G-LOCLTC William W. Pond, MD, FS

Chief Aerospace Medicine

G-LOC: Importance

Important cause : 1982-1998---26 aircraft lost 1985-1998---402 Class C Mishaps Decrease performance

G-LOC: Cause

Inadequate oxygen to the brain: Caused by inadequate blood flow: Caused by insufficient blood pressure

toward the head to overcome G forces pushing/pulling blood away from the head

G-LOC: Heart, Brain, Eyes

Heart has high metabolic requirement and has static inflation pressure, but coronary artery flow is little affected by Gs.

Brain loses consciousness in hypoxia. Eye loses vision, peripheral first . Vision lost earlier than consciousness due

to intraocular static pressure. 5-7 second reserve of oxygen

G-LOC: Effect on Eye

Decreased blood flow Eye reacts first

– Grayout– Tunnel Vision– Immediate return of function with restoration of

blood flow

G-LOC: Effects on Brain

Brain stays “turned off” even after flow restored.

Absolute incapacitation-----12-16 seconds– (Range 5-30)– Dream like state– Unaware of environment

Relative incapacitation----12 seconds– (Range 8-80)– May respond to “pull –up, pull-up” command

G-LOC: Recognition

May go unnoticed due to partial amnesia Suspect for sudden loss of altitude Tingling around mouth Sense of dreaming May recognize during debriefing Never use visual symptoms to test your

current G tolerance

G-LOC: Tolerance

Anti G Straining Maneuver Anticipation of G-onset Physical and psychological condition G awareness Combat Edge Reclined Seat

G_LOC: Recognition

(May occur unnoticed)