Reduction of the vertical vestibular-ocular reflex in military aircraft pilots exposed to tactical, high-performance flight

Giovanni Bertolini; Alberto Pagnamenta; Andres Kunz; Aleardo Del Torso; Denis Bron

doi:10.3389/fneur.2023.949227

Reduction of the vertical vestibular-ocular reflex in military aircraft pilots exposed to tactical, high-performance flight

Front Neurol. 2023 Jun 9:14:949227. doi: 10.3389/fneur.2023.949227. eCollection 2023.

Authors

Giovanni Bertolini^{1

2

3}, Alberto Pagnamenta^{4

5

6}, Andres Kunz¹, Aleardo Del Torso^#⁷, Denis Bron^#¹

Affiliations

¹ Aeromedical Center (AeMC), Swiss Air Forces, Dübendorf, Switzerland.
² Institute of Optometry, School of Engineering, University of Applied Sciences and Arts Northwestern Switzerland (FHNW), Olten, Switzerland.
³ Department of Neurology, University Hospital of Zürich, Zürich, Switzerland.
⁴ Clinical Trial Unit, Ente Ospedaliero Cantonale, Lugano, Switzerland.
⁵ Department of Intensive Care Medicine, Ente Ospedaliero Cantonale, Lugano, Switzerland.
⁶ Division of Pneumology, University Hospital of Geneva, Geneva, Switzerland.
⁷ Otolaryngology Unit, Centromedico PDS Medical, Bellinzona, Switzerland.

^# Contributed equally.

Abstract

Background: Exposure to high-performance flight stresses the vestibular system and may lead to adaptive changes in the vestibular responses of pilots. We investigated the vestibular-ocular reflex of pilots with different histories of flight exposure both with respect to hours of flight and flight conditions (tactical, high-performance vs. non-high-performance) to evaluate if and how adaptative changes are observable.

Methods: We evaluated the vestibular-ocular reflex of aircraft pilots using the video Head Impulse Test. In study 1, we assessed three groups of military pilots: Group 1 had 68 pilots with few hours of flight experience (<300 h) in non-high-performance flight conditions; Group 2 had 15 pilots with many hours of flight (>3,000 h) and regularly flying tactical, high-performance flight conditions; Group 3 had eight pilots with many hours of flight (>3,000 h) but not exposed to tactical, high-performance flight conditions. In study 2, four trainee pilots were followed up and tested three times over a 4-year period: (1) <300 h of flight on civil aircraft; (2) shortly after exposure to aerobatic training and with <2,000 h of overall flight; and (3) after training on tactical, high-performance aircraft (F/A 18) and for more than 2,000 h of flight.

Results: Study 1: Pilots of tactical, high-performance aircrafts (Group 2) had significantly lower gain values (p < 0.05) as compared to Groups 1 and 3, selectively for the vertical semicircular canals. They also had a statistically (p = 0.022) higher proportion (0.53) of pathological values in at least one vertical semicircular canal as compared to the other groups. Study 2: A statistically significant (p < 0.05) decrease in the rVOR gains of all vertical semicircular canals, but not of the horizontal canals, was observed. Two pilots had a pathological value in at least one vertical semicircular canal in the third test.

Discussion: The results evidence a decrease in the gain of the vestibular-ocular reflex as measured with the video head impulse test for the vertical canals. This decrease appears to be associated with the exposure to tactical, high-performance flight rather than with the overall flight experience.

Keywords: adaptation; aviation and aerospace; high-g flight; supersonic flight; vertical semicircular canals; vestibular-ocular reflex (VOR); video head impulse test (vHIT).