Some effects of the force environment on the heart, lungs and circulation

The data obtained in a series of human and animal experiments carried out during the last 45 years in centrifuges, specially instrumented dive bombers, and during changes in body position are the major bases for this paper. The integrated and highly effective cardiovascular reflexes which allow awake, upright humans to regain and/or maintain vision and consciousness during sustained inertial force environments several times greater than at the surface of planet Earth are particularly impressive. Multiplication of vertical gradients in interserosal pericardial, pleural, abdominal and cerebrospinal fluid pressures and/or forces in proportion, and in the resultant vectorial direction of the force environment play a critical role in this capability both in aerospace flight and everyday life on planet Earth. The differences between the near zero specific gravity of intra-alveolar gas and the (about) 1.05 value for the encompassing blood and tissue, render lung function highly susceptible to the weight determinant force environment. Creation of a womb-like environment by liquid whole-body immersion plus assisted breathing of a respirable liquid, both with specific gravities closely similar to bodily tissues, is a seemingly impractical but technologically and biologically documented expedient for allowing air breathers to endure very high sustained force and pressure environments.