Evaluation of miniature wireless vital signs monitor in a trauma intensive care unit

Abstract

A previous study demonstrated basic proof of principle of the value of a miniature wireless vital signs monitor (MWVSM, MiniMedic, Athena GTX, Des Moines, Iowa) for battlefield triage However, there were unanswered questions related to sensor reliability and uncontrolled conditions in the prehospital environment. This study determined whether MWVSM sensors track vital signs and allow for appropriate triage compared to a gold standard bedside monitor in trauma patients. This was a prospective study in 59 trauma intensive care unit patients. Systolic blood pressure, temperature, heart rate (HR), skin temperature, and pulse oximetry (SpO2) were displayed on a bedside monitor for 60 minutes. Shock index (SI) was calculated. A separate MWVSM monitor was attached to the forehead and finger of each patient. Data from each included pulse wave transit time (PWTT), temperature, HR, SpO2, and a summary status termed “Murphy Factor” (MF), which ranges from 0 to 5. Patients are classified as “routine” if MF = 0 to 1 or SI = 0 to 0.7, “priority” if MF = 2 to 3 or SI = 0.7 to 0.9, and “critical” if MF = 4 to 5 or SI ≥ 0.9. Forehead and finger MWVSM HRs both differed from the monitor (both p < 0.001), but the few beats per minute differences were clinically insignificant. Differences in MWVSM SpO2 (1-7%) and temperature (6-13°F) from the monitor were site specific (all p < 0.001). Forehead PWTT (271 ± 50 ms) was less (p < 0.001) than finger PWTT (315 ± 42 ms); both were dissociated from systolic blood pressure (r2 < 0.05). The SI distributed patients about equally as “routine,” “priority,” and “critical,” whereas MF overtriaged to “routine” and undertriaged to “critical” for both sensors (all p < 0.001). Our findings suggest that MF does not accurately predict the most critical patients, likely because erroneous PWTT values confound MF calculations. MF and the MWVSM are promising, but require finetuning before deployment.