NVG: Pain in the Neck!

Use of Night Vision Goggle (NVG) amongst helicopter aircrew is becoming a matter of concern [1]. On one hand, the pain in the neck is reportedly 29% amongst Australian helicopter aircrew [2], while it peaks to more than 90% Canadian Forces helicopter pilots with more than 150 hours of NVG flight [3]. Other likely causes of pain neck are “vibration, use of other helmet mounted devices, and cumulative flying hours” [1]. A back pain survey amongst Indian military helicopter pilots reportedly found neck being the second commonest site of pain, after the lower back [4].

In contrast, Landau et al. found cervical disc degeneration on MRI amongst 50% of the helicopter pilots studied, with none complaining of neck pain [5]. Similarly, 58.5% of helicopter aircrew were found to have spinal related disability (compared to 53.2 and 46.9 fighter and fixed-wing aircrew] in a survey of musculoskeletal disabilities amongst 232 military aircrew [6].

The load exerted by helmet-NVG (+ counterweight) combine varies between 2.3 to 3.6 Kg [7, 8], thus straining the neck musculature. Besides the prevailing vibration spectrum of the airframe, duty hours, operational environment, personal survival gear and lifestyle may also affect the reported incidence of pain in the neck.. Towards this, Harrison et al. undertook a pioneering work to evaluate the physiological characteristics of the cervical spine with electromyography (EMG), Near-Infrared spectroscopy (NIRS) and isometric force capacity, to collate with flying experience and reported neck pain [1].

In a sample of 40 aircrew of CH-146 helicopter, both pilots and flight engineers, Harrison et. al. found that 53% subjects reported neck pain. Statistically though, there was neither difference between the pilots and flight engineers “with respect to neck pain, flight experience or physical fitness”, nor in “the metabolic and neuromuscular characteristics” of the cervical musculature.

However neck pain amongst helicopter aircrew is a matter of occupational concern and needs to be answered methodically by appropriate screening methods during annual medicals [4] as well as well designed exercise regimen to strengthen neck musculature, besides defining optimal work-rest schedule.

Reference

1. Harrison MF, Neary JP, Albert WJ, Croll JC. Neck pain and muscle function in a population of CH-146 helicopter aircrew. Aviat Space Enniron Med 2011; 82: 1125-30

2. Thomae MK, Porteus JE, BrockJR, Allen GD, Heller RF. Back pain in Australian military helicopter pilots: A preliminary study. Aviat Space Environ Med 1998; 69: 468-73

3. Adams J. Results of NVG-induced neck strain questionnaire study in CH-146 Griffon aircrew. Toronto ON, Canada: Defence R&D Study Canada-Toronto; 2004. Report No.: TR2004-153 [as quoted in Harrison MF, Neary JP, Albert WJ, Croll JC. Neck pain and muscle function in a population of CH-146 helicopter aircrew. Aviat Space Environ Med 2011; 82: 1125-30]

4. Sharma S, Agarwal A. Cervicalgia amongst helicopter pilots using helmet mounted devices. Ind J Aerospace Med 2008; 52: 1-7

5. Landau DA, Chapnik L, Yoffe N, Azaria B, Goldstein L, Atar E. Cervical and lumbar MRI findings in aviators as a function of aircraft type. Aviat Space Environ Med 2006; 77: 1158-61

6. Taneja N, Pinto LJ. Diagnostic categories among 232 military aircrew with musculoskeletal disabilities. Aviat Space Environ Med 2005; 76: 581-5

7. Sovelius R, Oska J, Rintala H, Huhtala H, Siitonen S. Neck muscle strain when wearing helmet and NVG during acceleration on trampoline. Aviat Space Environ Med 2008; 79: 112-6

8. Weirstra BT. Ergonomic assessment of flight engineers at 403 SQN. New Brunswick, Canada; Camp Gagetown NB; 2001. Physiotherapy report 6600-1 [as quoted in Harrison MF, Neary JP, Albert WJ, Croll JC. Neck pain and muscle function in a population of CH-146 helicopter aircrew. Aviat Space Enniron Med 2011; 82: 1125-30]

Acknowledgement  Image courtesy Wikimedia Commons