Pulse oximetry has been a valuable tool in monitoring critically ill patients. The designated sites for pulse oximetry are fingers, toes, and earlobe. In many instances, the pulse oximetry sensor is placed on the forehead for ease of access and stability. This study is done to assess the reliability of forehead pulse oximetry measurements.
Out of 27 total patients enrolled in the study, 15 were ventilator-dependent, 2 had baseline hypoxia, and 10 were healthy individuals. For 16 ventilator patients and 2 hypoxic patients, arterial blood gas study (ABG), finger and forehead pulse oximetry were performed. Telemetry was applied to monitor heart rate and to compare oxymeter wave form. For 10 healthy volunteers, finger and forehead pulse oximetry and EKG wave forms were recorded. Nellcor Oxisensor II D-25 was used for pulse oximetry.
Finger and forehead pulse oximetry measurements did not differ significantly in normal volunteers and in patients who were well oxygenated on mechanical ventilation. In 2 hypoxic patients, forehead O2 saturation (SpO2) overestimated SpO2 compared to the finger (figure 1). In healthy volunteers, no significant difference was found between finger and forehead SpO2. During induced hypoxia of normal volunteers, one volunteer’s forehead SpO2 significantly overestimated compared to finger SpO2 (figure 2).
Finger pulse oximetry better correlates with actual ABG in patients and healthy volunteers. In addition, we observed that forehead pulse oximetry may overestimate O2 saturation in critically ill patients who are hypoxic and may lead to adverse event of the patient.
Based on our observation in critically ill patients and normal volunteers, forehead pulse oximetry is not a reliable method of monitoring tissue oxygenation; it may overestimate SpO2 and the practice should be strongly discouraged. Further study is warrented.
Z. Carrey, None.