The Predictive Studies Series: Correlation of physiologic responses to extreme environmental stresses

J M Clark
2004 Undersea & Hyperbaric Medicine  
Periodically over the past four decades, investigators at the Institute for Environmental Medicine have carried out correlated physiologic experiments programs that were from the outset designated individually and collectively as 'Predictive Studies.' Because of my long and close association, I have been invited to summarize the scope of these studies designed to identify and quantitatively measure in human subjects the physiologic and pathophysiologic effects of extreme respiratory gas and
more » ... iratory gas and ambient pressure environments that could limit or aid man's ability to live or work in those environments. Each of these eight broad studies was conceived, designed, and led by C. J. Lambertsen, and joined by selected collaborating participants from military, university, or corporate backgrounds. In most cases, the Predictive Studies employed a "dose-response" design, in which human subjects were exposed to a range of respiratory gases and pressures for durations that approached the limits of tolerance at both rest and during physical work. By measuring physiologic and/or toxic responses to each pressureduration dose and then interpolating between doses, the intent was to "predict" responses to pressure-duration combinations over the ranges of stresses studied. C.J. Lambertsen's earliest physiologic study of oxygen involved microtonometry to determine in-vivo relationships of PO 2 , PCO 2 , and hemoglobin O 2 saturation in the arterial blood of human subjects exposed to increasingly severe degrees of hypoxia (1). Ensuing analyses of arterial and brain venous blood at 3.5 ATA-inspired O 2 , beyond full saturation of hemoglobin, demonstrated that human subjects are functional without the benefit of hemoglobin for O 2 transport to the brain or CO 2 transport from it (2). These early observations, superimposed on extreme personal exposures to hyperoxia and oxygen poisoning in development of practical selfcontained diving (3, 4), led to seminal investigations of human respiration and brain circulation functions in hyperoxic states (5-7). Subsequently, the focus which emerged was on relations of evolving undersea and aerospace activity, in which Lambertsen played a special role as
pmid:15233158 fatcat:5gf4u4wskraojhacphptgcxxmu