Harnessing splenic adaptations to improve diving capabilities
Abstract
Current evidence indicates that efforts to optimize splenic function are important for Navy and Special Warfare divers given the potential to improve O2 carrying capacity, augment pH buffering, and/or enhance pro-inflammatory microparticle clearance. The resulting diver health and performance benefits of harnessing such splenic adaptations are wide-ranging and include improvements in gas exchange, which could improve physical and mental performance, a reducedrisk of CO2 (and/or O2) toxicity, and/or a lower risk of decompression sickness. Thus, the proposed project will experimentally determine if spleen size can be increased and/or spleen function can be improved with repeated breath-hold diving related exposures in people without breath-hold diving ancestry (Aim 1). We will also determine the genotypic (Aim 2) and environmental (Aim 3) modulators underlying the observed phenotypic adaptations. This will be accomplished by exposing men and women without a history of breath-hold diving to hypoxic challenges that simulate the demands of breath-hold diving over a 4 h period on each day for 14 consecutive days.The breath-hold diving exposures will start with five maximal breath-holds that will be equally spaced over the first 30 min. This will be followed by 3 h of breathing 14% oxygen. During the final 30 min, the participants will again complete five maximal breath-holds. The simulated breathhold diving exposures will take place during: i) head out cold water (22C) immersion, ii) headout thermoneutral water (35C) immersion, and iii) exposure to thermoneutral air (26C), which will be randomly assigned to a given participant. Primary dependent variables include spleen volume and spleen function, which is operationally defined as the capacity to: i) constrict the spleen and mobilize red blood cells during breath-holds, ii) clear circulating pro-inflammatorymicroparticles, and iii) clear dysfunctional (i.e., stiff) red blood cells. These variables will be measured before, during, and following simulated breath-hold diving exposures on the 1st, 7th, and 14th consecutive days of exposure. Changes in PDE10A gene expression, which is associated with both spleen size in native diving populations and augmented thyroid function in the generalpopulation, and associated downstream effectors (e.g., triiodothyronine, thyroxine, erythropoietin) will also be measured. Collectively, we expect that our project will provide the basis for future work aiming to directly exploit splenic adaptations to augment autonomous diving operations. This could be accomplished in three ways. First, we will work to identify and refine methods to optimize improvements in splenic volume and function in divers. Second, we will work to determine whether the observed splenic adaptations attenuate the risk of clinical outcomes associated with diving, such as the risk of decompression sickness, CO2 toxicity, or O2 toxicity. Third, we will work to examine whether the observed splenic adaptations and associated improvements in gas exchange provide an ergogenic advantage to the warfighter.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 20, 2020
- Source ID
- N000142012593
Entities
People
- Zachary J Schlader
Organizations
- Indiana University
- Office of Naval Research
- United States Navy