Hemoglobin Oxygen Saturation with Mild Hypoxia and Microgravity.

Introduction: Microgravity (μG) exposure and even early recovery from μG in combination with mild hypoxia may increase the alveolar-arterial oxygen (O2) partial pressure gradient.

Methods: Four male astronauts on STS-69 (1995) and four on STS-72 (1996) were exposed on Earth to an acute sequential hypoxic challenge by breathing for 4 min 18.0%, 14.

Venous Gas Emboli and Ambulation at 4.3 psia.

Introduction: Ambulation during extravehicular activity on Mars may increase the risk of decompression sickness through enhanced bubble formation in the lower body.

Hypotheses: walking effort (ambulation) before an exercise-enhanced denitrogenation (prebreathe) protocol at 14.7 psia does not increase the incidence of venous gas emboli (VGE) at 4.

Hypobaric Decompression Sickness Treatment Model.

Introduction: The Hypobaric Decompression Sickness (DCS) Treatment Model links a decrease in computed bubble volume from increased pressure (ΔP), increased oxygen (O2) partial pressure, and passage of time during treatment to the probability of symptom resolution [P(SR)]. The decrease in offending volume is realized in two stages: 1) during compression via Boyles law; and 2) during subsequent dissolution of the gas phase via the oxygen window.

Methods: We established an empirical model for the P(SR) while accounting for multiple symptoms within subjects.

The preferred walk to run transition speed in actual lunar gravity.

Quantifying the preferred transition speed (PTS) from walking to running has provided insight into the underlying mechanics of locomotion. The dynamic similarity hypothesis suggests that the PTS should occur at the same Froude number across gravitational environments. In normal Earth gravity, the PTS occurs at a Froude number of 0.

Probability of hypobaric decompression sickness including extreme exposures.

Introduction: The fitting of probabilistic decompression sickness (DCS) models is more effective when data encompass a wide range of DCS incidence. We obtained such data from the Air Force Research Laboratory Altitude Decompression Sickness Research Database. The data are results from 29 tests comprising 708 human altitude chamber exposures (536 men and 172 women).

Protective mechanisms in hypobaric decompression.

Background: To reduce bubble formation and growth during hypobaric exposures, a denitrogenation or nitrogen "washout" procedure is performed. This procedure consists of prebreathing oxygen fractions as close to one as possible (oxygen prebreathe) prior to depressurization before ascending to the working altitude or low spacesuit pressures. During the NASA prebreathe reduction program (PRP), it was determined that the addition of a light arm exercise to short, individually designed, performance-based heavy exercise (dual cycle ergometry) during an abbreviated 2-h prebreathe (F1O2 - 1.

Oxygen consumption at altitude as a risk factor for altitude decompression sickness.

Introduction: The existence of a general influence of exercise on the incidence of decompression sickness (DCS) has been known for more than a half-century. However, quantification of the effect has not been done for several reasons, including isolation of exercise as the only variable. The DCS database at Brooks City-Base, TX, contains detailed physiologic information on over 3000 altitude exposures.

Age affects severity of venous gas emboli on decompression from 14.7 to 4.3 psia.

Introduction: Variables that define who we are, such as age, weight and fitness level influence the risk of decompression sickness (DCS) and venous gas emboli (VGE) from diving and aviation decompressions. We focus on age since astronauts that perform space walks are approximately 10 yr older than our test subjects. Our null hypothesis is that age is not statistically associated with the VGE outcomes from decompression to 4.

Patent foramen ovale and paradoxical systemic embolism: a bibliographic review.

A patent foramen ovale (PFO) has been reported to be an important risk factor for cardioembolic cerebrovascular accidents through paradoxical systemic embolization, and it provides one potential mechanism for the paradoxical systemic embolization of venous gas bubbles produced after altitude or hyperbaric decompressions. Here, we present in a single document a summary of the original findings and views from authors in this field. It is a comprehensive review of 145 peer-reviewed journal articles related to PFO that is intended to encourage reflection on PFO detection methods and on the possible association between PFO and stroke.