A miniaturized nuclear probe (MNP) and multiple gated cardiac blood pe
el imaging (RCBI) were used to measure left ven tricular function duri
ng positive pressure breathing (PPB) while wearing sin extended-covera
ge (EC) vs. standard coverage (SC) anti-C-suit. Seven subjects were ex
posed to 4.0 and 9.3 kPa PPB wearing each anti-G-suit during 3 min of
PPB at ground level. Ejection fraction was unchanged using both techni
ques. The atrial component to diastolic filling was greater with the S
C suit (p < 0.02). Using the MNP, end-diastolic and end-systolic volum
es declined non-linearly over time at both PPB levels; these declines
were greater with the SC G-suit (p < 0.001). Left ventricular preload
declines during PPB. This is attenuated with increased G suit coverage
, confirming prior results using impedance cardiography. RCBI is less
sensitive than MNP's for measuring non-steady-state cardiac physiology
such as PPB.