Improving accuracy of SpO2 in children with chronic hypoxemia by buccal reflectance pulse oximetry
Pulse oximetry technology estimates arterial hemoglobin oxygen saturation (SaO2) using a light source and a sensor. Simplistically, it calculates the oxyhemoglobin saturation (SpO2) based on the total fixed vs pulsatile red and infrared light. The most common type is the transmission pulse oximeter which wraps around a finger, toe or ear. Another type is the reflectance pulse oximeter which is applied over a flat surface such as the forehead. Factors affecting the accuracy of pulse oximetry include dark skin pigmentation, tissue hypoperfusion, vasoconstriction and cold temperatures. Additionally, pulse oximeters are known to be inaccurate at lower saturation ranges, often overestimating the arterial saturation. In contrast, SaO2 measured via co-oximetry is the gold standard as they are unaffected by those variables.
Close monitoring of oxygen saturation is particularly important for children with baseline hypoxemia such as chronic lung disease, pulmonary hypertension and congenital heart disease, who are at high risk of cardiopulmonary decompensation. More children with complex cardiopulmonary disease are surviving due to advances in modern medicine. A number of these children live with baseline saturations below 90%. As the accuracy of pulse oximetry decreases with increasing hypoxemia, inadvertent overestimation of the arterial saturation can lead to false clinical reassurance; and worse, a delay in the diagnosis and treatment of life-threatening problems.
During cardiopulmonary decompensation, perfusion is preferentially maintained at the body core and the head at the expense of peripheral circulation. Pulse oximeter devices may fail to work as fingers and toes become vasoconstricted. Having a more accurate device for early detection of oxygenation decline is imperative for guiding clinical management in times of physiological stress.
We aim to build a reflectance-type pulse oximeter that can be placed buccally in pediatric patients for measurement of oxygen saturation. Perfusion of the buccal mucosa is reliable and fairly preserved even in times of hemodynamic instability. The buccal mucosa is also non-pigmented, thus circumventing the pigmentation barrier.
To our best knowledge, there are no commercial reflectance buccal pulse oximeter probes available. Published studies on buccal oximetry have used transmission pulse oximetry probes for traditional finger and toe placement that have been repurposed as buccal probe by pinching the cheek at the corner of the mouth.
We have built a prototype reflectance-type pulse oximeter by re-engineering commercially available probes. The performance of this device will be tested in patients with baseline hypoxemia (saturations below 90%) by simultaneous comparison of its readings to those of SaO2 obtained via co-oximetry and to upper and lower extremity (finger and toe) measurements with standard commercial transmission wrap pulse oximeters. This testing will be conducted via a prospective study in pediatric patients undergoing general anesthesia. Skin pigmentation of each patient will be noted via a pigmentation scale for correlation with the readings from the measured multiple sites.
If this project shows promising results, future plans are to test for practical use in awake infants with comparison to upper extremity wrap pulse oximeter probes.
- Skin pigmentation
- Mouth Mucosa
- Heart Defects, congenital