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INTRODUCTION
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 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 pressure-duration 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^sub 2^, PCO^sub 2^, and hemoglobin O2 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 O2, beyond full saturation of hemoglobin, demonstrated that human subjects are functional without the benefit of hemoglobin for O2 transport to the brain or CO2 transport from it (2). These early observations, superimposed on extreme personal exposures to hyperoxia and oxygen poisoning in development of practical self-contained 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 Chairman of the Man in Space Committee, Space Science Board, established by the National Academy of Sciences-National Research Council. He served concurrently as Chairman of the National Research Council Panel on Underwater Swimmer Technology. These joint roles influenced the beginnings and evolution of the Predictive Studies Series, most of which have blended research in undersea, aerospace,...