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The Effects of EVA and Long-Term Exposure to Microgravity on Pulmonary Function (PuFF)
11.06.09

Overview | Description | Applications | Operations | Results | Publications | Images

Experiment/Payload Overview

Brief Summary

Various breathing tests were performed before, during, and after flight to see if pulmonary function is affected by long-term exposure to microgravity or extravehicular activity (spacewalks). Changes due to long stays on-orbit, either from removal of gravity itself or from exposure to contaminants in the closed spacecraft environment, could adversely affect crew health. Changes associated with spacewalks could indicate an increased risk of decompression sickness, commonly known as the bends.

Principal Investigator

  • John B. West, M.D., Ph.D., University of California - San Diego, La Jolla, CA

    • Co-Investigator(s)/Collaborator(s)

  • G. Kim Prisk, Ph.D., University of California - San Diego, La Jolla, CA
  • Ann Elliott, Ph.D., University of California - San Diego, La Jolla, CA
  • Manuel Paiva, Ph.D., Universite Libre de Bruxelles, Brussels, Belgium
  • Janelle M. Fine, University of California - San Diego, La Jolla, CA
  • Trevor K. Cooper, University of California - San Diego, La Jolla, CA

    • Payload Developer

    Johnson Space Center, Human Research Program, Houston, TX

    Sponsoring Agency

    National Aeronautics and Space Administration (NASA)

    Expeditions Assigned

    |3|4|5|6|

    Previous ISS Missions

    Other pulmonary function experiments were conducted on STS-40, STS-55, STS-58, STS-78 and STS -90.

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    Experiment/Payload Description

    Research Summary

    • This experiment examined, using non-invasive techniques, the effect of long-term exposure to microgravity and the effects of extravehicular activity (EVA) on pulmonary (respiratory) function by studying crewmembers before and after flight, monthly during flight, and before and after performing EVAs.


    • It also measured aspects of pulmonary function that may be affected by long-term exposure to noxious gases or particulate matter that may accumulate in the atmosphere of the ISS. These measurements form a precursor set of studies that can be followed up in more detail when more complete hardware is available on the ISS.

    Description

    This experiment examined the effect of long-term exposure to microgravity and EVA on pulmonary function by studying crewmembers before and after they performed EVAs. It examined whether pulmonary function was affected by long-term exposure to noxious gases or to particulate matter that may accumulate in the atmosphere of ISS.

    There is a large difference in pressure between the inside of ISS and in the spacesuit used for EVAs. The effects of this difference in pressure pose a significant risk of decompression sickness (DCS), known in the diving world as "the bends", for spacewalkers, including bubble formation within the blood. Even if the symptoms of DCS do not occur, venous gas microbubbles can alter pulmonary function, increasing the risk of forming a venous embolism.

    Each Pulmonary Function in Flight (PuFF) session consisted of five noninvasive tests with the crew breathing only cabin air. The tests measured the pulmonary system's ability to exchange gases, the amount of air inspired and expired as a function of time, and the maximum pressure of the air inhaled and exhaled. The analysis looked for markers that indicate that the lungs have been weakened from exposure to microgravity, or that the body's ability to exchange and distribute gases has been disrupted.

    PuFF hardware, including a manual breathing valve and flow meter, was attached to the HRF gas analyzer system for metabolic analysis physiology (GASMAP) hardware, physiological signal conditioners, and the HRF computer. GASMAP measured the volume of gases inspired and expired, frequency of respiration, and ambient barometric pressure.

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    Applications

    Space Applications

    There is a large difference in pressure between the inside of the Station and in the spacesuit used for EVA (extra vehicular activity). The effects of that difference in pressure pose a significant risk of decompression sickness for spacewalking astronauts (similar to a scuba diver getting the bends), including bubble formation within the blood. Even if symptoms of decompression sickness do not occur, venous gas microbubbles can alter pulmonary function. Noninvasive tests of pulmonary function that are altered by changes in the pulmonary blood vessels are an ideal way to follow a subject over the course of multiple EVAs, especially since many EVAs are required for ISS construction and maintenance. This study also helped assess the effects on pulmonary function of the buildup of particulates or other contaminating gases that can occur in the closed spacecraft environment. Results from this experiment may help develop countermeasures for pulmonary problems that occur aboard the ISS, further safeguarding crew health.

    Earth Applications

    On Earth, many people experience decompression sickness or "the bends" while diving. This is a result from the gasses (oxygen, nitrogen and small amounts of other gasses) that are breathed in while diving. The gasses are under pressure, causing not all the oxygen to be absorbed but the nitrogen will be producing bubbles in the blood stream. The results from Puff may help develop an improved SCUBA systems that will provide maximize that about of oxygen absorbed by the body while diving.

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    Operations

    Operational Requirements

    Two to three Station crew members participated in the PuFF experiment each increment. The first data collection occurred approximately two weeks into the mission and sessions were repeated monthly thereafter. Crewmembers assigned to conduct EVAs performed a PuFF session within one week prior to the EVA and again after the EVA (preferably on the same day, but in practice on the day following the EVA). An abbreviated session of only two breathing tests could be implemented on the day of EVA, if dictated by time constraints, or if multiple EVAs were conducted close together.

