“…On the first day, negative chamber pressure was applied (i.e., the chamber was depressurized) in a linear ramp at a randomly assigned rate of −3, −6, or −9 mmHg/min to simulate a relatively slow, medium, or fast rate of bleeding. This was consistent with previous experiments demonstrating that −30, −60, and −90 mmHg LBNP approximate average blood losses of 450, 1000, and 1600 mL, respectively in a 70 kg human [ 22 ]. Pressure was quickly released (within 2 s) when subjects reached their hemodynamic decompensation point (indicated by a systolic blood pressure (SBP) of 80 mmHg or less, a sudden drop in heart rate (HR), symptoms consistent with clinical criteria of class III shock [ 15 ], or sustained an LBNP of −100 mmHg).…”