Journal of clinical monitoring and computing
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J Clin Monit Comput · Jun 2007
Importance and interpretation of fast-response airway hygrometry during ventilation of anesthetized patients.
Measurement of oxygen uptake (Vo2) should help detect non-steady state critical events and metabolic derangement during anesthesia. Vo2 requires measurement of respiratory relative humidity (RH) and temperature (T). We have developed a fast response T and humidity sensor (HS), which uses tiny wet and dry thermometers to determine RH by psychrometry, where low RH causes evaporation to decrease wet T below dry T. In laboratory bench studies, we determined that >/=5 l/min gas flow through the HS is required for valid psychrometry function. This study demonstrates that monitoring of flow through the HS enhances the accuracy of RH measurement and interpretation. ⋯ We conclude that airway flow monitoring enhances the interpretation and accuracy of the fast-response HS measurements during inspiration and expiration, allowing for the determination of Vo2 in patients during anesthesia.