Reliability and Validity of a Prototype Fluid Intake Monitor

The Fluid Intake Monitor FIM measures fluid consumed from a bladder hydration system. Bench and field tests were performed to assess reliability and validity of the FIM, Fluid volumes of FIM were compared to scale-weighed volumes of water. Bench Test Results an absolute percent error existed p 0.001 between sips, with the FIM significantly overestimating the first sip p 0.01 compared to the subsequent nine sips. A significant intraclass reliability coefficient ICC 0.83 was achieved for trials 2 through 10. There was no difference in mean sip volume measured using the FIM vs. the scale 25.7 10.7 ml vs. 25.6 8.7 ml, respectively. Field Test Results of 31 trials, 4 trials under-measured water consumption in excess of 15 29.4 to 47.1, and two trials over-measured water consumption in excess of 15 15.5 and 16.6. These units were neither reliable nor valid for use in the field. Software and hardware modifications identified should significantly improve FIM performance.