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Biomedical subjects

C F Sawin

Publications and source records attributed to C F Sawin.

18 recordsLinked to original sources
PubMed1996

Lessons from operational cardiovascular studies in space.

The Space Shuttle program has produced a database of information on the cardiovascular responses to spaceflight, based on in-flight as well as pre- and post-flight assessments undertaken as part of the assessment of the health, safety, and efficiency of Shuttle crews. The methods used in routine cardiovascular assessments of Space Shuttle astronauts are reviewed, and the major findings of these investigations are presented.

Cardiovascular Physiological Phenomena↗
PubMed1994

Preinflation before acceleration on tolerance to simulated Space Shuttle reentry G profiles in dehydrated subjects.

This study was conducted to determine if preinflation of a standard five-bladder anti-g suit 10 minutes before exposure to a centrifuge simulation of a Space Shuttle reentry would provide significantly better protection against orthostasis than the standard symptomatic inflation regimen. This study differed significantly from prior studies: The rate of g onset was slower, peak g was lower, duration of exposure was longer, and the subjects were dehydrated to mimic conditions observed in astronauts immediately postflight. Preinflation demonstrated physiological advantages as determined by arterial blood pressure and heart rate changes in seven healthy male, experienced centrifuge subjects.

Acceleration↗
PubMed1979

Exercise response to simulated weightlessness.

Two bed rest analog studies of space flight were performed; one 14 d and the other 28 d in duration. Exercise response was studied in detail during the 28 d study and following both the 14 d and 28 d studies. This paper relates the results of these studies to physiologic changes noted during and following space flight. The most consistent change noted after both bed rest and space flight is an elevated heart rate during exercise. A second consistent finding is a postflight or postbed rest reduction in cardiac stroke volume. Cardiac output changes were variable. The inability to simulate inflight activity levels and personal exercise makes a direct comparison between bed rest and the results from specific space flights difficult.

Adult↗
PubMed1976

Pulmonary function evaluation during the Skylab and Apollo-Soyuz missions.

Previous experience during Apollo postflight exercise testing indicated no major changes in pulmonary function. Pulmonary function has been studied in detail following exposure to hypoxic and hyperoxic normal gravity environments, but no previous study has reported on men exposed to an environment that was both normoxic at 258 torr total pressure and at null gravity as encountered in Skylab. Forced vital capacity (FVC) was measured during the preflight and postflight periods of the Skylab 2 mission. Inflight measurements of vital capacity (VC) were obtained during the last 2 weeks of the second manned mission (Skylab 3). More detailed pulmonary function screening was accomplished during the Skylab 4 mission. The primary measurements made during Skylab 4 testing included residual volume determination (RV), closing volume (CV), VC, FVC and its derivatives. In addition, VC was measured in flight at regular intervals during the Skylab 4 mission. Vital capacity was decreased slightly (-10%) in flight in all Skylab 4 crewmen. No major preflight-to-postflight changes were observed. The Apollo-Soyuz Test Project (ASTP) crewmen were studied using equipment and procedures similar to those employed during Skylab 4. Postflight evaluation of the ASTP crewmen was complicated by their inadvertent exposure to nitrogen tetroxide gas fumes upon reentry.

Aerospace Medicine↗
PubMed1976

Exercise cardiac output following Skylab missions: the second manned Skylab mission.

Cardiac output was measured during preflight and postflight exercise-stress tests on the Skylab astronauts. In the postflight tests immediately following the 28-, 59-, and 84-d earth orbital missions, the astronauts exhibited an approximate 30% decrease in cardiac output coupled with an approximate 50% decrease in cardiac stroke volume during exercise. These changes were accompanied by elevated heart rates and significant (p less than 0.01) increases in total systemic peripheral vascular resistance. Mean arterial pressure was unchanged. The hemodynamic alterations were transient in that all parameters returned to normal preflight values within 30 d of the end of the orbital period. Duration of the zero-G exposure did not appear to influence either the magnitude of the hemodynamic changes or the time-course of their return to normal. These results are discussed in relation to other cardiovascular findings and possible mechanisms responsible for the observations are outlined.

