partially, and future cardiopulmonary investigations should focus more on mechanisms. An improved understanding of underlying physiological mechanisms should also make it possible to address important operational questions more effectively. Postflight orthostatic hypotension remains one of the most important operational problems. Given the prospect of lunar or martian long-duration flights, orthostatic hypotension, aerobic deconditioning, and pulmonary particulate behavior in low- or 0-g environments must be understood and addressed. Important steps have already been taken, but current scientific knowledge and medical expertise must be increased to provide the level of security that will be required for such missions to proceed.

Much of the hardware needed for microgravity research with humans has already been developed for laboratory use, but flight or even portable units are often not available. Even less flight equipment and fewer facilities exist for animal research. Several techniques should be developed or obtained for space physiology research in both animals and humans. These are described briefly:

• Automated recording devices should be used extensively to capture physiological data with minimal additional astronaut involvement. Examples include exercise equipment that records astronaut identification, date, time, and workload; a simple body-mass measuring device; a dietary log system that does not require a manual logbook entry each time food or drink is consumed; and an automated urine measurement system that records void volumes, but also makes and records simple measures of electrolytes, creatinine levels, and so on. Such devices would greatly enhance the quality and quantity of physiological data obtained and would decrease the crew time required for such measurements.
• Accurate measurements should be made of cardiac output for both humans and animals. A human-rated, noninvasive foreign gas system would be appropriate for humans, but animal systems will require chronically implanted, stable, low-risk technologies, such as electromagnetic or Doppler flow probes.
• Systems for accurate measurement of heart rate and both cuff and beat-to-beat blood pressure should be readily available during all phases of flight. Such systems should be easy to apply and use and, where possible, should include data storage and suitable interfaces for down-link capability. Electrocardiograms and beat-to-beat blood pressure could be analyzed for first-order hemodynamics, variability, spectral content, power, and so on and correlated with other indices of cardiopulmonary function.
• Respiratory gas measurements are critical for most studies of pulmonary function. Equipment such as lightweight, stable mass spectrometers and ultrasonic flow meters, although complex, should be obtained and modified for flight.
• A scintigraphic imaging system should be developed for flight and should include a variety of imaging energy levels to support graphical and metabolic imaging of at least blood, bone, and muscle. Such a device would be multidisciplinary in its usage and would support metabolic, cardiopulmonary, and musculoskeletal discipline experiments. Ultrasound imaging systems should be available on the International Space Station. Magnetic resonance imaging (MRI) and computed tomography (CT) systems would be highly desirable for spaceflight and should be considered if continued advances in technology reduce their size and power consumption sufficiently.
• Exercise equipment should be multifunctional to permit exercise in multiple modalities, as well as testing and recording of astronaut data. Linkage with physiological monitoring equipment is also important.