeter placed on the index finger when compared to the second toe.