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Release date: 07/01

The Effects of EVA and Long-Term Exposure to Microgravity on Pulmonary Function (PuFF)

Missions: Expedition Three, ISS Mission 7A.1, STS-105 Space Shuttle Flight

Experiment Location on ISS: Human Life Sciences experiment which will use equipment in the Human Research Facility located in the U.S. Laboratory

Principal Investigator: John B. West, M.D., Ph.D., University of California, San Diego

Project Manager: Suzanne McCollum, NASA Johnson Space Center, Houston

Cosmonaut Vladimir N. Dezhurov performs Pulmonary Function in Flight (PuFF) training in the Space Station Destiny laboratory mockup/trainer at NASA's Johnson Space Center's Systems Integration Facility. Cosmonaut Vladimir N. Dezhurov performs Pulmonary Function in Flight (PuFF) training in the Space Station Destiny laboratory mockup/trainer at NASA's Johnson Space Center's Systems Integration Facility. (NASA/JSC)


Just as rising too quickly to the water's surface can cause scuba divers to suffer decompression sickness - commonly called "the bends," sudden exposure to high altitude can result in the same symptoms in pilots and space crews.

Decompression sickness results from exposure to low barometric pressures that cause inert gases - mainly nitrogen - that are normally dissolved in body fluids and tissues to come out of physical solution and form bubbles. A common symptom is joint pain, which is how the nickname "the bends" was earned. Symptoms in more serious cases include headaches, memory loss and blurred vision.

Extra vehicular activities (EVA) in space, or spacewalks, pose a risk of nitrogen bubble formation because they provide a very low pressure environment. The human body is normally exposed to 14.7 pounds per square inch (1.034 kilograms per square centimeter) of pressure - the pressure of the Earth's atmosphere at sea-level and inside the Space Station. A space suit provides only 4.3 pounds per square inch (0.302 kilograms per square centimeter) of atmospheric pressure.

Additionally, little is known about how the lungs can be effected by long-term exposure to microgravity - the near-weightlessness found in the environment of space.

PuFF, or pulmonary function in flight, research during Expedition Three focuses on lung function both following EVA and inside the International Space Station - laying the groundwork for future experiments which are key to understanding and maintaining crew health.

Experiment Operations

PuFF manual breathing valve assembly PuFF manual breathing valve assembly (NASA/JSC)

Each PuFF session includes five lung function tests, which involve breathing only cabin air. The focus is on measuring changes in the evenness of gas exchange in the lungs, and on detecting changes in respiratory muscle strength. Unevenness of gas exchange is a hallmark of virtually every pulmonary disease, and gas exchange can be temporarily disrupted by the filtration by the lungs of nitrogen bubbles in the bloodstream. Changes in respiratory muscle strength may result from long periods in the absence of gravity.

The first PuFF test is two weeks into the mission, then will occur monthly. Each time, the crew will set up and calibrate the equipment, perform the tests and collect the data, then take down and stow the equipment.

For each planned EVA, a crew member performs a PuFF test within one week prior to the EVA. Following the EVA, those crew members perform another test, either on the same day the EVA is completed or the following day.

If a crew member performs two or more EVAs in quick succession, tests are performed immediately after every EVA to document the effect of repeated exposure of the lungs to the low-pressure environment of the space suits.

This experiment utilizes the Gas Analyzer System for Metabolic Analysis Physiology, or GASMAP, located in the Human Research Facility (HRF), along with a variety of other PuFF equipment including a manual breathing valve, flowmeter, pressure-flow module, pressure and volume calibration syringes and disposable mouthpieces.

Data are stored in the personal computer located in the Human Research Facility and transmitted to the ground.

Background/Flight History

PuFF research on the International Space Station builds on research conducted during Spacelab missions during the last decade.

Comprehensive measurements of lung function in orbiting astronauts were first made during Spacelab Life Sciences (SLS) missions SLS-1 in June 1991 and SLS-2 in October 1993. Astronauts measured blood flow through the lungs, the ability of the lung to take up oxygen and lung volumes.

The Life and Microgravity Spacelab mission in June 1996 focused on lung function following heavy exercise, how the body reacts to inhaled carbon dioxide and how gas is distributed within the lung.

Spacelab's Neurolab mission in April 1998 measured respiration during sleep and on the body's mechanisms which control how much we breathe. PuFF research will continue during Expeditions Four and Five.


A better understanding of the effects of gravity - or lack of gravity - on the human pulmonary system may benefit clinical medicine on Earth. Gravity affects the way the lungs operate and may even exaggerate some lung disorders, such as emphysema and tuberculosis. For example, gravity causes blood flow through the lungs to be greatest near the bottom. Also, the weight of the rib cage and of the lungs themselves distorts the anatomy of the lungs.

In space, changes in lung anatomy may cause changes in lung performance. Research is important to maintain crew health as we prepare for longer missions in space. For crew members who stay inside a spacecraft, there could be a buildup of noxious gases that could adversely affect pulmonary function. During EVA, nitrogen bubble formation is possible even without symptoms of decompression sickness.

By utilizing future lung experiments on the International Space Station and research conducted during Expedition Three, scientists hope to find new ways to protect the health of space travelers in the years ahead, and to gain a better understanding of the effects of gravity on the lung here on earth.

More Information

For more about Expedition Three science experiments, visit:

Steve Roy
Public Affairs Office
(256) 544-0034

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