In-flight cerebral oxygen status: continuous monitoring by near-infrared spectroscopy

BACKGROUND: Little is known about the in-flight cerebral oxygen status (COS) of fighter pilots. The purpose of this study was to evaluate the COS of fighter pilots during an F-15DJ flight. METHODS: Three male F-15DJ fighter pilots volunteered to serve as test subjects during aerial gunnery training (AGT) missions. During the flight, the pilots' COS was continuously monitored from the right forehead using a NIRO-300G near-infrared spectrophotometer. This new instrument is capable of measuring the concentration changes in the brain of oxygenated hemoglobin (O2Hb), reduced hemoglobin (HHb), total hemoglobin (cHb, O2Hb + HHb), and the tissue oxygenation index (TOI, O2Hb/cHb). RESULTS: Continuous changes of COS within the brain were clearly demonstrated using NIRO-300G, the changes included reductions in O2Hb, cHb, and TOI with increased +Gz, in a mirror image fashion. The maximum decreased concentration of hemoglobin during flight ranged from 12.8 to 25.6 micromol x L(-1) (of brain tissue). CONCLUSIONS: We believe this study is the first monitoring of COS during F-15 actual flight. The monitoring of COS during F-15 flight showed that the effect of +Gz was to simultaneously lower blood flow in a mirror image fashion. Our results demonstrated that near-infrared spectroscopy (NIRO-300G) provides a reliable and sensitive method for the monitoring of pilots' COS during flight.