2007, Piran, Slovenia

Environmental Ergonomics XII
Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana 2007
40
EFFECTS OF 8-HR MISSIONS IN A FIGHTER AIRCRAFT ON
PLASMA VOLUME AND CARDIOVASCULAR REGULATION
Roger Kolegard, Mikael Gronkvist, Gerard Nobel 1 , Eddie Bergsten and Ola Eiken
Swedish Defence Research Agency
Berzelius vag 13, Karolinska Institutet, SE-171 77 Stockholm
1 Royal Netherlands Navy, Netherlands
Contact person: roger.kolegard@foi.se
INTRODUCTION
The latest version of the Gripen fighter aircraft has in-flight refueling capacity
allowing flight missions of up to 8-hr duration (in the following termed Long Flight
Missions, LFM). Such LFM will take place not only in Sweden but also during
international assignments in hot climates. The Gripen pilot wears a breathing mask
and an anti-G suit (AGS) that covers the legs completely and also the major part of
the abdomen. The AGS is tightly fitted and has a ready pressure of about 1.3 kPa at
normal gravitoinertial (G) load (1 G); suit pressure increases with increasing G load in
the head-to-foot direction to a maximum of 70 kPa at 9 G. We assumed that the Gsuit-induced
long lasting pressurization of the lower body will shift blood volume
from the lower body to the thorax. An increase in central blood volume will, in turn,
increase urine production, which together with sweating and inadequate intake of
liquid might result in substantial dehydration. Dehydration is known to affect
cardiovascular control with reductions in both orthostatic tolerance (Geelen &
Greenleaf, 1993, Frey et al. 1994) and the ability to withstand high G forces (G
tolerance) (Nunneley & Stribley, 1979).
The aim of the present study was to investigate the effects of wearing an anti-G suit
during extended time periods on plasma volume and cardiovascular control. The
specific questions posed were:
Will an 8-hr LFM, conducted in a warm environment and without any fluid intake,
reduce the pilot’s blood volume to the extent that his/her cardiovascular responses are
significantly affected?
If so, is it possible to counteract the blood-volume reduction by ad libitum fluid
intake?
METHODS
The study was carried out as two separate experimental series. Twelve male test
subjects participated in series I. Each subject was equipped with Gripen anti-G
garment and seated in a Gripen mock-up chair in a human-use centrifuge. He then
performed an 8-hr simulated LFM at 1G. The LFM was performed in a temperaturecontrolled
environment (28 o C) and the subject was not allowed to eat or drink during
the experiment. Throughout the LFM the anti-G suit and mask were pressurized, to
1.3 kPa and 0.3 kPa, respectively.
Blood samples were taken, for subsequent estimations of changes in plasma volume
(Dill & Costill 1974), before, as well as 1, 2, 4, 6 and 8 hrs into the LFM and again 45
min after the LFM (approx. 30 min after removing the anti-G suit). Before and after
the LFM, tests of orthostatic tolerance and relaxed G-tolerance were performed. G
tolerance was determined in a “worst-case scenario”, namely without pressure in the
anti-G suit.