Document Detail


Exercise carbon dioxide (CO2) retention with inhaled CO2 and breathing resistance.
MedLine Citation:
PMID:  22908838     Owner:  NLM     Status:  In-Process    
Abstract/OtherAbstract:
Combined effects on respiratory minute ventilation (VE)--and thus, on end-tidal carbon dioxide partial pressure (P(ET)CO2)--of breathing resistance and elevated inspired carbon dioxide (CO2) had not been determined during heavy exercise. In this Institutional Review Board-approved, dry, sea-level study, 12 subjects in each of three phases exercised to exhaustion at 85% peak oxygen uptake while V(E) and P(ET)CO2 were measured. Participants inhaled 0%, 1%, 2% or 3% CO2 in air, or 0% or 2% CO2 in oxygen, with or without breathing resistance, mimicking the U.S. Navy's MK 16 rebreather underwater breathing apparatus (UBA). Compared to air baseline (0% inspired CO2 in air without resistance): (1) Oxygen decreased baseline V(E) (p < 0.01); (2) Inspired CO2 increased V(E) and P(ET)CO2 (p < 0.01); (3) Resistance decreased V(E) (p < 0.01); (4) Inspired CO2 with resistance elevated P(ET)CO2 (p < 0.01). In air, V(E) did not change from that with resistance alone. In oxygen, V(E) returned to oxygen baseline. End-exercise P(ET)CO2 exceeded 60 Torr (8.0 kPa) in three tests. Subjects identified hypercapnia poorly. Results support dual optimization of arterial carbon dioxide partial pressure and respiratory effort. Because elevated CO2 may not increase V(E) if breathing resistance and VE are high, rebreather UBA safety requires very low inspired CO2.
Authors:
Barbara E Shykoff; Dan E Warkander
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Undersea & hyperbaric medicine : journal of the Undersea and Hyperbaric Medical Society, Inc     Volume:  39     ISSN:  1066-2936     ISO Abbreviation:  Undersea Hyperb Med     Publication Date:    2012 Jul-Aug
Date Detail:
Created Date:  2012-08-22     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9312954     Medline TA:  Undersea Hyperb Med     Country:  United States    
Other Details:
Languages:  eng     Pagination:  815-28     Citation Subset:  IM; S    
Affiliation:
Navy Experimental Diving Unit, Panama City, Florida, USA. barbara.shykoffca@navy.mil
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