Page 24 - JSOM Fall 2019

I See Red!

Red Light Illumination in Helicopter Air Ambulance Services

Patrick Schober, MD, PhD, DESA, MMedStat;
Lothar A. Schwarte, MD, PhD, MBA, DESA, EDIC*

ABSTRACT

Helicopter air ambulance services (HAA) increasingly operate Examples of this optical phenomenon, termed metamerism,
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during darkness, and the cockpit crew prefers a dimmed light were found both for the helicopter’s interior and for our
to be used in the cabin. Our HAA team is currently research- medical equipment, including the current propofol and eto-
ing the use of dimmed red light. We encountered a downside to midate medication ampules. This phenomenon is exemplified
the use of red light—some texts and symbols became virtually in Figures 1 and 2. The disappearance of red text on a white
invisible. background, and vice versa, can be expected in red ambient
light, particularly if no alternative light source is present. HAA
Keywords: helicopter; air ambulance; red light crews and other service personnel operating with dimmed red
light in darkness should be briefed and aware of this pitfall.
In addition, HAA teams may modify their medical equipment
accordingly (e.g., by adding alternatively colored medication
Introduction
labels). If in the future the use of red light becomes widely dis-
HAA increasingly operate during darkness, with the respective tributed in helicopter night operations, helicopter manufactur-
challenges. Herein, the cockpit crew (i.e., the HAA pilot and ers may also need to reconsider their red/white print schemes
1–3
the flight nurse) prefer for the HAA physician to use a dimmed on the helicopter’s interior warning signs. One solution could
light in the cabin or patient compartment. be the use of alternatively colored warning signs, where back-
ground and text prints are not red on white (as in Figure 2) but
instead are, for example, black on yellow.
Use of Red Light in Nighttime Operations
In this context, our HAA team is currently researching the use Multiple types of metamerism have been classified. 9–11 The
of dimmed red light for operations in darkness (e.g., during specific type described here, termed light source metamerism
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night flights) in the medical cabin compartment of the helicop- or illumination metamerism, may be defined as “two colors
ter. Compared with standard white light, sources from tacti- apparently differing under one illumination, but appearing
cal operations (i.e., the military and law enforcement) suggest equal under another illumination.” It is the most well-known
there are advantages to the use of colored light, including type of metamerism. In the maritime sector, printers of naval
4–6
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red light, for nighttime operations. A major advantage of maps and charts are widely replacing pure red color with ma-
dimmed red light reportedly is better-preserved scotopic vision genta (i.e., 50% red ink, mixed with 50% blue ink), intending
(i.e., darkness adaptation of the eyes) compared with equally to increase readability under red ambient lighting (e.g., that of
bright standard white light. the ship’s bridge). Illumination of printed standard colorized
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maps with blue or green light will obscure the recognition of
water or vegetation, respectively. However, because in our he-
Results
licopter operation we have not used printed maps for years,
In contrast to the advantages of red light currently under in- not even backup maps, these notions are less relevant to our
vestigation, we encountered a relevant downside of red light specific helicopter operation and validity cannot be confirmed
use in our HAA operation that might not be ubiquitously from our experience.
known. When using dimmed red light in our HAA operations,
we encountered that texts and symbols printed in red on a Conclusion
white background, and vice versa, became virtually invisible.
This phenomenon was confirmed with the use of three dif- We describe metamerism as a possible risk factor for crew
ferent red light sources (one torch and two head lamps) from and patient safety during HAA nighttime operations when red
different manufacturers. light sources are used.
*Correspondence to Lothar A. Schwarte, MD, PhD, MBA, DESA, EDIC, De Boelelaan 1117, 1007 MB Amsterdam, the Netherlands or
L.Schwarte@VUmc.NL
Drs Schober and Schwarte are affiliated with the Department of Anesthesiology, Amsterdam University Medical Center, Amsterdam, and HAA
Life Liner 1, Trauma Center, Amsterdam, the Netherlands.

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