Environmental physiology

The division of Environmental Physiology investigates the influence of environmental factors, such as gravity, ambient pressure and temperature, on physiological functions in humans.

Part of the Department of Physiology and Pharmacology

Human performance in extreme environments

Environmental physiology is commonly associated with human performance in extreme environments, such as aviation, diving and human activities in polar and desert climates. However, the physiological functions challenged under such conditions typically play fundamental roles even in more routine and daily-life activities. Thus, interventions used in environmental physiology research include different types of physical loading as means to tease out mechanisms underlying normal physiological functions.

The Environmental Physiology Division is situated Solna where it shares personnel and laboratory facilities with the Swedish Aerospace Physiology Centre, SAPC.

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Gunnar Schulte

Acting group leader
+46852487933

Staff and contact

Group leader

All members of the group

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Berzelius väg 13, Solna, 171 65 Solna

Environmental physiology

Research activities

Research at the Environmental Physiology commonly concerns medical and physiological problems that may occur in military settings, and the group is tasked to provide expert advice to the Swedish Armed Forces regarding physical load or risk for physical/medical injuries in humans. Accordingly, the research is to a large extent funded by grants from the Armed Forces. The research activities may be described by three main projects, which, in turn, consist of several minor projects:

In certain conditions, humans are requested to perform hard physical work in extreme climates or at high altitudes. The project investigates physiological responses during exercise in hot climates, particulary in individuals wearing airtight clothing and carrying heavy equipment, for instance military soldiers or fire fighters. In addition, the project investigates physiological responses to cooling of the body core (hypothermia) and peripheral regions. A current focus of the project is on the interaction between factors that per se increase the risk of central or peripheral cooling during cold exposure. Examples of such factors are hypoxia, physical fatigue and sleep depravation.

Barophysiology concerns effects on healthy humans as exerted by changes in the ambient pressure. Substantial changes in ambient pressure are induced upon ascent to high altitude or during diving. All living organisms are affected by hydrostatic pressure changes but, save for during extreme deep diving, effects induced by hydrostatic pressure changes per se are minute in comparison with effects induced by changes in the partial pressures of the breathing-gas components, either secondary to the changed ambient pressure or caused by introducing artificial breathing-gas mixtures. Thus, to a large extent, barophysiology concerns the effects of different gases on physiological responses in humans. Since humans cannot remain immersed more than a few minutes without breathing gas supply, a large portion of the research is focused on the interplay between the human and his/her breathing apparatus.

Gas mixtures and decompression tables

Within this project we develop and test decompression tables for breathing gases other than air (nitrox, trimix), to meet requests from the Swedish Navy. In addition, we conduct experiments aimed at increasing our understanding of the mechanisms underlying decompression sickness. The work includes both computer simulations and tests on healthy human subjects.

Physiology-based adjustments of breathing apparatuses

This project concerns investigations on the effects of breathing apparatuses on human respiratory functions, as well as techniques for surveillance and testing of oxygen dosage whilst using closed-circuit breathing apparatuses.

High-altitude physiology and hypoxia

Within this project we conduct investigations of the effects on physiological and cognitive functions of reduced partial pressures of oxygen and of high-altitude exposures. The project also investigates factors affecting decompression sickness in conjunction with flying aircraft with low cabin pressures.

Research in Aerospace Physiology comprises three projects: Spatial disorientation, Increased gravitoinertial load, Weightlessness.

Spatial disorientation

Spatial disorientation is the single most common cause of serious aircraft mishaps. Spatial disorientation develops during flying because visual references are commonly lacking and because the vestibular system is incapable of correctly detecting certain movements under conditions where the gravitoinertial force vector deviates from normal (1 G). We investigate how complex stimulation of the vestibular system in a centrifuge and/or aircraft affects an individual’s spatial orientation.

