Lathers CM, Charles JB, Bungo MW.

Aviat Space Environ Med. 1991 May; 62: 453.

USRA, Houston, TX.

INTRODUCTION. This study validated head-down bedrest as a model for space flight. METHODS. Cardiovascular function (CF) by echocardiography during 2,4, and 6 hrs of bedrest at head-down (-5 degrees) and head-up tilt angles (+10 degrees, +20 degrees, and +42 degrees) was compared to 4 to 6 hrs of flight. RESULTS. Head-down tilt decreased heart rate (HR) for the first 2 hrs; thereafter, values began to increase toward pre-tilt values. Stroke volume (SV) decreased from control at 2 and 4 hrs of head-down tilt and showed a slight increase at hr 6. HR and SV were increased early into space flight. Systolic, diastolic, and mean arterial pressures (SBP, DBP, MABP) were increased after 6 hrs -5 degrees tilt and after 6 hrs in space. Cardiac output (CO) decreased by 2 hrs at -5 degrees and increased by 6 hrs, but never increased above control as it was after a similar time in space. Total peripheral resistance (TPR) increased after 2 and (4 hrs of both -5 degrees bedrest and flight). However, 6 hrs of bedrest induced changes in TPR, CO, and left ventricular diastolic volume (LVDV) which differed from those in space, although LVDV was decreased 24 hrs in flight. Thus, of 8 parameters compared, only 4 (SV, SBP, DBP, and MABP) were elevated after 6 hrs at -5 degrees and also elevated after 4-6 hrs of flight. SBP, DBP, MABP, and TPR were increased after 6 hrs of bedrest at +10 degrees, +20 degrees, and +42 degrees and after 6 hrs of flight. HR was also elevated after 6 hrs of +20 degrees or +42 degrees tilt and after flight. CONCLUSIONS. The data indicate that no angle of tilt, whether head-down or head-up for 4 to 6 hrs, mimicked exactly the changes in CF recorded after 4 to 6 hrs of flight. Thus space and bedrest changes in LVDV may be similar but possess a different time course. Nevertheless, head-down tilt at 5 degrees for 6 hrs mimics some (SV, SBP, DBP, MABP), but not all, of the changes occurring in an equivalent time of space flight.

Publication Types:

• Meeting Abstracts

Keywords:

• Bed Rest
• Blood Pressure
• Cardiac Output
• Cardiovascular Physiology
• Echocardiography
• Head
• Head-Down Tilt
• Space Flight
• Stroke Volume
• Systole
• Vascular Resistance
• ultrasonography
• NASA Center JSC
• NASA Discipline Cardiopulmonary
• NASA Discipline Number 00-00
• NASA Discipline Number 14-10
• NASA Program Flight
• NASA Program Space Physiology and Countermeasures

Other ID:

• 95607883

UI: 102212711

From Meeting Abstracts