    Operational Protocols

    On the day of a PuFF session, the crew set up and calibrated the equipment. All participating crewmembers then took turns perfoming a predetermined sequence of breathing tests (either the full five-test session or the abbreviated session). After testing with all crewmembers was complete, the crew conducted a final calibration, saved the data on the computer, and disassembled the equipment for stowage. The data was downlinked to the ground at the next opportunity.

    In addition to the in-flight sessions, crewmembers were tested four times preflight and four times post-flight. These sessions included both the in-flight protocol plus additional tests that could not performed on-orbit due to hardware limitations.

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    Results/More Information

    Ten ISS crewmembers each performed pulmonary function tests several times preflight, at monthly intervals throughout their four to six month stays on the ISS and multiple times postflight. Data from the EVA portion of the study have been analyzed and results were presented at the 2004 meeting of the Aerospace Medical Association. Because measurements could only be performed on the day following EVA due to logistical constraints, the researchers were unable to determine an acute effect of EVA on lung function. However, the small effect observed on the day following EVA suggests that current denitrogenation protocols prevent the decompression stress associated with EVA from causing any major lasting disruption to gas exchange in the lung.

    Results of this investigation indicate that long-duration (four to six months) exposure to microgravity does not detrimentally affect the mechanical aspects of lung function, at least in terms of vital capacity, an indicator of environmentally caused changes in pulmonary function, and respiratory muscle strength, and does not result in an impairment of pulmonary gas exchange, although there appears to be a reduction in metabolic rate. Taken in the context of previous studies on Skylab, the results suggest that, provided that an environment with normal oxygen conditions and barometric pressure equivalent to sea level pressure is maintained, it is reasonable to expect no significant degradation in these most basic measures of pulmonary function in long-duration microgravity (Prisk, 2005, 2006, 2008).

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    Related Web Sites
  • NASA Fact Sheet
  • International Space Station Medical Project (ISSMP)
  • UCSD Physiology / NASA Lab

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    Publications

    Results Publications
    • Prisk GK, Fine JM, Cooper TK, West JB. Lung Function is unchanged in the 1 G environment following 6-months exposure to microgravity. European Journal of Applied Physiology. 2008 ;103: 617 - 623.
    • Prisk GK, Fine JM, Cooper TK, West JB. Vital Capacity, Respiratory Muscle Strength and Pulmonary Gas Exchange during Long-Duration Exposure to Microgravity. Journal of Applied Physiology. 2006 ;101:439-447.
    • Prisk GK, Fine JM, Cooper TK, West JB. Pulmonary gas exchange is not impaired 24 h after extravehicular activity. Journal of Applied Physiology 2005 ;99(6):2233-8.

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    Related Publications
    • Prisk GK. The Lung in Space. Clinics in Chest Medicine. ;26:415-438. 2005
    • Prisk GK, Guy HJ, Elliott AR, West JB. Cardiopulmonary adaptation to weightlessness. Journal of Gravitational Physiology. ;1(1):118-121. 1994
    • Balldin UI, Pilmanis AA, Webb JT. The effect of simulated weightlessness on hypobaric decompression sickness. Aviation, Space and Environmental Medicine. ;73(8):773-778. 2002
    • Dervay JP, Powell MR, Butler B, Fife CE. The effect of exercise and rest duration on the generation of venous gas bubbles at altitude. Aviation, Space and Environmental Medicine. ;73(1):22-27. 2002
    • Cowell SA, Stocks JM, Evans DG, Simonson SR, Greenleaf JE. The exercise and environmental physiology of extravehicular activity. Aviation, Space and Environmental Medicine. ;73(1):54-67. 2002
    • Pilmanis AA, Webb JT, Kannan N, Balldin U. The effect of repeated altitude exposures on the incidence of decompression sickness. Aviation, Space and Environmental Medicine. ;73(6):525-31. 2002
    • Prisk GK, Fine JM, Elliott AR, West JB. Effect of 6 degrees head-down tilt on cardiopulmonary function: comparison with microgravity. Aviation, Space and Environmental Medicine. ;73(1):8-16. 2002

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    Images

    imageAstronaut Peggy Whitson trains to perform a test of lung function as part of the PuFF experiment. Image courtesy of University of California.
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    imageAstronaut Don Thomas participates in ground training for the PuFF experiment. Crew members participated in tests of lung function following the decompression they experience after an EVA. Image courtesy of University of California.
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    imageNASA Image: ISS006E07133 - Astronaut Donald R. Pettit, Expedition Six NASA ISS Science Officer, works to set up Pulmonary Function in Flight (PuFF) hardware in preparation for a Human Research Facility (HRF) experiment in the Destiny laboratory on the International Space Station (ISS). Expedition Six is the fourth and final expedition crew to perform the HRF/PuFF Experiment on the ISS.
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    imageNASA Image: ISS006348005 - Astronaut Donald R. Pettit, Expedition 6 NASA ISS science officer, uses a camera during a session of extravehicular activity (EVA) on 15 January 2003.
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    Information Provided and Updated by the ISS Program Scientist's Office
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