“Set phasers to full body scan!” Radar gun technology similar to that used by police to catch speeding cars may someday be used to monitor vital signs in your emergency department.
Recent NASA research might have greater impact on your ED than on a space mission to Mars
Being a nontraditional medical student, I am old enough to remember the day the space shuttle Challenger exploded. Oddly, it spurred a great interest in space for me. I was amazed by the space shuttle, and the men and women who flew it. The sense of imagination and exploration that NASA evokes seems similarly to have affected and motivated many of us to study science. So, when it came time to select medical electives my third year of medical school, I applied and was accepted to NASA’s Aerospace Medicine Research clerkship for fall 2010. While there, I became familiar with some fascinating areas of technology that, while being researched for space medicine, might have greater implications for an ED in the future.
While I was amazed to be working in Houston with doctors, scientists and astronauts, I certainly noticed the air of uncertainly that loomed over the NASA complex. There were only three space shuttle missions left before the program was finished. People already were beginning to be laid off, and several personnel were leaving NASA to work for private aerospace companies. Many of the astronauts who had flown their final missions were taking retirement. So, while I was enjoying the tours of mission control, sitting in the space shuttle simulators and talking with astronauts, sadly I knew I also had a front row seat to the end of an era – possibly America’s finest.
During my time in Houston, I was astounded by the sheer amount of research – medical and otherwise – that NASA produces annually. The other thing that impressed me was that everyone genuinely seemed to enjoy their work. And why not? Working at NASA seemed like an adult, nerd-centric Disneyland! I felt right at home.
I was assigned to the advanced projects section of the space medicine division, which is responsible for the medical planning on long-range future space missions. In other words, we were planning for missions on spacecraft that haven’t been built yet. I was told: “Be original. Find novel technologies that are being developed and see if we can use them for space medicine.” With that in mind, I found three areas in the current research with plausible applications for future space missions: ultra-wideband (UWB) radar, IR video and remote photophlethysmography. These technologies, given further refinement, will likely be suitable for general and emergency medicine within the next few decades.
We are all familiar with the many uses of radar including air traffic control, Doppler weather radar and the infamous police radar, but there are new medical applications of radar on the horizon. Specifically, the field of ultra-wideband radar is promising. Ultra-wideband radar originally was developed by the U.S. Defense Department for non-cooperative imaging (e.g. spy satellites), and further developed by search and rescue personnel for detecting signs of life buried beneath rubble after earthquakes. UWB radar works by measuring the different dielectric properties of the various tissue compartments of the human body. This allows one to see tissue movement of internal organs up to 3 meters from the sensor with current medical technology. Several emerging medical uses have been researched for UWB radar including diagnosis and treatment of obstructive sleep apnea, aortic pressure measurement, breast cancer detection, monitoring vital signs where dermal monitor attachment is not practical (e.g. patients in a burn unit), myocardial ischemia, pulseless electrical activity, and research for the reduction of SIDS.
One advantage of UWB radar over other forms is that it transmits on a large bandwidth over a short time pulse, allowing a lot of information to be sent quickly. Additionally, UWB radar is nonionizing radiation, using smaller amounts of energy than other types of radar. It has higher temporal and spatial resolution and has no compatibility issues with established narrowband systems.
Recent studies have shown UWB radar to be able to monitor breathing and cardiac harmonics passively and remotely. While this could allow NASA to monitor astronauts inside or outside the spacecraft without taking the time to don vital signs monitoring equipment, it could just as easily be used to monitor Emergency Department patients, passively and continually, if no medical professionals are available in the room. I would hope that an ED of the future would employ some variance of this technology to monitor a patient’s vital signs without cumbersome electrodes, wires or the human error inherent in manual vital signs collection.
While this technology might prove useful in the future, current algorithms are unable to completely cancel signal noise with random body movement (such as the patient rolling over). Additionally, UWB radar, in its current state, cannot monitor for arrhythmias or blood pressure. A final weakness of UWB radar use for vital signs monitoring is that signal data are more difficult to attain accurately in overweight people. Because UWB radar uses very precise measurements to determine heart rate (typical displacement of 0.08 mm for most cardiac tissue), excess adipose tissue makes cardiac harmonics more difficult to attain. While this was not a problem in the astronaut population, it would certainly be problematic for an increasing percentage of the patient population in the United States.
