U.S. Department of Defense


Date of this Version



The Journal of Emergency Medicine, Vol. 43, No. 3, pp. 492–493, 2012; doi:10.1016/j.jemermed.2011.07.039


To The Editor:

I was impressed with the recent article, “In-flight Thoracic Ultrasound Detection of Pneumothorax in Combat,” by Dr. Justin Madill (1). It gives us all great pride to know of the life-saving and life-sustaining work that our nation’s military Emergency Physicians do every day in austere conditions in deployed environments!

The author is, indeed, correct to note that medical evacuation (and casualty evacuationdmedical evacuation in airborne or ground vehicles without intrinsic, dedicated patient care modalities) is very different from operating among the environs of the Emergency Department (ED). Hypobaria, hypoxia, hypothermia, vibration, noise, confined spaces, limited patient access, and other physical and physiologic stressors of flight contribute to these challenges (2).

I was particularly cued on the comment noting that “auscultation of breath sounds while in-flight would be futile due to the high ambient noise of the helicopter.” In fact, this is not a problem solely for the militaryd physicians are often required to evaluate, make clinical decisions, and initiate treatment under noisy conditions. Auscultation is a fundamental and powerful clinical tooldit is rapid, simple, inexpensive, portable, and repeatable. But meaningful auscultation is challenging at best, often impossible, in high-noise environments. This might include being in the back of an aircraft or vehicle, in a very noisy ED, or even at the point of injury in a noisy environment (e.g., a stadium). The U.S. Army Aeromedical Research Laboratory (USAARL), located at Fort Rucker, AL, has been addressing this challenge.

Recognizing the need for a device capable of adequate preservation of signal-to-noise ratio (SNR) under conditions of noise, USAARL partnered with Active Signal Technologies, Inc. (Linthicum Heights, MD), through a Small Business Innovative Research collaboration, to develop a “noise-immune stethoscope” (NIS) (3,4). The NIS is a hybrid dual-mode design stethoscope with both an acoustic (passive) and a Doppler (active) mode. It is designed for one-handed operation and is powered by two AA-cell batteries. The acoustic mode consists of a directly coupled piezoelectric ceramic stack, whereas the Doppler operates with a 2–3-MHz ultrasound carrier wave.