Gap DCS2: We do not know the contribution of specific DCS risk factors to the development of DCS in the Space Flight Exploration Environment.
Last Published:  07/30/21 01:05:31 PM (Central)
Responsible Element: Human Health Countermeasures (HHC)
Status: Closed
Closure Rationale

While DCS research and operational development is of high importance, this work is now funded by organizations other than HRP, in a collaborative joint effort. Details of DCS-related work that is already being done (or planned to be done) may be found in the comprehensive NASA technical paper “Integrated Extravehicular Activity Human Research and Testing Plan” (NASA/TP-2019-220232). As part of HRP’s new strategy, it will contribute to these operational efforts as needed.

Closure Documentation:
No Closure Documentation Available
Description

Initial State: 
It is well accepted that gas bubbles through some mechanism are the initial cause of the symptoms of DCS.  Gas bubble formation and growth can potentially occur during decompressions from higher to lower ambient pressure. Mechanisms that cause bubble formation, growth and elimination are not well understood. It is known that physiological and environmental factors contribute to DCS. We lack information on their importance or interrelationships in the space flight environment. For instance, DCS has been seen in ground-based PB validation studies, but has yet to be documented during spaceflight EVA. Several factors may contribute to this difference including the possibility that microgravity causes physiological changes in favor of reducing DCS risk. It could also be that flight operational procedures have always been implemented with greater safety margin than tested on Earth. With an expectation to get out the suit port and begin an EVA in 10-15 minutes, this safety margin will be gone.

Also, different tissues have different saturation rates that affect N2 elimination. Exercise can accelerate N2 elimination from tissues although it may speed up bubble formation, so there is a cost/benefit accounting required to use exercise as a benefit. There also may be a difference in tissue N2 elimination while in microgravity.



Interim Stages:

#

Task Title

Step #

Specific Aim

Step Weight

Status: 0=incomplete 1=complete

1

Nucleation Mechanisms

1

To understand the individual and combined effects of microgravity simulation (non-ambulation) and prebreathe exercise, under the operationally relevant conditions of the two hour PRP Phase II exercise prebreathe protocol.

30%

0

2

To understand if the order of heavy and light exercise is consequential in the generation and removal of exercise induced bubble nuclei.

10%

0

2

VGE in Microgravity

1

Development of VGE monitoring capabilities in microgravity while depressurized

10%

0

2

Understand the differences in VGE patterns in microgravity compared to Earth

15%

0

5

N2 Elimination

1

Understand the differences in N2 washout patterns in microgravity compared to Earth

10%

0

6

Intermittent Recompression

1

Understand the relationship of intermittent recompression as it relates to bubble elimination

10%

0

7

Animal Model of Recompression

1

Understand the effect of the 10.2 psi to 14.7 psi repress/depress scenario on VGE and DCS outcomes

5%

0

8

Abbreviated Purge

1

Empirical data to validate predicted DCS and VGE outcomes with different N2 concentrations remaining in the EVA suit

10%

0

Closure metric €= Step Weight x Completion Status

Gap Closure:

0%



Approach:

This will be a combined approach using data mining combined with ground and flight based studies on risk factors and/or ID precursor conditions to DCS. Certain tasks will evaluate factors that contribute to DCS on the ground and then test those same factors in-flight to determine the effect of microgravity on DCS. Other tasks will characterize the N2 elimination rates in different tissues, evaluate the effect of exercise on N2 elimination and study how microgravity may affect N2 elimination. Results of these tasks will then be used to increase the predictive accuracy of current DCS models.

 


Gas bubble formation and growth can potentially occur during decompressions from higher to lower ambient pressure. The NASA Tissue Bubble Dynamics Model (TBDM) characterizes bubble growth and is one the key models currently used by NASA to evaluate DCS risk, but the onset or genesis of bubbles is still not well understood. Tasks to address this gap will look at the mechanisms that cause bubble formation as well as the factors that affect bubble growth and elimination. Results of these studies will be included in the TBDM as well as new models evaluating the probability of DCS.

Target for Closure
Obtain effect size as a function of individual variance for each risk factor of interest in order to include in the DCS prediction model.
Mappings
Risk Risk of Decompression Sickness [inactive]
You are here! Gap DCS2: We do not know the contribution of specific DCS risk factors to the development of DCS in the Space Flight Exploration Environment.
Completed

Multi-Disciplinary Research Plans

Documentation:
No Documentation Available