Increased gravitoinertial load

Pilots flying high-performance aircraft may be exposed to gravitoinertial loads as high as 9 times the gravity vector (9 G), which results in considerable strain on several organ systems. For instance, to maintain adequate arterial pressure at the level of the head while exposed to 9G in the head-to-foot direction, arterial pressure at heart level must be increased threefold from normal values. This can be achieved by pressurizing both the pilot’s anti-G suit and his/her breathing gas, but also by means of blood-pressure increasing muscular straining maneuvers performed by the pilot. The project investigates physiological responses to increased G load and develops G-protective garments/techniques.

Weightlessness

Several of the physiological adaptations to weightlessness may be induced by means of ground-based (1 G) simulation models, of which prolonged, sustained recumbency (bed rest), in the horizontal or slightly head-down position, is the most common. The project investigates physiological responses - cardiovascular, musculoskeletal, metabolic - to sustained bed rest. Such experiments are typically conducted within the frame of a multinational collaboration. Brief exposures to weightlessness can be induced by controlled free fall in aircraft, commonly termed parabolic flight. The environmental physiology group uses also this technique to study physiological responses to weightlessness.

Experimental facilities

To a large extent, the equipment/facilities used at the Division of Environmental Physiology has been developed to cope with physiological problems that humans encounter during flying or diving.

Centrifuges

The gondola centrifuge in Solna, which at a peripheral speed of 117 km/h generates a centrifugal force fifteen times higher than the gravity force vector (15 G), was constructed because of the great number of military aircraft accidents induced by pilot loosing consciousness during advanced flying. In the centrifuge pilots could practice techniques to maintain adequate arterial pressure in the brain during exposure to high G loads. The centrifuge is, however, mainly used for research and development, for instance for development of G-protective equipment and for studies concerning basic physiology, e.g. circulatory, respiratory and vestibular functions.

The Division of Environmental Physiology conducts experimental studies also in the human-use centrifuge at Malmslätt close to Linköping. With a radius of 9.1 m (from the center of rotation to the center of the gondola) and a main engine weighing 90,000 kg this centrifuge has a capacity to accelerate to a peripheral speed of 150 km/h within a second. The gondola is equipped with one of the worlds most advanced flight simulators, termed “Dynamic Flight Simulator, DFS”, allowing the pilot/test subject to "fly" high-performance aircraft in a virtual surrounding whilst controling the G-force in the head-seat-direction by simulating turns with varying radius and at different velocities. The research conducted in this facility predominantly deals with risk factors encountered during military operations in high-performance aircraft and in helicopters, for instance G-induced loss of consciousness and spatial disorientation. Equipped with separate gimbal engines, the gondola can move (roll and pitch) irrespective of the resulting gravitoinertial vector, offering unique possibilities of investigating how human spatial orientation is governed by the different components of the vestibular system.

Pressure chambers and immersion pools

The predominant tools used to investigate the effects of changed ambient pressure are hyper- and hypobaric chambers. At the laboratory in Solna, the Environmental Physiology group has both a hypobaric chamber, in which high-altitude exposures (up to >20 000 masl) are simulated, and a hyperbaric chamber, in which diving is simulated (150 m Sea water). The Environmental Physiology group has a close collaboration with the Swedish Navy and hence has access to a swim flume, indoor pools and a free-escape tower located at the Diving and Naval Medicine Center (DNC) in Karlskrona as well as the large hyperbaric facility.

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Hans Berg

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Andreas Brink

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Antonis Elia

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Mikael Gennser

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Michail Keramidas

Assistant Professor

Roger Kölegård

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Maaike Moes

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Lena Norrbrand

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Dilja Sayfulaeva

Rickard Ånell

Affiliated to Research

Team - Lars Karlsson

Lars Karlsson Researchgroup

Our research group uses changes in the physical environment as tools to investigate physiological and pathophysiological processes in humans. Our research facilities include pressure chambers for altitude and diving simulations, a water tank for immersion studies, and a human centrifuge for high-gravity exposure.

Experiments in weightlessness are performed during parabolic flights and space flight under the coordination of the European Space Agency, ESA and National Aeronautics and Space Administration, NASA.

