Sept. 27, 2022 -- 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 health care setting and beyond. However, health care workers, patients and the general public have long been resistant to change when it comes to good hand hygiene. 

Efforts to to improve hand cleanliness in hospitals, clinics and doctors offices have included increasing the now-ubiquitous presence of alcohol-based hand sanitizer dispensers and signs and training, addressing organizational culture, and establishing accountability. Meanwhile, methods to measure ongoing hand-hygiene technique 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 in Connecticut.

The technique relies applying alcohol-based hand sanitizer, which leads to a temporary drop in skin temperature due to evaporation. Researchers placed the thermal camera on a tripod 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 measure the quality of hand hygiene practices among 12 volunteers. 

The thermal imaging allowed for noninvasive yet precise temperature measurement at three points on the dominant hand of the user (mid-palm, tip of third finger, tip of thumb) at four distinct times: before sanitizer, 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 temperature drop in skin temperature for all locations on the hand from before to after sanitizer was applied, 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 come up with the right amount of sanitizer.

Boyce, who was a co-author of the CDC Guideline for Hand Hygiene in Health-Care Settings and a contributor to the World Health Organization Guidelines on Hand Hygiene in Health Care, says, "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 tried to measure hand hygiene technique using ultra-violet powder or liquid, the thermal camera has the advantage of simplicity, with no extra ingredients required beyond the handheld equipment. 

The thermal camera is small, mobile, and easy to use after straightforward set-up on a smartphone. 

In an interview, Martinello, of Yale School of Medicine, says ,"This technology could potentially be used in in a variety of settings, including teaching, assessing, and evaluating staff competence."

But Boyce and Martinello cautioned that because of 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. More research is needed to test different types (gel, foam) of hand sanitizer, different brands, and varying amounts, and with greater variation in hand size. 

Emily Landon, MDexecutive medical director for ,infection prevention and control at UChicago Medicine, applauds 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, she says "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 [Apple] 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!"