title: Influence of alterations in loading produced by lower body negative pressure on aortic blood flow acceleration.
abstract: The objectives of this study were to evaluate the effects of alterations in loading induced by lower body negative pressure on aortic blood flow velocity and acceleration. Twenty-seven normal men were studied during various levels of lower body negative pressure (0 to -60 mm Hg) during which echocardiographic, Doppler and hormonal measurements were obtained. Lower body negative pressure induced a decrease in left ventricular diastolic diameter from 5.18 +/- 0.08 to 4.41 +/- 0.1 cm (p less than 0.0001) and in left ventricular systolic diameter from 3.33 +/- 0.09 to 2.84 +/- 0.1 cm (p less than 0.0001). Shortening fraction remained unchanged. The decrease in diastolic diameter resulted in a reduction in flow velocity integral from 13.8 +/- 0.8 to 7.5 +/- 0.4 cm (p less than 0.0001) and, therefore, in stroke volume from 89.6 +/- 4.7 to 49.5 +/- 2.8 ml (p less than 0.0001). Heart rate reflexly increased from 62.5 +/- 1.9 to 82.2 +/- 2.3 beats/min (p less than 0.0001) as did systemic vascular resistance from 1,280.8 +/- 69.5 to 1,863.4 +/- 121.4 dyne.s.cm-5 (p less than 0.0001). The increase in heart rate was insufficient to maintain cardiac output, which decreased from 5.53 +/- 0.29 to 3.99 +/- 0.21 liters/min (p less than 0.0001). Systolic, diastolic and mean arterial blood pressure was maintained. The negative pressure resulted in a concomitant significant increase in norepinephrine levels from 1.46 +/- 0.09 to 2.056 +/- 0.2 nmol/liter (p = 0.0019) but no change in plasma epinephrine: 0.845 +/- 0.22 to 0.78 +/- 0.11 nmol/liter (p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Division of Cardiovascular Medicine, University of Kentucky Medical Center, Lexington 40536.
authors.forename: M R
authors.initials: MR
authors.lastname: Berk
authors.forename: J
authors.initials: J
authors.lastname: Evans
authors.forename: C
authors.initials: C
authors.lastname: Knapp
authors.forename: M R
authors.initials: MR
authors.lastname: Harrison
authors.forename: T
authors.initials: T
authors.lastname: Kotchen
authors.forename: A N
authors.initials: AN
authors.lastname: DeMaria
mesh_terms: D000328:Adult; D001011:Aorta / Q000502:physiology*; D001783:Blood Flow Velocity; D003664:Decompression; D015150:Echocardiography, Doppler; D006801:Humans; D008150:Lower Body Negative Pressure; D008297:Male; D009200:Myocardial Contraction / Q000502:physiology*; D009638:Norepinephrine / Q000097:blood; D012016:Reference Values; D012039:Regional Blood Flow
chemical_list: D009638:Norepinephrine