Performance of a Digital PCO₂/SpO₂ Ear Sensor

Abstract

Objective.For determining the adequacy of ventilation, conventional pulse oximetry should be amended by PaCO₂ (= arterial carbon dioxide partial pressure). This study investigates the precision of carbon dioxide measurements of the first digitalear-clip sensor providing continuous non-invasive monitoring of PaCO₂, SpO₂ (= functional arterial oxygen saturation as estimated with a pulse oximeter) and pulse rate and compares it to two conventional analog oximeters. Methods.30 hypoxemia episodes in 6 adult volunteers were investigated in a standardized protocol. Equipment: Masimo^™ analog finger sensor, Nellcor^™ analog ear sensor, SenTec^™ digital ear sensor. Results.The difference between PCO₂ data (= PaCO₂ estimated from the measured PcCO₂ based on an algorithm by Severinghaus) (PcCO₂ = cutaneous carbon dioxide pressure) and the PaCO₂ is clinically unimportant. Therefore, we suggest, the two methods of estimating patient's carbon dioxide status can be used interchangeably. Conclusions.Combined digital SpO₂/PcCO₂ ear sensors are very promising to allow for a fast and reliable monitoring of patient's oxygenation, hyper-/hypocapnia and ventilation with one single non-invasive probe. Optimal primary signal processing – amplification and digitalisation within the probe – allow for fast and reliable downstream signal processing algorithms. The resulting short SpO₂ response times give the medical staff more time to take appropriate actions.