Panel on deliberate G-induced loss of consciousness: introduction

Over the last decade, G-induced loss of consciousness (G-LOC) has been recognized as a significant operational problem for pilots of high performance aircraft in both the U.S. Air Force and U.S. Navy. Consequently, government laboratories have initiated research studies to learn more about the G-LOC phenomenon in an attempt to reduce its hazards. Many of these studies require the occurrence of LOC during their conduct. For this reason, animal models have been developed to use in these studies. However, even though sophisticated animal models such as baboons can be taught to perform tasks before and after G-LOC has occurred, these models have deficiencies that can be overcome only by the use of human volunteers who willingly submit to G-LOC studies on the centrifuge. Such human G-LOC studies began in World War II and continue today. These studies are presently conducted without guidelines regarding subject selection, numbers of G-LOCs allowed per subject per unit time, restraint systems, or specific medical examinations required before, during, and after each episode of LOC, or after each completed study. This panel will discuss what is known about the pathophysiology of G-LOC, the limitations of animal models in these types of studies, the possible medical and psychological sequelae, and the legal implications of conducting deliberate G-LOC research. We hope that the information developed by this panel will be useful to laboratory human-use review committees in determining the requirements and the nature of guidelines for conducting such studies.