Effect of Hyperoxia and Hypergravity on Lung Ventilation and Perfusion

The primary aim of this project is to get further knowledge on the effects of + Gz accelerations and hyperoxia on lung ventilation in humans. The secondary aim is to study lung perfusion and cardiovascular function in these conditions.

Experiments were conducted in a human centrifuge. The protocol aimed at mimicking a routine peacetime flight in combat aircraft, and included 10-min exposure to +1.4 - +3.5 Gz. Subjects were exposed three times to this sequence, breathing air, 44.5% O2 or 100% O2. Ten volunteers wearing anti-G trousers participated in the study. The Ethics Committee Ile-de-France III and the French National Agency for Drug Safety (ANSM) approved the protocol (number 2009-A01092-55). Three different imaging techniques, electrical impedance tomography (EIT), pulmonary ultrasound and chest SPECT/CT were used and compared. EIT enabled ventilation monitoring in the human centrifuge, whereas pulmonary ultrasound and SPECT/CT gave functional and topographical information before and after exposure to +Gz accelerations. EIT analysis focused on regional ventilation, SPECT on global lung ventilation and perfusion, CT on the presence of atelectasis, and pulmonary ultrasound analysis looked for comet tails in 64 chest areas. Arterial blood pressure was recorded continuously by finger photoplethysmography. Cardiac output and stroke volume were computed from these recordings, using three different algorithms. Echocardiography was used as reference non-invasive technique for stroke volume determination and performed before and after exposure to +Gz accelerations.

"echocardiography (sub-aortic diameter), photoplethysmography (Liljestrand, systolic area and Windkessel algorithms)"

global (mL, area under the flow versus time curve) and regional (% change per quadrant at 5th intercostal space level)

Inclusion Criteria: normal lung function checked by pulmonary function tests Part 1 exclusion Criteria: past medical history of heart or lung disease current medical treatment for heart or lung disease smoking bad tolerance to +Gz accelerations (G-induced loss of consciousness, motion sickness) Part 2 exclusion criteria: past medical history of heart or lung disease current medical treatment for heart or lung disease smoking The use of medication for hypertension asymmetric values of left/right humeral arterial blood pressure significant echocardiographic abnormalities or bad echogenicity bad tolerance to +Gz accelerations (G-induced loss of consciousness, motion sickness)