Abstract
BackgroundManagement of a patient’s body temperature is an important aspect of care that should be addressed by targeted temperature management (TTM). Often, non-invasive methods like forced-air blankets are used. Especially in the operating room this management may be a subsidiary and repetitive task requiring constant observation of the patient’s body temperature and adaption using the limited set of available settings. Thus, automation of TTM is a feasible target to improve patient outcome and reduce caregiver workload.MethodsA Philips IntelliVue MP 50 patient monitor with an arterial PiCCO catheter system was used to measure patient blood temperature. Thermal management was performed with a 3M Bair Hugger 755 warming unit with forced air blankets. The warming unit was extended by a computer interface to allow for remote and automated control. A proposed closed-loop algorithm reads the measured temperature and performs automated control of the 3M Bair Hugger. Evaluation was performed in an experimental intensive care setting for animal studies. Two fully automated trials are compared with two manual and two uncontrolled trials in the same study setting using six female pigs for prolonged observation times of up to 90 hours in each trial.ResultsThe developed system and proposed algorithm allow more precise temperature management by keeping a set target temperature within a range of ± 0.5 °C in 88% of the observation time and within a range of ± 1.0 °C at all times. The proposed algorithm yielded better performance than did manual control or uncontrolled trials. It was able to adapt to individual patient needs as it is more dynamic than look-up table approaches with fixed settings for various temperatures.ConclusionsClosed-loop TTM using non-invasive forced-air warming blankets was successfully tested in a porcine study with the proposed hardware interface and control algorithm. This automation can be beneficial for patient outcome and can reduce caregiver workload and patient risk in clinical settings. As temperature readings are most often available, existing devices like the 3M Bair Hugger can easily be expanded. However, even if clinical application is feasible, open questions regarding approval and certification of such automated systems within the current legal situation still need to be answered.
Highlights
Management of a patient’s body temperature is an important aspect of care that should be addressed by targeted temperature management (TTM)
To address automation for temperature management, we developed a novel approach for closed-loop control of patient body temperature using a modified forced-air patient warming device and temperature readings from a patient monitor to automatically adapt the body to a predefined temperature and perform TTM
The proposed hardware solution for interacting with the 3M Bair Hugger temperature management unit via the developed add-on board and the proposed control algorithm was successfully tested in two automated trials of an ongoing animal study
Summary
Management of a patient’s body temperature is an important aspect of care that should be addressed by targeted temperature management (TTM). As soon as the patient is under general anesthesia, medication influences the core body temperature and vasodilatation leads to redistribution of the body heat causing a decrease in body temperature of about 0.5 °C to 1.5 °C within the first 30 minutes [3, 4]. Other important side-effects of perioperative hypothermia are changes in the potassium serum concentration [10] and reduction of the subcutaneous oxygen partial pressure [3] It has a crucial influence on the operation’s quality and the postoperative course. Patient temperature is often not regularly checked in the perioperative or ICU setting [14]
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