Effect of partial pressures of end expiratory gases on voluntary breath holding time

Abstract

Abstract : INTRODUCTION - The break
point of voluntary breath hold is believed to
be brought about by multiple factors including
partial pressures of arterial pCO2
and pO2. This study aims to look at the
effect of partial pressures of arterial blood
gases on voluntary breath holding time
(BHT). MATERIALS AND METHODS -
Breath holding time after 3 different maneuvers
(normal, after re-breathing, after
voluntary hyperventilation) were employed
on 13 subjects to obtain their end expiratory
partial pressures of gases before
breath hold and at break point. RESULTS
- The breath holding times for normal, rebreathing
and voluntary hyperventilation
were significantly different from each other
(p less than 0.03 in all three comparisons).
A negative correlation was observed between
end expiratory pCO2 (eECO2) before
breath hold and BHT (r equals -0.728,
p less than 0.0001). A positive correlation
was seen between end expiratory pO2
(eEO2) before breath hold and BHT (r
equals 0.682, p less than 0.0001). Analysis
of partial pressures of gases at break
point revealed comparatively
smaller deviations for end expiratory
pCO2 than that of pO2. A three dimensional
plot of eECO2 before breath hold,
eEO2 before breath hold and BHT
showed that all the data points fall along a
straight line. CONCLUSION - Our experiments
suggest a more significant role for
arterial pCO2 than arterial pO2. Strong
negative correlations between eECO2 before
breath hold and BHT, and between
eEO2 and eECO2 (r equals -0.965, p less
than 0.0001) could have resulted in a
positive correlation between eEO2 before
breath hold and BHT.
Keyword :Breath holding time, break
point, end expiratory partial pressures of
oxygen and carbon dioxide, correlation