title: Increased G-suit coverage improves cardiac preloading conditions during positive pressure breathing.
abstract: A miniaturized nuclear probe (MNP) and multiple gated cardiac blood pool imaging (RCBI) were used to measure left ventricular function during positive pressure breathing (PPB) while wearing an extended-coverage (EC) vs. standard-coverage (SC) anti-G-suit. Seven subjects were exposed 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 techniques. The atrial component to diastolic filling was greater with the SC suit (p < 0.02). Using the MNP, end-diastolic and end-systolic volumes 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.
authors.affiliation: Defence and Civil Institute of Environmental Medicine, Human Protection Systems Division, North York, Ontario, Canada.
authors.forename: L S
authors.initials: LS
authors.lastname: Goodman
authors.forename: M R
authors.initials: MR
authors.lastname: Freeman
authors.forename: L
authors.initials: L
authors.lastname: de Yang
authors.forename: T W
authors.initials: TW
authors.lastname: Hsia
authors.forename: J
authors.initials: J
authors.lastname: Chan
mesh_terms: D000328:Adult; D001794:Blood Pressure; D005260:Female; D015637:Gated Blood-Pool Imaging; D005676:Gravity Suits; D006439:Hemodynamics; D006801:Humans; D008297:Male; D011175:Positive-Pressure Respiration; D014655:Vascular Resistance; D016277:Ventricular Function, Left