Most of us are familiar with photophlethysmography (PPG) through the use of pulse oximetry finger and extremity cuffs. It originally was pioneered in the 1930s by Hertzman and has now become standard in healthcare settings. One shortcoming of current PPG technology is that it must be in contact with the patient’s tissue. There are some situations where this is undesirable or impracticable. However, in the future, we might be able to monitor burn or trauma victims with completely non-contact vital signs monitoring technology.
New research has been able to gather PPG data at up to 1 meter via non-contact sensors. While motion artifact has plagued non-contact PPG in the past, current technology via dual diode technology may overcome current limitations. Cennini et al. were able to determine non-contact measurement of heart rate in real time with the use of a multispectral illumination device consisting of blue and IR lights. Since hemoglobin absorbs blue light, a device concurrently measuring motion artifact with the IR light produces a usable signal at a distance of up to 1 meter by reducing the IR noise signal from the blue hemoglobin saturation signal.
When PPG was coupled with high-speed video cameras, Zheng et al. were able to attain three-dimensional waveform heart rate data that provided usable Lead II ECG-like data. Also, with the standard pulse oximeter monitors a few centimeters off the patient’s body surface, a high-speed camera coupled with a ring illumination source were able to track pulsation signals from the entire volar surface of the hand simultaneously in real time. The current, major weakness of remote PPG is that is not reliable under certain situations such as low-volume states, shock or abnormal temperature conditions – situations commonly encountered in the ED.
Finally, new advancements with commercial webcam technology could be used in hospital settings. Poh et al. recently were able to determine the heart rates of multiple persons simultaneously in normal ambient light with a commercial webcam. This wor
ks by visualizing volumetric changes in the test subjects’ faces by monitoring the red, green and blue light sensors incorporated into the webcam and determining the different light absorbing qualities of hemoglobin. This method of blood pressure monitoring was able to determine heart rate ± 2.29 bpm with subjects sitting still. The system was affected only slightly when the subjects were allowed to move, talk or laugh (±4.59 bpm).
The modest research project I conducted during my NASA clerkship provides a small example of the great research that originally was conducted for space exploration. After Atlantis’ last flight in July brought the space shuttle program to an end, our only current manned spaceflight program is through the Soyuz program in partnership with Russia. While it is unfortunate that far fewer personnel are currently involved in manned space research than at any time in NASA’s 54-year history, the remaining physicians and astronauts at NASA will continue to conduct aerospace medical research in preparation for possible future spaceflight – with continued benefit to traditional medical care. Perhaps, in the not too distant future, these novel space-aged technologies could be available in your ED.
*Christopher M. Perry is a fourth-year osteopathic medical student at Lincoln Memorial University – DeBusk College of Osteopathic Medicine in Harrogate, Tenn., and Navy HPSP student who aspires to become an emergency physician.
**Portions of this article were adapted with permission from contributing author, Sharmi Watkins, MD, and NASA from the following original publication: Perry, C., Watkins, S. (2011) Non-Contact Vital Signs Monitoring via Ultra-Wideband Radar, Infrared Video, and Remote Photoplethysmography: Viable Options for Space Exploration Missions. NASA TM-2011-216145. May 2011. http://ston.jsc.nasa.gov/collections/TRS/_techrep/TM-2011-216145.pdf
Cennini, G., Jeremie, A., Kaan, A., & Van Leest, A. (2010). Heart rate monitoring via remote photoplethysmography with motion artifacts reduction. 18 (5).
Hertzman, A. (1937). Photoelectric plethysmograph of the fingers and toes in man. 37 (529).
Poh, M., McDuff, D., & Picard, R. (2010). Non-contact, automated cardiac pulse measurments using video imaging and blind source separation. Optics Express , 10762-10774.
Zheng, J., Sinjung, H., Azorin-Peris, V. E., Chouliaris, V., & Summers, R. (2008). Remote simultaneus dual wavelenght imaging photoplethysmography: a further step towards 3-D mapping of skin blood microcirculation. 6850.