Improved portable measuring device for real-time humidity and temperature monitoring in intensive care unit

Abstract

Real time monitoring of temperature and humidity of the air conditioned by Heat and Moisture Exchangers (HMEs) and delivered to patients in intensive care units (ICU) is highly demanded by physicians. As demonstrated by recent literature, only in vivo monitoring of HMEs performances with compact portable measuring systems suitable for ICU routines could provide reliable results. One of the main challenges for these devices is represented by the response time of the integrated temperature and humidity sensors. Long response times might introduce delays and thus make it impossible to follow the actual parameter variation in real time during each breath. In order to overcome this issue, innovative commercial ultra-fast sensors for temperature and humidity monitoring have been properly integrated and characterized in a portable wireless system for in vivo HME monitoring. Tests were performed in laboratory under static and dynamic settings. Response times at 36.8% of about 32 ms and 155 ms were obtained, respectively, for temperature and for humidity sensors. An improvement respect to available devices was thus obtained, achieving a proper monitoring of humidity variations up to 35 acts/minute with a maximum error of 5%. Considering the typical range of respiratory frequency monitored in the ICU, these results make the system suitable for real time evaluation of air conditioning during mechanical ventilation, combining the portability required for integration in the ICU routine with measurement accuracy.