title: Cardiovascular effects of anti-G suit and cooling garment during space shuttle re-entry and landing.
abstract: BACKGROUND
  Many cardiovascular changes associated with spaceflight reduce the ability of the cardiovascular system to oppose gravity on return to Earth, leaving astronauts susceptible to orthostatic hypotension during re-entry and landing. Consequently, an anti-G suit was developed to protect arterial pressure during re-entry. A liquid cooling garment (LCG) was then needed to alleviate the thermal stress resulting from use of the launch and entry suit.
  
  
  METHODS
  We studied 34 astronauts on 22 flights (4-16 d). Subjects were studied 10 d before launch and on landing day. Preflight, crewmembers were suited with their anti-G suits set to the intended inflation for re-entry. Three consecutive measurements of heart rate and arterial pressure were obtained while seated and then again while standing. Three subjects who inflated the anti-G suits also donned the LCG for landing. Arterial pressure and heart rate were measured every 5 min during the de-orbit maneuver, through maximum G-loading (max-G) and touch down (TD). After TD, crew-members again initiated three seated measurements followed by three standing measurements.
  
  
  RESULTS
  Astronauts with inflated anti-G suits had higher arterial pressure than those who did not have inflated anti-G suits during re-entry and landing (133.1 +/- 2.5/76.1 +/- 2.1 vs. 128.3 +/- 4.2/79.3 +/- 2.9, de-orbit; 157.3 +/- 4.5/102.1 +/- 3.6 vs. 145.2 +/- 10.5/95.7 + 5.5, max-G; 159.6 +/- 3.9/103.7 +/- 3.3 vs. 134.1 +/- 5.1/85.7 +/- 3.1, TD). In the group with inflated anti-G suits, those who also wore the LCG exhibited significantly lower heart rates than those who did not (75.7 +/- 11.5 vs. 86.5 +/- 6.2, de-orbit; 79.5 +/- 24.8 vs. 112.1 +/- 8.7, max-G; 84.7 +/- 8.0 vs. 110.5 +/- 7.9, TD).
  
  
  CONCLUSIONS
  The anti-G suit is effective in supporting arterial pressure. The addition of the LCG lowers heart rate during re-entry.
authors.affiliation: Wyle Laboratories, Houston, TX, USA.
authors.forename: Sondra A
authors.initials: SA
authors.lastname: Perez
authors.forename: John B
authors.initials: JB
authors.lastname: Charles
authors.forename: G William
authors.initials: GW
authors.lastname: Fortner
authors.forename: Victor
authors.initials: V
authors.lastname: Hurst
authors.forename: Janice V
authors.initials: JV
authors.lastname: Meck
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000502:physiology; D002320:Cardiovascular Physiological Phenomena; D017679:Cryotherapy / Q000295:instrumentation*; D005260:Female; D005676:Gravity Suits; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D011187:Posture / Q000502:physiology; D012016:Reference Values; D019442:Space Suits; D018531:Spacecraft