CENTRAL VENOUS-PRESSURE IN-SPACE

Gravity affects cardiac filling pressure and intravascular fluid distr ibution significantly. A major central fluid shift occurs when all hyd rostatic gradients are abolished on entry into microgravity (PG) Under standing the dynamics of this shift requires continuous monitoring of cardiac filling pressure; central venous pressure (CVP) measurement is the only feasible means of accomplishing this. We directly measured C VP in three subjects: one aboard the Spacelab Life Sciences-1 space sh uttle flight and two aboard the Spacelab Life Sciences-2 space shuttle flight. Continuous CVP measurements, with a 4-Fr catheter, began 4 h before launch and continued into mu G. Mean CVP was 8.4 cmH(2)O seated before flight, 15.0 cmH(2)O in the supine legs-elevated posture in th e shuttle, and 2.5 cmH(2)O after 10 min in mu G Although CVP decreased , the left ventricular end-diastolic dimension measured by echocardiog raphy increased from a mean of 4.60 cm supine preflight to 4.97 cm wit hin 48 h in mu G. These data are consistent with increased cardiac fil ling early in I-IG despite a fall in CVP, suggesting that the relation ship between CVP and actual transmural left ventricular filling pressu re is altered in mu G