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Titolo:
ECHOCARDIOGRAMS DURING 6 HOURS OF BEDREST AT HEAD-DOWN AND HEAD-UP TILT AND DURING SPACE-FLIGHT
Autore:
LATHERS CM; RIDDLE JM; MULVAGH SL; MUKAI C; DIAMANDIS PH; DUSSACK LG; BUNGO MW; CHARLES JB;
Indirizzi:
NASA,INST SPACE BIOMED RES,SD5 HOUSTON TX 77058 UNIV SPACE RES ASSOC,DIV SPACE BIOMED HOUSTON TX 00000 KRUG INT HOUSTON TX 00000 KN NASDA HOUSTON TX 00000 MIT,DEPT AERONAUT & ASTRONAUT CAMBRIDGE MA 02139 HARVARD UNIV,SCH MED BOSTON MA 02115 NASA,LYNDON B JOHNSON SPACE CTR HOUSTON TX 77058
Titolo Testata:
Journal of clinical pharmacology
fascicolo: 6, volume: 33, anno: 1993,
pagine: 535 - 543
SICI:
0091-2700(1993)33:6<535:ED6HOB>2.0.ZU;2-C
Fonte:
ISI
Lingua:
ENG
Soggetto:
EARLY CARDIOVASCULAR ADAPTATION; ZERO GRAVITY; VOLUME;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
26
Recensione:
Indirizzi per estratti:
Citazione:
C.M. Lathers et al., "ECHOCARDIOGRAMS DURING 6 HOURS OF BEDREST AT HEAD-DOWN AND HEAD-UP TILT AND DURING SPACE-FLIGHT", Journal of clinical pharmacology, 33(6), 1993, pp. 535-543

Abstract

Left ventricular end-diastolic volume increased after 4 1/2 to 6 hours of space flight, but was significantly decreased after 5 to 6 days of space flight. To determine the role of acute gravitational effects in this phenomenon, responses to a 6-hour bedrest model of 0 gravity (G; 5-degrees head-down tilt) were compared with those of fractional gravity loads of 1/6G, 1/3G, and 2/3G by using head-up tilts of 10-degrees, 20-degrees, and 42-degrees, respectively. On 4 different days, six healthy male subjects were tilted at one of the four angles for 6 hours. Cardiac dimensions and volumes were determined from two-dimensionaland M-mode echocardiograms in the left lateral decubitus position at control (0), 2, 4, and 6 hours. Stroke volume decreased with time (P <.05) for all tilt angles when compared with control. Ejection fraction(EF) at -5-degrees was greater than at +20-degrees and +42-degrees (not significant); EF at +100 was greater than at +420 (not significant). For the tilt angles of -5-degrees, +10-degrees, and +20-degrees, mean heart rate decreased during the first 2 hours, and returned to control or was slightly elevated above control (+20-degrees) by 6 hours (not significant). At the +42-degrees angle of tilt, heart rate was increased above control at hours 2, 4, and 6. There were no significant differences in cardiac output at any time point for any tilt angle. Left ventricular end-diastolic volume did not change significantly with time or tilt angle, but there was a trend to a decrease by hour 2. Left ventricular end-systolic volume was increased at hour 2 (not significant) and at hour 4 (not significant) for subjects at -5-degrees. Systolic blood pressure did not change significantly. Left ventricular end-diastolic volume, left ventricular end-systolic volume, stroke volume, ejection fraction, heart rate, and cardiac output were at control values by hour 6 for all tilt angles. The lack of a significant immediate change in left ventricular end-diastolic volume despite decrements in stroke volume (P < .05) and heart rate (not significant) suggests that multiple factors may play a role in the adaptation to simulated hypogravity. The data indicate that no angle of tilt, whether head-down or head-up for 4 to 6 hours, mimicked exactly the changes in cardiovascular function recorded after 4 to 6 hours of flight. Thus space and bedrest changes in left ventricular end-diastolic volume may be similar butpossess a different time course. Nevertheless, head-down tilt at 5-degrees for 6 hours mimics some (stroke volume, systolic and diastolic blood pressure, mean arterial blood pressure, total peripheral vascularresistance), but not all, of the changes occurring in an equivalent time of space flight.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 28/09/20 alle ore 15:28:55