Flat spin and negative Gz in high-altitude free fall: pathophysiology, prevention, and treatment

Aviat Space Environ Med. 2013 Sep;84(9):961-70. doi: 10.3357/asem.3648.2013.


Introduction: Red Bull Stratos was a commercial program that brought a test parachutist protected by a full pressure suit to 127,852 ft (38,964 m), via a stratospheric balloon with a pressurized capsule, from which he free fell and subsequently parachuted to the ground. In light of the uniqueness of the operation and the medical threats faced, medical protocols specific to distinctive injury patterns were developed. One unique threat was that of a flat spin during free fall with resultant exposure to -Gz (toe-to-head) acceleration. In preparation for stratospheric free fall, the medical team conducted a review of the literature on the spectrum of human and animal injury patterns attributable to -Gz exposures. Based on the findings, an emergency medical field response protocol was developed for the rapid assessment, diagnosis, and treatment of individuals suspected of -Gz injury.

Methods: A systematic review was conducted on available literature on human and animal studies involving significant -Gz exposure, with subsequent development of an applicable field treatment protocol.

Results: The literature review identified pathophysiologic processes and mitigation strategies that were used to develop a prevention and treatment protocol, outlining appropriate interventions using current best medical practices. A medical field treatment protocol was successfully established for the high-altitude balloon program.

Discussion: Available literature provided insight into best medical practices for the prevention and treatment of significant -Gz exposures during high-altitude parachute activity. Using the protocol developed for the field medical response, injuries from sustained -Gz exposure can be effectively managed in similar high-altitude and space operations.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Review
  • Systematic Review

MeSH terms

  • Altitude*
  • Arrhythmias, Cardiac / physiopathology
  • Blood Glucose / analysis
  • Brain Edema / physiopathology
  • Cerebrovascular Circulation / physiology
  • Confusion / physiopathology
  • Coronary Circulation / physiology
  • Emergency Medical Services
  • Emergency Treatment
  • Eye Hemorrhage / physiopathology
  • Hemorrhage / physiopathology
  • Humans
  • Hypogravity / adverse effects*
  • Hypotension / physiopathology
  • Hypoxia, Brain / physiopathology
  • Intraocular Pressure / physiology
  • Lactic Acid / blood
  • Lung Diseases / physiopathology
  • Oxygen / blood
  • Proprioception / physiology
  • Pulmonary Circulation / physiology
  • Pulmonary Edema / physiopathology
  • Purpura / physiopathology
  • Pyruvic Acid / blood
  • Regional Blood Flow / physiology
  • Respiratory Rate / physiology
  • Syncope / physiopathology


  • Blood Glucose
  • Lactic Acid
  • Pyruvic Acid
  • Oxygen