iPhone Thermal Camera: A Handy New Method to Monitor Hand Hygiene

Katie D Schenk, PhD

September 20, 2022

New Haven, Connecticut — Sing "Happy Birthday"? Recite the ABCs? Count 20 seconds? What's the best way to ensure the effectiveness of hand washing?

Maintaining good hand hygiene practices remains key to preventing the spread of pathogens in the healthcare setting and beyond. However, hand hygiene habits have long proven resistant to change among healthcare workers, patients, and general public alike.

Interventions to improve hand hygiene among healthcare personnel have included increasing the now-ubiquitous presence of alcohol-based hand sanitizer dispensers and accompanied by signage and training, addressing organizational culture, and establishing accountability. Meanwhile, methods to assess ongoing hand-hygiene technique in the healthcare setting remain limited, and critics argue that a focus on compliance rather than quality misses the point, failing to serve the ultimate goal of improving patient care through the removal of pathogens.

Now, a new paper published in the American Journal of Infection Control reports on a pilot study of an innovative new method to detect unwashed spots on hands through the use of a portable thermal imaging camera attached to an iPhone. Authors John M. Boyce, MD, of M Boyce Consulting, and Richard A. Martinello, MD, of the Yale School of Medicine, describe the use of a forward looking infrared (FLIR) thermal camera to assess the hand hygiene technique among 12 staff members who volunteered to take part in the study within the Infection Prevention Department at Yale New Haven Hospital, Connecticut.

The technique relies on the observation that applying alcohol-based hand sanitizer leads to a temporary drop in skin temperature due to evaporation. Researchers placed the thermal camera on a tripod to standardize images and used its smartphone app to fine-tune the color palette of the resulting images. By observing skin temperature all over the hands before and after applying alcohol-based hand sanitizer, researchers sought to assess the quality of hand hygiene practices among the 12 volunteers.

The thermal imaging allowed for noninvasive yet precise temperature measurement at three predefined points on the dominant hand of the user (mid-palm, tip of third finger, tip of thumb) at four distinct time points (before applying sanitizer gel, immediately after hands felt dry, 1 minute later, and 2 minutes later). Researchers also explored the relationship between the amount of gel used and hand size to see if they were related to the temperature drop.

Observations of the resulting images showed that the handheld infrared technology was able to detect a significant (P < .01) temperature drop in skin temperature for all locations on the hand from before to after hand hygiene was performed, illustrated by a dramatic change in color. This, in turn, indicated appropriate sensitivity for monitoring the quality of hand hygiene practices.

Images also indicated that for one study participant with large hands, the coverage of hand sanitizer gel was insufficient to reach their fingertips, suggesting a possible role for using the device to calibrate an appropriate volume of sanitizing gel.

Dr John Boyce

Dr Boyce, who was a co-author of the Centers for Disease Control and Prevention Guideline for Hand Hygiene in Health-Care Settings and a contributor to the World Health Organization Guidelines on Hand Hygiene in Health Care, told Medscape Medical News, "Thermal imaging is not a technology that is familiar to most people involved in infection prevention and control, but it presents several potential advantages over observations of hand hygiene technique."

Though earlier studies have sought to evaluate hand hygiene technique using ultra-violet powder or liquid, the use of the thermal camera has the advantage of simplicity, with no extra ingredients required beyond the handheld equipment.

This small study of an innovative hand-held, smartphone-driven thermal camera suggests the potential utility of this approach for teaching and monitoring hand hygiene in healthcare settings. The thermal camera is small, mobile, and easy to use after straightforward set-up on a smartphone.

Dr Richard Martinello

In an interview with Medscape Medical News, Dr Martinello, of the Departments of Infection Prevention and Internal Medicine and Pediatrics at Yale School of Medicine, added that "This technology could potentially be used in in a variety of settings, including teaching, assessing, and evaluating staff competence."

But Drs Boyce and Martinello cautioned that owing to variations in body temperature, the thermal imaging technique will be most useful as a teaching and assessment tool when baseline images can be compared with images post-sanitizing. Further research is needed to validate the approach with different types (gel, foam) of hand sanitizer, different brands, and varying amounts, and with greater variation in hand size, and to correlate findings with empirical observations of microbicidal effectiveness.

Dr Emily Landon

Emily Landon, MD, associate professor of medicine and executive medical director, Infection Prevention and Control at UChicago Medicine, applauded the concept of thermal imaging to explore the quality of hand hygiene as being "super creative and very innovative — exactly what we need in infection control."

In an interview with Medscape Medical News, she noted that "Infection control is often about encouraging people to fight invisible problems and asking them to change their behaviors without having anything to show for it. This approach makes it visible…We already use iOS mobile devices for data collection and monitoring, so attaching something to an iPhone is something that is familiar and already within reach. The idea is feasible — it's affordable, accessible, portable, and easy to use…I'm excited!"

Am J Infect Control. Published online September 14, 2022. Full text

The study was independently supported. Equipment was purchased from the manufacturer FLIR. Dr Boyce serves as a consultant to GOJO Industries and Diversey. Drs Boyce and Martinello report no other relevant financial relationships. Dr Landon reports no relevant financial relationships.

Katie D Schenk, PhD, @skibird613 is an infectious disease epidemiologist based in Washington DC.

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