Adult↗
PubMed1976

Medical experiment M-171: results from the second manned Skylab mission.

Preflight, inflight, and postflight exercise response tests were conducted on the astronauts of the second Skylab mission (Skylab 3) as part of an evaluation of physiological adaptation to long-term weightlessness. The flight phase of this mission was 59 d in duration. An exercise protocol was designed around a bicycle ergometer which was used to apply work loads approximating 25, 50, and 75% of each crewman's measured maximum aerobic capacity (VO2 max). Respiratory gas exchange (VO2, VCO2, and VE), heart rate, and blood pressure were measured during all tests; cardiac output was measured at selected times during preflight and postflight tests. Data obtained both at rest and during exercise in flight showed no consistent changes which would indicate a degraded physical work capacity. In fact, heart rate during exercise actually decreased for all crewmen in flight. This response indicated improved physical fitness in flight relative to preflight. The improved physical condition of this crew relative to that of the first Skylab crew is attributed to frequent performance of high levels of aerobic exercise in flight. The postflight period of readaptation of 1 G was characterized by a marked tachycardia, during which time stroke volume was decreased. This response returned to normal within 5 d postflight.

Adaptation, Physiological↗
PubMed1975

Physiological response to exercise after space flight--Apollo 14 through Apollo 17.

Submaximal exercise stress tests were conducted preflight and postflight on the Apollo 14-17 crewmen. A bicycle ergometer was utilized to evoke target heart rates up to 160 beats/min while respiratory gas exchange, blood pressure, and cardiac output were measured. Three preflight tests were conducted during the month prior to flight to establish baseline values for postflight comparisons. Tachycardia was evidenced at rest and during exercise immediately postflight. This transitory tachycardia compensated for reduced stroke volume. Systolic blood pressure was reduced during exercise stress, but no consistent changes were observed in diastolic blood pressure. With the exception of the Apollo 15 crewmen, all crewmen had returned to preflight response levels by the day of following recovery. No changes were observed in mechanical or respiratory efficiency immediately postflight.

Aerospace Medicine↗
PubMed1975

Instrumented personal exercise during long-duration space flights.

This paper reports the results of instrumented personal exercise performed in flight by the Skylab 3 and Skylab 4 crewmen. These data include physiological responses to maximum aerobic exercise on a cycle ergometer at the conclusion of an 84-d exposure to zero-G (Sklyab 4). The bioinstrumentation provided continuous vectorcardiograph heart rate and cycle ergometer work level; minute updates of systolic and diastolic blood pressure, VO-2, V-CO-2, and VE. All Skylab 4 crewmen had higher V-O-2-max (cc/kg/min) at completion of the 84-d earth orbital mission than they had 4 d before launch. Two of these Skylab 4 crewmen, the scientist pilot and pilot, showed high levels of aerobic fitness with V-O-2-max of 54 and 51 cc/kg/min respectively at a heart rate of 185 beats/min and a workload of 286 w.

Adaptation, Physiological↗
PubMedDate not supplied

Skylab experiment M-171 "Metabolic Activity"--results of the first manned mission.

The experiment was performed to ascertain whether man's ability to perform mechanical work would be altered as a result of exposure to the weightless environment. Skylab II crewmen were exercised on a bicycle ergometer at loads approximating 25%, 50%, and 75% of their maximum oxygen uptake while their physiological responses were monitored. The results of these tests indicate that the crewmen had no significant decrement in their response to exercise during their exposure to zero gravity. Immediately postflight, however, all crewmen demonstrated an inability to perform the programmed exercise with the same metabolic effectiveness as they did both preflight and inflight. The most significant changes were elevated heart rates for the same work load and oxygen consumption (decreased oxygen pulse), decreased stroke volume, and decreased cardiac output at the same oxygen consumption level. It is apparent that the changes occurred inflight, but did not manifest themselves until the crewmen attempted to readapt to the 1-G environment.

Adaptation, Physiological↗