Lung Function Changes with Acute +G_z Exposure as Assessed by Impulse Oscillometry

INTRODUCTION: The introduction of fifth-generation fighter aircraft has raised concerns regarding the impact of high gravitational forces on lung function. This study aimed to investigate the acute effects of controlled +G_z exposure, up to +9 G_z, on lung function in military pilots using impulse oscillometry (IOS).

METHODS: These studies, conducted in Canada and the Netherlands, involved military pilots undergoing high G centrifuge training. IOS measurements were obtained using the Tremoflo^TM IOS device, which assesses lung function during normal tidal breathing without forced maneuvers. Included in the study were 30 military pilots of the Royal Canadian Air Force (RCAF) and 28 military pilots trained by the Royal Netherlands Air Force (RNLAF). Both performed baseline IOS measurements, with postexposure measurements obtained within 10 min in RCAF pilots and within 2 min by the RNLAF.

RESULTS: Both the RCAF and RNLAF studies showed significant increases in compliance (median = −1.605 and −2.085) and decreases in resistance (median = −0.611 and −0.230). Small airway resistance reduction was significant only in the RNLAF study (median = 0.176), indicating a greater effect at higher G_z levels.

DISCUSSION: The combined data showed no evidence that repeated exposure to high +G_z in combination with an anti-G suit and performance of the anti-G straining maneuver has acute negative effects on lung function. In fact, there was evidence of improvement in small airway function, perhaps as a result of the respiratory strain component of the anti-G straining maneuver, which increases intrathoracic pressure, possibly stretching the small airways, decreasing resistance, and increasing reactance.

Cornelissen SJWM, Frijters E, Gray G. Lung function changes with acute +G_z exposure as assessed by impulse oscillometry. Aerosp Med Hum Perform. 2025; 96(1):62–66.