Putcha L, Whitson P, Lane HW, Smolensky MH.
Aviat Space Environ Med. 1993 May; 64: 436.
NASA Johnson Space Center, Houston, TX.
Circadian and other rhythms of gastrointestinal, hepatic, and renal functions profoundly affect the chronokinetics of medications. Rhythms in drug-targeted tissues result in time-dependent differences in desired and adverse effects. Antiorthostatic bed rest has been used as a ground-based model of space flight for pharmacokinetic studies. However, activity profiles during bed rest may not reflect those of space flight. Also, chronophysiological characteristics of long-duration bed rest have not been investigated. This investigation examines circadian rhythms during 21-day bed rest by monitoring three sensitive physiological parameters, heart rate (HR), blood pressure (BP), and body temperature in conjunction with the metabolic and gastrointestinal parameters. Activity of subjects during bed rest was also evaluated using wrist actigraphy. Subjects wore an ambulatory blood pressure monitor (ABPM) before bed rest for 48 h., and during bed rest for at least 48 h. The ABPM was programmed to record BP and HR every 20 min during wakeful period and hourly during sleep. At the same time, they either recorded core temperature every two hours while they were awake or wore a continuous monitor with a tympanic probe. They also wore an actigraph on their non-dominant arm during bed rest and for 48 h. before and after bed rest. BP, HR, and temperature data were analyzed for circadian changes during bed rest. Actigraphy data was analyzed for wake-sleep ratios and quality of sleep. Preliminary evaluation of results indicates significant changes in the time and magnitude of mean arterial pressure and HR during bed rest compared to the ambulatory phase. Results also suggest a desynchronization of peak times on the third day after bed rest. No differences were noticed in temperature rhythms during or after bed rest.
Publication Types:
Keywords:
- Bed Rest
- Blood Pressure
- Blood Pressure Monitoring, Ambulatory
- Body Temperature
- Circadian Rhythm
- Heart Rate
- Monitoring, Physiologic
- Motor Activity
- Sleep
- Space Flight
- Temperature
- Time Factors
- NASA Center JSC
- NASA Discipline Number 18-10
- NASA Discipline Regulatory Physiology
- NASA Program Space Physiology and Countermeasures
Other ID:
UI: 102212607
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