Cerebral hemodynamics and brain oxygen changes related to gravity-induced loss of consciousness in rhesus monkeys.
The aim of the present experiment was to study the influence of +Gz acceleration (head-to-foot inertial forces) onset on cerebral oxygenation changes (cerebral oxy- and deoxy-hemoglobin) and cerebral blood volume (CBV) in order to evaluate the role of cerebral hypoxemia and ischemia in the appearance of +Gz-induced loss of consciousness (G-LOC). We used five rhesus monkeys which were equipped with near infrared spectroscopy optodes fixed onto the parietooccipital cranial bone. G-LOC (isoelectric electrocorticogram) was detected with silver balls electrodes in contact with the dura matter. The animals were centrifuged up to +12 Gz with two onset rates (0.1 and 3 G/s). Cerebral deoxy-hemoglobin increased significantly (max: +30 +/- 6% of control, P < 0.01) only during the 0.1 G/s run. At G-LOC, CBV changes were not related to G-onset rate (P = 0.30; mean change: -32 +/- 6% of control). We conclude that cerebral ischemia is the main mechanism in the occurrence of G-LOC.
Tran
Cong Chi
CC
Institut de Médecine Aérospatiale du Service de Santé des Armées, Département Physiologie, BP 73, 91223 Brétigny-sur-Orge Cedex, France. dtran@imassa.fr
Florence
Geneviève
G
Tinet
Eric
E
Lagarde
Didier
D
Bouy
Jean-Christophe
JC
Van Beers
Pascal
P
Serra
André
A
Avrillier
Sigrid
S
Ollivier
Jean-Pierre
JP
D000054:Acceleration / Q000009:adverse effects; D000818:Animals; D001921:Brain / Q000502:physiology*; D018470:Gravity, Altered / Q000009:adverse effects*; D006439:Hemodynamics / Q000502:physiology; D008253:Macaca mulatta; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology*; D010108:Oxyhemoglobins / Q000502:physiology; D014474:Unconsciousness / Q000378:metabolism
D010108:Oxyhemoglobins