title: Cerebral near-infrared spectroscopy to evaluate anti-G straining maneuvers in centrifuge training.
abstract: BACKGROUND
  Over the past decade, near-infrared spectroscopy (NIRS) has emerged as an easily manageable noninvasive method for the continuous monitoring of cerebral cortical oxygenation during +Gz exposure. NIRS is also used to evaluate pilot trainees' ability to adequately perform anti-G straining maneuvers in the course of centrifuge training. This study aimed to determine the general patterns and individual differences in NIRS recordings during +Gz exposure.
  
  
  METHODS
  There were 22 healthy male cadets who participated in the study. The centrifuge training profiles included a gradual onset run (GOR, onset rate of 0.1 Gz x s(-1)) and short-term repeated exposures, with Gz levels from 4 to 7 Gz at an onset rate of 1.0 Gz x s(-1) (rapid onset run, ROR). Cortical tissue hemoglobin saturation (tissue oxygenation index, TOI) and changes in the concentration of oxygenated hemoglobin (O2Hb) were recorded from the right forehead during the period of Gz exposure.
  
  
  RESULTS
  Most of the subjects successfully performed an anti-G straining maneuver and maintained or increased the cerebral oxygenation level during Gz exposure. In four subjects, however, oxygenation decline was observed at levels over 4 Gz, even though their anti-G systems were functioning. In contrast to the O2Hb response, TOI, which reflects intracranial oxygenation changes, was decreased during the anti-G straining maneuver at Gz onset or during the countdown to a ROR exposure.
  
  
  CONCLUSIONS
  Although NIRS is an effective tool for monitoring anti-G straining maneuver performance, it should be carefully evaluated in terms of intracranial oxygenation results.
authors.affiliation: The Aeromedical Laboratory Japan Air Self Defense Force, Tachikawashi, Tokyo, Japan. kobayashi3814@inet.asdf.mod.go.jp
authors.forename: Asao
authors.initials: A
authors.lastname: Kobayashi
authors.forename: Azusa
authors.initials: A
authors.lastname: Kikukawa
authors.forename: Mikihiko
authors.initials: M
authors.lastname: Kimura
authors.forename: Takuo
authors.initials: T
authors.lastname: Inui
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Miyamoto
mesh_terms: D000328:Adult; D001921:Brain / Q000098:blood supply / Q000378:metabolism*; D002498:Centrifugation; D006801:Humans; D008297:Male; D010100:Oxygen / Q000378:metabolism*; D012039:Regional Blood Flow; D012867:Skin / Q000098:blood supply; D019265:Spectroscopy, Near-Infrared; D055815:Young Adult
chemical_list: D010100:Oxygen