Effects of gravity on pulmonary function

The distributions of ventilation and perfusion in the lungs have been studied at zero gravity during space flight and at increased gravity in a human centrifuge. Recent findings based on the exchange of inert gas mixtures suggest that gravity-related factors are less important than previously thought for the distribution of ventilation, and that only inter-regional but not intraregional inhomogeneity of lung perfusion is gravity-dependent.

A better understanding of the effects of gravity on pulmonary function has important implications for intensive care patients. We have studied the topographical distributions of ventilation and perfusion during increased gravity in supine and prone position in humans in order to develop a model for ventilation/perfusion mismatch in severe pulmonary insufficiency.

Cardiovascular effects of space flight or long-term bedrest

The cardiovascular effects of long-term absence of gravity in the head-to-foot direction has been studied in healthy humans, either in astronauts during and after space flight or in volunteers during and after long-term bedrest. Time courses for the development of and recovery from cardiovascular deconditioning have been determined. Recent findings suggest that blood pressure control during dynamic and isometric exercise is impaired after long-term absence of gravity in the head-to-foot direction.

New diagnostic and therapeutic methods for patients with lung embolism

Divers are at risk of the formation of gas bubbles in the tissues and in the blood during decompression. So are astronauts and aviators when exposed to extreme altitude. We have shown that venous gas emboli - gas bubbles that are usually filtered by the lungs without causing decompression sickness - changes the nitric oxide excretion from the lungs. Similar changes take place in experimental lung embolism which suggests new diagnostic and therapeutic methods for patients with lung embolism.

Airway nitric oxide in microgravity (1)

Studies of signs of airway inflammation after subchronic dust inhalation in weightlessness where dust never settles.

Airway nitric oxide in microgravity (2)

Detection of venous gas emboli after decompression during space walks using exhaled nitric oxide as an indicator. Parallel ground-based studies include human experiments in our altitude chamber, and animal experiments where lung embolism is induced with gas and solid elements.

Hypergravity as a model of Acute Respiratory Distress Syndrome

Prone and supine humans are studied during up to 5 times normal gravity. Mechanisms of arterial desaturation are studied using Single-Photon Emission Tomography and interference with pulmonary hypoxic vasoconstriction.

Efficiency of dynamic leg exercise in hypergravity

The internal cost of leg motion is studied and effects of leg mass (inertia) is separated from those of leg weight (gravity).

Our research group has unique research facilities that may be used by other researchers at Karolinska Institutet, or by other universities or organisations:

Pressure chambers

  • 8 m3 hyperbaric chamber, for experiments in a high-pressure environment
  • Maximum pressure of 16 bar corresponding to a simulated water depth of 150 metres
  • Temperature control system with a very high capacity to compensate for pressure-induced changes in chamber temperature
  • 25 m3 hypobaric chamber for altitude experiments.

Both chambers have multiple hull penetrations for power and gas supply, gas analysis and signal transmission.

  • 7.2 meter radius human centrifuge, for high-gravity experiments
  • The centrifuge gondola can accommodate one subject and a total "payload" mass of 300 kg
  • Up to 9 times normal gravity (9 g) with humans and 15 g with equipment only
  • Platform designed for animal experiments on the opposite centrifuge arm
  • 50 slip-rings for signal transmission from the gondola or platform
  • 10 slip-rings for power transmission.

Routine monitoring of subjects includes audiovisual communication, electrocardiogram and peripheral vision. Additional physiological monitoring equipment includes invasive or non-invasive blood pressure, respiratory gas analysis and remote-controlled syringes for blood sampling or infusions.
 

Microgravity (weightlessness)

Access to this unique environment is obtained through the European Space Agency. Experiments requiring long-term microgravity are performed on the International Space Station and experiment requiring only transient microgravity are performed during parabolic flight in an aircraft.

Contact

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Lars Karlsson

Principal Researcher
+46852486890
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Dag Linnarsson

Professor
+46852482934