Influence of a reduced G-suit pressure schedule on G-duration tolerance using enhanced G-protection ensembles.
BACKGROUND
Reducing pressure to enhanced G-protection ensembles may diminish potential undesirable physiologic effects, as well as improve wear comfort and garment durability.


OBJECTIVE
G-duration tolerance will not be affected by reducing pressure to the Swedish tactical flight combat suit (TFCS). A second objective tested the similarity in G-duration tolerance between the TFCS and Combined Advanced Technology Enhanced Design G-Ensemble (COMBAT EDGE) combined with a prototype enhanced coverage G-suit.


METHODS
There were 12 Swedish pilots (mean = 30 yr) who experienced gradual onset (+0.1 G.s-1) runs (GOR) to +9 Gz, rapid (+6 G.s-1) onset runs (ROR) and simulated aerial combat maneuvers (SACM) with +5 to +9 Gz cycles. The GOR and ROR profiles had a sustained times of 60 s after reaching +9 Gz.


RESULTS
GOR duration tolerance was statistically decreased (p < 0.01) by the lower pressure (1.1 psig.G-1) when compared to standard pressure (1.5 psig.G-1). No statistical difference between TFCS and COMBAT EDGE was observed during the GOR trials. For all conditions, during the RORs, 90% of the subjects completed at least 30 s at +9 Gz. Many technical or medical difficulties during SACM trials limited statistical treatment of these data. However, no obvious among-condition differences were observed. Noteworthy among SACM trials were those of 3 subjects enduring more than 9 min before stopping; one completing 12.5 min (35 cycles). Neither heart rate, blood pressure, nor perceived exertion data revealed a condition-effect difference.


CONCLUSIONS
Moderately reduced pressure to the extended coverage anti-G suit, combined with positive pressure breathing, may yield decreased G-tolerance results during laboratory evaluation; however, observed differences are sufficiently small they are likely operationally insignificant.
Krock
L P
LP
Armstrong Laboratory, Brooks AFB, TX 78235-5119, USA.
Balldin
U I
UI
Harms-Ringdahl
K
K
Singstad
C P
CP
Linder
J
J
Siegborn
J
J
D000328:Adult; D000337:Aerospace Medicine; D000704:Analysis of Variance; D018592:Cross-Over Studies; D004867:Equipment Design / Q000009:adverse effects / Q000592:standards; D005221:Fatigue; D005676:Gravity Suits / Q000009:adverse effects / Q000592:standards*; D006339:Heart Rate; D006801:Humans; D018471:Hypergravity / Q000009:adverse effects*; D008297:Male; D008452:Maximum Allowable Concentration; D008875:Middle Aged; D008889:Military Personnel; D010807:Physical Endurance; D005082:Physical Exertion; D011312:Pressure / Q000009:adverse effects; D013548:Sweden; D014481:United States